Zero Feedback: Atmasphere vs. BAT

Do Atmasphere and BAT have similar sound because they both use low or zero feedback tube designs?

I am considering these amps for my 8 ohm 89db Spendor S8e's.

I am looking for smoothness, Transparency and sound on the warm side. I am leaning toward a BAT VK75, it can be upgraded and it runs AB instead of the hot class A. You can also upgrade to VK 150. From what I can gather the 140 watt MA1 is superior in the area of dynamics, that would be the main reason to go Atmasphere to the best of my knowledge as OTL is super fast and more of a rock out style.

I am looking for used gear that can be supported over the long term by a good company.
Atma-Sphere support is nothing short of excellant. They are readily available by e-mail or phone and help with troubleshooting, upgrade suggestions, and whatever your questions might be. They give practical advise that I find has been downright superb. The sound is accurate, detailed, and with excellant bass extension, definition, and control not often found in tubed gear. BIG sound stage, too. Highly recommended.

Scottlanterman - I read very positive review of Atmasphere (MA-1) but what makes them hot is amount of current that tube heaters consume. Each tube is about 6.3V 2.5A and there is 28 of them total. That equals to 441W dissipated power just for the heaters. Total power dissipated might be in order of 1kW.
Zero feedback OTLs ???
Hello Marakanetz,

If you look at the Atmasphere website they espouse very low to zero feedback and they claim to have achieved it. These guys often get very high praise by audio clubs that are not part of any audio magazine. I emailed them, and they do respond really well and are helpful even when dealing with someone looking to buy used gear. I think BAT is also very good from reputation and review. I wonder how they compare sound wise since one is AB the other is A?

I know VK as an engineer. No doubt about him. They use differential driving stages(balanced circuits) and classic push-pull output design that really doesn't need deep negative feedback just like most of the tube amps.

I also know that to achieve transformer-less low tube output impedance, you need deep negative feedback.

I'm not looking to buy Atmasphere equipment since it's not only within my budget, but it also too much heat, too much tubes to roll(upkeep) and lots of idle power consumption.
A few obserrvations based on 8 years of ownership of Atmasphere amps (M60s) and preamp (MP-1)

I spent 45 minutes on the phone this morning with Ralph. A friend of mine just bought used MA-1s and wanted to know if they have negative feedback. The answer is none. More importantly, I have never run across a company of any type run by people who are more accessible and available directly on the phone or via internet than the guys in Minnesota. You just about have to hang up on 'em to get rid of 'em! They desperately want you to be satisfied with your purchase and are in it for the long haul.

Heat output. I agonized over this for quite a while but finally pulled the trigger in 2000 and bought my monoblocks. I live just outside of New Orleans and, with the possible exception of Death Valley, nowhere in the contiguous 48 is hotter AND muggier than here. Honestly, it's a non-issue. They do put out heat but it just doesn't seem to affect the comfort level in my listening room summer or winter and I don't note any change in my A/C run time when I'm jamming. My friend with the MA-1s has a much smaller room than I and, unsolicited, made the same observation less than a week ago.

The Atmasphere sound can be characterized as purity incarnate. Purity is the holy grail of audio in my book. Purity is the single word embodiment of a whole slew of other audiophile destinations such as transparency,tone, musicality, dimensionality, etc. It's THE one descriptor to possess, IMHO. It just makes sense that eliminating one massive electronic "processor", if you will, should facilitate a cleaner, more direct connection with the music.

Finally, this all being said, I have nothing but respect for BAT. I have never heard a disparaging word about the company, its people or it's products. I have one friend who just bought a VK 600 to use with his Salk speakers but I've only heard it once and under very suboptimal conditions.

The usual caveat, of course, with the OTL design is that it needs to be partnered with impedance friendly speakers downstream. I'm running AG Duos.
It's a tough choice. I think if I want Atmasphere amps I will sell my Spendor's which I really like for their natural sound. I would look for something that could run on the M30, I thought that AudioKinesis Jazz Modules looked good with an M30.

I think with my S8e's I could enjoy BAT VK75 and then try a second and run Mono down the road if more power is required.

The question is should I sell and go with horns and low power class A? Should I keep what I have and go with something like the VK75? "Gold Plated Decibels", maybe that is what keeps the common man from having a world class system. Bottom line you may need effecient speakers to have the best gear feeding them at a reasonable cost.

That's where I am at today. Been listening to Spinnerette, Ghetto Love to distract me as I think about system re-design.

Thanks for your input.
Scott- Both of those amps are balanced. Are we correct in assumming you have a true balanced output pre-amp? I had a BAT pre-amp a few years ago and then a pair of M-60s. (BTW, its an s-30 stereo amp @ 30 wpc or an M-60 monoblock pair at 60 wpc). Both are quality products w excellent support; I would say that Atma is next step up from excellent, whatever that is. If you send a used product back to them for a check-up they will re-warranty it. Ralph was also very helpful when I was considering sending a used R to R tape deck to him for refurbishing. He actually advised me that the cost of having him do the work would greatly exceed the potential return. The Atma amps are pure class A and IMO do heat up a room, but so will a pair of the VK-75s w those huge output tubes. I've had a Joule VZN-80 that has the same complement of output tubes as the BATs, I'm pretty sure. They both get HOT!!! FWIW, Duke @ Audiokinesis also offers outstanding support. He sells Atma amps among others. Based on his contributions to this site, I would expect him to give you a very honest assessment of the differences between those two amps driving his speakers.
The BAT topology is not exactly push-pull, but rather single-ended floating bridge(similar to Atma-Sphere), as described by Victor Khomenko:

"The VK60 is neither a traditional single-ended design nor a push-pull design. We refer to the VK-60 through VK-1000 amplifiers as single-ended bridge designs. This fundamental circuit dates back to the early 1950's and was invented by Henry Wiggins while working for the ElectroVoice Company. The original name for this type of output topology was Circlotron. The single-ended bridge design relies upon two single-ended amplifiers arranged in a floating bridge formation. This differentiates it from other forms of bridge topologies, most of which effectively incorporate two push-pull sides. The output circuit is inherently balanced and is driven differentially from a preceding stage. The two DC bias currents that exist in each half of the output stage cancel each other in the load. It is a more expensive way of building an amplifier as it requires multiple floating power supplies, as opposed to the more traditional ground-referenced supplies. The benefits of this approach, however, include enhanced symmetry when compared to push-pull designs and lack of the DC saturation problem inherent to single-ended designs."

After hearing an Atma MA-1 I was ready to sell my VK-75SE, but instead set about modding the piece to the point that I feel I'm getting similar performance. Both manufacturers provide excellent customer service, with Ralph at Atma going the extra mile regarding customization, upgrades, and long-term personal relationships with customers.

You can't go wrong with either of these similar designs. However Atma OTLs need to be closely matched to speakers with benign impedances, and they do run hotter.
Atma-Sphere's RK has been very public here on Audiogon about his conviction that feedback is a no-no in amplification.
Hi Dgarretson,

Thanks for the message confirming that if you want an Atmasphere amp, start with that choice and then roll forward. If I go Atma, it would be an S30 and then find some speakers that can go with it. I was thinking of DIY speakers to try and get world class sound on a budget.

I checked out your system, I am blown away by your engineering of basic components into something totally unique. Amazing.

I own the Audiokinesis Jazz Modules and have heard them with the S-30 amp. I believe Duke even voiced them with the S-30. Atma-sphere amps have a high output impedance (the S-60 is 4.1 ohms). I think one of the reasons that Atma-sphere and Audiokinesis are a good match is due to the impedance (no lower than 8 ohms and closer to 12 ohms) and smooth frequency response of the speakers. I currently use mine with VAC Auricle Musicblocs.

Personally, I've never liked tubes and Spendors and I've owned a few pairs of the Classic Series (the Jazz Modules replaced 1/2e's). If you are considering selling the Spendors you could do a lot worse than an Atmas-sphere Audiokinesis combo.
For "smoothness and transparency and warmth" it sounds like you are looking for a Cary, CJ or other el34 based amp; or perhaps a 300b amp.

Atma, IMHO runs pretty neutral. BAT runs very lean - a bit like Audio Research. So, no, BAT and Atma do not sound similar. IMHO, the Atma and Audiokinesis combo will be very, very musical and better many systems costing much more. The big Atma will heat up a room, but with a properly matched speaker, you will be fine with the m30 or m60.
Well, I can confirm that the combination of the Atma-Sphere S-30 and the Audiokinesis Planetarium Beta is superb. I assume this would extend to the Jazz Modules as well. I live near Houston, which certainly gives New Orleans a serious run for its money with respect to most intolerable summers. The S-30 puts out heat, sure, but is really not a problem. It is as neutral as they come. Look elsewhere if you want warmth, at least the artificial kind.

By the way, guys, the model numbers are "S-30" and "M-60".

With all due respect, IMHO, you are taking a wrong approach. Speakers are a much more difficult DIY project than building amps. If you are on a budget and are interested in DIY, I would suggest you buy a pair of high efficient speaker used, something with at least 95db+ sensitivity; and build an amp to match it. If soldering isn't your cup of tea, than forget about DIY, save some more money and buy a used amp.

I used to be a DIYer myself may years ago and had built many amps and speakers. Most of the amps turned out great but none of the speakers were good.

Don't build speakers if you want to save money. You will end up spending more.
Your statement about BAT being "very lean" does not support my personal experience with various BAT pieces- BAT VK-75SE,
Not at any point of time, paired with different speakers, did any BAT sound anywhere close to being lean.
It sounds full- bodied, very dynamic and textured.
This is true. BAT tube amps have liquidity and suppleness similar to SETs. However, IME their paper-in-oil coupling caps slightly blunt dynamics, bass control, and resolution. With a swap to better coupling caps the BAT amps gain in these areas and in neutrality and perceived extension at frequency extremes-- which is characteristic of Atma-Sphere.
I followed Dave (Dgarretson) advice and replaced coupling caps and input hook up wires, to say the improvement was dramatic was an understatement. my 150SE, couple with Einstein pre, drives Aerial 20T, a very demanding load and manufacture suggests 300+ wpc of SS power as minimum, to the level I rarely hear else where.

I don't have much experience with Atma Sphere power amp, but I did hear their better pre amp and all I can say is Einstein is in a different league, but it should given the price difference.
It has been about 4 years since I have heard the BAT gear and perhaps it was poor synergy, but it sounded lean and a bit veiled to me. Many amps claim to sound like SET amps. SET amps sound like SET amps. Why buy a BAT and change the coupling caps and hope for the best when Scott could buy the Atma and the Audiokinesis and know he is getting excellent synergy?

I think the real question is whether Scott wants "warm and smooth" which means an el34 or 300b topology. Scott, I recommend the Atma/Audiokinesis if you are unable to audition. If you are able to audition, I recommend that you listen to BAT, Atma, an el34 and a 300b along with the appropriate efficiency speakers. Or, be patient and buy used gear and resell what does not float your boat. Good luck, Jeff
I lost count how many amps I have bought and sold in the past 10 years, but one thing I can say confidently is a stock BAT 75SE is not veil or lean. in fact, it's much more transparent than just about anything else and that's where I stopped. well, I did upgrade to 150SE.
A couple of years ago Nelson Pass (check out 1st Article on website, seems a must read for audio geeks) wrote on the subject of zero feedback. He talked about the distortion spectrum between an A circuit running zero feedback, and an AB running zero feedback, as well as the whole feedback concept creating less total distortion, but more of the complex unpleasant type. This was also covered in Stereophile, as they were gushing over a Cary 803C amp and zero feedback CJ Pre. In the back of that article the designer of the CAT Pre tried to inject some sanity in the conversation by saying it is not sooo simple.

Since I cannot listen to all the equipment in the world, I was wondering how BAT compared to Atma? From what I can tell their are fans of both with Atma perhaps being more trasnparent.

Still comes down to "Gold Plated Decibels" as a key factor if you want to have a class A set up, you gotta have effecient speakers if you want the option.

"...if you want to have a class A set up,you gotta have effecient speakers if you want the option."
I beg to differ.
Sorry about that Unsound.

You can purchase a Krell KSA 200 or a Threshold, or a Pass XA200 or something else in the BIG Class A Tube range like TRL Tube amps ot ATM1.

It's a lot of energy and possibly big upfront cost going that route. I stand corrected. Still looks like "Gold Plated Decibels" when you factor in your energy bill and a lot of heat in the summer if you go big class A.

Best Regards,
I just wanted to jump in and add a few thoughts, being a 20+ year Atma-sphere user (and now a dealer).

The OTL impedance matching issue with speakers is not as critical as one might think. I am currently using a 4 ohm speaker (with MA-1's) with the Speltz Zero autoformer to bring it up to 8 ohms. That being said, I am soon going to be trying a 16 ohm speaker, which I won't need the Zero with.

As far as heat, I believe I have heard it said that even class A solid state gets probably as hot as Atma amps. I can attest to the fact that the newest Atma designs run cooler than older ones, and one can always take out tubes and run with less power for summer time usage.

In my opinion, getting a great class A tube amp is the best way to get off the high end merry go round, at least as far as amplification is concerned.

And if that upgrade bug does eventually hit, rolling in NOS tubes are a great way to significantly increase the quality of sound for minimal cost.