Output Transformer vs. Caps?

[Tickwomp]

Hi all, 

I can't leave well enough alone and looking for something to do over the upcoming Holidays.  Has anyone replaced/modified their Foreplay to use transformer vs. the output cap section?  Looking for to step it up a notch. 

Thanks,

Tick

[Paul Joppa]

Yes, indeed. The usual approach is to remove the cathode follower entirely, and use the output cap as a parafeed cap from the voltage amplifier stage to the output transformer. One of the Magnequest B7 15K:500 transformers would be excellent, but Edcor makes some quite inexpensive units that are quite acceptable, especially for experimenting. A layout like the SEX amp provides good immunity to hum pickup from the power transformer.

Forum member richardl has done this - in fact, he then built another one using the Paramount upgrade kit (with 5670 tube, running higher voltages). Most listeners (including myself) think this is an improvement. The presentation is different, and there are a few losses to set against the many gains, so no guarantees!

If you do it, remember to give the transformers some time to break in - something like 100 hours is good. Also, experiment with the parafeed capacitor - Richard went as high as 24uF to (subjectively) optimize the bass.

[pro_crip]

Just curious, would this mod work with 6cg7 tubes? Thanks for listening.


Rich

[Paul Joppa]

Yes.