Review: Counterpoint SA-1000 Tube preamp
PAS-ifying the Counterpoint SA1000
This review might be more appropriate to file this under Dynaco PAS3 but it started with a Counterpoint SA1000.
Michael Elliott is a controversial figure in the audio community. Some fellow audiophiles consider him to be a genius, some outright hate him. I must admit I belong to the former camp.
Over the years I’ve owned quite a few of his creations: SA2000, SA1000 premium upgrade, SA5000, SA220, NPM basic upgrade, NP100 Basic and Premium Gold, and NP220 premium gold (my current reference power amp).
About 2 years ago I bought a matching set of SA1000 and SA100 on audiogon initially to build a second (or was it 3rd?) system. The SA100 eventually became my NP100 premium gold. I purchased the schematics for the SA1000 and decided I should perhaps do some mods to it.
Fellow Altavista Audio fans or observers may find that Michael has been very generous about sharing his ideas on modification on his website. Plitron transformers, Continental oil filled caps, Blackgate, Mills or Vishay resistors, the usual suspects.
A good friend of mine who’s very experienced with DIY audio offered to help me simulate an SA1000 rebuild. So we got some HexFreds, Blackgate caps, and Mills resistors, ripped out the fet follower and have the half of the single 6922 plate-drive the output through a 1uF Dynamicap per channel. The result: It’s clean, it’s open, but it lacks emotion and the ultimate in body and musicality.
At about the same time another friend loaned me his vintage Marantz 7 and I was blown away by how musical and emotional violin music and female vocals play through the Marantz 7. Despite the obviously muddy bass and rolled off mid highs I said, “I can live with this kind of sound.”
The friend who helped me mod the SA1000 has an old Dynaco PAS3. While he couldn’t get rid of the nasty hum, we both agreed that there is something about the Dynaco to be desired, and that the sonic signature resembles that of a less competent version of the Marantz 7.
Then an idea dawned on him, “Since you are using the SA1000 as a DIY platform anyway, why not make it into a Marantz 7 line stage? You don’t want to use the Phono anyway. It uses 12AX7s and has regulated filament and B+, and the layout is mighty nice.”
OK, then off to his bench it goes. After removing essentially all the resistors in the phono stage and reinstalling ones with the same value as in a Dynaco PAS3 line stage, cutting 2 traces and making 2 pairs of connections with hookup wires, and reconfiguring the 6922’s hookup, we basically got ourselves a Dynaco PAS3 with a 6922 as a cathode follower.
Boy it does sound like a Marantz 7 but with a lot more dynamics. The musicality is all there. Yet sometimes it’s a tad dry and very very rarely there’s still one or two squeaky notes. Well since I am not driving uber long interconnects and my NP220 has very high input impedance, I decided to have my friend rip out the 6922 follower and have each 12AX7 drive the power amp directly? If I don’t lose any bass or top end extension then that might be a better way to go, so I think.
The good news is that I don’t hear any noticeable loss of extension, the bad news is now that I’ve opened this can of worms, so starts the Mod-yssey of this Counter-PAS of a monstrosity. I was also fortunate enough to have a real Alta Vista Modified SA1000 premium with Plitron for comparison. The single 6922-based SA1000 premium sounded clinical and bland even with Amperex Pinch-waist or Telefunkens compared with the Counter-PAS.
First thing to go in was a Hammond 159T choke that adds an LC filter stage to the original single blackgate 100uF between the rectifiers (now Fairchild Stealth HexFreds) and the regulator. That gave the sound a much deeper background with more detail and finesse.
Then I swapped out the Blackgate 100+100 filter cap that serves each 12AX7 and with some creative logistics I was able to squeeze 2 ASC 50uF X386S oil cans as replacement. (Yes I should have read Michael Elliott’s description of how the Continental caps kick the butt of Blackgates on his website, I wonder how Continental caps sound compared to ASC X386S?) What I got was extremely smooth violins, so silky it reminds me of the Canary CA906, vocals are also uncannily lifelike and full bodied. But this sound comes at a price. Now the whole preamp does sound like a vintage preamp with a somewhat slow and syrupy sound.
To bring back that snappiness I decided to try separating the high voltage bypass caps and have the ASC oil cans service just the 1st gain stage and reroute the cap connection for the original line stage to the 2nd gain stage (2nd half of each 12AX7). There I use VALABs 500V 47uF film caps ($15 each on ebay, I might try Solen FastCaps next).
The result is a snappier bass with much better dynamic contrast while preserving the smoothness of the mids and highs.
Here I am on a roll to bring this thing to the ultimate level. I was able to source cheap Plitron transformers on Ebay (one for the B+ and the other for filament). That helped deepen the bass quite a bit. The whole preamp also sounds quieter with a darker background.
Finally I decided to rebuild the regulator which was essentially Zener diodes providing a reference voltage for an ST 2N3440 transistor. A few tiny holes here and there with a dentists drill, 2 resistors, a Supertex LR8N3, and a 2N3439 (the original 3440 couldn’t deal with the Plitron’s inrush current anyway) complete a new regulator stage.
So how does it sound? Even halfway through the mods I had to give up my MC-2A3 which I heavily modified. I’ve owned some great name preamps like SP10, Audio Research Ref 1 and this thing sounds leaps and bounds better, much more delicate and musical, at least in my system.
Is this preamp for every system? Probably not, it doesn’t have a cathode follower and I am not sure how it will perform with long interconnects and difficult load. Why does it sound good even though there’s no tube in the rectifier and regulation stage? I simply don’t know. Why didn’t you just build a PAS3 from scratch? It was a natural progression (pun somewhat intended) where one small mod leads to another. And I like the layout and the delay/mute circuit of the SA1000 anyway. Moreover the filament supply, though simple, is dead quiet. Do I think it might be easier to start with a $200 music angel preamp that uses 2 12AX7s (and a follower too)? Probably I’d be ripping everything out and replacing every single component anyway and the Music Angel probably doesn’t have the time delay mute.
I must admit that a good part of the fun is the enjoyment I get observing the results of every step of incremental mod. Next is to revisit the 6SN7 but I’d have to start with a whole new chassis.
Sonic Frontiers SFCD1 I2S mod
Sonic Frontiers Processor 3
Counterpoint AltaVista NP220 Premium Gold
Counterpoint SA1000 stock
Counterpoint SA1000 Altavista premium with Plitron
Counterpoint SA5000 stock
Audio Research SP10
Audio Research Reference 1
Ming Da MC-2A3