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In Reply to: Thoughts on (modified) Dynaco ST-70? posted by Q on February 25, 2007 at 08:30:00:
You might look for some Advents or KLH's that were designed with this kind of tube amplification in mind. A lot of modern speakers are too demanding for this amp and you end up with muddy bass and rolled-off highs.I ran a stock Dyna ST-70 for 30 years with a pair of KLH-5's, and was completely happy with the sound.
More recently, I rebuilt both. Still happy with the sound, although the ST-70 now has a different driver board and modern parts, so it's quite a bit different. The rolled-off highs are no longer truncated, and with power supply upgrades, the bass is stronger too. But the midrange magic is still there (the real joy of this amp).
Do you know if any circuit modifications were made to yours or just parts subs?
In any case, looks like a good deal, and should give you years of pleasure. Mine has, since 1968... Can't argue with that!
Follow Ups:
The caps, resistors, tube sockets were replaced, but the circuit is original. I think this amp with the Heresys will make a good match - hope so.
I used my Dynaco for a brief while with Klipsch Cornwalls and liked the sound a lot. I think you'll be pleased! And you should never run out of amp headroom either, which is good for longevity of both amp and speakers.In fact, you might think about wiring the amp in triode (or having your tech do it, if you're not comfortable doing the mod). It's about $2.00 in resistors and some wire, easily reversible if you don't like it. But I think you might.
Just my $.02
You can check out posts on the Dynaco in triode mode in the Dynaco Doctor forum here on AAHere's a clip from that board:
Posted by Killer Tomato on November 09, 2005 at 20:45:48
In Reply to: Simple ST-70 mods posted by BigErik on November 9, 2005 at 17:12:45:
The triode mod is probably the simplest of them all without changing anything on the circuit board. All you have to do is place a 100 Ohm resistor between pin 3 and 4 of each output tube and remove the ultralinear taps. This allows the EL34 to run in triode mode instead of the stock ultralinear. Power output will be reduced by half and dynamics won't be as powerful but the mids really shine.
HTHFrank
I'll keep it in mind. Seems that the Dynacos are great for tweaking, but I haven't got it yet - want to see what it sounds like. It's already been tweaked by someone with much more experience than I. My guess is that it sounds pretty good as is. Later on though....
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