Tube gurus: please help re. a bias setting question

[tommy_is_here]

Hi Tube Gurus,

 

I just got a sweet pair of NOS RCA 6v6 GTs. These are my 1st NOS tubes and I'm very excited about putting them into my point to point rebuilt Deluxe Reverb amp.

 

Now, I have a Weber bias rite, and I know how to make the bias adjustment. I am wondering at what setting I should put these tubes at? My current reading for the amp, which has Tunsol Reissue 6V6s is somewhere at:

 

plate voltage: 436

current: 26.4 ma

 

I have read that NOS need to be biased a bit higher (up to 30ma) so that plate voltage can run at 425. However, I just did the experiment with the Tungsols, adjusting the bias to 30M, but the plate volt never was still above 425...

 

Any suggestions? I want to make sure I don't damage these tubes.

 

Cheers,

Tom

[Casey4s]

 

Hi Tube Gurus, I just got a sweet pair of NOS RCA 6v6 GTs. These are my 1st NOS tubes and I'm very excited about putting them into my point to point rebuilt Deluxe Reverb amp. Now, I have a Weber bias rite, and I know how to make the bias adjustment. I am wondering at what setting I should put these tubes at? My current reading for the amp, which has Tunsol Reissue 6V6s is somewhere at: plate voltage: 436 current: 26.4 ma I have read that NOS need to be biased a bit higher (up to 30ma) so that plate voltage can run at 425. However, I just did the experiment with the Tungsols, adjusting the bias to 30M, but the plate volt never was still above 425... Any suggestions? I want to make sure I don't damage these tubes. Cheers, Tom

 

 

 

 

Most people bias at 65 or 70 percent.

 

Those 6V6 tubes are rated at 14 watts maximum plate dissapation.

 

So if your plate voltage is 439v, divide that into 14 (watts) and you get 0.03189 amps or 31.89 mA.

 

Multiply that by .70 and you get 22.32 mA (70%) or if you want to go 65% multiply 31.89 by .65 and you get 20.72 mA.

 

That's for each tube.

[tommy_is_here]

Thanks Casey!

 

I biased at 22 ma, which was less than 70%.

 

Tubes sounded amazing. Really lush, full and with a very smooth EQ curve across the board. Only problem: I noticed while playing that these tubes have filaments that rattle at certain frequencies. Its annoying, so I'll be returning the tubes. (unless someone has other suggestions)

 

Do a lot of NOS tubes have this issue (filament rattle)? I purchased the tubes from a reputable dealer.

 

Thanks,

Tommy

[Casey4s]

 

Thanks Casey! I biased at 22 ma, which was less than 70%. Tubes sounded amazing. Really lush, full and with a very smooth EQ curve across the board. Only problem: I noticed while playing that these tubes have filaments that rattle at certain frequencies. Its annoying, so I'll be returning the tubes. (unless someone has other suggestions) Do a lot of NOS tubes have this issue (filament rattle)? I purchased the tubes from a reputable dealer. Thanks, Tommy

 

 

No that is not a common problem with the RCA's in fact this is the first time I have heard of that in those tubes.

 

Some other great NOS 6V6 tubes are Real Tung-Sols, Brimar (British) and Mazda (French).

 

I put the Bimar in my DIY 5E3 Tweed Deluxe, I put 4 of the Mazda's in my DIY 5F6A Bassman variation and the Tung-Sols in a DIY Princeton Reverb variation. All of those tubes sound fantastic.