Troubleshooting: amplifier Musical Fidelity A1
 

Sala Massimo wrote:

Thanks to all for your help!

I measured the DC voltage accross the pot, at the middle volume: 10 mV on
channel, 28 mV the other!
How to read these values?


The Alps pot is not available in Italy.
I searched "stereo" pots, also third parties, on local shops and surplus.
They haven't.

Perhaps I found the pot at Farnell UK, ALPS RK27111250K (former 0071
50KAX2), Farnell code 697928.
Good news: it is £ 16.33 plus shipping cost to ITALY (about £ 8), because
Farnell Italy doen't sell to end-users... :-(

If anybody can help me to get the pot at a cheaper cost...

Don't know if its any cheaper, but you could try

http://www.hificollective.co.uk/comp...tiometers.html

Or I found this link in Italy

http://www.audiodesignguide.com/sele/sele.html

--
Nick

Troubleshooting: amplifier Musical Fidelity A1
 

In article ,
Sala Massimo wrote:
Good news: it is £ 16.33 plus shipping cost to ITALY (about £ 8), because
Farnell Italy doen't sell to end-users... :-(

If anybody can help me to get the pot at a cheaper cost...

Couldn't you order it through a local radio repair shop who have an
account with Farnell Italy?

--
*Why isn't 11 pronounced onety one? *

Dave Plowman London SW 12
RIP Acorn

Troubleshooting: amplifier Musical Fidelity A1
 

In article ,
Sala Massimo wrote:
Good news: it is £ 16.33 plus shipping cost to ITALY (about £ 8), because
Farnell Italy doen't sell to end-users... :-(

If anybody can help me to get the pot at a cheaper cost...

Couldn't you order it through a local radio repair shop who have an
account with Farnell Italy?

--
*Why isn't 11 pronounced onety one? *

Dave Plowman London SW 12
RIP Acorn

Troubleshooting: amplifier Musical Fidelity A1
 

In article , Sala
Massimo
wrote:
Thanks to all for your help!

I measured the DC voltage accross the pot, at the middle volume: 10 mV
on channel, 28 mV the other! How to read these values?

Not sure what you are asking.

If worried that the problem will recur. I would suggest replacing the
current pot location with fixed resistors, then then using the new pots in
a more conventional fashion as input attenuators. You can then add d.c.
break caps to the wipers if you wish as well. A-law 50k pots should still
work OK.

At a first glance, one of the big power caps (10000 uF 25 V) is strange:
its plastic dome is going yellow (the other three caps have a
transparent dome). Is this a clue of a incoming failure ?

I do not know the capacitors in question, but what you report does not
sound good. May be advisible to replace the caps.

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 , Sala
Massimo
wrote:
Thanks to all for your help!

I measured the DC voltage accross the pot, at the middle volume: 10 mV
on channel, 28 mV the other! How to read these values?

Not sure what you are asking.

If worried that the problem will recur. I would suggest replacing the
current pot location with fixed resistors, then then using the new pots in
a more conventional fashion as input attenuators. You can then add d.c.
break caps to the wipers if you wish as well. A-law 50k pots should still
work OK.

At a first glance, one of the big power caps (10000 uF 25 V) is strange:
its plastic dome is going yellow (the other three caps have a
transparent dome). Is this a clue of a incoming failure ?

I do not know the capacitors in question, but what you report does not
sound good. May be advisible to replace the caps.

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
 

Sala Massimo wrote:
So? You've obviously had a lot of enjoyment from the A1. Forget the
specs for a minute; do you still enjoy the sound that it makes? If
so, why bother whether it is class A up to full power? It's all just
numbers - it's your ears that have to be satisfied at the end of the
day!

Mick, I agree with you until the time the A1 volume pot broke.
It sounded good and I was very satisfied.
I never stressed the ampli, I used it in a "religious" way, always
wired to my Celestion 5 speakers.
Now I discover it is not a single failure, other users complain about
a bad design. I am very upset.

I stop trusting Musical Fidelity.
I purchased the A1 for its sound AND for its quality (hi-fi products
claims).
A1 design quality is worse than many consumer products... so I am
wondering about sound quality... it is really a thorn in my side.

But superficial build quality and engineering quality are two separate
things... Look at the new Ferrari Enzo - reports of trim bits falling off
in the first few hundred km but the core mechanicals are still well
engineered. Closer to the topic, the knobs on my Cyrus 2 lost all their
paint within a couple of years but 15 years on the amp still sounds great

Troubleshooting: amplifier Musical Fidelity A1
 

Sala Massimo wrote:
So? You've obviously had a lot of enjoyment from the A1. Forget the
specs for a minute; do you still enjoy the sound that it makes? If
so, why bother whether it is class A up to full power? It's all just
numbers - it's your ears that have to be satisfied at the end of the
day!

Mick, I agree with you until the time the A1 volume pot broke.
It sounded good and I was very satisfied.
I never stressed the ampli, I used it in a "religious" way, always
wired to my Celestion 5 speakers.
Now I discover it is not a single failure, other users complain about
a bad design. I am very upset.

I stop trusting Musical Fidelity.
I purchased the A1 for its sound AND for its quality (hi-fi products
claims).
A1 design quality is worse than many consumer products... so I am
wondering about sound quality... it is really a thorn in my side.

But superficial build quality and engineering quality are two separate
things... Look at the new Ferrari Enzo - reports of trim bits falling off
in the first few hundred km but the core mechanicals are still well
engineered. Closer to the topic, the knobs on my Cyrus 2 lost all their
paint within a couple of years but 15 years on the amp still sounds great

Troubleshooting: amplifier Musical Fidelity A1
 

On Fri, 19 Dec 2003 06:08:14 -0800, Sala Massimo wrote:

snip

Mick, I agree with you until the time the A1 volume pot broke.
It sounded good and I was very satisfied.
I never stressed the ampli, I used it in a "religious" way, always
wired to my Celestion 5 speakers.
Now I discover it is not a single failure, other users complain about
a bad design. I am very upset.

I stop trusting Musical Fidelity.
I purchased the A1 for its sound AND for its quality (hi-fi products
claims).
A1 design quality is worse than many consumer products... so I am
wondering about sound quality... it is really a thorn in my side.


If you are dissatisfied with the sound, why not build something like the
Zen? You can have true class A then.

I am thinking about "Death Of Zen" project (funny names...)
See Elliott Sound Products, http://sound.westhost.com
I appreciate really much his feelings about hi-fi and electronics
projects. Take a look at the very interesting web site!


Yep - I like that site! This is an interesting one too - he has replaced
the preamp in an A1 with a more conventional one:
http://www.mhennessy.f9.co.uk/mf_a1/#construction

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. :-)

--
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 06:08:14 -0800, Sala Massimo wrote:

snip

Mick, I agree with you until the time the A1 volume pot broke.
It sounded good and I was very satisfied.
I never stressed the ampli, I used it in a "religious" way, always
wired to my Celestion 5 speakers.
Now I discover it is not a single failure, other users complain about
a bad design. I am very upset.

I stop trusting Musical Fidelity.
I purchased the A1 for its sound AND for its quality (hi-fi products
claims).
A1 design quality is worse than many consumer products... so I am
wondering about sound quality... it is really a thorn in my side.


If you are dissatisfied with the sound, why not build something like the
Zen? You can have true class A then.

I am thinking about "Death Of Zen" project (funny names...)
See Elliott Sound Products, http://sound.westhost.com
I appreciate really much his feelings about hi-fi and electronics
projects. Take a look at the very interesting web site!


Yep - I like that site! This is an interesting one too - he has replaced
the preamp in an A1 with a more conventional one:
http://www.mhennessy.f9.co.uk/mf_a1/#construction

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. :-)

--
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'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