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.


Why don't you consider the Sanders Sound Systems amplifiers,(used of course in all cases given your budget) they are made/voiced for panel speakers. Spectron also makes some veryt popular higher powered amps. The ICE powered H20 amp etc, all these are a little pricier than what you want to spend but are in a different league than the Sunfire.
Thanks for the suggestions but these are way over my budget at the moment. I won't be walking into any money soon as I have to put two kids through college. The first just started and the second will be going in a few years. So what I'm proposing is a hard constraint. The speakers I have are pretty old. I've got to think they are more of a vintage speaker. I did see that someone is selling ICE Amp modules (monoblocks) that deliver about 550W/channel for less than 1K. Would they sound good? I think these are just off the shelf modules.
I second the Sanders ESL amp since I use one on my Martin Logan CLSIIA's and it's wonderful! I realize it's over your budget, but the predecessor to it is the Innersound version, used, should be in your price ballpark. Look for one of those.
Is there a specific model I should be looking for of the Innersound amps?
The least expensive long term solution is for you to use your current amps until you can afford a truly appropriate amp and crossover. Spending money for a stop gap solution is usually an inefficient use of money and effort.
I think the Innersound amp was just called the Electrostatic Amplifier. The newer model was the Innersound ESL300, then the i330. Any of those.
1- Re-read Onhwy61's post.
2- Although its probably not what you wanted as a response, it is excellent advise.
If you want a good amplifier for driving electrostatic speakers without breaking the bank look for a used Acoustat TNT 200.
I understand the statement of not spending the money and will consider this option. I am a little disappointed. I would assume that there were some excellent sounding amps capable of driving my speakers manufactured in the 1990s and early 2000s that would be heavily discounted in todays market. I will admit that I am not up on the changes in amplifiers over the last decade. In fact my previous system was over a decade older than the Soundlabs. Have the changes in amp designs been so significant that I would hear a substantial difference even with my twenty year old speakers?

I did look up the Innersound amp and it seems capable of easily driving my speakers. I will keep my eyes open for one of these amps.

I had read a couple of responses that said the Sunfire amp 400w or 600w sound good with these speakers which is why I was looking in this direction. It was also within my price range.

Thanks for all the responses
If you are willing to buy a used amp, a Rotel RB 1090 be a good choice. It should have no problem driving your speakers.
"Have the changes in amp designs been so significant that I would hear a substantial difference even with my twenty year old speakers?"

Absolutely not, but not all amplifiers will sound good with electrostatic speakers. All electrostatic speakers that I know of have the impedance characteristics you mentioned in your Soundlabs with a low impedance in the high frequencies and a high impedance in the low frequencies. This can bring out a lean sound with certain solid state amplifiers. However, this never seems to be a problem for tube amplifiers. Unless an amplifier is designed for use with electrostatic speakers like Innersound or the TNT 200 I mentioned I would not buy an amplifier without being able to audition it with your speakers.
Rrog thanks for the tip on amps designed specifically for electrostats. The tnt amp is an older design. I assume that one can pick one up cheaper than the Innersound. Have you ever compared the two. Does it come close to the Innersound SQ?
The inner sound amp would be perfect and right in your budget. They are great sounding amps and it nice that they sound as good as they do and don't run super hot and draw a lot of power at idle. I have had the esl 300 and now the dpr ref 500 and they are both great sounding. It might take a little persistence to find one used.
I will begin my search for an esl-300. Any idea what the price range on these amplifiers should be?
I have not compared the TNT 200 to an Innersound amp. However, I compared the TNT 200 to my Levinson 23.5 and VTL Ichiban amplifiers and the TNT 200 sounded better on electrostatics speakers. I tried many many amplifiers on Martin Logan CLS and I can tell you there are very few solid state amplifiers that will sound good on electrostatics. Has anyone mentioned Quad amplifiers?
Innersound esl 300 should go for around 1300
There is not a lot of literature on the amp. I did see that there are differences between the original and the mkll. Is one preferable over another.
I have been using Odyssey mono blocks on SoundLab speakers for years. I too have college bills coming in and can't afford to consider upgrading much of anything at this time. The Odyssey's have been amazing. I have never regretted purchasing them. Used ones should be in your price range.
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.

I have read your previous comments on amplifier choices for Soundlabs and they were among those that influenced my direction. I have no doubt that the Innersound or the Sunfire are among the few SS amplifiers within my budget that can drive the Soundlabs. You specifically cite the 600Wx2 Sunfire. I believe that my system differed from yours slightly in that I have the B-1S woofer. A portion of the bass output will be coming from the subwoofer. I was considering driving the speakers with the 425Wx5 amplifier. From the specs the 425x5 can deliver the current/power required for the high frequency. The two channels driving the B-1S would be loafing. Dr. West told me to limit the power to the B-1s to 400W or less. I guess what I am saying is that I may not need the voltage swing of the 600Wx2 to deliver the lowend punch. Is my conclusion wrong or would there be a substantial sonic difference between the two amps in my system.

Could anyone articulate the difference in amplifier sq between the innersound and sunfire?

A general question to others who have helped. What frequency should I crossover the B-1S at? At what freq does bass go non-directional.

As usual thanks for all the input.
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.
Thanks for the input. I've never heard of odyssey amps. I will look into them. A more robust power supply is definitely an advantage vs the 425x5. I will consider the 600w Sunfire. I was thinking of crossing at a higher frequency something like 60 or 80hz. There is not a lot space between my speakers as the room is only 15 feet wide where the speakers are located. The room does open up to over 20-30 feet wide and is about 50' long and over 12' high.
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.
I don't believe that will work for me as the b-1s does not go much belo.w 30hz. I will play around with the crossover point and do it as low as feasible.
Tthomas I did look up the Odyssey mono blocks. The reviews on these amps are quite impressive. I believe they should be able to handle the low impedance load of the Soundlab speakers. The other suggested amps can all provide high voltage excursions along with driving low impedance loads. My concern would be the ability to produce low frequency sounds with authority. I am currently using a 150W amp with the A-1s and for me the bass does not seem in balance with the rest of the sound coming out of the speaker. My room and system is far from being set up correctly so you have to take what I say with a grain of salt.

Have you been satisfied with the bass and bass transient response from the Odyssey since you have lived with these amps and Soundlab speakers? Does it change with volume level?

Grannyring, just FWIW the Atma-Sphere MA-1 would have been underpowered on many of the older Sound Labs.

BTW, Roger West has a new back panel that should be available as an update to any A-1 or similar Sound Lab. It seems to be based on a lot of the conversation that has been going on on some of the forums regarding the drivability, impedance and mods that can be done to the older back panels. The result *should* be a speaker that is a lot easier to drive!

People that have done some of the mods have thus been able to get the MA-1 to work fine. But others have reported that they got a lot better drivability when using transistor amps like the Parasound JC-1 as well.

You might want to read this thread and the one above it on audioasylum, there is a lot of info on the mods done to the back panel:

For someone trying to drive used Sound Labs on a budget I would expect this to be required reading.
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!
If you get top the line speakers why oh why would you be shopping for a budget amp. Why put cheap tires on a performance sports car.

I do have a budget and I chose to spend most of it on the speakers. The speakers that I purchased are twenty years old although they do sound good. They are not current top of the line. I believe that my choice of amplifier is critical because of the difficult load the Soundlab imposes. The suggestions provided by the contributors to the thread are all good. The Innersound, Sunfire, TNT-200, and Odyssey Monos amplifiers have all been proven to have good SQ with the Soundlabs. Moreover, they are all within reach of my budget which does not make any of them a compromise. Just good amps for my speakers.
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!
Bass response was one of the things that surprised me the most when I went to the Odyssey monos. It seemed to me that they handled the panel better than my old amps. I initially bought my SLabs from a long time SL dealer and he actually was the one that talked me into the Odysseys since I could not afford the big AtmaSphere amps. I have borrowed a few amps since then, but for my budget these have been the best.
So now I've come full circle. I have a great list of amplifiers I should look into that have been proven to work with Soundlabs. I will restate one of my initial questions. I am less constrained on my A-1s in requiring high voltage on the low end since I have the planar bass panel that I can drive with a separate amplifier. Would I be better off going with a lower power but higher resolution (on the high end) amp for the A-1s such as the mf2500a or the Odyssey Monos. Are we talking about very subtle or significant differences in sound signature.

One thing that I have decided is that I am going to try more than one of these amps to settle on one that I like.
Gwho, I realize that the budget is an issue but one thing you will have to face it its really hard to get Sound Labs to sing if you have transistors. Transistors as you know try to double power as the impedance of the load is halved, which is another way of saying that they cut power in half if the impedance is doubled.

With the Sound Labs both ways of looking at this are a concern. On the bottom end you can't make power, on the top end there is a tendency to make too much. To give you an idea, a 150 watt tube amp can easily keep up with a 600 watt transistor amp on this speaker due to this issue. A 600 watt transistor amp will only make about 150 watts on a Sound Lab due to the impedance. A tube amp will not loose so much power on this account.

It might help to understand something about how ESLs operate, which is to say that they work much better with an amplifier that behaves as a power source rather than a voltage source.

Don't worry if you did not understand that last sentence. Just read this article, its a quick read and there is almost no math :)

So if you plan to bi-amplify, you might be able to do just fine with a tube amp that makes only about 60 watts for the top end. This depends somewhat on your room. The reason people use high power transistors is because of the impedance in the bass, while a 200 watt tube amp is usually enough power in many listening situations.

Now if you apply the mods that I mentioned earlier, which are easy to do, the speaker gets a lot easier to drive. Customers have reported that our MA-1 had unlimited power (could not clip them) in their system after they did the mod. IOW the driver is fairly efficient, most of the problem of drivability has to do with the back panel. So if you do this and you bi-amplify, a 60 watt tube amp might do the trick, and will sound better than a transistor amp on that load.

Something to think about!
Thanks Atmasphere. I will keep this in mind. It does point out the difference in tube vs ss for driving a varying impedance speaker.
One thing I forgot to mention, every SS amp I have ever used with my SoundLabs has heated up a lot when I have done a lot of listening until I got the Odyssey amps. They barely get warm to the touch with my normal listening.

I will tell you that the best I ever heard my speakers sound was when they were hooked up to a pair of atma-sphere amps. Unfortunately, they were also out of my price range. Maybe when my boys are finished with college....
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.
Thanks for all of your responses. I learned a lot. Grannyring I will definitely take your advice. I am going to try the suggested amps until I find one I really like. I was looking at a 600x2 on ebay but it was pulled from the auction. I am also looking at the Odyssey. No Innersound or CJ in sight or price range. Ideally, I am going to sell some of my stuff to allow me to purchase two amps simultaneously to compare/sell. I will be patient as it appears that the amps only show up sporadically. Of course these funds will likely get siphoned towards college tuition. I can always use the other amp on the B-1S until I settle on a choice. Here's hoping the economy starts improving!

Perhaps my next topic will be preamps/room correction but I am not prepared for that now.
Grannyring, what mod did you perform? Did you remove the big resistor?
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.
Grannyring, from what I understand that shunt resistor is a problem for any amplifier, even transistors. There is a reason it is rated for so many watts- amplifier power is used to heat it up. It does not matter what kind of amp you have.

If you remove it you will find that you need less power to play the speaker and it will sound better too. It is this mod that allows the MA-1 to play that speaker with volume. Take a look at this link- its the one with the photo:

After the resistor is removed, the cap value can be reduced. This prevents the HF transformer from saturating.
You can PM more more info if you like.
The backplates on the U-1PXs here are going to Sound Lab very soon for upgrading to the new Consummate version and should be here later in the month. Any and all are invited to come for a listen here in the Chicago area. I can be contacted for pricing which should be known shortly.
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....
Here is a brief update. First, thanks for all the suggestions. I will be purchasing and comparing the suggested amplifiers. Ideally, I would like to have two different amps for comparison over the long term. Cull out the loser and move on to the next until settling on an amp for a while. I am looking for the innersound, sunfire, and perhaps the cj. I will be patient. I can probably pick up the acoustat or the hafler 9500 on the cheap for a test run as these are substantially older amps. I was able to find and pick up the Odyssey Monos within my budget. Obviously, these have the advantage of no power supply interaction between channels. They will have the upgraded transformer, 360K uf of capacitance per amplifier, and the Kismet (latest version) boards so they should be able to deliver power to a low impedance load. This is a newer amp so issues related to device component aging will be minimal. I have an older set of 1M straightwire maestros ic for connecting the amps to the speakers that I will be using (these came with my speakers).

My next question relates to preamplifiers. I am only going to be listening to music through a server. My goal is to just listen to music instead of fussing with the system day and night. Right now I have the squeezebox touch device with CDs converted to flac. I am also interested in devices having the ability to support room eq. I want simplicity so a combo device will be my compromise. The devices that come to mind are the Integra dhc-80.2, tact-2.2x, and lyngdorf. I can get these used within my budget. Although I do not have any sacds and the like this might be of interest to me in the future. Would I go wrong with any of these DSP pre-amps or any other suggestions?
Stay away from room EQ! If you want to complicate things (which you say you don't want to do) EQ is a good place to start. The problem you are up against is that you are dealing with a very transparent speaker, and the effects of DSP are easily audible on it. Yes, you may get the frequency response in the room to be flatter, but you will pay a big price sonically to get there. IMO/IME its not worth it unless you have cheap speakers.

The other thing you want to consider is that digital volume controls rob the signal of resolution at lower volumes. Again, consider the fact that the Sound Lab is one of the most revealing speakers made. You really do have to have your ducks in a row when you set them up, if you also want them to sound like music. So something with a good analog volume control is advised, perhaps even an active line stage to deal with that reality.
Thank you for your input. I am going to a server based system (all my music is in digital (no analog)). Would I be better off with something like a Benchmark Dac HDR directly to my amplifiers. Also I would need to crossover from my A-1s to my B-1s. I was looking at an all in one solution (pre-pro with room eq and crossovers). This may not be the way to go as you have stated. Although I have never used room eq, from what I read I thought the benefits out weighed any loss in resolution. I guess I did not take the Soundlabs into account. Others suggested using an older Meridian or Casablanca pre-pro that has good dacs to drive the 4 speakers. Are there other preamps/dacs for digital that I should be considering that work with my setup (2k or less).
Gwho, when you read that stuff about active eq/room correction, it really does not apply to a high resolution system or the people saying really aren't listening that closely.

If you want a crossover, talk to Tom Tutay 850-244-3041 he makes the best out there and the only ones I would consider for your application. Dunno what they cost though...
Any suggestions on preamps or dacs that work well with Soundlabs.
Is your amp single-ended input or balanced?
It has both types of inputs.
If your amplifier supports balanced inputs then I would feed it with a balanced source.

The reason there are balanced cables and a balanced system is that it offers you the ability to have the cables drop out of the overall system sound. I am sure by now you have noticed that you can hear differences in interconnect cables; the balanced line system was devised to eliminate that problem and it does it very well if you adhere to the balanced line standards.

I of course like tubes more than transistors; if you are looking at a preamp I would recommend a balanced tube preamp. If you are looking at DACs (and no preamp), you will want to find one with a balanced output and an analog volume control (digital controls reduce resolution as you turn them down). I think Ayre makes such a unit.