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Post by pauly on Oct 3, 2008 22:23:16 GMT -5
Hey everyone.
I saw a splawn page that showed a picture of variable resistor VR1.The description said it was the bias trim pot.
So I hooked up my weber bias rite to my Nitro and tested the stock JJ KT77's .They were all pulling between 32 and 33mA By my calculations, that's pretty normal.
I installed a matched quartet of two JJ KT77's and two JJ E34L's . All 4 tubes were on the cold side., only drawing between 20 and 22mA. I started turning VR1 to lower negative bias voltage / bring the bias up and not much was happening to the first two tubes but the 2nd two tubes were up to 40 mA, quickly.
Can you guys tell me how you've biased your Nitros and if my situation sounds abnormal ? Thanks
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Post by pauly on Oct 3, 2008 22:50:14 GMT -5
In the way of an update, the integrated quad isn't that well matched. The included KT77's are colder than the E34L's. Another question, what is the function of VR2 ? Thanks
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kent
Newbie
Posts: 23
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Post by kent on Oct 7, 2008 15:38:14 GMT -5
Hey Pauly. I know that one of the trim pots has something to do with hum cancelation, or something along those lines. I forget which one it is off hand, but one is for the bias adjustment and the other is for the hum.
Oh, and are you the same Pauly from the Petrucci Forums??
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kent
Newbie
Posts: 23
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Post by kent on Oct 7, 2008 15:41:46 GMT -5
Just checked, and the V2 is the hum balancer. And Im not too sure if the Nitro can do two different types of tubes at once like the Boogie Mark amps can. At least I've neer heard of anyone around here doing it. That might be a question for the man himself.
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Post by pauly on Oct 7, 2008 17:56:19 GMT -5
Hey Pauly. I know that one of the trim pots has something to do with hum cancelation, or something along those lines. I forget which one it is off hand, but one is for the bias adjustment and the other is for the hum. Oh, and are you the same Pauly from the Petrucci Forums?? Yep.That's me.Sounds like V2 is something similar to the Ampeg biasing circuit.I'm surprised Scott hasn't published instructions on how he wants the amp to be biased. As far as running the tubes as integrated pairs, it's ok if the tubes are all matched together. it's the same thing Eurotubes has been doing with rectifier series amps for a while now.they sort out El34's nad 6L6's that draw the same plate voltage. But in my case, it seems they didn't match the tubes well. |
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kent
Newbie
Posts: 23
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Post by kent on Oct 8, 2008 15:07:33 GMT -5
Well thats cool. I figured that it MIGHT work, but I thought that the whole using two different types of power tubes would only work on certain amps. Well you could allways try a different quad set. By the tubes that your trying to mix, it sounds like you might like KT88's in your Nitro. Theres a thread on here about the simple mod that had to be done. I beleive Fastredponycar has done the mod on his Nitro and loved it. If you can install guitar pickups, then it should be pretty simple to do.
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