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Posted: Wed Jul 14, 2010 8:30 am
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Rock Star
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Rebelsoul wrote:
Retroverbial wrote:
63supro wrote:
32-34 ma is where they really sing.


That's right in the same neighborhood where I bias all of my blackface 6L6 platforms as well, +/- around 1.0 mA depending upon whether they're NOS blackplate RCA's or mil-spec JAN's.

Arjay
I biased some JAN Philips 6L6s to 35ma in my BF Pro Reverb,so I'm glad that's good to hear from y'all....and it sounds really good.
I would freak biasing tubes into the 60ma range. :shock:
I'm usually a 6V6 tubie...28ma oooohhh. :wink:


Don't confuse milliamps with millivolts. When people are talking in the 60's there referring to millivolts not milliamps. 60ma would red plate for sure.

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Posted: Wed Jul 14, 2010 10:43 am
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63supro wrote:
Rebelsoul wrote:
Retroverbial wrote:
63supro wrote:
32-34 ma is where they really sing.


That's right in the same neighborhood where I bias all of my blackface 6L6 platforms as well, +/- around 1.0 mA depending upon whether they're NOS blackplate RCA's or mil-spec JAN's.

Arjay
I biased some JAN Philips 6L6s to 35ma in my BF Pro Reverb,so I'm glad that's good to hear from y'all....and it sounds really good.
I would freak biasing tubes into the 60ma range. :shock:
I'm usually a 6V6 tubie...28ma oooohhh. :wink:


Don't confuse milliamps with millivolts. When people are talking in the 60's there referring to millivolts not milliamps. 60ma would red plate for sure.


I assumed that when you were talking about 32-34 mA you were using a bias meter which would measure each tube individually. 60 mV measured at the Fender test point would correspond to 60 mA total, correct?

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Posted: Wed Jul 14, 2010 8:51 pm
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I checked my actual bias setting tonight. I was suprised to find that it was set at the factory to 64 mV. I ran it up to 68 mV and after playing for a couple for hours decided I did not like it that high with the stock GT tubes. With my normal amp settings (guitar plugged into input #2, clean volume at 5 or 6, gain at 10, master volume at 3, guitar volume set at 10) I found that the clean channel was begining to break up with the bias at 68 mV. This was not the case at 64 mV. There was no significant difference that I could hear in the drive channel between a bias setting of 64 mV vs 68 mV. I reset the bias to 65 mV and the clean channel is back to sounding clean at my normal settings.

I will probably try one of the complete retube kits from Eurotubes in another month or so. I just have to decide which one to get.

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Posted: Fri Jul 16, 2010 12:30 pm
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I picked up a better/more accurate DVM today and am goign to try this again tonight.

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Posted: Fri Jul 16, 2010 8:07 pm
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Bill, seems like you're on the right track, by using your ears and meter. If you find the function of bias vs sound interesting, I would consider a bias probe that lets you see what each tube is doing. For years, I just used the analog and dvm meters(only toasted a couple of Fluke fuses) measuring the current and voltages, but those probes with the switches and meters are fun and a heck of a lot safer! Just my opinion. Art

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Posted: Fri Jul 16, 2010 8:54 pm
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Well, I rebiased the tubes tonight using my new DVM. I ended up setting the bias at 75 mV. The amp definitely sounds different at 75 compared to 65 mV. I haven't decided yet if it sounds better.

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Posted: Sat Jul 17, 2010 5:40 pm
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Well, after several hours of playing at the 75 mV that I set the bias to last night, I dropped it back to the 65 mV that it was originally set to. It just didn't sound right at 75 mV. Although the bass seemed more controlled at 75, the overall sound just seemed harder. At 65mV the overall sound was sweeter and "bluesier". Next month I will probably upgrade to to one of the retube kits from Eurotubes and do this all over again. But for now, with the stock tubes, I think I am done.

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Posted: Sat Jul 17, 2010 6:13 pm
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Your ears are pretty much the final setting. :wink:

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Posted: Sat Jul 17, 2010 9:47 pm
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True dat! :)

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