Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: acheld on February 03, 2025, 02:00:27 pm

Title: Advice for a power transformer
Post by: acheld on February 03, 2025, 02:00:27 pm

My next build will be something like DaGeezer's Tweed Bluezmeister, Tubenit's version.

This amp features 2 12xx7's and 2 6L6GC tubes in self biased operation.  I've built only one self biased amp before, a BJ-IV version.

What would be a suitable estimate of B+ current ?   When I look at the data sheets for a 6L6GC, the plate current is listed at around 210mA in self bias mode.   Is this correct?  It seems very high to me -- I think I'm looking at the wrong spec . . .

Title: Re: Advice for a power transformer
Post by: SEL49 on February 03, 2025, 02:15:04 pm

Quote from: acheld on February 03, 2025, 02:00:27 pm

When I look at the data sheets for a 6L6GC, the plate current is listed at around 210mA in self bias mode.   Is this correct?  It seems very high to me -- I think I'm looking at the wrong spec . . .

Yeah, 210mA sounds wrong. You should be able to use a PT that's rated for 150mA or 175mA.

Title: Re: Advice for a power transformer
Post by: AlNewman on February 03, 2025, 03:48:50 pm

Probably depends on what voltage you want.
30W @ 300v is 100mA/tube.
30W @ 450v is 66mA/tube

Title: Re: Advice for a power transformer
Post by: AlNewman on February 03, 2025, 03:53:09 pm

Plus screens, preamp, etc...

Title: Re: Advice for a power transformer
Post by: mresistor on February 03, 2025, 04:31:05 pm

The original Tweed Bluesmeister uses 5881s (well I see 5881s on the layout and 6L6 in the schematic) but could use 5881s.   One would think that any PT for a Fender amp or equivalent using 6L6s would work well. 


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