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What's your favourite voltage regs?
David asked how we established this was the "best sounding".
I and a friend listened to: Thandar bench supply Two voltage LM1084 regs in series Two voltage LM1084 regs in series followed by a common mode choke Rod Coleman supply (with a straight transformer and reservoir cap, but otherwise as the circuit) Rod Coleman supply followed by a CMC We switched back and forth a few times between them and listened to two contrasting tracks. We both agreed that in listening terms the Rod Coleman supply was best (cleanest with most detail) followed by the voltage regs and CMC (softer, less detailed). Adding a CMC after the Rod Coleman supply sounded worse. Sorry - you'll have to take this at face value, since it wasn't double blind. i.e. clearly not proven but may, depending on how you feel about these things, show a trend in the stated direction, since we were both in agreement and both thought we could hear a difference. We're both suitably cynical and my colleague is an engineer. We were also sober!!! That's the best I can offer. Andy |
What's your favourite voltage regs?
On Tue, 22 Jan 2008 14:37:24 +0000, Nick Gorham
wrote: Don Pearce wrote: On Tue, 22 Jan 2008 13:43:04 -0000, "David Looser" wrote: "Andy Evans" wrote in message ... http://www.diyaudio.com/forums/showt...=&pagenumber=1 Can I ask you guys - David, Jim, Nick, Don etc. to have a look at this thread on www.diyaudio.com entitled "New DHT heater". I couldn't find it, where exactly is it? I found the thread using the search button, but the links in the first article are just 404s, and I can find no reference to Rod Coleman's work. A working link would be good. d Worked for me, this is the diag in the thread. http://img65.exs.cx/img65/702/BUFFEREDDHTFILAMENT.png That's one hell of a lot of circuit for very little purpose. He should just have used the cathode resistors as current sensors into a comparator against a suitable voltage and fed the resulting current into the base of the MJE15029 - that would be job done, no need for gyrators. d -- Pearce Consulting http://www.pearce.uk.com |
What's your favourite voltage regs?
In article , David Looser
wrote: "Jim Lesurf" wrote in message ... In article , David Looser wrote: "Jim Lesurf" wrote in message ... *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. Why should the PSU *not* be a perfectly floating one?. Because in reality the PSU will exhibit parasitic capacitance, inductances, etc. to its surroundings. For example parasitic capacitance via the transformer windings (or electrostatic screen if present), and via the wires. I'm afraid that in the real world you are unlikely to find a perfectly floating PSU. Just ones which may sufficiently well isolated for a given use. So the effects may be too small to worry about in some cases. But that does not mean they don't exist, or can never have a significant effect. As I pointed out before we are talking audio here, not HF. The most significant effect will be capacitance to ground from the PSU and it's wiring, and since this will be in parallel with a low-value resistor and probably a high-value capacitor as well the effect will be truly negligible. 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. 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. 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... I had assumed you would be aware of this, and would have realised that we were talking about different issues. We do seem to be. I'm talking about common-cathode audio amplifers, you seem to be talking about HF amplifiers with signal applied via the cathode. 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. 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?
In article
s.com, Andy Evans scribeth thus David asked how we established this was the "best sounding". I and a friend listened to: Thandar bench supply Two voltage LM1084 regs in series Two voltage LM1084 regs in series followed by a common mode choke Rod Coleman supply (with a straight transformer and reservoir cap, but otherwise as the circuit) Rod Coleman supply followed by a CMC We switched back and forth a few times between them and listened to two contrasting tracks. We both agreed that in listening terms the Rod Coleman supply was best (cleanest with most detail) followed by the voltage regs and CMC (softer, less detailed). Adding a CMC after the Rod Coleman supply sounded worse. Sorry - you'll have to take this at face value, since it wasn't double blind. i.e. clearly not proven but may, depending on how you feel about these things, show a trend in the stated direction, since we were both in agreement and both thought we could hear a difference. We're both suitably cynical and my colleague is an engineer. We were also sober!!! That's the best I can offer. Andy Ah!, but you didn't try a wet acid cell did you;!?.... -- Tony Sayer |
What's your favourite voltage regs?
In article , Don Pearce
scribeth thus On Tue, 22 Jan 2008 14:37:24 +0000, Nick Gorham wrote: Don Pearce wrote: On Tue, 22 Jan 2008 13:43:04 -0000, "David Looser" wrote: "Andy Evans" wrote in message ... http://www.diyaudio.com/forums/showt...8&perpage=25&h ighlight=&pagenumber=1 Can I ask you guys - David, Jim, Nick, Don etc. to have a look at this thread on www.diyaudio.com entitled "New DHT heater". I couldn't find it, where exactly is it? I found the thread using the search button, but the links in the first article are just 404s, and I can find no reference to Rod Coleman's work. A working link would be good. d Worked for me, this is the diag in the thread. http://img65.exs.cx/img65/702/BUFFEREDDHTFILAMENT.png That's one hell of a lot of circuit for very little purpose. He should just have used the cathode resistors as current sensors into a comparator against a suitable voltage and fed the resulting current into the base of the MJE15029 - that would be job done, no need for gyrators. d Indeed.. I'd like to know why we have to have two transformers for a start;!.. -- Tony Sayer |
What's your favourite voltage regs?
That's one hell of a lot of circuit for very little purpose. He should
just have used the cathode resistors as current sensors into a comparator against a suitable voltage and fed the resulting current into the base of the MJE15029 - that would be job done, no need for gyrators. d Indeed.. I'd like to know why we have to have two transformers for a start;!.. My first reaction was rather similar - what do the two transformers and all those caps add. The answer would be that there is filtering between the two transformers and the smaller caps are faster. How audible that is I don't know. However, I would caution against dismissing it out of hand since it does actually sound the business. It may be overkill, but these DHT filaments are very sensitive and Rod clearly spent time on this circuit, which he uses in his own setup. As for batteries - I did try those as well, and I didn't think they sounded any better than this. |
What's your favourite voltage regs?
"Andy Evans" wrote in message
news:5bde0ef2-b2ba-40cd-9820- My first reaction was rather similar - what do the two transformers and all those caps add. The answer would be that there is filtering between the two transformers Filtering can go in front of the one transformer (almost always does of course), I see no advantage in using two and the smaller caps are faster. Faster?, what do you mean by "faster"? How audible that is I don't know. However, I would caution against dismissing it out of hand since it does actually sound the business. It may be overkill, It is. but these DHT filaments are very sensitive Are they? and Rod clearly spent time on this circuit, which he uses in his own setup. Which proves absolutely nothing I'm afraid As for batteries - I did try those as well, and I didn't think they sounded any better than this. Now there I beleive you. David. |
What's your favourite voltage regs?
"Andy Evans" wrote in message
... David asked how we established this was the "best sounding". I and a friend listened to: snip Sorry - you'll have to take this at face value, since it wasn't double blind. i.e. clearly not proven but may, depending on how you feel about these things, show a trend in the stated direction, since we were both in agreement and both thought we could hear a difference. We're both suitably cynical and my colleague is an engineer. We were also sober!!! That's the best I can offer. Did you listen together, and discuss what you were hearing?, if so the fact that there were two of you means nothing. What you could have done is for one of you to do the switching (in a random order), whilst the other listened in another room, then swap over and compare results later. That would have been a better test (if that is what you actually did I apologise for doubting you). For 5 years of my life my job was running double-blind listening tests. OK, they were for voice communication systems (low bit-rate codecs for mobile phones, that kind of thing) not HiFi equipment. But the principle is the same, so I do know just how hard it is to eliminate anything that might bias a listener. None of our listeners was allowed to know anything at all about the equipment or algorithm being tested or even the reason for the test (anyone who asked was contacted after the test was over and told then). We used a minimum of 24 listeners per test, each of whom heard the test conditions in a different order as that can also make a difference to the perception of "quality" etc. Even then it could be hard to get statistically meaningful results. David. |
What's your favourite voltage regs?
In article , David Looser
scribeth thus "Andy Evans" wrote in message news:5bde0ef2-b2ba-40cd-9820- My first reaction was rather similar - what do the two transformers and all those caps add. The answer would be that there is filtering between the two transformers Filtering can go in front of the one transformer (almost always does of course), I see no advantage in using two and the smaller caps are faster. Faster?, what do you mean by "faster"? How audible that is I don't know. However, I would caution against dismissing it out of hand since it does actually sound the business. It may be overkill, 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;!... -- Tony Sayer |
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