After two years with my ST70 amp I thought it might be time for a review. I bought an ST70 from Bob Latino in Massachusetts in April of 2009 and have used it virtually every day ever since. I work at home so I put a lot of hours on the stereo. I also have a Bryston 2B SST^2 which is a $3k 100-wpc solid state amp, or as Bob calls them, a "sand amp."
Description: this is properly a "replica" Dynaco Stereo 70. (Link below.) It's made from all-new parts and doesn't contain any parts from a vintage unit. The input board is the VCA70 PCB which is also available as a mod/replacement/upgrade for vintage units.
I had Bob build mine. It's also available as a kit if you want to build it yourself. Even hand built, it's remarkably cheap--I believe mine cost a little over $1k "loaded" with all the (c. 2009) options.
I've had my amp configured with KT-66's (shown in the pic) and EL-34's. They both sound great but a little different--the KT-66's are a little more liquid and detailed but a little thinner-sounding. I prefer EL-34's. It would depend on your speakers (and tastes) I suspect. I have several sets of EL-34s and I wish I could remember where I got the set I'm using now--I bought them from Ebay but I can't recall from whom.
The critical tube is the center input (small) tube. Some options are just noisy and hissy and don't work. The Mullard CV4024 is the one to use.
If the amp has any fault it's that it's a little hard on the (tube) rectifier, and goes through them fairly quickly. I bought an expensive NOS Mullard which is supposed to be bulletproof, and so far has been. Bob recommends JJ GZ34s and those work well. I think they even sound a touch better than the old Mullard, but I wouldn't swear to that. In two years, one JJ and two Mesa rectifiers in my amp have gone the way of all things.
Don't care about that, though. If you don't like the idea of caring for and feeding a tube amp, you should probably go with something designed to be easy to use like the Prima Lunas.
I suspect you need tube-friendly speakers for this amp, and there aren't many of those around any more. In England, Peter Comeau designed an upgraded replica Dynaco A-25 and a floorstanding version of same which was marketed as a kit or in various states of assembly by _Hi-Fi World_ magazine's "World Designs" subsidiary, but Peter (former chief designer of Mission speakers, among others, if you don't know the name) got a job overseeing a speaker factory in China (or something like that) and off he went. The World Designs tube amps have been resuscitated by another party, but not the speakers, as far as I know. Icon Audio in England also makes a deliberately tube-friendly speaker called the MFV 3. I'd try a pair but they want $561 shipping to Wisconsin which is a tad excessive. I have some old Tannoys which I keep trying to get rid of but can't, and they are also a good match for a 35-wpc push-pull tube amp. I've heard that Vienna Acoustics Mozarts are also a good match. I'm sure there are others, but those are the ones I know. I wish one of the snooty stereo magazines would write an article on tube-friendly speakers (other than horns for flea-powered SET amps, I mean) but I guess that would be entirely too practical for them. They don't seem too interested in speakers that cost less than the price of a luxury car anyway. But I digress.
Bottom line: I totally love this amp. It's one of the best hi-fi purchases I've made in my life, and that's saying something because I've been an unregenerate over-purchaser of audio equipment over the years. It's far from the most expensive amp I've owned--or own now--but it's the one that has given me the most pleasure. My 3X-as-expensive Bryston is a bit punchier and more articulate in the bass, but the ST-70 betters the Bryston in every other parameter I can think of. And I actually prefer the bass of the ST-70 with my Tannoys--it's not as hi-fi, but it sounds more like the real thing to me. (I listen mostly to ensemble jazz.)
It does take a bit of patience to deal with tube-rolling and biasing (I bias the amp about every other month--you need a multimeter (I got mine from Radio shack) and a small screwdriver), but to me it's well worth the trouble. I just love the sound--liquid, dimensional, rich, musical.
I should probably add that this doesn't sound very much like an original Dynaco ST-70, which I recall as being easy on the ears but woolly and soft and somewhat slow. The current version just sounds like any really good modern tube amp, not like a gloss on the old vintage amp. The speed and transients are in a different category at least. It's been a long time since I've heard an old Dynaco ST-70, though.
Given the price, this is a great bargain, especially if you are competent to put it together yourself. Even if you're not, though, it's still a great amp for the money.
I've built my system around this amp and will continue to do so as long as I'm able to.
Bob (who I've never met) is good to deal with and responds to questions promptly. He makes two other amps, the ST-120 (KT-88s, 60 wpc) and the new M-125 monoblocks, which can be configured for 65 wpc with 2 KT-88's each, or 120 wpc with 4 KT-88's each.
Oh, by the way: if you get this amp, get the capacitor upgrade but don't bother with the Triode switches (unless those aren't an option any more)--my amp has them but I much prefer the sound in push-pull (pentode) mode. If you have ONLY a CD player, I see you can now get the amp with a volume control on it so you can run your system without a preamp. Mine doesn't have that.
Negatives? It looks like a Dynaco. I like that about it, but your wife might not.
Hope this has been of use or interest to someone out there. Keep it fun!
