Review: Counterpoint SA-100 Tube amp

Category: Amplifiers

Over the years, more than a few pieces of high end audio equipment have achieved "legendary" status.
Quad ESL 57, Mark Levinson ML2, Marantz 7, 8b, and 9 just to name a few.
I think few of us would consider any of the Counterpoint SA-series hybrid amps (the SA4 Futterman is a different story) to have achieved legendary status save for their experience with output stages blowing up in spectacular fashion when its overdriven or when speaker wires are shorted, spectacular enough to be legendary.
So why am I writing this SA-100 review 13 years after the demise of Counterpoint? I am a happy owner of an Altavista Audio NP-220 premium gold, which is a completely redesigned hybrid amp inside an old Counterpoint chassis. Why should I bother with old flakey SA-100s?
Those still reading this, you might fall into one of these 3 camps:
• curious about hybrid amps because you don’t want to dump any more $$ into power-tube rolling with those so called re-issue tubes.
• have a failed Counterpoint amp in storage and you wonder if you want to sell it on Craigslist/Ebay or fix it.
• Tempted to buy those “minty yet needs repair” SA-12 or SA-100 power amps that appear once every few days on Ebay.

It had to be 20+ years ago or when I had the opportunity to listen to an SA-20 driving Maggies. That system threw a huge, wide, and deep soundstage and that started my interest in hybrid amps.

I bought my first SA-220 in 1993 and drove Maggies, Apogees, Thiel, and even Martin Logan CLS2Z without incident until I found the sound to be too dark and lumpy and moved on the Krell KSAs (wrong move!)

Fast-forward many years and many Audio Research amps and lots of $$ thrown into KT88s, 6550Cs, 6C33B (BAT) and even 300Bs (Canary and VAC) later I decided to give hybrid amps another chance.
First was a pair of NPMs, then an SA-100 just for nostalgia sake. I found that my requirements have indeed changed. The misty sound just wouldn’t cut it anymore. Willing to further pursue the ultimate hybrid power amp, I had Michael Elliot upgrade the SA-100 to NP-100PG. Then I stumbled upon an NP220PG and I happily settled with that till the present. During that time also tried a hot-rodded Moscode 600, but absolutely cannot tolerate the grainy texture and overshooting transients when playing piano music. (Despite the use of Auricaps and all sorts of tweaks in that hotrod mod, even a Xindak Hybrid beats it.)

Good as the NP220PG is, I feel that something is missing. There are some qualities inherent to an old classic SA-10/SA-220 that makes it present a more tube-like bloom than the NPs. With the NP, strings always sound a tad less texturally rich enough to be convincingly real. I’m not saying that the NP has no bloom, but when compared to a pure-bred triode tube amp there is some distance to cover in that department, that’s where the old SA amps are actually closer to tube sound. This perhaps can be explained by the SA’s use of Mosfets vs. the NP’s bipolars, the use of a tubed driver stage instead of a solid-state driver stage, and single-end simple triode gain stage vs. balanced.

While Michael’s rebuilt puts a completely new amp into the chassis, a Japanese fellow at repairs the SA-12s using 2SK1530 and 2SJ201. I kept wondering if an updated SA-220 using premium, modern components would actually get me what I wanted.

Just to establish a A-B comparison, I bought an old broken SA-220 over a year ago for dirt-cheap and re-installed mosfets (I happen to have 4 matching ones), new coupling caps (Russian PIOs), and new B+ bypass B+ caps and got it to work again. I compared it with my NP-220PG and found that the SA has some very desirable characteristics to its sound... to the point where I think in some ways it's actually better than the NP-220. It has the virtues of the old Counterpoint sound minus the blurriness and overly dark character. Overall the NP220 still wins, especially in terms of the ultimate detail and pace. If I have the time, I will probably put in the usual mods of Hexfred / Schottkys, Nichicon filter caps, B+ and filament chokes, and perhaps B+ regulation to do the SA the ultimate justice. Whether it will improve in the finesse and detail and “speed/pace” department to match the NP while retaining its musically involving character, the jury’s still out.

I am not ready to part with my SA-220 (definitely not my NP220) and several friends have asked me how they can get that kind of an amp without breaking the bank. I always tell them to get a broken SA and either get an Altavista Basic rebuild or put in new, modern mosfets. With the former the sonic signature changes quite a bit, with the latter some creative mounting is required. They all shyed away from it.

Recently I came across this company GreenStreetAudio that makes a rebuild kit that retrofits into SA100s. Out of curiosity, I ended up buying a whole rebuilt SA-100 from them:

This restored SA-100 has all the right ideas that I would likely implement if I were to rebuild one myself:
Exicon mosfets (although I would have used 2SJ102 and 2SK1530), hexfred diodes, Mundorf bypass caps,
an improved biasing circuit on a custom output board where the new mosfets are mounted, Nichicon Gold tune filter caps... etc. etc. The website provides a lot of details of the components used.

Once I turned it on I was very impressed by its sound.
It's has exactly the old classic counterpoint sound but with newfound stability and clarity. Old SA-100s never had the punch of this unit. No mosfet mist, no dark sounding blurriness, and absolutely no transient overshoots. Best of all, the image and body of the instruments have more “meat” to it than my NP!

With the NP (even with my darker and warmer tuned driver stage with 196 Ohm naked vishays) the texture of strings are always slightly thinner and leaner (not sharp or
hard but it has less body than an all triode amp). Not so with this SA-100. This thing is extremely musical and conveys the texture and timbre of instruments just right.

This circuitry of this rebuilt SA-100 is all true-to-original other than the output stage bias regulator. The values of the caps and resistors are same as stock. I even verified the reference voltages to be exactly the same as the ones depicted in the schematics (a gentleman from Italy has the SA-100 drawn out and is downloadable everywhere). It has no choke, no B+ regulator, no 6SN7s (I’m just just Sylvania 6922 I have for spare), no naked vishays of course, considering the price. But I can definitely say it’s a world-class amp especially in terms of musicality and beats my NP220 in this department.

Currently the amp is “on rotation” at a couple of fellow audiophiles’ systems. Among a bunch of friends we’ve auditioned this amp with modified Utopia Divas and BC Acoustique ACTs, with other speakers at other friends’ rigs waiting in line. I haven’t decided what I’d do to possibly further improve the sound. Perhaps better coupling caps(not that Auricaps are bad),a B+ choke, lowering the gain a wee bit by changing out the plate resistors of the gain stage, or maybe adding a for-filament-only transformer so I can use 6FQ7 gain stage tubes.

I would highly recommend this kit to those who want to
repair their SAs but want to preserve that old Counterpoint sonic signature, take away the mist, and add reliability. Seriously, it's that good.

Happy listening.

Associated gear
SF-Processor 3
Ming Da MC-2A3 (complete rebuild)
DIY linestage referencing MFA Lumi
Focal JM Lab Utopia Diva
Avalon Eidolon
BC Acoustics Art

Similar products
Counterpoint SA-220 (stock with minor cap upgrade)
Counterpoint NP-220 Premium Gold
VAC Phi 70 mono
Sonic Frontiers Power 2 running at 1/2 power in triode mode
Thanks J for the update. Very interesting.
I had a chance to borrow this SA100 amp from the OP for a few days. I have to say that I am very impressed by this amp. Before I go on, let me state the gear I have.

I also have a Counterpoint NP100 with the Platinum package from Alta Vista Audio and extra goodies like V-caps, Bybees, choke, oil can cap, etc. I spent around $6K for it. I agree with the OP that it is a bit relax sounding. This amp was voiced by Mike E. to have the SET amp sonic signature, similar to the Aria WT-100 reviewed in 6Moons.

Now let me get to the point. In my main system, this modified SA100 has perfect highs and mids, with a nice bloom in the upper bass. My NP100 also started from a SA100. If I have to use one word to describe SA100, it would be musicality. This modified SA100 has preserved that sonic signature and provides a more refined sound than the original SA100.

The only down side I can detect from this modified SA100, as compared to my NP100-P, is that its bass is a bit boomy with my Focal JMlab Alto Utopia Be speakers. These speakers have big woofers and their impedance drops at the low frequencies. This is not too surprising as the NP100-P has a much bigger transformer in the power supply.

When I moved this modified SA100 amp to my second system that has a set of smaller 3-way floor standing speakers, it did not sound boomy anymore. It was pure music!
@Johnson Wu: PLease contact me at this email address: I have some VERY interesting feedback regarding the NP220(i own one) that you will likely want to hear about.