6v6's in a 1987x???

hot_tube_tone · Post by **hot_tube_tone** » Thu Dec 14, 2006 10:41 pm

I was wondering if it is possible to replace the EL34s in a 1987x with 6v6s. I have added a PPIMV to it, but if it was running on 6v6's then I don't think that I would need it. Just wondering. Small clubs + big amps = pissed club owners. If it is possible please give a little insight into value and wiring changes that would need to be done.

Thanks in Advance!!!

tooloud · Post by **tooloud** » Fri Dec 15, 2006 7:12 am

look at the schematic here for 6v6 plexi from mark huss
6V6 Plexi

novosibir · Post by **novosibir** » Fri Dec 15, 2006 7:55 am

A 1987x is about 450V B+ and that would kill even NOS 6V6's.

The B+ where 6V6 are reliable and are sounding good is from 320V up to 380V.

Shure, the Jim Kelly amp was running four 6V6 w/ a B+ of 490V

(a voltage, where russian 6V6's would die within a minute), but this amp literally was 'eating' tubes

There's a way to lower the B+ of your amp w/o the need of another PT - the zener trick - but I don't know, how knowledgeable you are, to make the tweak by yourselves.

Larry

sweetwilliam · Post by **sweetwilliam** » Fri Dec 15, 2006 3:52 pm

I heard somewhere that EH6V6's can handle close to 450v on the plates. Anyway, I built a plexi-style amp with 6V6's and it sounds great. It would be cool if you could find a PT to fit your 1987 chassis that supplied the right voltage. I got mine out of an old radio console and put it in a custom chassis.

stoo · Post by **stoo** » Sat Dec 16, 2006 9:58 am

JJ claims their 6v6 can handle" 450V in triode mode and 500V in pentode mode". I have a set and ran them for a month or so at 440v and they survived.
Stew

hot_tube_tone · Post by **hot_tube_tone** » Mon Dec 18, 2006 1:42 pm

So what I am hearing is that I can get some JJ 6v6s and install them without any mods? What would I need to set the bias to?

Bow · Post by **Bow** » Thu Dec 21, 2006 10:36 pm

stoo wrote:JJ claims their 6v6 can handle" 450V in triode mode and 500V in pentode mode". I have a set and ran them for a month or so at 440v and they survived.
Stew

Yup

I run JJ 6V6's in my homebrew amp with a JCM-type power section with 475V on the plates.

no sweat... it it gets pretty fooking loud

JimmyR · Post by **JimmyR** » Sun Dec 24, 2006 10:21 am

What does it sound like? I am very interested in this idea! Would you bias them at 25mA?

stoo · Post by **stoo** » Sun Dec 24, 2006 10:54 am

JimmyR wrote:What does it sound like? I am very interested in this idea! Would you bias them at 25mA?

I thought they sounded like a 6L6's little brother. A little extra compression but still with chimes.
The JJ6V6 is a 14 watt tube IIRC. So your bias is plate voltage times cathode current equals (.7 x 14) 9.8 watts.
Stew

kannibul · Post by **kannibul** » Sun Dec 24, 2006 10:20 pm

novosibir wrote:A 1987x is about 450V B+ and that would kill even NOS 6V6's.

The B+ where 6V6 are reliable and are sounding good is from 320V up to 380V.

Shure, the Jim Kelly amp was running four 6V6 w/ a B+ of 490V (a voltage, where russian 6V6's would die within a minute), but this amp literally was 'eating' tubes

There's a way to lower the B+ of your amp w/o the need of another PT - the zener trick - but I don't know, how knowledgeable you are, to make the tweak by yourselves.

Larry

JJ's 6V6 is insanely over-built compared to spec. They could handle it

novosibir · Post by **novosibir** » Mon Dec 25, 2006 5:52 am

kannibul wrote:JJ's 6V6 is insanely over-built compared to spec. They could handle it

Interestingly!

But I'd at least recommend, to increase the screen resistor value to 2.2K, to reach an acceptable longevity.

Larry

Bow · Post by **Bow** » Mon Dec 25, 2006 8:02 pm

JimmyR wrote:What does it sound like? I am very interested in this idea! Would you bias them at 25mA?

Well, I have a 4 gain stage preamp, so it rocks.

I have yet to open it up too far yet, do to my wife threatening me with bodily harm....

But to me it sounds good.

I have them Biased to around 16ma

jcs · Post by **jcs** » Sun Jan 28, 2007 2:44 am

with the variac set to about 105 volts i occasionally use nos 6v6gt in my 71 marshall small box 50..

my 71 has a later drake power tranny, i have no problem getting the plate-screens down to safe territory with the variac..

i would describe the tone as smaller and kind of like what i hear in older ampeg amps..

kind of a raw bark versus a big mean roar with mullard el34s in the same amp

not a bad workable tone at all just doesnt have the punch/power of el34s

Gabel · Post by **Gabel** » Sun Feb 04, 2007 5:27 pm

You can put a set of THD Yellow Jackets in there, they will work really well!

guitronics · Post by **guitronics** » Tue Feb 20, 2007 3:14 am

A zener ain't gonna do it.They won't take the current...and I don't know if you can find one for 300+ volts!

Best bet is to use a big honkin' wire-wound power resistor, an adjustable one.

Be careful with that much voltage!