Svetlana 6L6 Bias BDRI

[Jon Barr]

Hello all,

I switched tubes in my BDRI. Jan Phillips 5771 (v1), tungsol ax7 (v2) and tungsol AT7 (v3). Power tubes are Svetlana 6L6gc. After playing for an hour the bias is reading 92.3V. Is this too high?

The Svetlanas are orange and a slight blue colour. Pre amp tubes are orange. No red. It’s a nice sound and I’d like to keep it around this setting, just don’t wanna cook the tubes out too fast. I’m on a poor mans budget lol. If anyone could chime in, that’d be great, special thanks!

Jr

[Gtrjunior]

Re: Svetlana 6L6 Bias BDRI

What’s your plate voltage?

[Jon Barr]

Re: Svetlana 6L6 Bias BDRI

With the amp in standby the reading is 58V. With the amp fully on, the reading is 92.3V

[Gtrjunior]

Re: Svetlana 6L6 Bias BDRI

Plate voltage is typically +\- 500v. I’m not familiar with your particular amp but all 4 of my tune amps read somewhere in that region (el34).
I suspect your not reading the voltage correctly.

[Lake Placid Blues]

Re: Svetlana 6L6 Bias BDRI

What is a BDRI?

[Gtrjunior]

Re: Svetlana 6L6 Bias BDRI

Not your exact amp but I’ll bet it tells you what you need to know.

https://youtu.be/19IUadZJf-c

[Gtrjunior]

Re: Svetlana 6L6 Bias BDRI

What is a BDRI?

Blues deluxe reissue I’m assuming.

[Gtrjunior]

Re: Svetlana 6L6 Bias BDRI

More info backing the setting in the video.

https://forums.fender.com/viewtopic.php?t=41432

[Lake Placid Blues]

Re: Svetlana 6L6 Bias BDRI

After looking up some information, the test point is for both tubes. The plate voltage is about 410v. With 6L6GCs, 92ma (mv = ma in this case) is 46ma per tube which is 63% of the plate dissipation. That's safe and not too hot or too cold.

[JMP/HBE]

Re: Svetlana 6L6 Bias BDRI

Pretty clear you don't know what you're doing.

Take your amp to someone who does.

[Jon Barr]

Re: Svetlana 6L6 Bias BDRI

Thanks for the help guys! The bias at 92ma seems hot but no cherry red. My strat sounds fuller. The 59 humbuckers in my sg really push the amp at this bias. There’s lots of distortion and overall much louder. Is this normal?? I’m thinking it’s just the hotter output of the Hums and there breakin up. Please correct me if I’m wrong.

Jr

[Gtrjunior]

Svetlana 6L6 Bias BDRI

Thanks for the help guys! The bias at 92ma seems hot but no cherry red. My strat sounds fuller. The 59 humbuckers in my sg really push the amp at this bias. There’s lots of distortion and overall much louder. Is this normal?? I’m thinking it’s just the hotter output of the Hums and there breakin up. Please correct me if I’m wrong.

Jr

Your bias is waaaaaaay too hot man. 60mA
Didn’t you watch the video I posted?

[JMP/HBE]

Re: Svetlana 6L6 Bias BDRI



"She was sounding really good just before the smoke & flames."

[Lake Placid Blues]

Re: Svetlana 6L6 Bias BDRI

It depends on the actual plate voltage of the specific amp. And if the power tubes are a matched pair. Reported plate voltages vary quite a bit from around 400v to 455 volts. So take it to some one that can safely measure the plate voltage of your specific amp.

[Lake Placid Blues]

Re: Svetlana 6L6 Bias BDRI

Don't scare the OP. 30 ma per tube is only 60% if the tubes are 5881s and the plate voltage is as high as 455. If the tubes are 6L6GC then it's less than 50% plate dissipation, even at 455 plate volts. That's pretty cold. But the tubes are more likely to last past the warranty. As the current increases the plate voltage will drop some too.