Hi all,

Would anyone have an output transformer for a Pioneer SM83 - type number AT6123. I believe it is a 7K split primary (push pull load for a pair of 6AQ5's) to multiple impedance output (4 to 16 ohm: 4 wire). It is a fairly compact transformer - 78mm x 65mm x 65mm. I realise I may have to get it rewound, but thought I would ask here first. I believe many of the quality 60s and 70s pioneer tube amps have these transformers. I have larger transformers that would work, but too big for the case. Happy to swap or buy etc.

Robert

Rob, I believe this will work:

http://www.altronics.com.au/p/m1136a-10-60w-100v-line-pa-ei-core-transformer/

Yes it's designed for PA work but it has been used as a PP output transformer with success by many. No good for a SE amp due to the lack of an air gap but it should work just fine for PP application where the DC magnetisation currents are canceled out. I'm about to try it driven by a pair of 6GV8s (no, not 6GW8s).

Thanks Ian,

I'll have a look at that tranny.

Rob

Hi Rob.

I made a mistake with the part number of that transformer. That one won't work for you.

The one that will is the M1120. I have one running at the moment with a pair of 6BQ5s in ultralinear mode (screens to primary taps). The connections are:

1.25W - upper plate
2.5 W - upper screen
5 W - B+ (315V in my case)
10W - lower screen
C - lower plate.

8 ohm load is connected between "4 ohm" and "16 ohm".

This prototype I'm working on has a long-tail-pair splitter driving the 6BQ5 grids using fixed bias via cathode followers. It's making just under 25 watts RMS at the onset of clipping. The cathode followers are to allow class B type drive (i.e. into grid current) - without incurring bias pump-up and resultant crossover distortion. I'm aiming for an amp that overdrives cleanly, with predominantly even harmonic distortion. The performance of that transformer is impressive.

So I think the M1120 will work in your SM83.