Troubleshooting: amplifier Musical Fidelity A1
 

Form@C wrote:

I'm just experimenting with a source-follower single-ended MOSFET
headphone amp, with an op-amp voltage gain stage. Its rather good but not
enough output (yet!) for speakers. :-)


You could always try a gainclone

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

--
Nick

Troubleshooting: amplifier Musical Fidelity A1
 

On Fri, 19 Dec 2003 18:35:41 +0000, Nick Gorham wrote:

Form@C wrote:

I'm just experimenting with a source-follower single-ended MOSFET
headphone amp, with an op-amp voltage gain stage. Its rather good but not
enough output (yet!) for speakers. :-)


You could always try a gainclone


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

I *could*, but I rather like the look of something like this:
http://digilander.libero.it/essentia...ybrid_home.htm
'cos I suspect it has more chance of *really* sounding good, rather than
being based around a chip being used for other than its designed purpose!
(ducks down behind 0.2C/W heatsinks to hide from gaincloners hurling
flaming 1000uF capacitors...)

:-)

--
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 Fri, 19 Dec 2003 18:35:41 +0000, Nick Gorham wrote:

Form@C wrote:

I'm just experimenting with a source-follower single-ended MOSFET
headphone amp, with an op-amp voltage gain stage. Its rather good but not
enough output (yet!) for speakers. :-)


You could always try a gainclone


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

I *could*, but I rather like the look of something like this:
http://digilander.libero.it/essentia...ybrid_home.htm
'cos I suspect it has more chance of *really* sounding good, rather than
being based around a chip being used for other than its designed purpose!
(ducks down behind 0.2C/W heatsinks to hide from gaincloners hurling
flaming 1000uF capacitors...)

:-)

--
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 Fri, 19 Dec 2003 18:35:41 +0000, Nick Gorham wrote:


Form@C wrote:

I'm just experimenting with a source-follower single-ended MOSFET
headphone amp, with an op-amp voltage gain stage. Its rather good but not
enough output (yet!) for speakers. :-)


You could always try a gainclone



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

I *could*, but I rather like the look of something like this:
http://digilander.libero.it/essentia...ybrid_home.htm
'cos I suspect it has more chance of *really* sounding good, rather than
being based around a chip being used for other than its designed purpose!
(ducks down behind 0.2C/W heatsinks to hide from gaincloners hurling
flaming 1000uF capacitors...)

:-)


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.

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

:-)

--
Nick

Troubleshooting: amplifier Musical Fidelity A1
 

Form@C wrote:

On Fri, 19 Dec 2003 18:35:41 +0000, Nick Gorham wrote:


Form@C wrote:

I'm just experimenting with a source-follower single-ended MOSFET
headphone amp, with an op-amp voltage gain stage. Its rather good but not
enough output (yet!) for speakers. :-)


You could always try a gainclone



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

I *could*, but I rather like the look of something like this:
http://digilander.libero.it/essentia...ybrid_home.htm
'cos I suspect it has more chance of *really* sounding good, rather than
being based around a chip being used for other than its designed purpose!
(ducks down behind 0.2C/W heatsinks to hide from gaincloners hurling
flaming 1000uF capacitors...)

:-)


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.

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

:-)

--
Nick

Troubleshooting: amplifier Musical Fidelity A1
 

Form@C wrote:

On Fri, 19 Dec 2003 18:35:41 +0000, Nick Gorham wrote:

Form@C wrote:

I'm just experimenting with a source-follower single-ended MOSFET
headphone amp, with an op-amp voltage gain stage. Its rather good but
not enough output (yet!) for speakers. :-)


You could always try a gainclone


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


Strange design. Linear taper volume control, only 1000uF supply smoothing
for a chip than can output 56 watts and why throw away all the loudspeaker
damping by inserting a series resistor? And if it is a phones amp why use
such a meaty chip?

Ian

Troubleshooting: amplifier Musical Fidelity A1
 

Form@C wrote:

On Fri, 19 Dec 2003 18:35:41 +0000, Nick Gorham wrote:

Form@C wrote:

I'm just experimenting with a source-follower single-ended MOSFET
headphone amp, with an op-amp voltage gain stage. Its rather good but
not enough output (yet!) for speakers. :-)


You could always try a gainclone


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


Strange design. Linear taper volume control, only 1000uF supply smoothing
for a chip than can output 56 watts and why throw away all the loudspeaker
damping by inserting a series resistor? And if it is a phones amp why use
such a meaty chip?

Ian

Troubleshooting: amplifier Musical Fidelity A1
 

Ian Bell wrote:
Form@C wrote:


On Fri, 19 Dec 2003 18:35:41 +0000, Nick Gorham wrote:


Form@C wrote:

I'm just experimenting with a source-follower single-ended MOSFET
headphone amp, with an op-amp voltage gain stage. Its rather good but
not enough output (yet!) for speakers. :-)


You could always try a gainclone



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



Strange design. Linear taper volume control, only 1000uF supply smoothing
for a chip than can output 56 watts and why throw away all the loudspeaker
damping by inserting a series resistor? And if it is a phones amp why use
such a meaty chip?

Ian


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

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.

--
Nick

Troubleshooting: amplifier Musical Fidelity A1
 

Ian Bell wrote:
Form@C wrote:


On Fri, 19 Dec 2003 18:35:41 +0000, Nick Gorham wrote:


Form@C wrote:

I'm just experimenting with a source-follower single-ended MOSFET
headphone amp, with an op-amp voltage gain stage. Its rather good but
not enough output (yet!) for speakers. :-)


You could always try a gainclone



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



Strange design. Linear taper volume control, only 1000uF supply smoothing
for a chip than can output 56 watts and why throw away all the loudspeaker
damping by inserting a series resistor? And if it is a phones amp why use
such a meaty chip?

Ian


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

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.

--
Nick

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... :-)