1979 Splawn Modded Marshall new filter caps...would you?

[harddriver]

Change the mains and screens filtering from 100uf back to the 50uf Marshall values? I'm not sure what values Scott ended up using the Quickrod but when he was modding Marshalls back circa 2003 he would disconnect the two paralleled 50uf/50uf caps in series for the Mains and Screens Filtering so instead of 50uf for the mains and screens it was 100uf. Everything else is standard Marshall values, 50uf/50uf for the preamp and 100uf for the Phase Inverter.

I am getting ready to replace all the electrolytics in the entire amp, 1uf Cathode bypass caps, 10uf bias caps, and all the 50/uf/50uf filter caps. The 32 year old LCR's are getting long in the tooth but no leaking or bulging as the amp get's played regularly.

I have all the ARS 50/50 caps to go back to the standard Marshall values as I don't think the 100uf brings a whole lot to the table except maybe lower the noise floor a tad and maybe make the amp a bit stiffer.

So would you keep it as modded or convert it back to stock?

 

[RedPlated]

Do you mean he would disconnect the second cap that’s in series on the mains and on the screens so that they would be 100uf? So the voltage rating was effectively cut in half?

 

[harddriver]

Do you mean he would disconnect the second cap that’s in series on the mains and on the screens so that they would be 100uf? So the voltage rating was effectively cut in half?

Yes the second cap that was in series for the mains and screens filtering is disconnected.

The two sets of 50uf/50uf caps(four dual 50/50 caps) that are usually two in series in a stock Marshall for the mains and screens filtering he would only use one 50uf/50uf cap(100uf) each for the mains and one 50uf/50uf (100UF)cap for the screens.

So yes the effective voltage rating would drop from 1000 to only 500DCV for the incoming voltage surge upon startup for the mains/screens is pushing things a bit.

It was something that Splawn did on those early mods for some reason. I'm thinking it would be better to return the amp to the original filtering scheme.

 

[RedPlated]

I would absolutely run them in series to get the higher voltage rating.

You can use 220uf filters from ARS in series to keep the filtering where it’s at now but restore the voltage handling.

I like 220’s in the mains as they keep the low end more composed at higher volumes. But it’s a subjective thing. And also depends on the rest of the amp. Mesa and Soldano run high mains filtering, but much lower preamp filtering. It’s a totality of the circumstances type thing.

I’ve done testing many times by paralleling in caps to increase the mains and screens. With the mains, I notice a noticeable shift in the midrange almost more than anything else. It’s interesting.

Screens filtering affects the feel much more, in my experience.

 

[harddriver]

I would absolutely run them in series to get the higher voltage rating.

You can use 220uf filters from ARS in series to keep the filtering where it’s at now but restore the voltage handling.

I like 220’s in the mains as they keep the low end more composed at higher volumes. But it’s a subjective thing. And also depends on the rest of the amp. Mesa and Soldano run high mains filtering, but much lower preamp filtering. It’s a totality of the circumstances type thing.

I’ve done testing many times by paralleling in caps to increase the mains and screens. With the mains, I notice a noticeable shift in the midrange almost more than anything else. It’s interesting.

Screens filtering affects the feel much more, in my experience.

Thanks for the input on this. I just picked up 4- 220uf/500DCV radial caps from ARS in case I want to keep the 100uf mains, 100ufscreens specs.

I think I like the idea of 100uf on the mains and the stock 50uf on the screens but we'll see.

I already have the classic 68plexi and 72 superlead with stock filtering so I kinda want the Splawn Marshall pushed a bit more modern but still Marshally.

 

[RedPlated]

I run that combo a lot. Two 220’s in mains and two 50/50’s in screens.

The ARS 220’s are single cans. Not dual like the originals. So there’s only two terminals, not three. Actually makes wiring them up a little easier.