To Tube or not to Tube, that is the question

However, the ST70 uses a pentode for this task, where the ST70 uses a much more linear triode.

@atmasphere  This seems to be a typo, did you mean theST35 is a linear triode?

BTW I read your article on amp design paradigms this morning. Good Stuff! I think your thoughts are along the similar lines as Nelson Pass's on this subject, no? Meaning that his Firswatt designs are an exercise in creating tube sound with solid state components. 

I really respect when creator's like yourself willingly and openly share thoughts on design and function. It helps keep this hobby from being a total marketing exercise.

This seems to be a typo, did you mean theST35 is a linear triode?

@bruce19 No.

The feedback is taken from the speaker terminals and then applied to an early point in the amplifier circuit; in this case the cathode of the input tube. In the original ST35 circuit, the input tube was a 7247, which is a dual triode 9-pin signal tube with one section being that of a 12AX7 (the input voltage amplifier) and the other being that of a 12AU7 (for driving the power tubes).

By contrast the ST70 uses a tube that has a pentode input section, which isn't as linear. They were able to get away with using the 7247 in the ST35 since the EL84 power tubes are so much easier to drive than the larger EL34s of the ST70, so less gain was needed.

Clear as mud??

If the ACA's work with the F6's you might look into the Elekit 6L6 based single ended amp kit.

It's well reviewed and still available at various vendors for around $900 (link is for details/specs).

Looks like a lot of the amp "kits" are out of stock (including the Dynaco re-pops mentioned).

DeKay

Found a ST35 kit in stock, but not familiar with it.

http://www.tubes4hifi.com/ST35.htm

DeKay

@dekay 

Thanks but the ST35 is also available from Dynakit directly. I learned this when I gave him a call. Seems the business has been paired back to a one man operation from home and he prefers to take orders by phone. Apparently he has not updated the web site, but the owner seems like a very nice fellow. He had one available for me but I was not quite ready to order yet.

@russ69 Thanks for that comment. It kind of helped bring into focus the fact that for me the desire to build something new is at least as much of a driving factor in this as any new sound I will experience. I notice that very frequently the momentum at Audiogon is for buying something new regardless.