[Spica]

I'd like to increase the filter capacitance of a 21 year old subwoofer amp from the
current two 10,000uf 75v caps to a pair of 20,000uf 75v caps. The current rectifier is
a Fagor FB2502. Do you think this rectifier can handle the increase or should I
upgrade it? Also, for reference, the amp uses a single power chip per side as
opposed to discrete xistors if that matters. Thanks.

[Richard Crowley]

"Spica" wrote ...
I'd like to increase the filter capacitance of a 21 year old subwoofer amp
from the
current two 10,000uf 75v caps to a pair of 20,000uf 75v caps. The current
rectifier is
a Fagor FB2502. Do you think this rectifier can handle the increase or
should I
upgrade it? Also, for reference, the amp uses a single power chip per
side as
opposed to discrete xistors if that matters. Thanks.

Probably no easy way to establish that except to try it. If it holds, then
you didn't need to beef it up. If it blows, then you were thinking about
replacing it anyway. :-)

[David Nebenzahl]

On 4/11/2010 7:46 PM cjt spake thus:

Spica wrote:

I'd like to increase the filter capacitance of a 21 year old
subwoofer amp from the current two 10,000uf 75v caps to a pair of
20,000uf 75v caps. The current rectifier is a Fagor FB2502. Do you
think this rectifier can handle the increase or should I upgrade
it? Also, for reference, the amp uses a single power chip per side
as opposed to discrete xistors if that matters. Thanks.

Why?

That's my question too: are you hearing hum through the subwoofer? (I
highly doubt it.) Or do you want to increase the transient power
handling capacity of the amp? Seems like you'd possibly be stressing
some other part of the unit by beefing up the capacitators.


--
The fashion in killing has an insouciant, flirty style this spring,
with the flaunting of well-defined muscle, wrapped in flags.

- Comment from an article on Antiwar.com (http://antiwar.com)

[Peter Larsen[_3_]]

Richard Crowley wrote:

"Spica" wrote ...

I'd like to increase the filter capacitance of a 21 year old
subwoofer amp from the
current two 10,000uf 75v caps to a pair of 20,000uf 75v caps. The
current rectifier is
a Fagor FB2502. Do you think this rectifier can handle the increase
or should I
upgrade it? Also, for reference, the amp uses a single power chip
per side as
opposed to discrete xistors if that matters. Thanks.

Probably no easy way to establish that except to try it. If it holds,
then you didn't need to beef it up. If it blows, then you were
thinking about replacing it anyway. :-)

I can't comment on the actual device, that would be to go beyond my skill
level, but doubling the filter capacitance of my Linsley-Hood dual 75 watt
amp had a beneficiary influence on its bass range. Undetected alumium spill
from drilling the holes had a negative influence later ... I gave it to
someone who might be able to use the very fine mains transformer in some
other context.

A learning experience.

Kind regards

Peter Larsen

[cjt]

Spica wrote:
I'd like to increase the filter capacitance of a 21 year old subwoofer amp from the
current two 10,000uf 75v caps to a pair of 20,000uf 75v caps. The current rectifier is
a Fagor FB2502. Do you think this rectifier can handle the increase or should I
upgrade it? Also, for reference, the amp uses a single power chip per side as
opposed to discrete xistors if that matters. Thanks.



Why?

[Arny Krueger]

"cjt" wrote in message

Spica wrote:

I'd like to increase the filter capacitance of a 21 year
old subwoofer amp from the current two 10,000uf 75v caps
to a pair of 20,000uf 75v caps. The current rectifier
is a Fagor FB2502. Do you think this rectifier can
handle the increase or should I upgrade it? Also, for
reference, the amp uses a single power chip per side as opposed to
discrete xistors if that matters. Thanks.

Why?

Good question.

Just about the only reasonable justification I can think of is that the
existing caps have lost significant capacitance. This may or may not happen.
I've seen electrolytics that were still well over 100% of nameplate
capacitance after over 40 years, and others that were under 10% after 3
years.

YMMV!

10,000 uF is actually quite a bit of overkill - a minimum number might be
2,500 uF - 3,300 uF.

The real question is "what sounds bad"? I suspect that most "capacitor
upgrades" satisfy psychological and social needs, not technical needs.

[Audio Empire]

On Mon, 12 Apr 2010 05:47:14 -0700, Arny Krueger wrote
(in article ) :

"cjt" wrote in message

Spica wrote:

I'd like to increase the filter capacitance of a 21 year
old subwoofer amp from the current two 10,000uf 75v caps
to a pair of 20,000uf 75v caps. The current rectifier
is a Fagor FB2502. Do you think this rectifier can
handle the increase or should I upgrade it? Also, for
reference, the amp uses a single power chip per side as opposed to
discrete xistors if that matters. Thanks.

Why?

Good question.

Just about the only reasonable justification I can think of is that the
existing caps have lost significant capacitance. This may or may not happen.
I've seen electrolytics that were still well over 100% of nameplate
capacitance after over 40 years, and others that were under 10% after 3
years.

YMMV!

10,000 uF is actually quite a bit of overkill - a minimum number might be
2,500 uF - 3,300 uF.

The real question is "what sounds bad"? I suspect that most "capacitor
upgrades" satisfy psychological and social needs, not technical needs.



My experience is that MOST of the time, second-guessing a piece of
equipment's designer(s) results in retrograde performance. SOMETIMES in some
(admittedly rare) instances, so-called upgrades and tweaks are worthwhile,
but not usually. I replaced some crossover caps in a speaker system with
'Wondercaps' of the same value once and speakers immediately sounded cleaner,
more transparent. I replaced the LM301 op-amp in an old Crown IC150 preamp
with a higher-slew rate pin-for-pin compatible J-Fet op-amp once and got
measurably lower distortion (using a borrowed high-end distortion analyzer),
but I couldn't actually HEAR any difference. It's a crap shoot. And honestly,
the designer generally knows what he's doing and has chosen the values for
his filter caps for a reason. It might be something as simple as the
determination that a larger value adds only expense to the final product,
without adding any measurable or discernible improvement in performance, or
something more critical, like the values chosen matched the rectifier diodes
and a significantly larger value will over stress them. It's best to leave
things alone. If you have determined that the current caps are leaking, or
have failed in some other way (resulting in hum), I suggest that you replace
them with caps of the same value. Most likely "more" will not equate to
"better".

[Audio Empire]

On Mon, 12 Apr 2010 12:08:33 -0700, GregS wrote
(in article ):

In article ,
wrote:
On Mon, 12 Apr 2010 05:47:14 -0700, Arny Krueger wrote
(in article ) :

"cjt" wrote in message

Spica wrote:

I'd like to increase the filter capacitance of a 21 year
old subwoofer amp from the current two 10,000uf 75v caps
to a pair of 20,000uf 75v caps. The current rectifier
is a Fagor FB2502. Do you think this rectifier can
handle the increase or should I upgrade it? Also, for
reference, the amp uses a single power chip per side as opposed to
discrete xistors if that matters. Thanks.

Why?

Good question.

Just about the only reasonable justification I can think of is that the
existing caps have lost significant capacitance. This may or may not
happen.
I've seen electrolytics that were still well over 100% of nameplate
capacitance after over 40 years, and others that were under 10% after 3
years.

YMMV!

10,000 uF is actually quite a bit of overkill - a minimum number might be
2,500 uF - 3,300 uF.

The real question is "what sounds bad"? I suspect that most "capacitor
upgrades" satisfy psychological and social needs, not technical needs.



My experience is that MOST of the time, second-guessing a piece of
equipment's designer(s) results in retrograde performance. SOMETIMES in
some
(admittedly rare) instances, so-called upgrades and tweaks are worthwhile,
but not usually. I replaced some crossover caps in a speaker system with
'Wondercaps' of the same value once and speakers immediately sounded
cleaner,
more transparent. I replaced the LM301 op-amp in an old Crown IC150 preamp
with a higher-slew rate pin-for-pin compatible J-Fet op-amp once and got
measurably lower distortion (using a borrowed high-end distortion
analyzer),
but I couldn't actually HEAR any difference. It's a crap shoot. And
honestly,
the designer generally knows what he's doing and has chosen the values for
his filter caps for a reason. It might be something as simple as the
determination that a larger value adds only expense to the final product,
without adding any measurable or discernible improvement in performance, or
something more critical, like the values chosen matched the rectifier
diodes
and a significantly larger value will over stress them. It's best to leave
things alone. If you have determined that the current caps are leaking, or
have failed in some other way (resulting in hum), I suggest that you
replace
them with caps of the same value. Most likely "more" will not equate to
"better".


I had also considered replacing the Crown op-amp but I didn't think it would
be worth it. Seems like there are many wanting to fool with the filter caps,
and I
have never arbitrarily replaced any after working on dozens and dozens of
amps
and receivers.

Those early op-amps, the 709s, 741s, LM301s, etc. simply weren't very good
for "hi-fi". Oh, they were fine for low performance applications,like
telephones and portable radios, but the combination of asymmetrical slew
rate, and high-noise made them marginal for "hi-fi". You are right about
filter caps. The rule of thumb should be: "if it ain't broke, don't fix it."

As for amps, a cheap transformer and big caps owe more to peak music power,
and good transformers and moderate caps tend to work out best. Upgrade the
caps
if you like. The peak current of the diodes is going to be the peak of the
transformer,
not so much the actual capacitance. Of course I make amplifiers with
a soft start, with a relay and resistance.

Good idea, always.

greg

the diodes

[GregS[_3_]]

In article , wrote:
On Mon, 12 Apr 2010 05:47:14 -0700, Arny Krueger wrote
(in article ) :

"cjt" wrote in message

Spica wrote:

I'd like to increase the filter capacitance of a 21 year
old subwoofer amp from the current two 10,000uf 75v caps
to a pair of 20,000uf 75v caps. The current rectifier
is a Fagor FB2502. Do you think this rectifier can
handle the increase or should I upgrade it? Also, for
reference, the amp uses a single power chip per side as opposed to
discrete xistors if that matters. Thanks.

Why?

Good question.

Just about the only reasonable justification I can think of is that the
existing caps have lost significant capacitance. This may or may not happen.
I've seen electrolytics that were still well over 100% of nameplate
capacitance after over 40 years, and others that were under 10% after 3
years.

YMMV!

10,000 uF is actually quite a bit of overkill - a minimum number might be
2,500 uF - 3,300 uF.

The real question is "what sounds bad"? I suspect that most "capacitor
upgrades" satisfy psychological and social needs, not technical needs.



My experience is that MOST of the time, second-guessing a piece of
equipment's designer(s) results in retrograde performance. SOMETIMES in some
(admittedly rare) instances, so-called upgrades and tweaks are worthwhile,
but not usually. I replaced some crossover caps in a speaker system with
'Wondercaps' of the same value once and speakers immediately sounded cleaner,
more transparent. I replaced the LM301 op-amp in an old Crown IC150 preamp
with a higher-slew rate pin-for-pin compatible J-Fet op-amp once and got
measurably lower distortion (using a borrowed high-end distortion analyzer),
but I couldn't actually HEAR any difference. It's a crap shoot. And honestly,
the designer generally knows what he's doing and has chosen the values for
his filter caps for a reason. It might be something as simple as the
determination that a larger value adds only expense to the final product,
without adding any measurable or discernible improvement in performance, or
something more critical, like the values chosen matched the rectifier diodes
and a significantly larger value will over stress them. It's best to leave
things alone. If you have determined that the current caps are leaking, or
have failed in some other way (resulting in hum), I suggest that you replace
them with caps of the same value. Most likely "more" will not equate to
"better".


I had also considered replacing the Crown op-amp but I didn't think it would
be worth it. Seems like there are many wanting to fool with the filter caps, and I
have never arbitrarily replaced any after working on dozens and dozens of amps
and receivers.

As for amps, a cheap transformer and big caps owe more to peak music power,
and good transformers and moderate caps tend to work out best. Upgrade the caps
if you like. The peak current of the diodes is going to be the peak of the transformer,
not so much the actual capacitance. Of course I make amplifiers with
a soft start, with a relay and resistance.

greg

the diodes

[Mark Zacharias[_2_]]

"GregS" wrote in message
...
In article ,
wrote:
On Mon, 12 Apr 2010 05:47:14 -0700, Arny Krueger wrote
(in article ) :

"cjt" wrote in message

Spica wrote:

I'd like to increase the filter capacitance of a 21 year
old subwoofer amp from the current two 10,000uf 75v caps
to a pair of 20,000uf 75v caps. The current rectifier
is a Fagor FB2502. Do you think this rectifier can
handle the increase or should I upgrade it? Also, for
reference, the amp uses a single power chip per side as opposed to
discrete xistors if that matters. Thanks.

Why?

Good question.

Just about the only reasonable justification I can think of is that the
existing caps have lost significant capacitance. This may or may not
happen.
I've seen electrolytics that were still well over 100% of nameplate
capacitance after over 40 years, and others that were under 10% after 3
years.

YMMV!

10,000 uF is actually quite a bit of overkill - a minimum number might
be
2,500 uF - 3,300 uF.

The real question is "what sounds bad"? I suspect that most "capacitor
upgrades" satisfy psychological and social needs, not technical needs.



My experience is that MOST of the time, second-guessing a piece of
equipment's designer(s) results in retrograde performance. SOMETIMES in
some
(admittedly rare) instances, so-called upgrades and tweaks are worthwhile,
but not usually. I replaced some crossover caps in a speaker system with
'Wondercaps' of the same value once and speakers immediately sounded
cleaner,
more transparent. I replaced the LM301 op-amp in an old Crown IC150 preamp
with a higher-slew rate pin-for-pin compatible J-Fet op-amp once and got
measurably lower distortion (using a borrowed high-end distortion
analyzer),
but I couldn't actually HEAR any difference. It's a crap shoot. And
honestly,
the designer generally knows what he's doing and has chosen the values for
his filter caps for a reason. It might be something as simple as the
determination that a larger value adds only expense to the final product,
without adding any measurable or discernible improvement in performance,
or
something more critical, like the values chosen matched the rectifier
diodes
and a significantly larger value will over stress them. It's best to leave
things alone. If you have determined that the current caps are leaking, or
have failed in some other way (resulting in hum), I suggest that you
replace
them with caps of the same value. Most likely "more" will not equate to
"better".


I had also considered replacing the Crown op-amp but I didn't think it
would
be worth it. Seems like there are many wanting to fool with the filter
caps, and I
have never arbitrarily replaced any after working on dozens and dozens of
amps
and receivers.

As for amps, a cheap transformer and big caps owe more to peak music
power,
and good transformers and moderate caps tend to work out best. Upgrade the
caps
if you like. The peak current of the diodes is going to be the peak of the
transformer,
not so much the actual capacitance. Of course I make amplifiers with
a soft start, with a relay and resistance.

greg

the diodes


A friend of mine has a Dynaco Stereo 410 which had the popular filter cap
mod whereas the filter capacitance was doubled.

That thing went through power switches every couple of years until I added a
soft start circuit. That switch is over 10 years old and still working...

Mark Z.

[Arny Krueger]

"Audio Empire" wrote in message
.com

I replaced some crossover caps in a
speaker system with 'Wondercaps' of the same value once
and speakers immediately sounded cleaner, more
transparent. better".

What were the origional caps like? NP electrolytics or film caps?

[Audio Empire]

On Tue, 13 Apr 2010 05:03:53 -0700, Arny Krueger wrote
(in article ) :

"Audio Empire" wrote in message
.com

I replaced some crossover caps in a
speaker system with 'Wondercaps' of the same value once
and speakers immediately sounded cleaner, more
transparent. better".

What were the origional caps like? NP electrolytics or film caps?



They were those yellow Mylar caps. You know, the ones that aren't
cylindrical, but look as if someone had stepped on one? The speakers were a
set of Magnaplanar Tympani 3Cs. The ones with EIGHT panels: 2 tweeter panels,
two midrange panels and four bass panels. At the time, they were Magnepan's
top of the line speakers.

[GregS[_3_]]

In article , wrote:
On Tue, 13 Apr 2010 05:03:53 -0700, Arny Krueger wrote
(in article ) :

"Audio Empire" wrote in message
.com

I replaced some crossover caps in a
speaker system with 'Wondercaps' of the same value once
and speakers immediately sounded cleaner, more
transparent. better".

The only thing that is likely different is the dielectric absorption, and
if you change values accordingly, you can equalize that effect, if
it really exists. I ALWAYS listen and change values using pink noise.
If you don't do that, your a fool. You can't hear transparency with pink
noise, it just sounds different, and the difference can be explained in detail

I see an example how DA works, but they just show a series resistance.
I would just show it a a decrease in capacitance.

greg




What were the origional caps like? NP electrolytics or film caps?



They were those yellow Mylar caps. You know, the ones that aren't
cylindrical, but look as if someone had stepped on one? The speakers were a
set of Magnaplanar Tympani 3Cs. The ones with EIGHT panels: 2 tweeter panels,
two midrange panels and four bass panels. At the time, they were Magnepan's
top of the line speakers.

[Arny Krueger]

"GregS" wrote in message


I see an example how DA works, but they just show a
series resistance.
I would just show it a a decrease in capacitance.

DA in film capacitors can only be an issue in high impedance systems, never
in loudspeakers.

The standard equivalent circuit of DA is a very large resistance (on the
order of megohms) in series with relatively large amounts of capacitance.

It is a big issue in circuits like sample-and-holds, and not so much most
other places, but pretty much zero in speaker crossovers.

http://electronicdesign.com/article/...yhow-6096.aspx