KT77 bias in Dynaco ST-70

[BuzzK]

I think I might have an issue with my old Mullard EL34s after all. :tears:

So I think I might try a quad of Gold Lion KT77s.

Dyna ran the original Mullards at 50 mA each.

What do folks recommend for these?

Thanks.

Buzz

 

[goldear]

The new gold lions sound better overall to my ears than do the old Mullards. Although I've recently been comparing a number of the current-production modern EL34 equivalents on my HF-89, and frankly, my favorite of the bunch which I have tried are the JJ KT77s. My second favorite is a tie between the gold lions, and the Svetlana EL34s.

IMO the JJs have a more "magical" sounding midrange, but the gold lions are probably more accurate-sounding.

 

[quadtech]

I bias them at 40ma and they sound great.

 

[Tom_r]

I bias my GL KT77's at 45mA each

 

[BuzzK]

Thanks y'all!

 

[Westy56]

I could never get the bias reading below 1.68 with 6L6GC's in a stock circuit.


Steve

 

[Kegger]

You would want to bias them to 45-50ma each for best performance.

 

[GordonW]

I'd tend to hit about 45ma. Good balance between not over-running the plate dissipation, and still having enough current for good sonics.

Regards,
Gordon.

 

[mech986]

You might want to review dcgillespie's thread about the ST70 and maybe ask about the KT77 in that application.

 

[goldear]

I could never get the bias reading below 1.68 with 6L6GC's in a stock circuit.


Steve

I thought that 6L6GCs screen voltage rating was a little low for safe use in an ultralinear configuration at that high of a voltage. I believe that to safely use 6L6s in a stereo you need to have a regulated screen (true pentode mode), with a lower voltage, like Audio Research did with their stereo 70 mod kit.

 

[Westy56]

I thought that 6L6GCs screen voltage rating was a little low for safe use in an ultralinear configuration at that high of a voltage. I believe that to safely use 6L6s in a stereo you need to have a regulated screen (true pentode mode), with a lower voltage, like Audio Research did with their stereo 70 mod kit.

I put about 600 hrs on a quad of C's knowing that they were running a little high.
The tubes still sound nice in another amp for now.

Bob [dynaco guy] gave some advice how to run 6l6gc's/kt77's, but
I forgot what he said.

 

[sled108]

My GL KT77s run on 50mA each, and sound Great.

 

[derekva]

I'm running about 45mA, but have thought about bumping it up to 48mA or so.

-D

 

[MRL_Audio]

I bias my GL KT77's at 45mA each

+1 here.