I bought an Eurotubes Pro One Bias Probe.

leadfootdriver · Post by **leadfootdriver** » Sun Mar 30, 2014 3:48 pm

I did away with the 1 Ohm resistors, and installed a PEC locking bias pot. This bias probe is really nice to work with. I always hated pulling the amp out of the chassis to bias.

I think I like a colder bias in this amp. Everything seems to hold together better. Check it out.

http://www.tonefinder.com/files/561396193725-TWVOC.mp3

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rooster · Post by **rooster** » Sun Mar 30, 2014 5:20 pm

That's the Heyboer OT, right? What are you tubes, btw? And when you say colder, what's that number in mas?

leadfootdriver · Post by **leadfootdriver** » Sun Mar 30, 2014 5:24 pm

Those are Chinese EL34's and JJ ECC83 MG's. The tone in that recording was biased at 50%

Classic Tone tranny's.

rooster · Post by **rooster** » Sun Mar 30, 2014 5:32 pm

Thanks for the info. Yes, I forgot, you were digging those MGs. 395 plate volts, you're at 34 mas?

Is this the ClassicTone TW OT?

leadfootdriver · Post by **leadfootdriver** » Sun Mar 30, 2014 5:35 pm

I think the actual bias voltage is a bit different for each set of tubes. But mine figures at 31.2 ma's.

rooster · Post by **rooster** » Sun Mar 30, 2014 6:22 pm

Alright, thanks for that, LF. I have also reduced my bias voltage and changed my power tubes, running the Mullard xf2 single getter and running them at 28 mas. I also changed out my pres with some Amperex and Mullard versions.

It has been suggested to me that even 20 mas would not be out of the question with these tubes and this amp but I tried 24 mas and I didn't like it that much. Nice clip BTW, but the verb you are using adds a slight metallic ring to things, not pretty. Ha, upgrade your recording process, not your amp maybe! If you want to hear what I'm talking about, send me a Dropbox link to a clip without any verb and I will add something to the clip that will explain things. Ha, or not. Take care.

leadfootdriver · Post by **leadfootdriver** » Sun Mar 30, 2014 6:44 pm

Thers no reverb on the guitars.

Structo · Post by **Structo** » Mon Mar 31, 2014 12:35 am

Man, that clip sounds awesome!

For what it's worth, I use those PEC locking bias pots in several of my amps.

Seems to be a good stable pot.

You can lock it down a bit and still adjust for fine adjustments.

leadfootdriver · Post by **leadfootdriver** » Mon Mar 31, 2014 2:55 am

Thanks! I got a 50k for my Jet City combo, and have been playing with the bias on that amp too.

pleasantbullet · Post by **pleasantbullet** » Mon Apr 07, 2014 2:19 pm

That amp is a beaut! Sounds great too.

Curious. I was thinking of doing the same, chassis mounted bias pot.
Is there anything to take into account when doing this?

wiring, proximity to other parts etc..

any info would be great. I get my triode kit next week.

I was a bit nervous about getting the classic tone trannys, but after hearing your beast. I'm pumped!

was your express a triode kit?

leadfootdriver · Post by **leadfootdriver** » Wed Apr 09, 2014 4:57 am

No, I pieced everything together.

I don't think there's any capacitance problems since the bias is in a negative voltage. That said, I picked an available spot, and avoided any parallel runs near power were possible. I don't have a pic of it in the Wreack, but I do have one of my JCA5012C that I did recently.

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