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peavey_impact

47ma seem like a safe bias current for kt88? (Vht D60)

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I had my Deliverance for a couple of weeks before a tube lost vacuum. I bought a couple of Gold Lion KT88's then I called up VHT and they said they would ship me a free replacement set (which still hasn't shown up btw :mad:). I got tired of waiting on their replacements so I popped in the Gold Lions and broke out my Weber Bias-Rite.

 

Problem is, my bias-rite is broken :mad: and it apparently always has been since the day I got it. I hooked it up and my voltmeter was reading NOTHING. After screwing with it for a few minutes I found that if I jammed my thumb down hard on the bias-rite VI switch it would give me a reading. I ended up seeing 500 plate volts and set the bias to 47ma, which according to a chart created by Duesentrieb SHOULD be safe, unless I'm just an idiot and read it wrong.

 

Does that reading sound about right to anyone? I'm really worried that I can't rely on my bias-rite readings.

 

I will say that after I closed it back up and plugged in the amp sounded amazing and I jammed for about 25 minutes and didn't notice any redplating. I just want to make sure my tubes are safe.

 

:wave:

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When I said I *loved* my Gold Lions at 45 to 48....everyone said I was biasing 'em too low....they're certainly safe at 500V up to around 55 (from memory) so you should be golden.

 

I regret selling those tubes...damn they were the best sounding KT-88s I've had so far (out of Sovtek, Ruby and JJ that is)

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I thought I remembered reading that they should be set from 33-40 or so at 500v at the plate?

 

I got the tubes in my 5150 at 36 mA and they're all right around 500v at the plate with those tubes.

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I thought I remembered reading that they should be set from 33-40 or so at 500v at the plate?


I got the tubes in my 5150 at 36 mA and they're all right around 500v at the plate with those tubes.

 

That sounds right for 6L6's. Are you running Kt88's in your 5150?

 

-W

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at 500V B+, you can run them safely up to 58.8mA each at LEAST.

 

you have to look at the max plate dissipation of the tube, not the amp's rated wattage. with KT88s, that is 42W each, so (42*70%)/500=.0588=58.8mA.

 

in practice one can get 100W out of a pair of KT88s, but you gotta do it just right:D

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I seriously think my tungsols are at 70mA each on my d60. They were even hotter when I got them but the dang bias pot doesnt allow for much of anything. Usually its fighting to get the bias up, not down :facepalm:

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yeah, if it sounds good to you at 47, you won't burn the tubes up.

 

you might want to noodle with it a bit just to see if you like it better somewhere else...

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