1948 Supro?....my first project..need help.....

[skallywampus]

150 hours into my first amp project. I'm told amp had lower volume than designed...how to tell? Is it just by experienced ear? The 6sl7 seems to be overdriving the second stage of the tube at 1/2 volume causing distortion. Here is my schematic and I lam asking for suggestions!
Thanks, Skallywampus

[shooter]

try swapping the 25uF cathode cap to 5 - 10uF, see if that helps

[DummyLoad]

what value is 2W resistor between 40uF/50V and 10uF/450V filters? what are plate, screen supply, and cathode voltages of output stage? what are preamp supply voltages? what are the OT and power transformer specs/model#/mfg.?

3A fuse is big-time overkill for 10W parallel SE amp.

first stage will easily push second into clipping.

pics of the build & sound-clip would help. 

--pete

[66Strat]

Unless I'm missing something, I don't see a ground connection for the first triode. I see a shorting jack that grounds the grid when nothing is plugged in, but is open when a plug is inserted. A bypass cap across the 6V6 cathode resistor would help with volume.

[bmccowan]

I'm curious about the origin of that schematic. Was that adapted from the 1948 amp with a single 6V6 and a 6SL7? An original Valco design or other? The single 6V6 1948 is a great sounding amp - nice and warm but it does break up early. I have one that was private labelled for a Chicago music store (Loney). And I built one from scratch. That schematic, and a 1947 is attached, as is a 6SL7 preamp with 1 or 2 6V6 and might be worth looking at.

[bmccowan]

Hmm - something went wrong with the other two attachments - gotta eat dinner, but will check back

[bmccowan]

Attached hopefully are the other two schematics.
And I would suggest that you make sure it is working right before you start make mods to increase the volume. In my experience, every time somebody states that the amp is not as loud as they expected, they find a problem and the volume goes way up. If it ain't loud, something is likely wrong, rather than mods are needed.