As I think I mentioned in my original post on this subject, my new 200S needs new caps. The tech asked whether he wants me to replace the can cap with a series of individual caps OR with an SDS module from Triode Electronics in Chicago which is supposed to be especially good with Dynaco transformers. I would appreciate opinions on this.
I plan to gig with this amp so reliability is important. I found a lightweight variac to use with it to keep voltage at 105-110.
Here is what Soundmasterg posted on the forum in 2005 about using a series of replacements:
"There are a couple problems with using can caps in amps, and in particular, one problem with using those exact caps in a Sunn.
"The problem with can caps is that each cap section has the same ground, which can cause ground loops and hum. It is better to use individual caps and modify the layout so each cap is close to the circuit it is supplying. It is also best to modify the grounding scheme so everything isn't grounded via chassis ground. However thats a lot of work, and you can usually get ok performance from using a can cap in an amp. The can caps are also more expensive than using individual discrete caps.
"The second problem with can caps, and the more important one in regards to using it in a Sunn, is that with today's wall voltage, that 525v rating on the caps is not high enough. My Sunn 200S, which is very similar to a Sonic 2, had around 560v at idle, and on standby that was even higher. Using a cap with a 525v rating in a circuit like that will lead to premature failure of the cap.
"A better solution is to take two individual 350v axial caps of the same value, wire them in series for a total rating of 700v, and put a 220k 1w resistor in parallel with each cap so neither cap will take the full voltage. In the first section you could use a couple 80uf 350v caps, and when hooked up in series, you essentially end up with 1 40uf 700v cap, which is more than adequate for the voltages today. In my personal 200S, since I use it for bass, I went with 110uf 700v in the first stage, and 50uf 700v in the second stage. This gives it a lot more bass response than stock and sounds a lot better. For the next two stages, the voltages are low enough to use a single 20uf 450v cap for each stage instead of two in series.
"It takes a little more time to do it this way, and you have to drill some holes to be able to mount the extra caps and the terminal boards to mount them on, but it is better in the long run, and your amp will thank you by not blowing out caps. Also, years down the road, you'll be able to find new axial caps a lot easier to replace these ones than a 4 section can cap.
"But if you want to go with a can cap, then that one listed at AES is the same as original."
Soundmasterg summarized this approach in another post last December.
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Here is a link to the page on which the SDS module is listed:
http://triodeelectronics.com/sdslabcapboa.htmlSoundmasterg mentioned this in another 2005 post on the subject but only that it was an option, not that he or anyone else had tried it. Either approach would seem to address my reliability concern. However, the SDS product seems a little cleaner solution in some ways IF there is room to mount it. Opinions? Thanks.
