6v6 express

[wafdaddy]

Hi guys, I built an express and have been using el34's and it's a great amp but I'm wanting to try out some 6v6's in it and I have searched through the posts trying to find a definitive bias setting range for them but to no avail. I've built alot of amps but I'm no guru like some of you here and the tube data sheets I've found just confuse me on the push pull set ups. I installed the 1 ohm resistors on pin 8 of the power tubes so I can check the ma being dissipated, what should I shoot for with the 6v6's

[Structo]

It depends on what your plate voltage is.


Here is a handy chart that I refer to sometimes.

As long as you are in the window between 70% and lower, you can adjust it til it sounds good to you .

You might have to change the resistor (R31) that affects the range of the bias sweep if you can't get the bias current you desire.
But I think going to a lower powered tube you will be fine there.

http://members.shaw.ca/house-of-jim/Htm ... ables.html

[wafdaddy]

thank you so much!

[bluegate]

If your plate voltage is between 390 - 400 V then you can set the 6V6GTs at 21 - 20 mA.
If you have 400 - 410 V then set for 20 - 19 mA.
These values will set you at roughly 70% dissipation.

I use 6V6GT tubes in both my express amps.

Google: weber bias calculator for more settings or other tubes.

[paulster]

At 400V on the plates I had about 27mA at the cathode for 70% on a set of 6V6 tubes. That would have included the screens current at just over 2mA.

Based on Ken's bias specifications for EL34s and 6V6es he liked to run them really hot, so that's where I tried them. The EL34s soon went back in though!

[Structo]

Yeah, I don't generally take out the screen current in my calculations.
I just consider it a safety buffer.

[racerx23]

I just installed a set of JJ 6V6's in my express last night
I had 415 plate voltage and set the bios to 23 ma, a little hot
I won't get a chance to run it until tonight,
hope this helps.

Regards, Craig.

[2tone]

Tho Ken's brochures said you could just drop in 6v6'v and didn't need to rebias usually, I found a little rebias helped the performance. Of course 6v6's should be able to take the 400 plate volts easy. In fact, my Express with the old transformers has had 6v6's in almost since i got it, and sounds grand. It's my favorite all around rock amp..Using old RCA's and Sylvannia's mostly.

[rooster]

I run the J/J 6V6s in one of my clones and Seimens EL34s in the other. Yeah, 2tone, I read Ken's words in the literature and it does occur to me that you could find a close match and run this way. Probably this was a guiding idea here - to have an amp that you could swap EL34s and 6V6s in? I say this because he was very keen in the VG mag articles of the day to swap 6V6s out in more than a few Fender amps. Heck, the 390 plate volts Marshall MarkIIs would have been a strong candidate but I never saw him talk about this swap much. Those OT were seeing 3600 ohms on the primary though so maybe he had a different thought here.

Any, I like the 6V6s better but I also run a smaller OT in that amp, the TS 35 watt OT in the EL34 version. ....And, no, I do not have the 4/12 box with all those magic Celestions on board - which would probably have caused me to be expremely happy with the 35 watt Express and therefore never would have built the 25 watter!!!!!!

Its 24ma on the 6V6s and 32ma on the EL34s, BTW.

Hey 2tone? Did Ken ever give you a bias # that he prefered for his amps? Whether you know it or not, Glen runs his EL34s @ 40ma, and so do a bunch of people here. I would be curious, of course.

[dave g]

I run my personal express at 46 mA per EL34

I would not bias a customer's amp that hot. I only run mine that way because it happens to sound so spectacular!

[rooster]

DG - Yeah, I went to Alan Phillip's site, Carol Ann amps, and I see where he now sells power tubes. As you click on the various tubes, he has also included a bias # as well. Check them numbers out is all I can say. Clearly, I am not cooking my burger as well as I could!

But its up the the guy. Too, there is this great story told about EVH regarding that first album. I was told that he had two rather large cardboard boxes full of Mullard EL34s on hand for the session. Meaning that the bias # was so high the tubes didn't live too long. ?? I have never seen him talk about this in print but I would like to know if this is/was true, of course. Go Eddy!

[dave g]

There is definitely something to be said for running a hotter bias on amps that get their distortion primarily from the output tubes. I don't always feel comfortable going over 40mA, but if I cool them off to the 35-40 range the bloom isn't as magical.

[2tone]

Ken used to say anywhere beyween 10 and 40 ma was safe for most amps. I think he liked the expresses at around 32 ma. I had mine set for years around there, but in the last few years have bumped them up to around 40. The voltage on the tubes is still pretty low compared to other 34 amps. Some amp techs familiar with Expresses also recommend around 40, for the richest tone. But bias's around 26 to 30 have a little more clean spank i think..

['67_Plexi]

DG - Yeah, I went to Alan Phillip's site, Carol Ann amps, and I see where he now sells power tubes. As you click on the various tubes, he has also included a bias # as well. Check them numbers out is all I can say. Clearly, I am not cooking my burger as well as I could!

But its up the the guy. Too, there is this great story told about EVH regarding that first album. I was told that he had two rather large cardboard boxes full of Mullard EL34s on hand for the session. Meaning that the bias # was so high the tubes didn't live too long. ?? I have never seen him talk about this in print but I would like to know if this is/was true, of course. Go Eddy!

Thank you...its a misprint.

[breakfastbuddy]

its no set current pull for each type of tubes , its individual . a tube can have different resistence .so its no set ma value . its general depending on voltage and tube resistence