Classic Tone Trainwreck OT question

[SilverFox]

As I recall Classic Tone has a good reputation. I'm in the process of putting together a stereo power amp based on the Sunn 100s output section, but using 6L6's running at B+ 450. The OT's won't be UL. I was looking at the Classic Tone Trainwreck OT with 6.6k primary as output. Is there any reason I should not use these in this build? I've got a 100 watt PT that will likely end up in the power supply.

silverfox.

[pdf64]

Surely, at 30 watts, that OT is under rated for the application?

[SilverFox]

Yes I realize the PT will be sufficient and the one I have on hand is from a Carvin 100 watt, MTS 3200. I want to make sure Classic Tone is a good buy and the 6.6k is a good match for the 450 B+.

There also will be two on the chassis as this is a stereo power amp; so 60 watts total. I'll delve into the power supply design next.

Thanks pdf,

silverfox.

[BLT]

There's nothing wrong with Classictone. I've used many with great results. I've seen impedance at around 4k for 2 6L6 at 450V. I think that your standard Express OT is a bit under powered for 2 6L6 at 450V. I think that the minimum rating is about 50W. But it is early here and my math skills get better as the day wears on.

[M Fowler]

You guys think that 300mA is under rated?

[pdf64]

Is this intended for hifi or a stereo guitar rig?

[SilverFox]

I'm putting together a stereo power amp for guitar. I think I finally got all the bugs worked out with the 6L6 version of that Sunn 100s amp. My intentions are to run two of the Classic Tone 30 watt TW OT and use the PT from a Carvin MTS 3200 100 Watt amp.

I had forgotten the 6L6 biased correctly will put out 23 Watts ea. Glad I checked since this sounds like, without some sort of current limitation I could fry two OT, over hard! Course that's only if I ever turned it ALL THE WAY UP!

Perhaps I should consider a different OT. Something in the 40 watt range? Or a different PT. I'm trying to save $100 or more on the PT.

silverfox.

[M Fowler]

Those classictone TW OT and PT are conservatively rated at 30w.

That PT is 300mA and I am quite sure that OT is good for 50w or more.

[SilverFox]

I finally bought the trannies a couple weeks ago and received them from Amp Parts Direct in FL. Great service.

They are 6.6K and as far as I know I'll be running them at 450 VDC B+. The output tubes are likely going to be JJ 6L6. Seems like 450 V is high but I've seen them run at much higher in the GC version of the tube. And yes they look much more than 30 watts.

Any precautions here with the 6L6 at those voltages?

Thanks for the feedback on the original post. The amp build is underway.

silverfox.

[David Root]

Running two 6L6GC into a 6k6 primary rather than ~4k will drop the output power somewhat. 450V on current production 6L6GC should be OK but one never knows. You might want to drop the screen voltage a bit with 2k2 to 4k7 screen resistors.
That OT should be fine currentwise if it's rated for 300mA.

At that voltage it could be safer as well to put in three flyback diodes on each side of the primary, like in a TW Express. Flyback voltages increase with above optimum power output primariy impedances.
Express runs only at 400V, not 450V, but into EL34s not 6L6GC.