Pool clone output tranny problems

[PeteRH]

I have a 5K heyboer output tranny installed in my liverpool clone (4-EL84 output section).
If the tranny is set to 5K, with the amp running flat out the oscilloscope shows the resultant square wave with quite a few horizontal lines at the peaks. Very messy looking. Winding back the amp the peaks start to get crisper and then at 28 watts without any distortion the signal is crisp as!!
If I set the tranny to a 2.7K impedance the signal is crisp and one line even when running flat out.....and still basically puts out 28 watts RMS.

Noting the Vox AC30 runs 4.2K impedance I thought the 5K would be fine. Ken seems to run the Express amp with a higher than normal impedance and I assumed 5K on a liverpool would be fine.

Has anyone experienced similar findings running 5K or 6.6K trannies?

Can anyone advise what is happenning to get this hash on the scope when running the OT at 5K? Doesnt look like a parasitic.

Is anyone running the 6.6K trannies in their Liverpool clones? Are you intentionally mismatching speaker taps to run 3.3K?

I have not tried the 2.7K impedance other than on the scope so cant really comment on how it sounds....but am lloking forward to trying this at volume. maybe tomorrow if I get home from work early enough.

Cheers
Pete

[Funkalicousgroove]

I can't speak from experience, but from the Data sheets on a GE 6BQ5 it seems to operate about the same from 5K to 6.6K as far as overall distortion goes, and even higher distortion in the 3.7-4.2K range (Vox)- With this topology of 1+2 I get funny things on my scope too, but the amp IS designed to distort, so that could be what you're seeing as you crank it.

[PeteRH]

Doing some more research I notice that the matchless Lightning runs 4K with two EL84 This equates to running the 4-EL84 at 2k load impedance!!!...and the guys are loving it.
If they can run at that low an output impedance my 2.7K can not hurt. I think I will just try and hear what sounds better.

I still wish I knew what all that hash on the scope was. Maybe it is what a Pool should look like....but it doesnt seem right.

Cheers
Pete

[goodtone77]

the matchless dc30 runs 4k on the output transformer. only the lightning is mismatched with 4k to 2el84, if you switch the low power switch in the back of a dc30 disconnecting two tubes you get 4k on 2xel84