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Nakamichi PA 5E class A Stasis amplifier hum problem
Nakamichi PA 5E class A Stasis amplifier hum problem
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Old 14th February 2018, 06:29 PM   #41
Sixtron is offline Sixtron
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Yes i have seen this before that usually the metal side is inflated but it can also happen that the bottom of a capacitor is inflated and the liquid is coming out from the bottom.
Btw. replaced the 3.3 ohm resistors by 2.0 ohm. Still working well enough. Very few hum, but not disturbing.
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Old 14th February 2018, 06:36 PM   #42
Mooly is offline Mooly  United Kingdom
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Nakamichi PA 5E class A Stasis amplifier hum problem
These resistors are often around 4.7 ohm (or thereabouts) in a lot of equipment. It is good to know it has solved the problem for you.
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Old 4th March 2018, 10:29 AM   #43
Sixtron is offline Sixtron
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To make it complete here: I have changed the mylar capacitors 10uf 200V with the new yellow matched ones. See photo.
This resulted for my ears in worse sound quality. Less bass, harder middle tones, less dynamic. Few differences but to hear. So i put the old one's back.
Nearly the same numbers but worse sound. How can this be ?
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File Type: jpg IMG_20180304_121019.jpg (297.1 KB, 54 views)
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Old 4th March 2018, 10:52 AM   #44
Mooly is offline Mooly  United Kingdom
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Nakamichi PA 5E class A Stasis amplifier hum problem
Do you mean the old ones now don't sound as good as you remember them ?

If so, then this is not uncommon and is usually down to our perceptions and expectations rather than a real effect that could be picked out by a blind listening test. It is something that I have had happen to me in the past.
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Old 4th March 2018, 01:28 PM   #45
Sixtron is offline Sixtron
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No, the new one's don't sound good. After testing the new one's i have now installed the old one's back and it's better. So the old one's are still good and not broken.
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Old 4th March 2018, 01:42 PM   #46
Mooly is offline Mooly  United Kingdom
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Nakamichi PA 5E class A Stasis amplifier hum problem
Fair enough If they really do sound poor then trust your ears and stick with what works.

Alternatively, leave the new fitted and give them a listen for a few days. I still wouldn't rule out some expectation issue... you want the new to be really good and special and... they just didn't really change anything. I've been there myself and know its a real effect. It could even be down to just seeing a large oversized part and thinking it doesn't visually look as good and that alone colours your perceptions.

Also, large caps like that have a much larger surface area and can be more prone to stray pickup of RFI and EMI hash in the vicinity. That can genuinely cause audible effects.
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Old 5th March 2018, 09:33 PM   #47
northpaw is offline northpaw  United States
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Sixtron - Interesting to read of your experience with the mod of upping the 10F C102/C202 cap to a much larger value, to match what was in the similar Threshold Stasis amps. I've read those same posts, but had little inclination to try the mod given my positive listening experience with the PA-5.

Mooly - You might not be familiar with this particular unit, but Sixtron's last photo shows both the new (yellow) cap he tried, and the original U-Sigma cap (large gray one just to the right). Perhaps the surface areas of the new yellow ones are somewhat larger than the original gray ones, but it would not be by a large factor, although the geometric differences could come into play as well. I tend to think (like to think) the Nak engineers choose quality parts in their better gear, like this amp. That said, your points about expectation and listener acclimatization are duly noted.
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