OTL amps with Wilson Watt/Puppy 6s

OK I'm in the market looking for an OTL amp to mate with a pair of Wilson Watt/Puppy 6s. The speakers are rated at 93 dB and 4 ohms. My room size is 16 x 19 x 8 so its not too large or too small. So far I have on my list:

Joule Electra

Are there any others that people recommend I consider?
Those are all excellent amps. We just took a pair of Joule Electra Marquis to a customers home who has already great mono blocks the Nemo's with the Wilson Watt Puppy 6's and they were stunning. These are great amps although they do warm up a room.

On page 147 of the latest Absolute Sound Harry Pearson has a nice short review about the Joule Electra mono blocks under Golden Ears.
bryan..i can whole-heartedly vote for the tenors..i recently bought a pair of the 75 wi's to go with my piega p10s that are 89db efficient. they are superb amps. they are the most musical,transparent,tonally correct amps i have ever heard.they will drive your wilsons' easily and give you the most breathtakingly beautiful music,imo,you have ever heard.let me know if i can be more help. dave smith 'calloway'
David Berning ZH-270, stable into 2 ohms (maybe a little less), does not use up alot of power and has way more bass than most of the other OTL's you have mentioned, also utilizes quite possibly the most advanced power supply within the audio realm. It also INCREASES output power as impedence curve dips, not the opposite like the other OTL amplifiers. You may also adjust feedback on the fly, auto biasing, has A/B input switches for use direct with a source if thats what you wish, boasts a 20 year life span on tubes and uses way, way less idle power and less power at full ouput than the other power mongers out there. You may also utilize the channel strapping option with (2) ZH-270's which will provide you with 105W @ 8 ohms. My single 270 is happy as ever running full-range Soundlab Pristine ll's with no problems. What other amplifier that weighs 9 pounds puts out enough power to drive full-range SL's?? Notta, none.

Best of luck,
From everything I've read about OTL's, mating them with a low impedance load like the WATT/Puppy is a no no. I personally wouldn't do it. My WATTS go to LESS than 2 ohms in the critical midrange, even though they are a nominal 4 ohm speaker. You'll get some thin sounding speakers IMHO. They also have some very wild impedance swings with frequency, they are a tough load to follow. OTL's like high impedance speakers. I suggest the Coincident line (10-14 ohm load) as a better match with OTL's, if that is what gets your heart a-pumpin'. Good luck.
Rlennan: Which version WATTs do you have?

I have heard the Wilson Watt Puppy 6's with Atma-sphere MA1 MKII.2's, MA2 MKII.2's and the Tenor 75 Wi. They all played beautifully. You can clip the lower power OTL amps at over 100db with the WP 6's, but it really takes an awful lot to do so. I would not sacrifice the transparency, extension and purity of an OTL for any other type of amplifier.

An important question I would ask is what size is your room and how loud do you listen?

I certainly favor the Tenor's by a wide margin, but since I handle the product, that should be considered. :)

Good Luck!
Yes OTLs like high impendance load but thanks to the Zeros, I am driving a pair of Vandersteen 4A full range (5-way, 4 ohms nominal, with double 12 inch sub woofers) with a pair of Atma-Sphere M60 MkII monos. See this link for info about the Zeros. http://www.condor-connection.org/asog/tweaks/ps/zero/index.html
Call Paul Speltz up and he will help you. Also see the numerous postings on the Zeros on ASOG (http://www.condor-connection.org/asog/bbs/index.html) and Audio Asylum (www.audioasylum.com) sites.
Good Luck
I read somewhere that Wilsons' N.American sales mngr uses the Atma-Sphere OTL's on his personal pair of MAXX's.
I think it was the 140ish watt monos, so not even the biggest of the OTL's.
I've heard WP6's with a variety of amps, including a Linn Classik @ 75 tiny ss watts into 4 ohms, it sounded quite lovely.
i spent 2 weeks with the Atmasphere MA2 mkII.2 and 1 week with the Tenor 75Wi with my previous speakers, the Watt/Puppy 6. both were excellent......easily the best 2 amps i have ever heard.

the Atmasphere was perfectly matched with the power hungry WP6.....plenty of power, no dynamic limitations i could perceive, excellent extension and resolution, with ease and purity. in fact, i was ready to buy the Atmasphere........

then i heard the Tenor. not as perfectly matched to the WP6, good dynamics within it's performance envelope, but at higher than normal volume levels it could get hard on peaks or go into soft clipping. no problem at normal listening levels. but the Tenor was more extended and articulate in the bass, had better clarity and refinement, and was faster than the Atmasphere.

i bought the Tenor, but also got different speakers. my recommendation for WP6 speakers would be either the Tenor or the Atmasphere, depending on listening priorities, size of room, and musical choices. you will love either of these great amps. OTL is the only way to go IMHO.
Most OTL's need a speaker that operates within higher impedence curves in general to function normally with overall stablilty. There is only one OTL amplifier in exsistance that does not use brute force design requireing massive power consumption to achieve a moderately high amount of output power which steadily increases as the impedence curve dips. This is the current David Berning designed push-pull OTL power amplifier (ZH-270). Only the highly advanced design of this amplifer makes the following possible - To achieve all the positive sonic attributes of an OTL design without ANY of the usual restrictions, pitfalls and drawbacks. Sure, one cannot expect an amplifer which outputs 84W at the onset of clipping @ 8 ohms to drive anything, but what amplifier of 80 Watts could?? Add the tube life, reliability, funtionality, versitility and the sum is an incredible product that belies other OTL's costing many times as much.

I think I'm done rambling, let me look into the amps stability and power ouput into impedences of >2ohms and get back with you guys.

Best Regards,


The EAR 534 is a great amp - low maintenance and versatile - independent gains per channel and balanced input options and can be bridged for mono - looks great also .
How about Graff?
The Berning amps are not OTL amplifiers.
The EAR amp is not an OTL amplifier!
The Berning amps are OTL amplifers, read the technical data on the David Berning website. They are a highly advanced OTL design, I believe that is why this may confuse you. Just because this design does not correlate with other designs based roughly upon original Futterman principals and/or designs certainly does not mean this is not an OTL amplifer. Read the technical data on the website or e-mail me for more specifics which are clearly laid out within the pages of the instruction manual. This is clearly not anything like the old school of thought on conventional OTL's which for the most part incorperate "brute force" technology. There is nothing wrong with the sound or design of many of the favored OTL companies/products and that is not the point that I am attempting to make. It is my point to illustrate that the current David Berning designs represent a state of the art assault on traditional OTL design drawbacks and represent a giant leap forward in OTL design technology. Who would gripe if every OTL amplifer possessed the ability to mate with much larger varieties of loudspeakers as a result of impedence swing tolerances and at the same time retain the wonderful sonic characteristics of an OTL???

Wb6rhq brings up an interesting point here, he's kind of right when he says that the Berning is not a OTL amp, if you mean OTL in the respect of the 50-60 year old design that is still being currently used by most OTL designs.

Technology has come a long way since then, the Berning uses a RF matching transformer, the audio signal is piggy backed on a RF frequency, the transformer is therefore for the RF frequency, not the audio signal, which gets a trouble free ride, what you end up with is a new type of OTL, sophisticated cutting edge, able to drive low impedance.

So the question is, do you want to listen to music as it was reproduced 50 years ago, maybe?
The other choice is to listen to music as it can be reproduced today, with today's technology, designed by a brilliant Physicist.
Hi Chris

You have touted the Berning in many threads. Certainly one would be curious about its performance relative to other OTL designs with all the other pluses it offers, low heat and an ability to drive speakers with low impedance dips. It really seems to me that there aren't too many audiophiles that have done direct comparisons with ALL the popular OTL's with a few exceptions, Atmasphere and Tenor come to mind as of late. I have traced back to all threads on this site and AA for comparisons of various OTL amps. They all have their pluses and drawbacks but there seems a consistency in their overall presentation of music, pure midrange, frequency extension and ultra-transparency. A window into the music. The SE Class A designs seem described by concensus a bit purer and maybe harmonically a little richer(?) than the Transcendent which is a direct coupled AB design. Problem with those (Atmasphere, Joule, Graff) is the heat, the Transcendent runs a bit cooler.

So are you saying the Berning offers the sonic trademark of other OTL amps? Have you compared and to which ones in particular?

Hi Will,

Thanks for your note, I think your curiousity about the Berning products is absolutely valid in regards to how it compares sonically to other OTL amplifers on the market. Aside from the information I have read in various articles and columns I have not yet had the opportunity to listen to another OTL amplifer. Very soon however, a friend of mine and myself are going to Chicago to listen to the Atmasphere MA 1 Mk11's on a pair of Soundlab U1's and we are taking along 2 Bernings with the channels strapped for comparison. I think this should prove interesting and make for an excellent comparison of two different designers out to achieve what they believe is possibly the best sound attainable from audio amplification today. It should be a very intrigueing adventure :)

Chris I certainly look forward to your impressions. The Transcendent OTL amp has been a revelation in my system. It outperforms, by a significant margin, every tube and solid state amp I've listened to of late including the Rogue m-120's and Pass amps which are highly regarded in this price range. It is an incredible value at 2.1K and the performance is so good that it could encourage one to look for a speaker system to match with its limitations.

I am considering the Joule VZN 80 for my Merlin VSMs (the choice of Bobby P) and would certainly love to hear the Berning. I could use a bit more power at times in my room. One thing is for certain, after having an OTL in the system there is no going back!
Chris, please keep us informed. I would love to hear your comments on this comparison. Thanks much.
I agree with you completely Will about sticking with the OTL sound once you have heard one with the right gear. I have never felt so strongly about any other amplifier I've owned or heard thus far as I feel about the ZH270. I'll bet the Joule's with the Merlins would be great indeed, I would like to hear that combo sometime.
I will report about our experiences in Chicago with the OTL's as soon as we return. It should be an audio day to remember, this is certain :)

I used to have 5.1's. Like I said, they dip to almost a short circuit in the critical midrange, and are VERY resistive in the bass. I've never understood why speaker designers do this kind of stuff. I played with OTLs before, but have moved on to low powered SETs and horns. I find DHT's to have much lower inherent distortion than any other amplification device ever made. Other designs get good measurements with negative feedback. Same goes for horns for speakers. I used to laugh at 'em, now I love 'em (with triodes).
Wow, great idea - using an autoformer to match impedance. I would guess that without these things, OTL's on the WATT Puppies would have a frequency response curve that looked horrible. Thanks for the post!
Through the generosity of Chris, I received a Berning ZH270 to audition in my system. I must say that my first impression was, "Damn it's small". Don't let the "small" matter fool you.

I read the manual and it is evident that the engineering of this amp is completely different from other OTLs. It is an all out effort to bring out the benefits of OTL design and overcome some of the shortcomings including heat and current limitations. There are three settings to adjust the feedback so one can tailor the sound to the system and taste. The late Harvey "Gizmo" Rosenberg gave the design a thumbs up and so do I. It is one of those special innovative products that take a back seat to the mainstream way of thinking. It also has the sonic attributes unique to OTL designs. Then there's the bass...it almost defies belief that a 10 lb amp can put out this degree of well defined natural bass with power. It never ran out of gas although I have efficient speakers with no impedance dips. I'm sure it would work very well with the Wilson's.

Bryans I would encourage you to add this amp to your audition list regardless of your budget.
You should hear two ZH270's strapped Mono, your speakers wouldn't know what hit them :)
These tiny little giants are just awesome, I'm so glad you enjoyed it.
Certainly breaks the mold " bigger is better" doesn't it?
hey tubegroover...
is the bering any competition for the t-8s w/ the merlins?

inquiring minds want to know
Hi Ryan

I haven't heard a pair of mono T-8's in my system so I can't compare directly. What the Berning does do over the Transcendent is probably a result of the extra power but a direct comparison would have to be done to be sure. On large orchestral music I noted that more of the musical information is preserved during busy passages. High frequency extension is better as is space/ambient information. My wife noted this immediately. She loved it. The T-8 stereo gets a bit polite or should I say stays polite at such times, not nearly the dynamic performance of the Berning, not enough power. You have to remember Rhyno that the T8's are very large. A pair would take up a lot of space. Plus you have 16 output tubes and 10 driver tubes total. The Berning has 4 output tubes and 6 driver tubes total. Power rating would then be equal. The Berning could be used with a wider variety of speakers, the Transcendent would have to be matched more closely. 4 ohms is the max impedance dip for a pair of monos.

I love the Transcendent but have realized almost since I first acquired it that it wasn't enough power for some music in MY room which has a large volume. Always figured I would upgrade to monos or look at other options. I need to listen to Joules before I commit to anything else but I'll tell you the Berning is in the running. An incredible amp it is.

Allan, I can't even imagine 2 ZH270's strapped, it must be an awesome experience.
Tubegroover.....Awesome in Mono's
Bernings ZH270's is everything you want and nothing you don't..... well it could be bigger and prettier but then again, it could cost $10K.

I bet you if the ZH270 had a line of tubes going out the door and was the size of your microwave and consume the same amount of power as it, people would really be impressed :), even if it does not sound as good as it does now.

I once sold one to a guy that thought I sent him a little scaled model of the amp :)
For those that remember Berning amps back in the 70's, they were big, really big but still cutting edge back then, some had high speed switching power supplies.
We used 2 Berning 270's on Soundlab Pristine ll's several weeks ago and it was spectacular! More drive, more dynamics, more energy, just an amazing event. One ZH270 is very, very good with the Soundlabs, two is out of this world, they absolutely soar with vibrance, energy and encompass the room with sound. I've had amplifiers that weighed over 6 times as much as a single ZH270 not sound as large and in charge, I never knew anything like this was possible from such physically small amplifer. It is my opinion that the technology found in this piece is matched by no other OTL tube amplifer at this time. Anybody who's curious about some of the other unique features, just ask Tubegroover (Will), he has a manual and I'm sure he has read it by now :) However, he may have a hard time typing and reading with all the bass coming from his listening room :)

I have 5.1's and wondered why my ARC VT-100mk2 didn't get the job done. I then tried a 335 and my jaw hit the floor. Instruments were much more full bodied and the tonal balance smoothed out making marginal recording much easier to listen to. The ARC had a slight advantage in reproducing the sense of space/air, but the Levinson is not far behind. The improvement in the bass control alone convinced me that, at least with the 5.1's, short of a massive tube amp transistor is better. Thanks to you I know why.
After extended listening since last Saturday I am buying the Berning ZH270, thanks Chris, Allan and especially David Berning. I won't belabor what has already been stated above because only listening to this most incredible product can convey what a marvelous accomplishment of engineering, innovation, performance, economy and size it is. It just has to be heard to be believed and then maybe you still won't believe it. A MUST AUDITION for anyone in the market for any amp in this price range and up, even below, you may hold off until you can get it :*) It should drive virtually any speaker on the market.

This amp is like no other in too many ways to go into here. Check the Berning site for reviews and especially the article by Charles Hanson in Glass audio. It is a technical tour de force.
Are OTL Transcendent T8 monoblock amplifiers a good match with Hales Transcendent T8 speakers...?
Maybe, as long as you don't listen above 60db :) I think those big Hales might suck the juice right out of the Transcendent T8 monos, their names match well though, catchy :) Lets see, they dish out 80W @ 8ohm, 50W @ 4ohm, probably don't tolerate impedences below 4 ohms at all. I really feel a different OTL amplifier would be in order if you really want to go that route. A certain OTL amplifier comes to mind, you might want to peak at some of the above threads about a special OTL that CAN tolerate and drive more difficult loads with ease. Hint : 270 :)
I own a David Berning ZH270, and I whole heartedly agree with the above statements. The ZH270 will run just about anything very well with plenty of dynamics and finesse to boot. This is truly a world class amplifier, and I dare any other OTL amplifier to match it performance at this price level, or any price level! I have no doubt that the Berning will run the Wilson's with ease.