Your journey with lower-watt tube amps -- Can a kit be good enough?

@sns To be clear, the Klipschorn rolls off sharply below 45 Hz.

The older Klipschorns are not designed to be driven by an amplifier that has a low output impedance like an ST70. You'll know if your speakers are like this (the Klipschorn has been in production since the 1950s which is a bit of a record) if there are level controls on the back for the midrange horn and tweeter.

SETs are a technology which I call the Power Paradigm. PP amps like the ST70 are Voltage Paradigm technology since the ST70 employs enough feedback to allow it to behave as a Voltage source. IOW this has to do with the output impedance of the amplifier; whether or not its low enough for the amplifier to behave as a Voltage source. If your Klipschorns have level controls, essentially they are Power Paradigm technology also and there will be tonal aberrations if you try to use them with an amp that is Voltage Paradigm.

For more on this topic see http://www.atma-sphere.com/en/resources-paradigms-in-amplifier-design.html

@hilde45 

congratulations. The first thing I would do is upgrade those footers. 

@hilde45 Nice! I'll be interested to hear your comments. I saw that amp on ebay as well and really had to think about buying it just so I could see how far I could push it.

A couple of friends I helped with on their Altec-Onken 102 db horn speaker creations use modified ST35s on rotation when taking their custom modified AudioNote 300B amps out of the loop. They seem to like them and use them quite a bit to save their WE300Bs. I demoed one once, it was different sound from other amps I've tried in my system.  Fairly plush sounding too.  

@decooney , @hilde45 , One weakness of that amp is seen in the schematic.

The 4 power tubes share a single resistor (bypassed by a capacitor) to set up the bias of the output tubes. There really should be a resistor and cap for each output tube pair. This was a space and cost saving move on Dynaco's part.

That's a pretty well known issue in this amp and the SCA35 which uses the same transformers. By separating the channels in this manner the amp performs and sounds better.