schematic check please?

[John]

Hi, if you'd all be good enough to take a gander and make sure I'm not missing or screwing up something obvious. The base circuit I've built several times, but this is the first time I'm using a reverb tank instead of the Belton module.


I'm sure I'll have to tweak some of the component values to get the sound right, since I'm using the octals instead of a 12ax7.


Thanks in advance!

[TIMBO]

Looks good

[PRR]

No ground symbol shown where 1.2K and 295r cathode resistors return.

No value shown for reverb recovery plate load.

You could live without the heater elevator. Take heater CT to output tube cathode, which is a significant and clean positive DC voltage.

You could avoid a choke by moving wire AA over to point A. Output power will drop a few percent but this isn't a barn-shaker in any case.

I don't think the 0.01u/0.022u switch will do much. 'Specially since you have so much choice at the second cathode. If, on test, you agree, make one choice much smaller, like 0.003u.

[John]

Thanks for giving it the once over. (you too Timbo!)


I've gotten in the habit of elevating heaters ~ 50 volts since I like those quirky octals. I just make the divider part of my filter board.


I decided to use the choke since it's all in the same set as the PT and OT (from Webcor reel to reel). I use the "less hum" double filter caps where at all possible. This amp is just sitting in the guy's basement, so weight is not a big deal.


I might up the second value on that switch then. He also plays a lot of slide, and slide players like the darker sound a bigger coupler gives them (they say). Maybe I'll do a .01/.047 or something like that, or even lower and higher value.


Oh, no ground is misdrawn/forgot, and forgot the plate load value, which is 82K. Seems to work well with the 6SL7s.


Thanks again!

[DummyLoad]

what is power tube? yes, pinning is octal so assuming a 6v6/6l6/5881, etc., but which one? OT specs?


--pete

[John]

Oops, sorry. Power tube is a 6P3S-e (Russian 5881). (side note: the 6P3S is not nearly as nice sounding as the *e tube)


No idea of OT specs. The PT is a 270-0-270. OT ran a 6V6 and sometimes a 6aq5 as well, if I read the Webcor schematic right. (always doubtful). I've built 2 amps using this circuit but with a digital reverb brick. This is my very first time using a tank and transformer, and just wanted to make sure I wasn't going to either fry something or have no sound.