Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: dude on January 23, 2019, 11:55:08 am

Title: Matching tubes by current draw
Post by: dude on January 23, 2019, 11:55:08 am

Can satisfactory matching be obtained by just matching current draw, talking power tubes?


I have several 6V6s, various makes and have just used the biasing pot to find ones that match in current draw. Usually shoot for within 3 to 5 mAs draw.


Thanks,
al

Title: Re: Matching tubes by current draw
Post by: sluckey on January 23, 2019, 12:05:32 pm

yes

Title: Re: Matching tubes by current draw
Post by: dude on January 23, 2019, 01:01:50 pm

I figured it's good enough. You can find unmatched, untested tubes on fleabay for cheap, nice RCA, GE's (and some with other name brands that were made by RCA, GE etc. sleepers). I've had good luck just matching the current draw but there's always a tube or two that buzzes and the mA draw is way off. I've match a few pairs that were buzzy and wayout of range on my bias R, they almost always sounded weak and noisy, just toss them.


Thank for the quick reply,
al   

Title: Re: Matching tubes by current draw
Post by: PRR on January 23, 2019, 02:31:38 pm

Satisfactory to WHO?

For High-Fidelity seeking *lowest* THD numbers, or for a tube limiter, you want close match ALL up and down the current scale, testing at something near your in-use voltages.

For a guitar amp, little wrong with a horse-and-mule combination.

Title: Re: Matching tubes by current draw
Post by: dude on January 24, 2019, 10:58:29 am

Ok, sorry PRR, I was talking about push/pull guitar amps.


I like the analogy to the horse and mule  :icon_biggrin: