Gadnabbit, my matched pair of Winged C came 10mA apart

[57GoldTopAztec]

Was biasing them into my Silver Jube 2554 last night and one came in 45.0 mA and the other 35.5. I went ahead and biased them at 70 percent mpd.

(One actually ended up at about 65 percent mpd and the other 75 percent. I just split the difference.)

Checked them against a pair of cheapie matched Ruby tubes that came with the amp, just to be sure it wasn't something other than the tubes. The Rubys were matched.

No fun. I'm sure the vendor will send me out a matched pair. But biasing is a time-consuming task that involves a lot of care.

I'd rather just play.

 

[bluesforstevie]

Was biasing them into my Silver Jube 2554 last night and one came in 45.0 mA and the other 35.5. I went ahead and biased them at 70 percent mpd.

Checked them against a pair of cheapie matched Ruby tubes that came with the amp, just to be sure it wasn't something other than the tubes. The Rubys were matched.

No fun. I'm sure the vendor will send me out a matched pair. But biasing is a time-consuming task that involves a lot of care.

I'd rather just play.

If the amp has a bias pot and you have meter or DMM then it shouldn't be too hard.

I had a pair of Russian KT66 Gold Lion that came exactly matched...but after several hours started to drift.

Thats one of myriad problems that exist with crappy Russian or Chinese tubes. They don't hold their bias very long.

No excuse for arriving to you 10ma apart but it can happen down the road when you can no longer send them back....and that sucks too.

 

[57GoldTopAztec]

I have one of those nice little bias probes to make it easier. I just don't like taking the chassis out because the trim pot is on the inside of it. I realize this is par for the course on many amps, I just prefer to do this once instead of twice if I can avoid it.

By the way, your old ThroBaks are now in in the R4 you see pictured in my Avatar! They sound so sweet with the wraptail tone.

Rawk On.

 

[bluesforstevie]

I have one of those nice little bias probes to make it easier. I just don't like taking the chassis out because the trim pot is on the inside of it. I realize this is par for the course on many amps, I just prefer to do this once instead of twice if I can avoid it.

By the way, your old ThroBaks are now in in the R4 you see pictured in my Avatar! They sound so sweet with the wraptail tone.

Rawk On.

Yeah? Cool!! I'd love to hear them!!

 

[skhan007]

I have some brown base XF1 Mullard EL34's that are about that far apart too. I use them in a cathode biased amp. If I recall, about 100 mA & 110 mA, which is about 10% difference between 'em, so I'm good. They sound incredible. I'm told it's "asymmetrical distortion." Works for me.

 

[57GoldTopAztec]

I like the tone. I worry about the split a bit. Basically means I have one running at 75 percent MPD and the other 65 percent.

I know I could just lower them down to a 70-60 split for total peace of mind, but that just seems a bit cool to me. I'm nuts.

 

[roadrunner]

There's a lot stuff to worry about these days, a 10mA difference in a set of power tubes isn't one of 'em. Fender, Marshall, Vox, Hiwatt... insert your fave amp maker here... didn't measure power tubes before they put 'em in their amps. Yeah, back in the day the tubes were of much, read: MUCH, better quality but still, they didn't match them... they just stuck 'em in the amp.

10mA off is just fine, in fact your amp will probably sound better having tubes mismatched like that. Matched tubes make for a real linear and hi-fi sounding guitar amp... linear and hi-fi are two things that should never be used to describe a good guitar amp.

Plug it in, turn it on, play it and have fun!:dude:

 

[57GoldTopAztec]

The tubestore is already sending me a matched set for replacement.

 

[bluesforstevie]

There's a lot stuff to worry about these days, a 10mA difference in a set of power tubes isn't one of 'em. Fender, Marshall, Vox, Hiwatt... insert your fave amp maker here... didn't measure power tubes before they put 'em in their amps. Yeah, back in the day the tubes were of much, read: MUCH, better quality but still, they didn't match them... they just stuck 'em in the amp.

10mA off is just fine, in fact your amp will probably sound better having tubes mismatched like that. Matched tubes make for a real linear and hi-fi sounding guitar amp... linear and hi-fi are two things that should never be used to describe a good guitar amp.

Plug it in, turn it on, play it and have fun!:dude:

I usually agree with you...but 10ma apart, even with real good tubes, much less todays fare, is too much for me...I'd stick with 5mA diff, maybe a 6mA if it sounded good...but that's just me.

And XF1 or any Mullard should not be run drawing that much current. They'll fry. XF1 are for collectors and Stereo guys. They're worth too much money and offer less durable construction than the early to mid 60's Mullard EL34.

 

[57GoldTopAztec]

10 mA apart just makes it a little danger to me to keep a bias as hot as I'd like. It is a vintage amp, after all, that is new to me. So I prefer having a more evenly split idle, instead of one running 65 mpd and the other 75 mpd.

If I want a little room between the mA readings, I'm sure I can just keep the two I like the best out of the four I will now have to choose from.

 

[roadrunner]

I usually agree with you...but 10ma apart, even with real good tubes, much less todays fare, is too much for me...I'd stick with 5mA diff, maybe a 6mA if it sounded good...but that's just me.

And XF1 or any Mullard should not be run drawing that much current. They'll fry. XF1 are for collectors and Stereo guys. They're worth too much money and offer less durable construction than the early to mid 60's Mullard EL34.

I hear ya Dan... and those are valid points/concerns. I actually, because I didn't have a choice of anything else at the time, have used tubes that are 20 mA apart and things sounded surprising good, if not great. I never bias the hot one over 70%, that helps a bit.
5 to 6 for a difference is my fave as well and usually what I shoot for when putting new power tubes in an amp.

 

[bluesforstevie]

I hear ya Dan... and those are valid points/concerns. I actually, because I didn't have a choice of anything else at the time, have used tubes that are 20 mA apart and things sounded surprising good, if not great. I never bias the hot one over 70%, that helps a bit.
5 to 6 for a difference is my fave as well and usually what I shoot for when putting new power tubes in an amp.

Hey Gary,

The bottom paragraph in my post..about the Mullard XF1 was in response to another members post.

I know, you know, how to bias them puppies and keep good ones from blown'.:salude