Anyone try the DynakitParts 550v (OE was 525v) Quad Cap?

[MrCreosote]

I found this a while back and created a thread back then.

Thread is now stale.

Just thinking that by now, someone must have tried this 550v cap.

Thanks
Tom

[Ryan Phelps]

I have not tried the new 550V quad caps. However, I just re-capped a 1967 100S and with modern AC wall voltage (about 122 - 125VAC at my house) the output from the 5AR4 rectifier tube is 560VDC. So even the new quad cap would be pushed beyond its limits.
I typically leave the old quad cap in-place for vintage appearance and then add discrete caps on terminal strips inside the chassis. I use a pair of 100uf x 450V caps in a totem pole configuration with 220K 2 watt balancing resistors (ala' Fender) for the first stage after the choke. Then I use 20uf x 600V caps on the subsequent stages. The plate and screen voltages are still higher than original spec, so you need to increase the bias voltage to compensate. That is still not perfect.....but you could add a reverse-biased zener diode between the center-tap of the high voltage secondary on the power transformer and ground to drop all the voltages. If you use diode rectification (instead of tube) and higher filter capacitance, then a thermistor between the center-tap and the zener is recommended to avoid damage to the zener from voltage spikes when the amp is switched on. R.G. Keen has designed a circuit that connects to the B+ that drops the voltage as well; see his website...Geo FX. There may be some residual problems with these approaches, but short of a custom-wound power transformer this is likely the closest you will get to the original operating voltages. Any other insights from the rest of you Sunn guys?

[BassHog]

I used one of those caps when I recapped my Sceptre. Worked great. The cap can handle up to 600V(surge) so it should not have a problem working in your amp. I have been giging the amp weekly for over a year now and it's rock solid.

[Ryan Phelps]

If your wall voltage is low enough (like 120VAC), you might get by with the 550V can cap. Then again, you might play a venue with slightly higher wall voltage (say 125VAC), and that can be enough to blow the cap. Bear in mind that the surge value is just that.....to accommodate the higher voltage spike when you first turn on the amp, not the continuous working voltage.

The discrete caps will typically cost less, fit under the chassis, provide more than adequate voltage headroom and you won't be faced with recapping the amp if the can cap does blow. But, to each his own.

Also, Triode Electronics carries an SDS cap board (totem-poled caps for high voltage capacity) that work quite well in Sunn amps. I used them in my Dynaco Mark III's (you'll remember that the earliest Sunn amps actually were Dynaco's) to replace the original can caps and they work great.

[Isaac]

I have the SDS board in my 200S. Works great.

[Oli]

Hi,

I use these in my 350B for app. three years now:

http://www.die-wuestens.de/eindex.htm

...very happy with these!

Greetings

Oli