Ceriatone Forum

Interested to know what your bias readings are and whether you have experimented with alternate values.

TIA

Hywel Harris

around 9-10.00 gives enough of what i like...laurie   i have done a few mods though

You are referring to power tube biasing, I think. If so, then I can say that the Tung Sol 6L6s that Nik supplied, sound the same to me anywhere from 25 to 35. I keep them at 30 based on my amp tech's advice. I am currently running Tung Sol 5881's at 35-36mA. They sound fine, I think I like them a little better than the 6L6s. I have been wanting to try some TAD 6L6WGC-STRs  (short bottle like the 5881s). They were my favorites in my super reverb, very musical, nice sparkly natural overdrive, not the most clean headroom. I biased them at about 35mA in the SR but it was running close to 500 volts (and they only lasted about 6 months). I would try them at 30-35mA in the OTS. My experience that that bias does not effect tone except near the extremes of the range and if you operate out there you are burning up tubes or damaging other components.

im running tung sol 5881's at about 37mA they sound pretty good but i think they lack some headroom

I've got my Winged C's biased at 37~38mA.  Headroom is good, but I run the internal trimmer low & keep the clean volume around 7.5.  OD Vol & Ratio is set conservatively, too.  I live on the OD channel with my Gretsch & OD + PAB with my Les Paul.

Sovtek 5881 at about 34-35mA

At 235v wall voltage I get a plate voltage of 449 v.
My bias setting is 38 mA with Tung-Sol 6L6 GC str. I bias my amp after 15-20 min when voltages are not fluctuating any more due to heat in the amp.

I experimented with 30-35 mA it's too cold, less harmonics, no singing notes.

40mA is over the top; the bass response is way too heavy with that setting.

hm maybe I should turn it up a bit.

Tung Sol 6L6 GC

455V on plates 36mA last time I measured.

I use to have it a little higher but I dropped it a little and it sounds fine to me.

What made me ask was this I read on Eurotubes 
http://www.eurotubes.com/euro-l.htm#5 (http://www.eurotubes.com/euro-l.htm#5)

Going as high as 55mA with plate voltages of 485v. But then he is in the business of selling new tubes :-)

I'd be interested in hearing the tone at that level but would be wary of doing it myself!

What I've always been confused about is the fact that no matter where you set the bias, when you are actually playing through the amp the bias current is jumping all over the place. While it is recommended to set the bias at 70% maximum plate dissipation for that tube, you still will occasionally exceed that 100% max plate dissipation value during actual operation of the amp.

Has anyone actually used the JJ 6v6's and where did you set the bias for them?

I would give Bob at Eurotubes a strong recommendation. His tube matching is consistently impeccable. His recommendations have always been right on. I have spoken to him in person a couple times and believe tubes and customer service are this guy's life. He is so busy that the last thing he would do is mislead somebody to sell more tubes. That said, I can see no reason to bias that hot, even if Bob says its OK.

Winged C 6L6 at @ 38ma

Jim

Tube amp doctor 6L6WGC-STR @ 37-38 mA

How are the TADs working in your OTS?

They were a big improvement compared to the Tungsol's I got from Nik, but then again I don't think those Tungsols were a 100 % ok. I just built my second Ceria overtone for a friend, and this amp was equipped with JJ 6L6, and we did a quick comparison, and we both agreed that the TAD's opened the amp up a little more, and there was a more defined bass response..

Both amps were equipped with NOS ECC83 (mullard tubes), and the V1 and V2 preamp tubes makes a big difference in sound compared to the powertubes... So I would start with the preamp tubes

Thanks for the feedback. I burned out 2 sets of the TADs in my Super Reverb over the course of about year. But they sounded great in that amp. I am going to get some for the OTS.

I agree about the effect of the pre-amp tubes when going from really bad tubes to good quality tubes. I have about 30 spare pre-amp tubes, and about a dozen NOS tubes, including Mullards. But I still find myself going back to the JJ ECC83S all the time.