6V6 voltages in an express build...

[MCK]

Hi, I have a quick question. I know many have put 6V6s to good use in their express builds and so have I. It sounds good and puts out less volume making life easier at home etc... My question is with regards to the voltages 6V6s are designed to take...

The datasheets (ie http://www.r-type.org/pdfs/6v6gt.pdf) refer to 250V to 285V in a push pull circuit. Express runs significantly higher than that...

Do you do anything to lower the voltages to this range when you put 6V6s in your express build? Am I reading the datasheet wrong?

Thanks much!

[cbass]

6V6gt's will handle 400 volts no problem.Deluxe reverbs run over 420 volts on 6v6's.I have run old stock 6v6's at over 450 volts with no problems.I'm not recomending that though.

You probaly wanna check your bias just to make sure but it should be pretty close.If you have it biased for el-34's

[MCK]

Thanks for the input. I have a bunch of Bendix 5992s which are considered 6V6 equivalents and they also have 250V max listed in the datasheet so I was wondering about this before I send them harm's way! Good thing is I have the VVR installed in my amp so I can actually dial back voltages if I need to but wanted to check with you guys first... For the record, I did put in used old RCA 6V6s in my express build and adjusted bias for the 6V6 and it works and sounds great!

[cbass]

I'm not familiar with the 5992's but this guy is claiming they're no good for voltages over 400. http://www.audioasylum.com/audio/tubes/ ... 21999.html

Who knows he could've just got a bad set.

[MCK]

That was a nice link. Thanks much! I will keep the 5992 for another amp where I can ensure < 350V or so then. Have enough old 6V6GTs on hand anyways.

[billyz]

I have run good quality 6v6gt*'s at 400vdc and 20-22ma per tube for years.
the older 6v6 designs and older russian and chinese might not stand up to it for very long though.

The JJ's are not true 6v6's and can handle the higher operating conditions.

[MCK]

the older 6v6 designs ... might not stand up to it for very long though.

These 5992s I have are bone-dry NOS from 1958/1959... What do you reckon? Not worth the risk right? They're real nice tubes as they are...

[Cliff Schecht]

Yup the old 6V6GT's are some super rugged tubes. Fender (and many others) were obviously knowledgeable of this and took advantage of this fact. 6V6's run at such a high voltage really open up IMO, they can sound dark/muddy in a lower voltage circuit with negative feedback applied. Not that they sound bad like this, I just like 'em more better with higher plate and screen voltages.

It's not uncommon to buy an old tube amp that comes with good or usable original tubes, especially in the lower power amps. EL84's don't seem to be as tough as old 6V6's and preamp tubes can be all over the map, but I've consistently pulled good sets of 6V6's out of various equipment with a good success rate. EL34's seem to stay strong as well. 6L6's are hit and miss for me, for example I recently pulled a set of real 6L6GB's (the non-5881 versions) and the getters are going white..

The Express works well with good 6V6's but I couldn't enjoy the reduction in headroom. Volume doesn't drop much IME, you just lose headroom (the 6V6 grids draw current earlier than EL34 types) and change the flavor of the amp.

[Firestorm]

These 5992s I have are bone-dry NOS from 1958/1959... What do you reckon? Not worth the risk right? They're real nice tubes as they are...

Pretty valuable, too. Highly regarded for hi-fi. One look at them tells you they were built for the same guys who paid $435 for a hammer

[MCK]

Pretty valuable, too. Highly regarded for hi-fi. One look at them tells you they were built for the same guys who paid $435 for a hammer

or $700 for a toilet seat... Oh well.

[jjman]

I use the lower winding of the Toneslut tranny on mine with 6v6. 324 net plate volts cathode biased (344-20.) 35ma, 11watts each. Similar to tweed Deluxe specs AFAIK.

[MCK]

I use the lower winding of the Toneslut tranny on mine with 6v6. 324 net plate volts cathode biased (344-20.) 35ma, 11watts each. Similar to tweed Deluxe specs AFAIK.

Hmmm, too bad I cut mine short already but then again with VVR I can tune the voltages down. I just need to measure things and make a mark on the faceplate... Should work fine.

[LarryLarry]

I put a 'bias range' switch on my Express with 2 different bias resistors, one for 6V6s and 1 for EL34s. (They are tailored to the 2 sets of tubes I use)

[MCK]

I did put in a set of old RCA 6V6 and with them I was able to bias the amp using the same pot range I was using when I had the EL34 in there. Not sure if mine is the norm or an exception.

[LarryLarry]

Another photo of the label under the impedance switch and one of the OT schematic (WOT45LHR).