Review and Measurements of Dynaco ST 70

[Deleted member 87496]

It was actually my ST-70 that got reviewed and I also had a PAS-3. I think ST-70's are fine for tube amps and if there was such thing as tube sound, which I don't believe, then it would come from the power amp and not the pre-amp. I can not recommend the PAS-3 except for collector reasons. They have several issues that are hard to deal with:

1. The pots get noisy and they are very unusual pots that are difficult to find and the circuits they are in don't work right without the right pots.
2. Because of a compromise they made to save money the tone controls will only work right with an amp with extremely high input impedance (Like the ST-70), the PAS-3 will not work right with any modern and many other vintage amps because of this.
3. Cross talk on every PAS-3 I have experienced is very high.

If you want to play with tubes I would start with a tube power amp and a modern pre-amp (or DAC with volume control). ST-70 are fine but many have been "modified" and as far as I have seen no modification, not matter how much people talk about hearing magic, has ever been measured to be an improvement. I would get a stock one that has been carefully and skillfully updated as needed over the years or a better and safer bet is to buy a new kit from DynaKit, and put it together.

In any case have fun.

Thanks so much for sharing your thoughts and expertise. I so appreciate it. Sounds like I should steer clear of the PAS 3 preamp, thanks for the heads up. I've been reading up on Dynaco, and I would guess the same concerns apply to the PAS-3X? I know it won't work with SS without not cheap mods, but maybe the crosstalk wouldn't be so high with the ST 70? I kind of like the aesthetics of a Dyanco stack (but definitely not at the expense of the sound) Anyway, many thanks, I truly appreciate the time you took here to help me find my way through all this.

 

[Sal1950]

Amir, great review, many thanks. I'm interested in adding this tube amplifier to my system, especially to listen to older recordings (jazz, blues, country) from the 40s-mid-60s, before the era of SS. This comes with a matching preamp (PAS-3, I believe). I'm kind of new here, and not at all technically savvy, so my question may be an ignorant one, but here goes: would you have to measure the PAS 3, too, to get a sense of how it and the ST 70 would perform in the listening environment? Thank you.

Well the distortion and noise of a PAS-3 would be added to those of ST 70, not exactly a match made in heaven.
The problems with the PAS-3 listed by others here are right on point.
I'm not sure why your interested in going this route, if it's simply for a collectors idea of fun, great, go for it.
If you want to hear the old recordings close to what a listener in those days would hear with all the distortions and problems the ancient gear brings with it, that's also kool but not something I would chase.

The "sound" of those actual recordings is already locked into them, the artists were using the tube amps, mikes, and other gear of the day that they, loved the sound of. Also the recording engineers were using the tube consoles/mixers and tape recorders of the time, along with all the tube gear in the LP creating/pressing path.
All that beloved sound of 40s-60s recordings is locked into whatever source your using to play them and can best be reproduced using modern accurate
solid state gear. Using old tube gear at home can only add more distortions to those recordings. I have hundreds of hours of early big band recordings like the collection, Frank Sinatra - The Capitol Years with Nelson Riddle, etc;. Over the years each time I made real, objective, improvement to the sound of my rig, the sound of those old recordings improved, letting me hear deeper and with better detail into those ancient recordings.
YMMV