Troubleshooting: amplifier Musical Fidelity A1
 

On Sat, 20 Dec 2003 11:34:40 +0000, Nick Gorham wrote:

snip

Well you could try this then

http://www.petemoore.pwp.blueyonder....rschematic.jpg

I didn't see the need as the one I built was being fed by a valve stage
anyway. They are fun things, I was quite shocked just how good they are
for £30. Of course you could go to the other extreme.


Now - there's an idea.... :-)


http://www.lurcher.org/nick/audio/vi...ul/v4212-1.jpg

:-)

I'm *really* jealous now... I've always wanted a pair of 211s to play
with! (with the appropriate ironmongery that is!). :-)

That's a hell of a setup! (plus obligatory !!!!!! courtesy of ebay)
I particularly like the king-size timber & ply chassis system....

--
Mick
http://www.nascom.info for Nascom & Gemini information
Also at http://www.mixtel.co.uk where the collection started.
Currently deserting M$ for linux... :-)

Troubleshooting: amplifier Musical Fidelity A1
 

Form@C wrote:
On Sat, 20 Dec 2003 11:34:40 +0000, Nick Gorham wrote:

snip

Well you could try this then

http://www.petemoore.pwp.blueyonder....rschematic.jpg

I didn't see the need as the one I built was being fed by a valve stage
anyway. They are fun things, I was quite shocked just how good they are
for £30. Of course you could go to the other extreme.



Now - there's an idea.... :-)



http://www.lurcher.org/nick/audio/vi...ul/v4212-1.jpg

:-)


I'm *really* jealous now... I've always wanted a pair of 211s to play
with! (with the appropriate ironmongery that is!). :-)

That's a hell of a setup! (plus obligatory !!!!!! courtesy of ebay)
I particularly like the king-size timber & ply chassis system....

Sadly not mine, and no its not at 211, its a 212 (and assorted
variants). one day I may get to play with toys like that, but first
stage 6em7.

For comparison, this pic is a ecc83 on the left, the next is a 211, and
then various 212 (ish) valves, Paul would go into great and interesting
depth about the differences. And under them all a GM100.

http://www.lurcher.org/nick/audio/vi...l/v4212-20.jpg

--
Nick

Troubleshooting: amplifier Musical Fidelity A1
 

Form@C wrote:
On Sat, 20 Dec 2003 11:34:40 +0000, Nick Gorham wrote:

snip

Well you could try this then

http://www.petemoore.pwp.blueyonder....rschematic.jpg

I didn't see the need as the one I built was being fed by a valve stage
anyway. They are fun things, I was quite shocked just how good they are
for £30. Of course you could go to the other extreme.



Now - there's an idea.... :-)



http://www.lurcher.org/nick/audio/vi...ul/v4212-1.jpg

:-)


I'm *really* jealous now... I've always wanted a pair of 211s to play
with! (with the appropriate ironmongery that is!). :-)

That's a hell of a setup! (plus obligatory !!!!!! courtesy of ebay)
I particularly like the king-size timber & ply chassis system....

Sadly not mine, and no its not at 211, its a 212 (and assorted
variants). one day I may get to play with toys like that, but first
stage 6em7.

For comparison, this pic is a ecc83 on the left, the next is a 211, and
then various 212 (ish) valves, Paul would go into great and interesting
depth about the differences. And under them all a GM100.

http://www.lurcher.org/nick/audio/vi...l/v4212-20.jpg

--
Nick

Troubleshooting: amplifier Musical Fidelity A1
 

On Sat, 20 Dec 2003 22:03:11 +0000, Nick Gorham wrote:

snip

Sadly not mine, and no its not at 211, its a 212 (and assorted
variants). one day I may get to play with toys like that, but first
stage 6em7.

For comparison, this pic is a ecc83 on the left, the next is a 211, and
then various 212 (ish) valves, Paul would go into great and interesting
depth about the differences. And under them all a GM100.

http://www.lurcher.org/nick/audio/vi...l/v4212-20.jpg


wow! That is serious glassware...

I assume that the GM100 isn't for a preamp then.... Sheesh! :-)

Much as I love Paul's collection of heavy-duty audio, It can only be
regarded as an interesting conversation piece when installed like that. It
doesn't exactly blend in with the decor does it? grin
Lovely - my Mrs would kill me... Especially now I've found this pic:
http://www.lurcher.org/nick/audio/vi...paul/paul1.jpg

I've dug my old 6L6 p-p project out again. I may just get to complete it
soon! My nasty little parallelled ECC82 p-p amp still runs nicely, but
there is a bit of a hum on one channel that needs looking at. Low power,
but interesting; and a lot cooler and lighter than a 212 collection. Takes
less juice in total than the heater on one of those...
(photos on mixtel site under Rough Audio).

--
Mick
http://www.nascom.info for Nascom & Gemini information
Also at http://www.mixtel.co.uk where the collection started.
Currently deserting M$ for linux... :-)

Troubleshooting: amplifier Musical Fidelity A1
 

On Sat, 20 Dec 2003 22:03:11 +0000, Nick Gorham wrote:

snip

Sadly not mine, and no its not at 211, its a 212 (and assorted
variants). one day I may get to play with toys like that, but first
stage 6em7.

For comparison, this pic is a ecc83 on the left, the next is a 211, and
then various 212 (ish) valves, Paul would go into great and interesting
depth about the differences. And under them all a GM100.

http://www.lurcher.org/nick/audio/vi...l/v4212-20.jpg


wow! That is serious glassware...

I assume that the GM100 isn't for a preamp then.... Sheesh! :-)

Much as I love Paul's collection of heavy-duty audio, It can only be
regarded as an interesting conversation piece when installed like that. It
doesn't exactly blend in with the decor does it? grin
Lovely - my Mrs would kill me... Especially now I've found this pic:
http://www.lurcher.org/nick/audio/vi...paul/paul1.jpg

I've dug my old 6L6 p-p project out again. I may just get to complete it
soon! My nasty little parallelled ECC82 p-p amp still runs nicely, but
there is a bit of a hum on one channel that needs looking at. Low power,
but interesting; and a lot cooler and lighter than a 212 collection. Takes
less juice in total than the heater on one of those...
(photos on mixtel site under Rough Audio).

--
Mick
http://www.nascom.info for Nascom & Gemini information
Also at http://www.mixtel.co.uk where the collection started.
Currently deserting M$ for linux... :-)

Troubleshooting: amplifier Musical Fidelity A1
 

Form@C wrote:

I assume that the GM100 isn't for a preamp then.... Sheesh! :-)

There was a actual working amp using them at VSAC

http://img.audioasylum.com/cgi/i.pl?...f=MVC-001F.JPG


Much as I love Paul's collection of heavy-duty audio, It can only be
regarded as an interesting conversation piece when installed like that. It
doesn't exactly blend in with the decor does it? grin
Lovely - my Mrs would kill me... Especially now I've found this pic:
http://www.lurcher.org/nick/audio/vi...paul/paul1.jpg


Its still a work in progress, he does have plans to make it into two
monoblocks, that can be put in the back of a van.

I've dug my old 6L6 p-p project out again. I may just get to complete it
soon! My nasty little parallelled ECC82 p-p amp still runs nicely, but
there is a bit of a hum on one channel that needs looking at. Low power,
but interesting; and a lot cooler and lighter than a 212 collection. Takes
less juice in total than the heater on one of those...
(photos on mixtel site under Rough Audio).


As I said, I have yet to build a SE amp, but after hearing the amps in
the pictures, I am going to give it a try, there was a nice sounding
6em7 amp there, (sort of rat amp construction), so I am going to give
that a try in the new year.

http://www.lurcher.org/nick/audio/vi...ul/v6em7-1.jpg

--
Nick

Troubleshooting: amplifier Musical Fidelity A1
 

Form@C wrote:

I assume that the GM100 isn't for a preamp then.... Sheesh! :-)

There was a actual working amp using them at VSAC

http://img.audioasylum.com/cgi/i.pl?...f=MVC-001F.JPG


Much as I love Paul's collection of heavy-duty audio, It can only be
regarded as an interesting conversation piece when installed like that. It
doesn't exactly blend in with the decor does it? grin
Lovely - my Mrs would kill me... Especially now I've found this pic:
http://www.lurcher.org/nick/audio/vi...paul/paul1.jpg


Its still a work in progress, he does have plans to make it into two
monoblocks, that can be put in the back of a van.

I've dug my old 6L6 p-p project out again. I may just get to complete it
soon! My nasty little parallelled ECC82 p-p amp still runs nicely, but
there is a bit of a hum on one channel that needs looking at. Low power,
but interesting; and a lot cooler and lighter than a 212 collection. Takes
less juice in total than the heater on one of those...
(photos on mixtel site under Rough Audio).


As I said, I have yet to build a SE amp, but after hearing the amps in
the pictures, I am going to give it a try, there was a nice sounding
6em7 amp there, (sort of rat amp construction), so I am going to give
that a try in the new year.

http://www.lurcher.org/nick/audio/vi...ul/v6em7-1.jpg

--
Nick

Troubleshooting: amplifier Musical Fidelity A1
 

In article , Nick Gorham
wrote:
Ian Bell wrote:

http://home.student.utwente.nl/f.s.b...rtedLM3875.gif


The original post said "not enough output (yet!) for speakers" so it
wasn't a suggestion for a headphone amp. The lin pot is used as its in
the feedback loop, and in conjunction with the next R provides a log
(ish) response.

Well, the pot does interact with the loop, but it isn't a design I'd
choose. I'd need to look at it in practice to be sure, but the design rings
alarm bells with me regarding things like noise, bandwidth, and
instability.


The 1000uf, is because they sound better with less cap's, the design is
all about speed, and bigger caps seem to produce a more sluggish result.

I find that baffling. The caps mean that if you were drawing about an Amp
(reasonable enough for a power amp) the ripple would be of the order of
10V. Since the rail is only of the order of 30V that is a hell of a lot.

Ideally, the amp should ignore power line variations below those that make
it clip. However if it does, then the size of the cap should not have any
effect upon the sound, and it would not be possible to say its sound was
affected by the choice of capacitor size.

If the cap size *does* affect the sound it implies that the amp is either
sensitive to the rail variations, or is clipping. Clipping should be
self-evidently bad news. Sensitivity to rail variations implies that you
will be leaking ripple and d.c. variations onto the signal output in a
level dependent manner. It may also mean distortion is transferred from the
rails to the output. Also distorted crosstalk for stereo.

Do some people like their music with 'added ripple, distortion, and d.c. LF
fluctuations'? If so, then that may be OK. However it doesn't seem much
like good audio to me.


The R22 is because no one trusts these amps at first to connect to their
speakers.

0.22 Ohms is too low to add much to the stability margin. Also not much use
as a short-term current limiter, although it will presumably fuse after a
while. (However that may not be relevant given the 1000 microF caps as
these imply almost no long-term current sustainability.) High enough to
alter the frequency response in a speaker-dependent manner, though.

Its not just a bad design, its all done for a reason, maybe not a normal
or even good reason, but a reason never the less.

I'm afraid it does not look much a like a *good* design to me. :-/

Unless you want added ripple, possible instability, noise, added LF
variations, gain dependent bandwidth, and not much sustained power. This
does not seem like 'speed' to me.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

Troubleshooting: amplifier Musical Fidelity A1
 

In article , Nick Gorham
wrote:
Ian Bell wrote:

http://home.student.utwente.nl/f.s.b...rtedLM3875.gif


The original post said "not enough output (yet!) for speakers" so it
wasn't a suggestion for a headphone amp. The lin pot is used as its in
the feedback loop, and in conjunction with the next R provides a log
(ish) response.

Well, the pot does interact with the loop, but it isn't a design I'd
choose. I'd need to look at it in practice to be sure, but the design rings
alarm bells with me regarding things like noise, bandwidth, and
instability.


The 1000uf, is because they sound better with less cap's, the design is
all about speed, and bigger caps seem to produce a more sluggish result.

I find that baffling. The caps mean that if you were drawing about an Amp
(reasonable enough for a power amp) the ripple would be of the order of
10V. Since the rail is only of the order of 30V that is a hell of a lot.

Ideally, the amp should ignore power line variations below those that make
it clip. However if it does, then the size of the cap should not have any
effect upon the sound, and it would not be possible to say its sound was
affected by the choice of capacitor size.

If the cap size *does* affect the sound it implies that the amp is either
sensitive to the rail variations, or is clipping. Clipping should be
self-evidently bad news. Sensitivity to rail variations implies that you
will be leaking ripple and d.c. variations onto the signal output in a
level dependent manner. It may also mean distortion is transferred from the
rails to the output. Also distorted crosstalk for stereo.

Do some people like their music with 'added ripple, distortion, and d.c. LF
fluctuations'? If so, then that may be OK. However it doesn't seem much
like good audio to me.


The R22 is because no one trusts these amps at first to connect to their
speakers.

0.22 Ohms is too low to add much to the stability margin. Also not much use
as a short-term current limiter, although it will presumably fuse after a
while. (However that may not be relevant given the 1000 microF caps as
these imply almost no long-term current sustainability.) High enough to
alter the frequency response in a speaker-dependent manner, though.

Its not just a bad design, its all done for a reason, maybe not a normal
or even good reason, but a reason never the less.

I'm afraid it does not look much a like a *good* design to me. :-/

Unless you want added ripple, possible instability, noise, added LF
variations, gain dependent bandwidth, and not much sustained power. This
does not seem like 'speed' to me.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

Troubleshooting: amplifier Musical Fidelity A1
 

On Sun, 21 Dec 2003 10:28:02 +0000, Nick Gorham wrote:

Form@C wrote:

I assume that the GM100 isn't for a preamp then.... Sheesh! :-)

There was a actual working amp using them at VSAC

http://img.audioasylum.com/cgi/i.pl?...f=MVC-001F.JPG


Now that is an AMP 7/8ths !!!!!!!!!


snip

Its still a work in progress, he does have plans to make it into two
monoblocks, that can be put in the back of a van.


He could build on one chassis - and put the wheels and a tow bar straight
on... :-)

snip

As I said, I have yet to build a SE amp, but after hearing the amps in
the pictures, I am going to give it a try, there was a nice sounding
6em7 amp there, (sort of rat amp construction), so I am going to give
that a try in the new year.

http://www.lurcher.org/nick/audio/vi...ul/v6em7-1.jpg


I've been digging in the shed again, and come up with a couple of
nondescript SE OPTs, a couple of Sovtek 6L6GCs, a few assorted 6SN7s and a
6SL7. I feel the urge to build SE again... :-) Pity there's no mains
tranny bigger than 60mA in there :-(

Now - where's the plywood...

--
Mick
http://www.nascom.info for Nascom & Gemini information
Also at http://www.mixtel.co.uk where the collection started.
Currently deserting M$ for linux... :-)