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In Reply to: RE: Bypass caps smear the sound due to different speeds. posted by Ralph on July 24, 2024 at 09:48:33
Hi Ralph.
Thanks for your response. I can't argue with your comments, you obviously know far more about amps than I do. However, the sound I am getting from the modded amp does not seemed smeared, on the contrary the amp sounds faster, and more resolving now, the way it was before seemed smeared. Obviously the new Mundorfs are more resolving than the old ones, and this more than makes up for any problems caused by the Dynacap bypass caps I guess.
I like what I'm hearing but now I'm very interested in trying the amp without the bypass caps. Is this something that I could do myself? I just can't keep lugging this 65 pound amp back and forth to my tech. I do have a very basic soldering gun, but no other equipment. Do you need a tool to suck up solder when you remove something? I assume the bypass caps are soldered in place. I think removing bypass caps would be pretty simple, but I have zero experience working inside of amps. Maybe I should just leave things be and enjoy the new sound I am getting.
The amp is definitely quieter since the mods, and power transformer mechanical hum (not through the speakers, just near the amp) has been cut way down. I put that down to the bypass caps on the power supply caps. Those are definitely staying.
Follow Ups:
isn't fixed by bypass caps. Its more likely that the screws that hold the end shells to the laminations were loose. That can happen over 20 years and can cause the transformer to rattle.
You don't need to solder to remove the pesky bypass caps around the main coupling caps. A set of diagonal cutters will do the job nicely. But if you're not comfortable knowing your way around the insides of the amp I'd take it to someone who does!
You'll hear no loss of highs, but you may notice it seems smoother.
Were the power supply filter caps replaced when you had this work done? The amp is old enough that would be a good idea. The 'half life' of the filter caps in tube amps ('half life' meaning about half of them are ready to fail) is about 20 years (due to heat).
Thanks again Ralph for the info.
Regarding the power transformer, not only are the screws tight, the previous modifications done 10 years ago included some kind of rubber padding to help reduce mechanical noise in the PT. I don't know what they did in the current modification (I don't think they did anything to the PT), but the buzz is now much reduced. So I assumed it was because of bypassing the power supply caps. As for the power supply caps, they were upgraded 10 years ago.
Regarding cutting the bypass caps, wouldn't that ruin them for future use? What if I liked the sound better with them in? They are about $30 each, seems wasteful to destroy them.
Question. Why would Rogue include bypassing the coupling caps in their upgrade package for the Stereo 90 if it is so bad to do so. That's why I did it in the first place.
Those power supply caps can hold a significant charge, possibly lethal! All you need to do is make contact with one positive terminal and any other metal part of the amplifier to possibly electrocute yourself or at least learn the lesson that electricity can hurt. The power supply bypass caps have nothing whatsoever to do with transformer hum and probably not much to do with the sound of the amp. Leave them be.
Despite your testimony to the contrary, I have a hard time understanding why anyone, trying to improve the sound, would bypass a quality capacitor (Mundorf SIO) with a lower quality cap. It just makes no sense at all, financially or technically. Maybe they don't really like the sound of the higher quality cap and want to mitigate its contribution. I would ask the tech.
berate is 8 and benign is 9
In my preamp I have recently changed/renewed the 1,0uF line coupling caps with Mundorf MCap Supreme Silver Gold Oil. After burn in (more than 300 hours) I have bypassed them with the Duelund JDM 0,01uF pure silver axial cap and I am very satisfied with the result.
The Duelund JDM cap has dropped in price and they are now less expensive than before (USD 54 incl. VAT).
You can read reviews about the Duelund's among many other brands at Humble Homemade HiFi. When a cheaper cap was needed in a lower quality speaker/amp or a higher quality cap in a high end speaker/amp I have used his reviews as a guideline. I think his reviews and gradings are very spot on.
https://www.humblehomemadehifi.com/Cap.html
mojul
If you can get them unsoldered that would be better. But again, if you're not comfortable knowing your way around the innards of the amp, take it to someone who does. Knock-on effects aren't worth the trouble!
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