Does Recapping Change the Sound

I have had a few people tell me to recap my 52 AMI "D" and I have a cap kit
on the way. But so far no one has told me what effects this will have on the
sound?!?! In fcat I have had at least a few guys tell me not to recap as the
amp then looses its "warm" feeling? So they seem to think recapping is abd
thing not a good thing. I know its good to help preserve the output xfmr but
am I gonna hat ethe sound afterwards?

Thanks
Mike Purcell
Full Tilit Amusements

Recapping the amp (with the original values) and checking and correcting the
resistor values where needed should bring the amp back into spec. so it
sounds like it did when it was new. Keep in mind that the speakers and the
pickup may also be affecting how the box sounds. If you didn't like the
sound of the box when it was new, then recapping will probably make you
unhappy with it.

--
Charley

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"Mike Purcell" wrote in message
...
I have had a few people tell me to recap my 52 AMI "D" and I have a cap
kit
on the way. But so far no one has told me what effects this will have on
the
sound?!?! In fcat I have had at least a few guys tell me not to recap as
the
amp then looses its "warm" feeling? So they seem to think recapping is
abd
thing not a good thing. I know its good to help preserve the output xfmr
but
am I gonna hat ethe sound afterwards?

Thanks
Mike Purcell
Full Tilit Amusements

Hi Mike,

I'm not in the audiophile camp, so take my comments in this light. I think
the sound could change quite a bit depending on how leaky and in what stages
the bad caps are to be found. I not a believer that the type of cap used
has much to do with the sound quality. As Jim stated in a earlier post, cap
leakage can cause shifts in the operating points of the audio stages that
range from subtle to dangerous. This will effect the characteristics of the
amp. Leaky and out of tolerance caps in tone shaping stages will also have
a possible effect on the voicing of the box. From my perspective, I'd rather
have the box running as it was intended and forgo any euphonic effect(s) due
to these aging characteristics. The increase in reliability far outweighs
any perceived sonic benefits to leaving things as is. Remember that these
boxes are not Hi-Fi (despite some of the marketing hype). They do have a
sound that was engineered by the designers based on a number of factors.
The boxes were voiced for pop recordings practices of the day, the intended
room types and sizes encountered in the field and to cover up record wear
due to the many playings they would experience.

If you are really concerned about this, I'd suggest changing out the caps in
stages and listening for changes in the sound. Start from the output stage
coupling caps and work your way back to the front end. The output stage cap
leakage is the most troubling area because leakage here causes the output
tubes to conduct more that they should at idle. This can result in a
toasted output transformer and/or destruction of the output tubes. You want
a reliable low leakage modern film cap in this location (there are two in
the typical push-pull output stage). As you move to the small signal
stages, the shift in bias will not cause any damage and you just might be
able to live with this if you like the sound. I'd also replace any of the
supply bypass caps as these will have little effect on the sound, but may
prevent motorboating and/or high frequency oscillations. Hope this makes
some sense and is of help to you.

Mark


"Mike Purcell" wrote in message
...
I have had a few people tell me to recap my 52 AMI "D" and I have a cap
kit
on the way. But so far no one has told me what effects this will have on
the sound?!?! In fcat I have had at least a few guys tell me not to recap
as the
amp then looses its "warm" feeling? So they seem to think recapping is
abd
thing not a good thing. I know its good to help preserve the output xfmr
but
am I gonna hat ethe sound afterwards?

Thanks
Mike Purcell
Full Tilit Amusements

The whole thing about recapping and taking away the ``warm sound`` has
to do with the old capacitors values going up as they leak .
A .01 cap may read .05 or more . I did one amp where almost every cap
went over .1 What that does is cut the high end or trebble out of the
music making the audio fools think its a warmer sound .

If you recap an amp , have it playing and hold a second capacitor across
one in the amp on some of them you will notice a decrease in trebble .

Mike Purcell wrote:

I have had a few people tell me to recap my 52 AMI "D" and I have a cap kit
on the way. But so far no one has told me what effects this will have on the
sound?!?! In fcat I have had at least a few guys tell me not to recap as the
amp then looses its "warm" feeling? So they seem to think recapping is abd
thing not a good thing. I know its good to help preserve the output xfmr but
am I gonna hat ethe sound afterwards?

Thanks
Mike Purcell
Full Tilit Amusements


Just what is "warm feeling"? That can mean anything. If the caps are
leaky (low internal resistance) they can cause problems such as
upsetting the bias on output tubes which can cause distortion as well a
allowing the tubes to draw excessive current, cause excessive strain on
the power supply as the caps will pass dc current. When caps get leaky
they act more like resistors than capacitors.
When they talk about the amp loosing it's "warm" feeling, what do they
think it sounded like when it was new and all the caps had very low
leakage? If the old caps cause a difference in the sound, the obviously
the old caps aren't doing the job they did when new. I hope you didn't
pay too much for that cap kit. You can purchase caps from many suppliers
and the ones usually hyped in those cap kits are no better that very
econominal caps you can purchase.
Any piece of electronic equipment has old wax coated paper caps should
be completely recapped as those old caps are most certainly to be out of
specs as far as leakage.

Hi Ken,

I'm not sure I agree with your statements. I wonder if the readings you are
finding are a result of the leakage increase causing the cap meter to read
incorrectly. I can't think of any way that the cap could increase its value
with age. I would expect the opposite. In order for the value to increase,
the dielectric constant of the paper would have to increase or its thickness
decrease. In any event, an increasing capacitance in a coupling cap would
allow more low frequencies to pass. It would not affect the treble
response. In most designs, the coupling cap is chosen such that the low
frequency response is already way below the cutoff of the speakers so
further lowering of the bass response would not alter the sound (although it
may waste amp power due to passing sub sonic garbage).

Mark

"Ken G." wrote in message
...
The whole thing about recapping and taking away the ``warm sound`` has
to do with the old capacitors values going up as they leak .
A .01 cap may read .05 or more . I did one amp where almost every cap
went over .1 What that does is cut the high end or trebble out of the
music making the audio fools think its a warmer sound .

If you recap an amp , have it playing and hold a second capacitor across
one in the amp on some of them you will notice a decrease in trebble .

Mark Robinson wrote:

Hi Ken,

I'm not sure I agree with your statements. I wonder if the readings you are
finding are a result of the leakage increase causing the cap meter to read
incorrectly. I can't think of any way that the cap could increase its value
with age. I would expect the opposite. In order for the value to increase,
the dielectric constant of the paper would have to increase or its thickness
decrease. In any event, an increasing capacitance in a coupling cap would
allow more low frequencies to pass. It would not affect the treble
response. In most designs, the coupling cap is chosen such that the low
frequency response is already way below the cutoff of the speakers so
further lowering of the bass response would not alter the sound (although it
may waste amp power due to passing sub sonic garbage).

Mark

Digital meters that can read capacitance will usually show increased
capacitance if the cap is leaky.

All i know is in certain circuits in the amp if yo replace a leaky
capacitor the trebble boosts if you trade that capacitor back for the
original one it cuts trebble .

The warm sound these guys talk about is the ``no trebble`` sound .

By the way, that's "treble" ...

In article ,
(Ken G.) wrote:
All i know is in certain circuits in the amp if yo replace a leaky
capacitor the trebble boosts if you trade that capacitor back for the
original one it cuts trebble .

The warm sound these guys talk about is the ``no trebble`` sound .

Doo yoo hav aneething elts too ad

``Tony``