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What's your favourite voltage regs?
For 5 years of my life my job was running double-blind listening tests
etc.. I'm in complete agreement that to pass on a conclusion to a third party who had nothing to do with an experiment needs an objective and repeatable method. But what if circumstances don't provide this? What if all you have is a rank order of preference? Such a rank order could be with one, two or twenty listeners. We admit that the method is flawed, but what do we do with this rank order: a) Decide that it is no better than chance and ignore it? b) Decide that if you had to chose unknown items with no other information than such a rank order, that your initial assumption would be that the rank order would be a better bet than chance? |
What's your favourite voltage regs?
On Wed, 23 Jan 2008 20:31:49 +0000, tony sayer
wrote: It is. but these DHT filaments are very sensitive 'ere wot abaht puttin summatt around the filament to keep it in?. This might catch on;!... And suppose you coated it with something that was really good at boiling off electrons. And suppose you gave it a bit of thermal mass so you could use AC rather than DC to heat it. That would make a much better valve - wouldn't it? d -- Pearce Consulting http://www.pearce.uk.com |
What's your favourite voltage regs?
Don Pearce wrote:
On Wed, 23 Jan 2008 20:31:49 +0000, tony sayer wrote: It is. but these DHT filaments are very sensitive 'ere wot abaht puttin summatt around the filament to keep it in?. This might catch on;!... And suppose you coated it with something that was really good at boiling off electrons. And suppose you gave it a bit of thermal mass so you could use AC rather than DC to heat it. That would make a much better valve - wouldn't it? d Unless the new emmiter couldn't supply enough electrons at high current peaks or for class C use, then you might still prefer a thorated fill. Having said that, it can't be that simple, a 6c33c is indirectly heated, but it does have a huge cathode. Anyway, more files, I emailed these links to you yesterday Don, but maybe they got lost after the night out :-). http://www.lurcher.org/nick/heater/2a3-sq-V.wav http://www.lurcher.org/nick/heater/2a3-sq-I.wav http://www.lurcher.org/nick/heater/2a3-sweep-I.wav http://www.lurcher.org/nick/heater/2a3-sweep-V.wav -- Nick |
What's your favourite voltage regs?
In article ,
Nick Gorham wrote: Don Pearce wrote: On Wed, 23 Jan 2008 20:31:49 +0000, tony sayer wrote: It is. but these DHT filaments are very sensitive 'ere wot abaht puttin summatt around the filament to keep it in?. This might catch on;!... And suppose you coated it with something that was really good at boiling off electrons. And suppose you gave it a bit of thermal mass so you could use AC rather than DC to heat it. That would make a much better valve - wouldn't it? Unless the new emmiter couldn't supply enough electrons at high current peaks or for class C use, then you might still prefer a thorated fill. I'm following this thread with interest. If only I understood a 10th of it. -- *How many roads must a man travel down before he admits he is lost? * Dave Plowman London SW To e-mail, change noise into sound. |
What's your favourite voltage regs?
On Wed, 23 Jan 2008 23:56:54 +0000, Nick Gorham
wrote: Don Pearce wrote: On Wed, 23 Jan 2008 20:31:49 +0000, tony sayer wrote: It is. but these DHT filaments are very sensitive 'ere wot abaht puttin summatt around the filament to keep it in?. This might catch on;!... And suppose you coated it with something that was really good at boiling off electrons. And suppose you gave it a bit of thermal mass so you could use AC rather than DC to heat it. That would make a much better valve - wouldn't it? d Unless the new emmiter couldn't supply enough electrons at high current peaks or for class C use, then you might still prefer a thorated fill. Having said that, it can't be that simple, a 6c33c is indirectly heated, but it does have a huge cathode. Anyway, more files, I emailed these links to you yesterday Don, but maybe they got lost after the night out :-). http://www.lurcher.org/nick/heater/2a3-sq-V.wav http://www.lurcher.org/nick/heater/2a3-sq-I.wav http://www.lurcher.org/nick/heater/2a3-sweep-I.wav http://www.lurcher.org/nick/heater/2a3-sweep-V.wav No sign of them in the inbox, I'm afraid. I'll have a listen now. d -- Pearce Consulting http://www.pearce.uk.com |
What's your favourite voltage regs?
On Thu, 24 Jan 2008 00:38:01 +0000 (GMT), "Dave Plowman (News)"
wrote: In article , Nick Gorham wrote: Don Pearce wrote: On Wed, 23 Jan 2008 20:31:49 +0000, tony sayer wrote: It is. but these DHT filaments are very sensitive 'ere wot abaht puttin summatt around the filament to keep it in?. This might catch on;!... And suppose you coated it with something that was really good at boiling off electrons. And suppose you gave it a bit of thermal mass so you could use AC rather than DC to heat it. That would make a much better valve - wouldn't it? Unless the new emmiter couldn't supply enough electrons at high current peaks or for class C use, then you might still prefer a thorated fill. I'm following this thread with interest. If only I understood a 10th of it. It really helps that I did all my early design work in valves. It just wasn't audio back then - apart from the trivial amount in the TVs I was designing. d -- Pearce Consulting http://www.pearce.uk.com |
What's your favourite voltage regs?
On Wed, 23 Jan 2008 23:56:54 +0000, Nick Gorham
wrote: Don Pearce wrote: On Wed, 23 Jan 2008 20:31:49 +0000, tony sayer wrote: It is. but these DHT filaments are very sensitive 'ere wot abaht puttin summatt around the filament to keep it in?. This might catch on;!... And suppose you coated it with something that was really good at boiling off electrons. And suppose you gave it a bit of thermal mass so you could use AC rather than DC to heat it. That would make a much better valve - wouldn't it? d Unless the new emmiter couldn't supply enough electrons at high current peaks or for class C use, then you might still prefer a thorated fill. Having said that, it can't be that simple, a 6c33c is indirectly heated, but it does have a huge cathode. Anyway, more files, I emailed these links to you yesterday Don, but maybe they got lost after the night out :-). http://www.lurcher.org/nick/heater/2a3-sq-V.wav http://www.lurcher.org/nick/heater/2a3-sq-I.wav http://www.lurcher.org/nick/heater/2a3-sweep-I.wav http://www.lurcher.org/nick/heater/2a3-sweep-V.wav Well, apart from a tiny difference around 25Hz which I'm pretty sure is some interaction with the leakage inductance of the output tranny, those curves overlay each other perfectly right up to 46kHz. The difference you were identifying aurally was at the top end, wasn't it? They are both on here. http://81.174.169.10/odds/dual_fr.gif If there is a difference it isn't in the frequency response. Do you want to try the distortion test again in case something shows that we didn't see using the shunt C method? Incidentally did you listen to the test amp with and without the shunt C to check if you could still hear the difference in that mode? d -- Pearce Consulting http://www.pearce.uk.com |
What's your favourite voltage regs?
Don Pearce wrote:
On Wed, 23 Jan 2008 23:56:54 +0000, Nick Gorham wrote: Don Pearce wrote: On Wed, 23 Jan 2008 20:31:49 +0000, tony sayer wrote: It is. but these DHT filaments are very sensitive 'ere wot abaht puttin summatt around the filament to keep it in?. This might catch on;!... And suppose you coated it with something that was really good at boiling off electrons. And suppose you gave it a bit of thermal mass so you could use AC rather than DC to heat it. That would make a much better valve - wouldn't it? d Unless the new emmiter couldn't supply enough electrons at high current peaks or for class C use, then you might still prefer a thorated fill. Having said that, it can't be that simple, a 6c33c is indirectly heated, but it does have a huge cathode. Anyway, more files, I emailed these links to you yesterday Don, but maybe they got lost after the night out :-). http://www.lurcher.org/nick/heater/2a3-sq-V.wav http://www.lurcher.org/nick/heater/2a3-sq-I.wav http://www.lurcher.org/nick/heater/2a3-sweep-I.wav http://www.lurcher.org/nick/heater/2a3-sweep-V.wav Well, apart from a tiny difference around 25Hz which I'm pretty sure is some interaction with the leakage inductance of the output tranny, those curves overlay each other perfectly right up to 46kHz. The difference you were identifying aurally was at the top end, wasn't it? They are both on here. http://81.174.169.10/odds/dual_fr.gif If there is a difference it isn't in the frequency response. Do you want to try the distortion test again in case something shows that we didn't see using the shunt C method? Incidentally did you listen to the test amp with and without the shunt C to check if you could still hear the difference in that mode? d Its still using the shunt C, I haven't had chance to hook up the reg yet. I will, but it might not be until the weekend. I could try and listen to it, ut of course I only threw one chan together. I could try the shunt C on my 211 that I do listen to, but would have been a pain to measure. -- Nick |
What's your favourite voltage regs?
"Andy Evans" wrote in message
... For 5 years of my life my job was running double-blind listening tests etc.. I'm in complete agreement that to pass on a conclusion to a third party who had nothing to do with an experiment needs an objective and repeatable method. But what if circumstances don't provide this? What if all you have is a rank order of preference? Such a rank order could be with one, two or twenty listeners. We admit that the method is flawed, but what do we do with this rank order: a) Decide that it is no better than chance and ignore it? b) Decide that if you had to chose unknown items with no other information than such a rank order, that your initial assumption would be that the rank order would be a better bet than chance? It's your amp, and you are going to be the one listening to it, so if you think that particular filament PSU makes the amp sound best go with it. I don't have a problem with that. What a *do* have a problem with (and this is not addressed to you) is when people make assertions that A *does* sound better than B, based entirely on their own non-blind listening. To be honest I remain unconvinced that there actually is any objective difference in the sound of a DHT amp caused by the form of filament PSU (unless it is grossly unsuitable). I know that sometimes my own system sounds really good to me, and othertimes it sounds crap. The difference is not in the system, it's in me. Human perception is a very fallible thing, what we apparently experience is not necessarily what is objectively there. David. |
What's your favourite voltage regs?
In article , Don Pearce
scribeth thus On Wed, 23 Jan 2008 20:31:49 +0000, tony sayer wrote: It is. but these DHT filaments are very sensitive 'ere wot abaht puttin summatt around the filament to keep it in?. This might catch on;!... And suppose you coated it with something that was really good at boiling off electrons. And suppose you gave it a bit of thermal mass so you could use AC rather than DC to heat it. That would make a much better valve - wouldn't it? d Yeah right!!, it would save the weight of all those trannies;).. -- Tony Sayer |
What's your favourite voltage regs?
On Thu, 24 Jan 2008 08:04:04 +0000, Nick Gorham
wrote: Don Pearce wrote: On Wed, 23 Jan 2008 23:56:54 +0000, Nick Gorham wrote: Don Pearce wrote: On Wed, 23 Jan 2008 20:31:49 +0000, tony sayer wrote: It is. but these DHT filaments are very sensitive 'ere wot abaht puttin summatt around the filament to keep it in?. This might catch on;!... And suppose you coated it with something that was really good at boiling off electrons. And suppose you gave it a bit of thermal mass so you could use AC rather than DC to heat it. That would make a much better valve - wouldn't it? d Unless the new emmiter couldn't supply enough electrons at high current peaks or for class C use, then you might still prefer a thorated fill. Having said that, it can't be that simple, a 6c33c is indirectly heated, but it does have a huge cathode. Anyway, more files, I emailed these links to you yesterday Don, but maybe they got lost after the night out :-). http://www.lurcher.org/nick/heater/2a3-sq-V.wav http://www.lurcher.org/nick/heater/2a3-sq-I.wav http://www.lurcher.org/nick/heater/2a3-sweep-I.wav http://www.lurcher.org/nick/heater/2a3-sweep-V.wav Well, apart from a tiny difference around 25Hz which I'm pretty sure is some interaction with the leakage inductance of the output tranny, those curves overlay each other perfectly right up to 46kHz. The difference you were identifying aurally was at the top end, wasn't it? They are both on here. http://81.174.169.10/odds/dual_fr.gif If there is a difference it isn't in the frequency response. Do you want to try the distortion test again in case something shows that we didn't see using the shunt C method? Incidentally did you listen to the test amp with and without the shunt C to check if you could still hear the difference in that mode? d Its still using the shunt C, I haven't had chance to hook up the reg yet. I will, but it might not be until the weekend. I could try and listen to it, ut of course I only threw one chan together. I could try the shunt C on my 211 that I do listen to, but would have been a pain to measure. I've just redone the comparison a bit more carefully - I removed that last bit of odd LF stuff before doing the FFT, and both are now absolutely identical, including at 25Hz.Overlaying the two traces on one graph, you can only see the last one you put on. d -- Pearce Consulting http://www.pearce.uk.com |
What's your favourite voltage regs?
"Jim Lesurf" wrote in message
... In article , David Looser That may or may not be so. However you may find effects like audible clicks. Note also that the effect of a bypass capacitor reduces at *LF* as the frequencies fall below the turnover of the relevant RC time constant. You are moving into a whole new area here. If you want to open up the discussion to deal with issues of the filtering of mains-borne interference that's fine. But please don't try to pretend that that is what the discussion was about before. Of course the effect of the capacitor reduces at LF, but then so does that of the parasitic capacitance to ground from the PSU and it's wiring! Again, I can't speak for DHT audio amps. But I have encountered various items of 'audiophile' kit that show clicks, etc, for reasons like this in SS circuitry. Indeed. I can't say if there will be problems or not with DHT amps whose design I have never seen or tested. TBH I doubt you can, either, but... No I haven't. That doesn't mean that I see any reason why interference should not be a problem with DHT amps as well. But as I said this isn't what the thread was about. Whereas the distinction I point out was that you were referring to the internal heater resistance of the valve, and I + others had been talking about the impedance of the PSU. Well no. I (and the others) were talking about the output impedance of the power supply *in relation* to the impedance of the filament. But we were talking about the impedance across the floating supply which is in parallel with the filament. Only you, as far as I can see, have been talking about the impedance *to ground* of the PSU. David. |
What's your favourite voltage regs?
Don Pearce wrote:
On Thu, 24 Jan 2008 08:04:04 +0000, Nick Gorham wrote: Don Pearce wrote: On Wed, 23 Jan 2008 23:56:54 +0000, Nick Gorham wrote: Don Pearce wrote: On Wed, 23 Jan 2008 20:31:49 +0000, tony sayer wrote: It is. but these DHT filaments are very sensitive 'ere wot abaht puttin summatt around the filament to keep it in?. This might catch on;!... And suppose you coated it with something that was really good at boiling off electrons. And suppose you gave it a bit of thermal mass so you could use AC rather than DC to heat it. That would make a much better valve - wouldn't it? d Unless the new emmiter couldn't supply enough electrons at high current peaks or for class C use, then you might still prefer a thorated fill. Having said that, it can't be that simple, a 6c33c is indirectly heated, but it does have a huge cathode. Anyway, more files, I emailed these links to you yesterday Don, but maybe they got lost after the night out :-). http://www.lurcher.org/nick/heater/2a3-sq-V.wav http://www.lurcher.org/nick/heater/2a3-sq-I.wav http://www.lurcher.org/nick/heater/2a3-sweep-I.wav http://www.lurcher.org/nick/heater/2a3-sweep-V.wav Well, apart from a tiny difference around 25Hz which I'm pretty sure is some interaction with the leakage inductance of the output tranny, those curves overlay each other perfectly right up to 46kHz. The difference you were identifying aurally was at the top end, wasn't it? They are both on here. http://81.174.169.10/odds/dual_fr.gif If there is a difference it isn't in the frequency response. Do you want to try the distortion test again in case something shows that we didn't see using the shunt C method? Incidentally did you listen to the test amp with and without the shunt C to check if you could still hear the difference in that mode? d Its still using the shunt C, I haven't had chance to hook up the reg yet. I will, but it might not be until the weekend. I could try and listen to it, ut of course I only threw one chan together. I could try the shunt C on my 211 that I do listen to, but would have been a pain to measure. I've just redone the comparison a bit more carefully - I removed that last bit of odd LF stuff before doing the FFT, and both are now absolutely identical, including at 25Hz.Overlaying the two traces on one graph, you can only see the last one you put on. d Oh, well, at least that shows that the tests are at least reproducible :-) What I need to take great care with when I use a real voltage reg, is that the actual voltages the fill sees are close enough. -- Nick. |
What's your favourite voltage regs?
On Thu, 24 Jan 2008 09:59:36 +0000, Nick Gorham
wrote: Oh, well, at least that shows that the tests are at least reproducible :-) What I need to take great care with when I use a real voltage reg, is that the actual voltages the fill sees are close enough. Yes, a small difference in emissivity could easily mask what we are trying to measure. d -- Pearce Consulting http://www.pearce.uk.com |
What's your favourite voltage regs?
Don Pearce wrote:
On Thu, 24 Jan 2008 09:59:36 +0000, Nick Gorham wrote: Oh, well, at least that shows that the tests are at least reproducible :-) What I need to take great care with when I use a real voltage reg, is that the actual voltages the fill sees are close enough. Yes, a small difference in emissivity could easily mask what we are trying to measure. d Well, this is with a real voltage reg, I have set the voltage across the fil as close as possible, within 20mv anyway. The results are rather interesting. http://www.lurcher.org/nick/heater/2a3-1k-I.wav http://www.lurcher.org/nick/heater/2a3-1k-V.wav http://www.lurcher.org/nick/heater/2a3-swp-I.wav http://www.lurcher.org/nick/heater/2a3-swp-V.wav -- Nick |
What's your favourite voltage regs?
On Thu, 24 Jan 2008 21:34:13 +0000, Nick Gorham
wrote: Don Pearce wrote: On Thu, 24 Jan 2008 09:59:36 +0000, Nick Gorham wrote: Oh, well, at least that shows that the tests are at least reproducible :-) What I need to take great care with when I use a real voltage reg, is that the actual voltages the fill sees are close enough. Yes, a small difference in emissivity could easily mask what we are trying to measure. d Well, this is with a real voltage reg, I have set the voltage across the fil as close as possible, within 20mv anyway. The results are rather interesting. http://www.lurcher.org/nick/heater/2a3-1k-I.wav http://www.lurcher.org/nick/heater/2a3-1k-V.wav http://www.lurcher.org/nick/heater/2a3-swp-I.wav http://www.lurcher.org/nick/heater/2a3-swp-V.wav Yup - absolutely identical frequency response again between voltage and current. But when it comes to distortion, the current driven version is considerably worse - particularly the higher order harmonics. That is sort of counter-intuitive, but it would account for the difference in sound at the top end. I can just hear the difference between the two by joining a one second chunk of each in sequence and letting them loop. I can tell which bit I am in without looking at the monitor. So yes, there is a difference now. The current feed has more of a "valve" sound - ie more distorted. I guess that if you like that sound you would find it preferable. I'm totally stumped for a mechanism though. It has worked out backwards from the way we were expecting. d -- Pearce Consulting http://www.pearce.uk.com |
What's your favourite voltage regs?
Don Pearce wrote:
On Thu, 24 Jan 2008 21:34:13 +0000, Nick Gorham wrote: Don Pearce wrote: On Thu, 24 Jan 2008 09:59:36 +0000, Nick Gorham wrote: Oh, well, at least that shows that the tests are at least reproducible :-) What I need to take great care with when I use a real voltage reg, is that the actual voltages the fill sees are close enough. Yes, a small difference in emissivity could easily mask what we are trying to measure. d Well, this is with a real voltage reg, I have set the voltage across the fil as close as possible, within 20mv anyway. The results are rather interesting. http://www.lurcher.org/nick/heater/2a3-1k-I.wav http://www.lurcher.org/nick/heater/2a3-1k-V.wav http://www.lurcher.org/nick/heater/2a3-swp-I.wav http://www.lurcher.org/nick/heater/2a3-swp-V.wav Yup - absolutely identical frequency response again between voltage and current. But when it comes to distortion, the current driven version is considerably worse - particularly the higher order harmonics. That is sort of counter-intuitive, but it would account for the difference in sound at the top end. I can just hear the difference between the two by joining a one second chunk of each in sequence and letting them loop. I can tell which bit I am in without looking at the monitor. So yes, there is a difference now. The current feed has more of a "valve" sound - ie more distorted. I guess that if you like that sound you would find it preferable. I'm totally stumped for a mechanism though. It has worked out backwards from the way we were expecting. d Yes, I didn't expect this result. I am going to repeat tomorrow, just to make sure I didn't do something stupid. I would be tempted to suggest that the first stage is contributing something, and there is some cancelation going on, but both the even and odd order harmonics seem to be affected, so I don't believe thats the case. I will try with a 300b tomorrow, and see if the results repeat. I do tend to beleve the results are correct thogh, if I had done somethiung stupid like got the fil temp differemt in the two cases, I would have expected the fundimental to be alteres by more than it was. -- Nick |
What's your favourite voltage regs?
In article , David Looser
wrote: "Jim Lesurf" wrote in message ... In article , David Looser That may or may not be so. However you may find effects like audible clicks. Note also that the effect of a bypass capacitor reduces at *LF* as the frequencies fall below the turnover of the relevant RC time constant. You are moving into a whole new area here. If you want to open up the discussion to deal with issues of the filtering of mains-borne interference that's fine. But please don't try to pretend that that is what the discussion was about before. Please don't confuse yourself by assuming that was what I was doing. :-) I note you have snipped away the point you made to which the above was a response. Plus you removed the other relevant points. This means you have taken the above out of its context. Hence your confusion and the erronious assumption that it was an attempt to "pretend" something. Whereas the distinction I point out was that you were referring to the internal heater resistance of the valve, and I + others had been talking about the impedance of the PSU. Well no. I (and the others) were talking about the output impedance of the power supply *in relation* to the impedance of the filament. But we were talking about the impedance across the floating supply which is in parallel with the filament. Only you, as far as I can see, have been talking about the impedance *to ground* of the PSU. What I wrote was to clarify what Nick had said and give a better worded explanation for a point he made. He emailed me later to confirm this. So far as I can see, what then happened was that you dealt with another matter to the one I was referring to, and have misinterpreted what I was saying. I have tried to explain this to you. Simple matter of cross purposes. Sorry if you are still unable to accept this, but - as above - it may be because you are not keeping things in the relevant contexts, and thus are forming inappropriate assumptions. Slainte, Jim -- Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm Audio Misc http://www.audiomisc.co.uk/index.html Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html |
What's your favourite voltage regs?
Don Pearce wrote:
On Thu, 24 Jan 2008 21:34:13 +0000, Nick Gorham wrote: Don Pearce wrote: On Thu, 24 Jan 2008 09:59:36 +0000, Nick Gorham wrote: Oh, well, at least that shows that the tests are at least reproducible :-) What I need to take great care with when I use a real voltage reg, is that the actual voltages the fill sees are close enough. Yes, a small difference in emissivity could easily mask what we are trying to measure. d Well, this is with a real voltage reg, I have set the voltage across the fil as close as possible, within 20mv anyway. The results are rather interesting. http://www.lurcher.org/nick/heater/2a3-1k-I.wav http://www.lurcher.org/nick/heater/2a3-1k-V.wav http://www.lurcher.org/nick/heater/2a3-swp-I.wav http://www.lurcher.org/nick/heater/2a3-swp-V.wav Yup - absolutely identical frequency response again between voltage and current. But when it comes to distortion, the current driven version is considerably worse - particularly the higher order harmonics. That is sort of counter-intuitive, but it would account for the difference in sound at the top end. I can just hear the difference between the two by joining a one second chunk of each in sequence and letting them loop. I can tell which bit I am in without looking at the monitor. So yes, there is a difference now. The current feed has more of a "valve" sound - ie more distorted. I guess that if you like that sound you would find it preferable. I'm totally stumped for a mechanism though. It has worked out backwards from the way we were expecting. d I tried to repeat the process, using a 300b this time, no sign of the difference that seemed to exist with a 2a3. I will repeat with the 2a3 again later. But I just thought of a possible reason, see wht you think. unlike a 300b, the 2a3 I used has dual anodes, its effectivly two 45 in parallel in the one envelope. I wonder if regulating the fil supply with a current source instead of a voltage source is allowing different fil temperatures in each half, and that inbalance is whats causing the higher distortion. Just a thought. -- Nick |
What's your favourite voltage regs?
On Fri, 25 Jan 2008 22:12:26 +0000, Nick Gorham
wrote: Don Pearce wrote: On Thu, 24 Jan 2008 21:34:13 +0000, Nick Gorham wrote: Don Pearce wrote: On Thu, 24 Jan 2008 09:59:36 +0000, Nick Gorham wrote: Oh, well, at least that shows that the tests are at least reproducible :-) What I need to take great care with when I use a real voltage reg, is that the actual voltages the fill sees are close enough. Yes, a small difference in emissivity could easily mask what we are trying to measure. d Well, this is with a real voltage reg, I have set the voltage across the fil as close as possible, within 20mv anyway. The results are rather interesting. http://www.lurcher.org/nick/heater/2a3-1k-I.wav http://www.lurcher.org/nick/heater/2a3-1k-V.wav http://www.lurcher.org/nick/heater/2a3-swp-I.wav http://www.lurcher.org/nick/heater/2a3-swp-V.wav Yup - absolutely identical frequency response again between voltage and current. But when it comes to distortion, the current driven version is considerably worse - particularly the higher order harmonics. That is sort of counter-intuitive, but it would account for the difference in sound at the top end. I can just hear the difference between the two by joining a one second chunk of each in sequence and letting them loop. I can tell which bit I am in without looking at the monitor. So yes, there is a difference now. The current feed has more of a "valve" sound - ie more distorted. I guess that if you like that sound you would find it preferable. I'm totally stumped for a mechanism though. It has worked out backwards from the way we were expecting. d I tried to repeat the process, using a 300b this time, no sign of the difference that seemed to exist with a 2a3. I will repeat with the 2a3 again later. But I just thought of a possible reason, see wht you think. unlike a 300b, the 2a3 I used has dual anodes, its effectivly two 45 in parallel in the one envelope. I wonder if regulating the fil supply with a current source instead of a voltage source is allowing different fil temperatures in each half, and that inbalance is whats causing the higher distortion. Just a thought. Provided they are wired in parallel they are pretty much self-aligning. If a fil is at a lower temperature its resistance will be lower, so it will take more current, hence more power. That will apply whether they are voltage or current driven.. Of course if you run them in series, whichever finds itself a little hotter will tend to run away at the expense of the other. d -- Pearce Consulting http://www.pearce.uk.com -- Posted via a free Usenet account from http://www.teranews.com |
What's your favourite voltage regs?
Don Pearce wrote:
I will repeat with the 2a3 again later. But I just thought of a possible reason, see wht you think. unlike a 300b, the 2a3 I used has dual anodes, its effectivly two 45 in parallel in the one envelope. I wonder if regulating the fil supply with a current source instead of a voltage source is allowing different fil temperatures in each half, and that inbalance is whats causing the higher distortion. Just a thought. Provided they are wired in parallel they are pretty much self-aligning. If a fil is at a lower temperature its resistance will be lower, so it will take more current, hence more power. That will apply whether they are voltage or current driven.. Of course if you run them in series, whichever finds itself a little hotter will tend to run away at the expense of the other. d Yep, I was just about to post that the last should be ignored, as it was rubbish, a voltage on the valve pins, is a voltage, don;t matter how its derived. -- Nick |
What's your favourite voltage regs?
I'm full of admiration for Nick and Don's research here - do you want
me to send you a ready built Rod Coleman supply to test? could be interesting! If so just email and I'll put it in the post. Andy |
What's your favourite voltage regs?
Andy Evans wrote:
I'm full of admiration for Nick and Don's research here - do you want me to send you a ready built Rod Coleman supply to test? could be interesting! If so just email and I'll put it in the post. Andy I would certainly be interested, but given what we have found so far I don't know if we wioll manage to measure any difference. But I would love the chance to try. -- Nick |
What's your favourite voltage regs?
On Sat, 26 Jan 2008 09:43:56 +0000, Nick Gorham
wrote: Andy Evans wrote: I'm full of admiration for Nick and Don's research here - do you want me to send you a ready built Rod Coleman supply to test? could be interesting! If so just email and I'll put it in the post. Andy I would certainly be interested, but given what we have found so far I don't know if we wioll manage to measure any difference. But I would love the chance to try. Have you found any clues yet to the odd distortion change in that last test? I was wondering if you had been able to repeat it. d -- Pearce Consulting http://www.pearce.uk.com |
What's your favourite voltage regs?
"Jim Lesurf" wrote in message
... I know exactly what this thread was about before your first contribution to it. It was about the difference between driving the DHT filament with a voltage source, and a current source, and that's all. The issue of how "perfectly" the PSU was floating didn't come into it. The comments you made in your first post did not address this issue at all, but were, apparently, based on the misapprehension that we were discussing the effect of the PSU not floating "perfectly". This suggested to me that you had not read the thread properly before contributing, I still think that to have been the case. What I wrote was to clarify what Nick had said and give a better worded explanation for a point he made. In view of the fact that you were addressing an entirely different issue to the one we were discussing, it did not "clarify" anything, rather it confused the issue. He emailed me later to confirm this. Well so you said before, but I note that he has not taken the opportunity to say that here. David. |
What's your favourite voltage regs?
Don Pearce wrote:
On Sat, 26 Jan 2008 09:43:56 +0000, Nick Gorham wrote: Andy Evans wrote: I'm full of admiration for Nick and Don's research here - do you want me to send you a ready built Rod Coleman supply to test? could be interesting! If so just email and I'll put it in the post. Andy I would certainly be interested, but given what we have found so far I don't know if we wioll manage to measure any difference. But I would love the chance to try. Have you found any clues yet to the odd distortion change in that last test? I was wondering if you had been able to repeat it. d No, not yet, I admit I am skeptical that its real, I will repeat today, I thought I would use my wave analiser to get another way of measuring the same thing. Not that its more accurate than the PC (its not, only good to -80dB), but its quicker as its in the same room as the test amp. -- Nick |
What's your favourite voltage regs?
On Sat, 26 Jan 2008 10:51:57 +0000, Nick Gorham
wrote: Don Pearce wrote: On Sat, 26 Jan 2008 09:43:56 +0000, Nick Gorham wrote: Andy Evans wrote: I'm full of admiration for Nick and Don's research here - do you want me to send you a ready built Rod Coleman supply to test? could be interesting! If so just email and I'll put it in the post. Andy I would certainly be interested, but given what we have found so far I don't know if we wioll manage to measure any difference. But I would love the chance to try. Have you found any clues yet to the odd distortion change in that last test? I was wondering if you had been able to repeat it. d No, not yet, I admit I am skeptical that its real, I will repeat today, I thought I would use my wave analiser to get another way of measuring the same thing. Not that its more accurate than the PC (its not, only good to -80dB), but its quicker as its in the same room as the test amp. At the levels we are talking about, -80dB is just fine. d -- Pearce Consulting http://www.pearce.uk.com |
What's your favourite voltage regs?
Nick Gorham wrote:
Have you found any clues yet to the odd distortion change in that last test? I was wondering if you had been able to repeat it. d No, not yet, I admit I am skeptical that its real, I will repeat today, I thought I would use my wave analiser to get another way of measuring the same thing. Not that its more accurate than the PC (its not, only good to -80dB), but its quicker as its in the same room as the test amp. Ok, confusion over, at 2.5v output, the voltage reg was going into shutdown, so reducing the fill voltage to about 1.6v, so all we were seeing was the effect Steve Bench had already seen that you can get lower distortion by reducing the fill voltage. Making sure the voltages remain constant, the measured distortion stayed the same between the I and V supply. The driver was producing -50dB of second harmonic, so I think I will try and repeat this next time I have a real SET on the bench with a more capable driver stage. But so far, "notying to see here, move along" -- Nick |
What's your favourite voltage regs?
In article , David Looser
wrote: "Jim Lesurf" wrote in message ... I know exactly what this thread was about before your first contribution to it. It was about the difference between driving the DHT filament with a voltage source, and a current source, and that's all. Actually, that is incorrect. It started with a call from Andy to suggest what PSU designs we favoured for applications like heating in the context he gave. (cf below) What you refer to was one of the various topics that subsequently arose. The issue of how "perfectly" the PSU was floating didn't come into it. Indeed. Nor have I ever said otherwise. Once again you are jumping to erronious conclusions. I am afraid that your habit of taking things out of context and snipping away what has been responded to has confused you again if you assumed otherwise. :-) The comments you made in your first post did not address this issue at all, but were, apparently, based on the misapprehension that we were discussing the effect of the PSU not floating "perfectly". This suggested to me that you had not read the thread properly before contributing, I still think that to have been the case. I am afraid that your habit of snipping what others have said and then taking things out of their context is still confusing you. Above you state various opinions as if they were facts. It may therefore be useful to copy some of what was actually written to restore some relevant context. So, according to my records the first posting I made in this thread was actually as follows: ] Newsgroups: uk.rec.audio From: Subject: ] What's your favourite voltage regs? Date: Wed, 16 Jan 2008 13:35 ] ] In article ] , Andy ] Evans wrote: ] ] ] So - which voltage regs are your fave choices here? Good quality ] output important, but cost also a consideration. This looks right up ] Jim's street for starters. ] ] FWIW I tried various types of 'IC voltage regulator/stabiliser chip' ] some years ago and decided I wasn't keen on any of the common types. Too ] prone to oscillations or excess noise, etc. Newer ones may be better, ] but I lost interest in using them. :-) ] ] So I have tended to use variations on the kind of topology shown on ] ] http://www.audiomisc.co.uk/Armstrong/700/730PSU.gif ] ] As you can see, the zener sets the nominal voltage, and a capacity ] multiplier pass device smooths over the noise and gives a slow ] start/stop. ] ] That example was for about +/-20V up to about 100mA, used for the rails ] in a preamp. But the same topology has been used many times by my old ] research group for voltages in the few V region at currents up to a few ] amps, so may serve your purpose. [1] Just alter the components to suit. ] Make the pass transistor a form of darlington pair if needed. I found a ] single device was usually fine for currents of the order of an amp or ] two. But if you need high current the single-pack darlingtons made for ] cheaper SS amps might well do that well if you wanted. But these may ] need to be checked for oscillation problems. ] ] Main advantages of the topology are low noise and a gradual windup and ] rundown rather than coming on or going off with a crack. Kinder for your ] valve heaters, perhaps. You may also like the fact that it has no ] overall feedback. :-) ] ] No idea if it will suit you, but since you mentioned my name... ] ] For power amps, though, I always just used a decent transformer and ] large caps, then designed the amp to reject power line variations. So no ] need for any active smoothing/stabilisation/regulation. ] ] Slainte, ] ] Jim ] ] [1] e.g. for the PSU for 5-12V 1A Gunn diodes where noise from the PSU ] needs to be minimal as it would introduce noise sidebands to the 94GHz ] output. If you want I can see if I can dig out a diagram of the variable ] and fixed versions used for that, but they are in essence the above. It was in other postings later one we got to various other topics... What I wrote was to clarify what Nick had said and give a better worded explanation for a point he made. In view of the fact that you were addressing an entirely different issue to the one we were discussing, it did not "clarify" anything, rather it confused the issue. I appreciate that it has confused you, since that was a different posting on another issue to the above. As above, your problem here seems to be that you have conflated and confused various issues and points that have arisen in this thread. Since you have lost awareness of what I actually wrote here is the first posting I made on the topic: ] Newsgroups: uk.rec.audio From: Subject: ] What's your favourite voltage regs? Date: Fri, 18 Jan 2008 09:35 ] ] In article , Eeyore ] wrote: ] ] ] Nick Gorham wrote: ] ] Ian Iveson wrote: ] ] and the voltage reg will try and regulate that away, with a current ] reg, the signal is common mode, so not affected. ] ] UH ? ] ] Can only speculate at this point as I have never tried using these ] circuits for heaters in audio amps. However... ] ] With 'direct' heating the heater psu is - I presume - connected to the ] same physical place as the cathode signal. Having a 'constant current' ] PSU means the PSU looks like a high impedance connection, so will be ] less likely to have a loading effect on signal drive to the cathode if ] the PSU common mode isolation is poor. i.e. the problem is that the ] cathode signal has to drive any loading it sees due to the PSU, so a ] high impedance might be preferred. ] ] Slainte, ] ] Jim ] And as I pointed out, Nick and I then exchanged emails about this. I also made responses to other points you made. Unfortunately, due to the way you snip and then take things out of context, these then became conflated in your mind, leading to more confusion on your part. The question of 'floating' PSU is clearly relevant to the above point since it may be a factor in whether or not the above has an effect on performance. Indeed, you might note the phrase "...if the PSU common mode isolation is poor..." :-) But, as I have said countless times, since I have never made or tested a DHT audio amp I can't comment on the extent to which any of the above may matter in practice. I was just trying to clarify what others had said. So you could even note the use of "...*if*..." in the above. ;- Well so you said before, but I note that he has not taken the opportunity to say that here. I could also note that neither he, nor indeed anyone else, has supported your own confusions. :-) TBH I assume that he and others have had better things to do, and are content to let me waste my own time. Nick has been reading this group for long enough to know how patient I can be. ;- Indeed, Nick and Don have had quite an informative discussion in this thread. Slainte, Jim -- Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm Audio Misc http://www.audiomisc.co.uk/index.html Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html |
What's your favourite voltage regs?
Yes - as the original poster I was looking for any useful input, which
has been richly provided by all concerned. I don't think it was about one thing and not another - I meant it as an open thread about different ways of supplying the filaments on DHTs, which covers a lot of potential ground. I particularly appreciate the input from guys like Jim who may not have ever used DHTs but are still ready to throw their considerable expertise into the ring. I think the basic elements are pretty close to building a good linear PSU, something which I expect most of us have done several times! Particularly interesting input on how filaments work from Dave, Nick and Don - I'm sending Nick some boards to test! |
What's your favourite voltage regs?
"Jim Lesurf" wrote in message
... In article , David Looser wrote: "Jim Lesurf" wrote in message ... I know exactly what this thread was about before your first contribution to it. It was about the difference between driving the DHT filament with a voltage source, and a current source, and that's all. Actually, that is incorrect. It started with a call from Andy to suggest what PSU designs we favoured for applications like heating in the context he gave. (cf below) What you refer to was one of the various topics that subsequently arose. Yes, you are correct, I had slipped my mind that you had posted on the original discussion on "favourite voltage regulators". The issue of how "perfectly" the PSU was floating didn't come into it. Indeed. Nor have I ever said otherwise. Once again you are jumping to erronious conclusions. Am I?, quote I think we were talking about the use of resistors *external* to the heater element, and in which the signal current would not appear if the PSU were genuinely floating. *Not* the resistance of the valve between its heater terminals. The point of the resistors being to reduce any effect of the PSU not being a perfectly floating one. unquote I am afraid that your habit of taking things out of context and snipping away what has been responded to has confused you again if you assumed otherwise. :-) See above. I snip because when threads get long (as this one has) if people don't snip the possibility (nay, probability) is that confusion really will set in. I am afraid that your habit of snipping what others have said and then taking things out of their context is still confusing you. Above you state various opinions as if they were facts. It may therefore be useful to copy some of what was actually written to restore some relevant context. So, according to my records the first posting I made in this thread was actually as follows: Yes OK, you really didn't need to post the whole lot just to make that point. I accept that I was in error in refering to your "first" post. It was in other postings later one we got to various other topics... What I wrote was to clarify what Nick had said and give a better worded explanation for a point he made. Yet I still cannot see how your post "clarified" one of his. In view of the fact that you were addressing an entirely different issue to the one we were discussing, it did not "clarify" anything, rather it confused the issue. I appreciate that it has confused you, since that was a different posting on another issue to the above. As above, your problem here seems to be that you have conflated and confused various issues and points that have arisen in this thread. Since you have lost awareness of what I actually wrote here is the first posting I made on the topic: ] Newsgroups: uk.rec.audio From: Subject: ] What's your favourite voltage regs? Date: Fri, 18 Jan 2008 09:35 ] ] In article , Eeyore ] wrote: ] ] ] Nick Gorham wrote: ] ] Ian Iveson wrote: ] ] and the voltage reg will try and regulate that away, with a current ] reg, the signal is common mode, so not affected. ] ] UH ? ] ] Can only speculate at this point as I have never tried using these ] circuits for heaters in audio amps. However... ] ] With 'direct' heating the heater psu is - I presume - connected to the ] same physical place as the cathode signal. Having a 'constant current' ] PSU means the PSU looks like a high impedance connection, so will be ] less likely to have a loading effect on signal drive to the cathode if ] the PSU common mode isolation is poor. i.e. the problem is that the ] cathode signal has to drive any loading it sees due to the PSU, so a ] high impedance might be preferred. ] ] Slainte, ] ] Jim ] This is the post from you which I erroneously called your "first" post. And now we come to the crux of the matter. In this post you refer to "a loading effect on the drive signal to the cathode if the common-mode isolation of the PSU is poor" By talking about "the drive to the cathode" you are suggesting that you see this as a cathode driven amp. With common-cathode audio amps (which is what we have here) there probably isn't even a signal *at* the cathode, let alone one *to* the cathode. This is why I regard your post, repeated above, as being utterly confusing. Now by "common-mode isolation" I take it you are referring to what we have above referred to as "perfectly (or otherwise) floating". In other words this is the impedance *to ground* from the PSU, not the impedance *across* the PSU. As the cathode is probably at cathode potential as far as signal is concerned the common-mode isolation of the PSU is a matter of no importance whatsoever. Whether the impedance *across* the PSU is high or low will not affect this common-mode isolation anyway. And as I pointed out, Nick and I then exchanged emails about this. Well so you have said. But as I have never seen these emails, nor has Nick posted anything about them here, as far as I am concerned they do not exist. You cannot use "secret evidence" to prove your point. I also made responses to other points you made. Unfortunately, due to the way you snip and then take things out of context, these then became conflated in your mind, leading to more confusion on your part. You made other points agreed. Some of them were interesting and relevant. Unfortunately you tried to use them to justify what you wrote in the post quoted above which, as I have already said, did not address the question of the difference between current and voltage regulated PSUs at all. I could also note that neither he, nor indeed anyone else, has supported your own confusions. :-) I'm not the one claiming that Nick has sent me emails supporting me. TBH I assume that he and others have had better things to do, and are content to let me waste my own time. Nick has been reading this group for long enough to know how patient I can be. ;- Indeed, Nick and Don have had quite an informative discussion in this thread. I agree, I've followed it with interest. To be honest I think our argument has shown a remarkable amount of patience on both sides. If you still think that: quote ] With 'direct' heating the heater psu is - I presume - connected to the ] same physical place as the cathode signal. Having a 'constant current' ] PSU means the PSU looks like a high impedance connection, so will be ] less likely to have a loading effect on signal drive to the cathode if ] the PSU common mode isolation is poor. i.e. the problem is that the ] cathode signal has to drive any loading it sees due to the PSU, so a ] high impedance might be preferred. unquote has any relevance to the issue of current vs. voltage regulated filament PSUs for common-cathode audio amplifiers, or "clarifies" anything that was said before, or since for that matter, then all I can say is that I cannot even begin to understand why. As far as I am concerned that post from you shows that you were seriously confused about the point under discussion. David. |
What's your favourite voltage regs?
In article
, Andy Evans wrote: I particularly appreciate the input from guys like Jim who may not have ever used DHTs but are still ready to throw their considerable expertise into the ring. I think the basic elements are pretty close to building a good linear PSU, something which I expect most of us have done several times! Thanks, Andy. I appreciate that. Happy to try and help if I can. Although as you know I don't have any personal interest in building valve audio amps, so can't comment on any PSU effects in them from personal experience. Particularly interesting input on how filaments work from Dave, Nick and Don - I'm sending Nick some boards to test! I have also been interested in what they have said. Intriguing just how much there is to learn despite people having done R&D on valve amps for many years! Slainte, Jim -- Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm Audio Misc http://www.audiomisc.co.uk/index.html Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html |
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