Black Spragues

[Bob S]

Anyone have any experience using using these caps?
I've hopefully gotten over my Marshall with mustards only works phase.
No code on them - says "Buffer" on a couple of them.
My time is limited lately so I wondered if anyone had already been down this road.

[Colossal]

I've hopefully gotten over my Marshall with mustards only works phase.

Hi Bob, I can't really offer anything on the Spragues (aside from 'they're lovely') but if it puts you more at ease with going off the reservation on using Mustards only with a Marshall, I built a high gain Marshall variant with metal film and metallized polypropylene caps throughout the signal path (coupling and bypass). In a blind taste test with some local players who have no bias (or real knowledge) on dialectrics or resistor substrates, they swore it was one of the warmest and clearest Marshalls they'd heard.

[Phil_S]

Sell them on eBay. You'll probably get enough to buy parts for a complete amp.

[Cliff Schecht]

Those are the style of Sprague black caps that you don't want to use. They are oil-impregnated film caps that were vacuumed and sealed many many moons ago. IME every one of these caps I have tried is bad, leaky, out of spec and really just no good to use. They were *really* high quality back in the day but just weren't designed to last.

You can tell these apart from Di-Film and other style caps by the little blob of solder coming out one side of the casing. This is where they sealed the cap and attached the lead after forming the bakelite shells around the internals. Non-oil impregnated caps won't have seals and true paper-in-oil caps have the solder blobs on both sides and usually a metal casing (for the 50's-60's era caps). These are my favorite caps to use just for how damn cool they look in a circuit and how little color they add. My opinion on voicing an amp with passive components is well documented here..

[Bob S]

Thanks Cliff - I had my suspicions about their construction.
Nice to have it confirmed without having to learn the hard way.
You guys are a great source of wisdom.
Bob

[dreric]

Since we're on the subject, What's the story with these? Any good?

Thanks

Eric

[Cliff Schecht]

Eric the ones with the reddish labels are the types that are good to use. Note they have no solder blob on either end. The ones with the yellow labels have the solder blob and IME are no good for our purpose. Might be good inside of a guitar where there is no voltage present however.

[passfan]

Red ones are black beauties. Some of the molded circles will have the number 2 in them. Excellent paper in oil cap. These look NOS with max lead length. and usually fetch up to 10 bucks a pop depending on value.

[diagrammatiks]

The red ones should say 160p somewhere on them. Those are the good ones to use.

Some of the yellow ones are ok too but it depends on the era. They usually have much higher voltages.