Soundlab Speakers - Budget Amp Suggestions


I have tried to read as much as possible about different types of amplifiers capable of driving electrostatic speakers. Thanks to everyone for the great articles and discussions. In particular, I am looking for a ss amplifier that can drive Soundlab speakers. The Soundlabs have a low impedance at high frequencies and a high impedance at low frequencies. A high power ss amp that can drive difficult loads appears to be the ticket (I'm not interested in tube amps). High current is needed for the high frequency/low impedance (but not necessarily high power) while the high voltage (albeit at lower power) can drive the high impedance at low frequencies.

While looking for speakers I came across the Soundlab speakers and really liked the sound. I basically blew my budget on them, which for me is not a bad compromise because I don't want the speakers to be the weak link in the chain.

So this is what I have:
1. Two Soundlab A-1 speakers (1992 vintage)
2. One Soundlab B-1S subwoofer (pre 1990) - This is a stereo subwoofer having two separate inputs to drive each interior panel.
3. The A-1s have the toroidal and impedance upgrade.
4. I had all the speakers reskinned with the px mylar.

There will be some type of crossover between the A-1s and the B-1S (the frequency and type of crossover is undetermined at the moment)

I believe that having the B-1S reduces some of the constraint of having the highest power amplifier to drive the A-1s (e.g. 500-600W) since a lot of the bass will be coming from the B-1S. I was told to limit the power to the B-1S to a 400W or less ss amplifier. I am thinking that perhaps I could get away with a lower power amplifier for the A-1s because of this scheme. Please let me know if I am wrong.

As I said my budget is limited. I have about 1.2K and perhaps up to 2K to spend on an amp. The amp I have targeted is a Sunfire Cinema Grand Series II 5-Channel amplifier that outputs 425W a channel. The channels driving the B-1S won't be delivering a lot of power as the impedance is 16 to over 30 ohms. The amp should be able to drive the A-1s adequately. As a side note I have a couple of amps (Crown K1 or Citation 7.1 which output between 300-400W) that I could use to drive the B-1S if needed.

Are there some vintage or other budget amps that I should be considering. Is my analysis wrong? Any suggestions on crossover frequency? I appreciate any and all input. I want to thank every one in advance for their thoughts.

Regards,
GWHO

gwho

Showing 8 responses by grannyring

I think the 600 is a better amp as the transformer and power supply drive two channels only and the same hardware has to drive all of the multi channels in the other amp. Just my feeling however. I also ran two subs with my M1's, but drove my SL's full range and only used the subs at 30 htz and below. I like the bass on the SL speakers and used the subs as just a little added foundation.
Having owned your speaker, modified it, used many amps on it etc... I can
tell you what your best two options are by a proverbial mile.

The Sunfire Signature 600 stereo amp. This one is just special with your
speaker. Sounds fantastic and bested amps costing up to $20,000.

One other fantastic choice which I also paired with your speaker is a
Conrad Johnson 2500a. It was also a special match.

I liked these amps better then the PARASOUND JC1s and the Atmasphere
MA1's and that must tell you something as both these amps are wonderful
in their own right.

If you find a Sig600 send it to the only authorized service center for Carver
and have Bill work on it for $400. He will go through the amp and do all it
needs and you can be sure it will sound better than the way you purchased
it. The power supply filter caps will most likely be replaced plus the voltage
rails adjusted for better performance. Mine had a whole new right channel
board put in and many other parts replaced. It came back sounding
absolutely amazing.

Good amps mentioned above, but I know both of these sound better then
the ESL 300 mentioned. Your speaker has impedances down to 2 ohms in
the highs and up into the 50's in the bass. SS amps don't like impedances
that go this high and put out only a small fraction of their rated power in the
bass area of your speaker. The Carver drives them with ease and never
even gets warm. The CJ surprised me and also drove them very well.

I also tried some digital amps and found both the Sunfire and CJ had more
body, warmth and scale.

Good luck on your search.
If you cross that high you may muddy the all important mids and rob the music of some life and transparency. This has been my experience of crossing to high with any subs.
Atmasphere, you are spot on and yes the SL's needed more power. I bet the MA2's would be heaven!

I did complete the mods mentioned on my A1's as well as several other mods found on the now pretty quiet SL forum. Roger West was very helpful and actually drew me an easy diagram to follow. He even put my name on the schematic! Great guy!
The CJ MF2500a is also very special. Not as powerful as the Sunfire, but sounded better and had enough power as an FYI. These "budget" amps can hold their own with big dollar amps. They will make the SL's sing!
Gwho, you will simply need to try one of these amps and decide for yourself. I liked the CJ and Sunfire and know you will find them quite acceptable. My experience is that tube amps have a harder time with the highs where the impedance drops, even with the mod that I did perform.

My room is 18x24 and with 100-125 tube watts it would clip in the highs on difficult music like piano and orchestra. Clipping would occur at levels 87db and higher in my room.

If you are lucky enough to get a Sig600 and decide to sell, they typically sell in a couple of days.
Hi Atmasphere, I have done them all including bypassing the brilliance knob, biwire option, cap value and quality rolling and reducing the resistance. I have not totally removed the shunt resistor as that would not work with my SS amps as you know.

I just read all the NEW stuff going on at the SLOG and WOW! Seems many good things are happening with SL's! New transformers and backplate changes as well as totally removing the shunt resistor as a possible mod with tube amps only. Well, I wish I had the MA1's still as I would remove that 8 ohm resistor and play! I bet the MA1's would not clip with that mod.

I wish I still had the speakers and the MA1's as it was the best sound I ever had up to 85db. Problem was the amps would clip too fast for any loud listening. Seems there may well be an answer that is pretty darn simple.
Atmasphere, I have read that if you remove the shunt resistor when using a high powered SS amp you can damage (saturate) the transformer on the SL speaker. This is not the case with tube amps and the technical explanation goes on from there.....I'm not smart enough to follow it yet......but learning....