Dynaco ST-70 Clone

[slovell]

I have a Dynaco ST-70 clone with the VTA board. Can I use KT88's with this amp and, if so, would I gain any power? Is it even worth it? I've got the tube rolling itch again.
Thanks, Sam

 

[NOSValves]

Is that an aftermarket power transformer or the original Dynaco? If aftermarket what is current specifications on all taps? If its an original Dyanco power transformer I wouldn't take the leap to KT-88 if I was you.

EDIT: corrected would to wouldn't sorry for the brain cart on my part.

 

[Tom Bavis]

The heater current of KT88s is only slightly higher than EL34s, so that shouldn't be a problem. The idle current shouldn't be increased with a stock ST-70 transformer, but some of the aftermarket ones might take it. Might be necessary to change some parts in the bias supply to get them to idle where you want.

There won't be much more power, if any. KT-88s can deliver more power with a higher supply voltage and/or a lower transformer impedance. Looks like you already have a SS rectifier. Operated within the EL34 ratings, they should last a long time. And the transformers are likely the limiting factor at bass frequencies - the Dynaco ones will saturate above 35W at 20 Hz, don't know about the Edcors.

 

[slovell]

It's an original Dynaco power transformer as far as I know.

 

[crispycircuit]

Looks like a fun amp. I've never seen the front knockouts still in place. An after market chassis? The pwr transformers also looks like a beefed up aftermarket. Somebody spent some money for a custom ST-70. How does it sound?

 

[slovell]

It's a clone built with all new parts, chassis, and wiring. Sounds really sweet, distinct highs, full midrange, good bass. Much better in stereo the my Adcom 5500. I bought it off a guy on A'Gon for a bit over $500.