6W6 as a driver

[Cassiel]

6w6 as a driver

Hi guys:

I did a SE amp with NOS GE 6w6's and like the sound a lot. Now they are wired as triode with a 100 ohm resistor, there's a little blue glow in both valves, is this a problem?

Operating point is: 320v anode, 27mA dropping 38 volts in the cathode. About 8,5 watts dissp.: maximun is 10. I know 320 is over the maximun for this valve(300) but i've heard American NOS are tough and can stand the abuse. But not sure so i ask.

Another question concerning this valve. I saw the Karma amplifier wich uses this valve as a driver, saying is a sleeper? tube, very linear and very low distortion. Now could somebody provided me with operating points to use this tube as a driver? Very similar as a 45 i've read. But don't know.

Thanks in advance,

al

 

[amperex]

I did not review voltages, but a blue glow is not an issue. I read triode connected 6W6GT are linear & good sounding. You may wish to try some other manufactures as well. I seen these tubes sell for NOS at $2.50 each on epay.

 

[Sch3mat1c]

6W6's only shortcoming is low plate dissipation. Next to that it's a great tube with high current capacity, especially given the low screen voltage. The perfect vertical sweep tetrode, but then, linearity isn't bad when brought over to audio either!

Triode mode is just fine for tubes with really low Vs ratings because the plate still attracts more electrons than the screen and excess screen dissipation isn't a concern.

Tim

 

[whatsnext]

So would 6W6 make a good driver tube? I ask because I have at least a dozen NOS ones and they would look nice driving a pair of EL-34s.
John.....

 

[amperex]

Yes.....

Triode connected 6W6 are very good & linear- excellent driver tube overlooked by many audiophiles..

 

[Cassiel]

Thanks for the answers.

Ok, i will find the correct operating points in some schematic in which the 45 drives a 300b or something, have read that 6w6 can replace the 45 as a driver with no need for adjustments, other than the filament voltage.

About the blue glow...it went worse so i did some tests. It happens that when i remove the capacitor and leave the cathode unbypassed the blue dissappears I'm using a 220uf 100 volts cap. Really confused here, any ideas?

Thanks,


Al

 

[Sch3mat1c]

Geez, WTH you need a tube half as big as the output for?! Even a 100MHz transmitter, using an EL34, which doesn't really even handle 100MHz (hence my point) doesn't need anywhere near that much drive!

I've whipped 6W6s before and never noticed any blue glow, it might be parasitic oscillation? That would possibly explain the cathode bypass response. You put in a screen grid stopper resistor, right?

Tim

 

[astouffer]

Hey Tim, guess you never looked at what Sakuma did Used an 845 to drive another 845. The preamp might have been an 801, not sure. This gets me thinking about the 6W6s in my collection...

 

[Colt45]

320 - 38 = 282, 282 < 300

anyways, they can probably take a fair bit more than 300 without blowing up.

but max plate voltage is in reference to the cathode, not ground.

 

[Cassiel]

The SE6W6 is finally completed, i had a bad solder which was causing me headaches, now it's doing fine. In the future i'll try 6v6´s to compare.

Geez, WTH you need a tube half as big as the output for?! Even a 100MHz transmitter, using an EL34, which doesn't really even handle 100MHz (hence my point) doesn't need anywhere near that much drive!

Well a 6dj8 is driving the 6w6 in my amp. But i like experimenting and i thought about the possibility of using the 6w6 as a driver for another project , that´s all.

but max plate voltage is in reference to the cathode, not ground

This sentence clears many doubts i had.

This is all, i'll post the pic of my amp soon. Thanks to all who helped.

Al.