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Post by edoetsch on Feb 23, 2007 11:59:59 GMT -7
I have a Route 66 now and it has a Sovtek 5AR4 Rectifier.
I also have an JJ GZ34 which is supposed to be a direct replacement.
Will I need to rebias if I switch?
I know if I change power tubes or switch to a 5U4 rectifier I would need to rebaias.
I assume the preamp tubes can be switched in and out at will. Is that true?
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Post by aj1169 on Feb 23, 2007 12:11:23 GMT -7
You shouldn't have to rebias. Preamp tubes can be changed whenever with no bias adjustment.
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Post by Curt on Feb 23, 2007 13:32:46 GMT -7
I have a Route 66 now and it has a Sovtek 5AR4 Rectifier. I also have an JJ GZ34 which is supposed to be a direct replacement. Will I need to rebias if I switch? I know if I change power tubes or switch to a 5U4 rectifier I would need to rebaias. I assume the preamp tubes can be switched in and out at will. Is that true? 1. A rec is not a pre amp tube 2. no rebias when swapping pre amp tubes 3. Bias needs to be checked when changing the Rec even if the exact same mfg./model, etc. on fixed bias amps (i.e. your Route66).
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Post by JASON (aka jgleaton) on Feb 23, 2007 14:04:34 GMT -7
Yes, exactly what Curt said...
you should check the bias in a class A/B fixed bias amp when swapping rectifiers...
it might be fine, or need to be tweaked a bit... or maybe even alot.
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Post by benttop (Steve) on Feb 23, 2007 15:37:56 GMT -7
Yes! And it doesn't hurt to just check it from time to time either. I know I've seen significant change in BIAS over time on at least two of my amps.
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Post by myles on Feb 23, 2007 15:42:59 GMT -7
Yes! And it doesn't hurt to just check it from time to time either. I know I've seen significant change in BIAS over time on at least two of my amps. I agree 110%. I check the bias (and generally readjust) two to four weeks after installing new output tubes as they burn in and the bias can change.
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Post by dongiesen on Feb 23, 2007 18:45:12 GMT -7
Questions for Myles. How do we determine bias value? Does it require engineering data for that particular tube and if so where does the do it yourselfer obtain the information. Have 2 Mullard 5AR4 tubes on the way around 1964 vintage. The only info I have so far is f32B412. Some sort of grading or engineering or run number? Will be putting one in a 1999 Ghia and one in a 2004 Maz 18 w/reverb. Also wondering if the reverb unit in a combo is in a bag because it's further away from the electronics whereas in a head it may have to be isolated differently? Also curious why a 18 head has a bottom of box mount instead of staying top mount like a combo. Heat perhaps? I'm guessing there is some reason as it makes mfg a bit less universal with the front and rear face plate lettering. And by the way, thanks for all that you do to help the average guy with your wealth of expertise.
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Post by Curt on Feb 24, 2007 14:04:54 GMT -7
Questions for Myles. How do we determine bias value? Does it require engineering data for that particular tube and if so where does the do it yourselfer obtain the information. Have 2 Mullard 5AR4 tubes on the way around 1964 vintage. The only info I have so far is f32B412. Some sort of grading or engineering or run number? Will be putting one in a 1999 Ghia and one in a 2004 Maz 18 w/reverb. Also wondering if the reverb unit in a combo is in a bag because it's further away from the electronics whereas in a head it may have to be isolated differently? Also curious why a 18 head has a bottom of box mount instead of staying top mount like a combo. Heat perhaps? I'm guessing there is some reason as it makes mfg a bit less universal with the front and rear face plate lettering. And by the way, thanks for all that you do to help the average guy with your wealth of expertise. Uh...5Y3 in a Ghia right fella's??? Carefull with that.
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Post by mward on Feb 24, 2007 21:07:36 GMT -7
He's got a mazjr also. It's in his sig.
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Post by myles on Feb 26, 2007 11:42:31 GMT -7
Questions for Myles. How do we determine bias value? Does it require engineering data for that particular tube and if so where does the do it yourselfer obtain the information. Have 2 Mullard 5AR4 tubes on the way around 1964 vintage. The only info I have so far is f32B412. Some sort of grading or engineering or run number? Will be putting one in a 1999 Ghia and one in a 2004 Maz 18 w/reverb. Also wondering if the reverb unit in a combo is in a bag because it's further away from the electronics whereas in a head it may have to be isolated differently? Also curious why a 18 head has a bottom of box mount instead of staying top mount like a combo. Heat perhaps? I'm guessing there is some reason as it makes mfg a bit less universal with the front and rear face plate lettering. And by the way, thanks for all that you do to help the average guy with your wealth of expertise. Uh...5Y3 in a Ghia right fella's??? Carefull with that. Ghia = 5Y3 .... yes
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