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I have posted on the relevant forums asking experience and one response. Thinking either people don't like otl or never tried.
i am sort of surprised. Joule and atmasphere i thot were pretty widely used.... apparently not. especially by horn users.
any thots?
Follow Ups:
I have the Berning Siegfried amp, which is an OTL/SET amp. It sounds wonderful with horns- Avantgarde Duos. Enjoy listening.
I decided that the advantages of an OTL amp could be most fully realized if it, besides, discarding the output transformer, also did well what solid state amps are best at.So I designed my OTL to be dc coupled input to 6as7 output, like an op amp, although I roll the gain off to unity at DC to minimize offset and reduce the likelihood of upstream electronic failure putting disastrous amount of dc across voice coils.
I use moderate AC negative voltage feedback (26 db) but also positive current feedback to get damping factors in the 100+ range through the audio range, so its frequency response and distortion are less dependent on load impedance than expected from tube amps. However, it still drops in power output with load impedance, although it is stable into as low as 2 ohms.
It has the best sound throughout the audio range of any amp I've heard - my Lux MB3045's modded with all polypropylene coupling caps comes close to it in the midrange, though.
I use a Luxman MQ-36 OTL amp with my Quad ESL. Absolutely the best amp I have ever used with electrostats, and I have owned MANY amps both tube and SS. Sounds utterly transparent and have frequency extention not even matched by Levinson ML-2s. But it sounds just ordinary when driving conventional cone speakers or horns (tried it with a few JBL and Altec horns).
surprised... wonder why.
Hi,Well I've been using an original Futterman H3 with six 6FW5's per channel on Quad ESLs this is match made in heaven..for real fun I stack a pair of Quads and run them in series to the Futterman.
The Futterman is grainy yet lifts veils of smog out of a good recording . I run mostly vintage amps: Citation II, Marantz8b etc and none can compete with the clarity of the Futterman. I've tried Atmashpere and if I did'nt have the Futterman I'd consider it otherwise not worth the expense. Now the Berning with the right speakers is a different story.
All amps are compromises. The Futterman gives up nothing to missed detail yet may not have the "slam" of larger PP amps ...yet the larger amps "may" be more veiled. Speaker match is everything especially with an OTL. Personally, with an OTL I'd pick my speakers first to match the OTL without autoformers!.
Too bad Harvey Rosenberg is gone. I think he advocated small OTL's and DHT amps for tweeter amps.You may try over at the triode guild website..there is some OTL info there as Rosenberg founded NYAL and carried on the modernized Futterman circuit after Futterman's passing.
Good Luck...do a search on OTL ..some of the Italians and other Europeans are really into this type of amp and have chat groups.
finally some responses. got zero on other forums. I knew had to be some of u out there cuz of the companies producing....1. can someone tell me what u getting with otl vs ss or high powered tube amp? why like the sound and choose it.
2. and most of u seem to be atmasphere owners, and not joule or berning. Is it cuz cheaper? the russian tube of the Joule sure looks interesting.
thx!!!
Hmmmm.....seems that there are a lot of OTL's out there to be had (AtmaSphere, Joule, Transcendent, etc.) for someting that 'nobody seems to be running'. They do have certain requirements in terms of appropriate speakers and the like....but doesn't any amp?I know I love my Atmas. And, contrary to what might have you think, not everyone uses an autoformer on the back side.
....sT
Merlins and OTL seem to go together like peanut butter and jelly. Merlin owners use Atmosphere, Joule and Berning quite a bit. OTL seems to be particularly synergistic with Merlins and are quite popular in that application.
Well, here is an OTL owner (Transcendent SE OTL). It's not my only amp, but it certainly does not at all fall behind my vintage tube amps. I guess had I known how well it matches with Khorns, I might not have bought my Marantz and McIntosh amps. To these ears the SE OTL is a very neutral (in a positive sense) and musical unit. I am a very happy customer indeed (and not affiliated with the company).Wolfram
I also have the SE-OTL and think it is a truly great sounding amp. You just can't use inefficient or low impedance speakers with it
Alan
I agree with the posts below but why not make a multi driver/line array with the drivers in series to get the impedance up. Eight 8ohm drivers would give you about 64ohms load for your OTL's.
like me, check the gallery
Without trying to insult or irritate OTL fans look at the basic concept. OTL likes looking into higher impedances rather than lower.
What dynamic loads do most speakers present? Not simple resistance.
Most speakers have very reactive loads. Then there are the OTL schemes. Circlotronic and Totem Pole. Both need banks of output tubes to develop power. Look at the loudspeakers favored to bring OTL amps into superlative performance - electrostatic. These have transformers to match amp to load. So, although your amp may be OTL, the speaker itself has a transformer. Maybe there really is something to having just one output device SE in class A. Sensitive speakers ( horns ) allow you to hear what the amp is doing in the less than 1 Watt range. Perhaps weaknesses in the overall OTL scheme are more easily heard with horns.Anyway, some thoughts on the subject. I should clarify that the last OTL amps in my system were Futterman H3aa's, though I have heard lots of others: Transcendent, Fourier, Atma-Sphere. Bottom line: if they sound good in your system, enjoy them. Too me it always seemed a bit silly to use an OTL if it was recommended to use an "autoformer" or transformer between amp and speaker to give the amp an edge through impedance matching. Happy listening!
I thought the Electro Voice Circlotronic circuit was a transformer coupled design derived from the "unity coupled" concept (ie... a competitor with Mc).Furthermore you say that "Both need banks of output tubes to develop power." I thought the banks of "output tubes" were used to lower the output impedence, not to develope the initial voltage swing in the output section.
Finally, though I totally agree with your autoformer statement, I think it is misleading to state that SE topologies have a single output device because this power tube is coupled through a transformer and the amp is is suceptable to any vagueries in the output tube, transformer, speaker interactions.
Rodney
Check out Atma-Sphere's web site and note the Circlotronic references.
I refer to the basic topology or circuit notion not to actual Electro-Voice Circlotron amplifiers.Banks of output tubes are the mechanism to effect lowering working impedance. They also deliver power. Voltage gain in such schemes comes with the input tube.
A transformer whether on an amplifier chassis or sitting on the floor behind ( or in ) your loudspeakers is still a transformer.
Cheers.
I did a little reading at the Atma-Sphere site. The "bridge circuit" which was transformer coupled in the EV amp is generally refered to as Circlotronic, no matter the speaker coupling topology. I guess if I had thought about the power issue for a few minutes, it would have been obvious. The power being developed on through the bank of output tubes refers to the lowering of impedence and a cocomitant increase in current. This would be a linear relationship (I=V/R). However, power is the the square of current multiplied by resistance. Thus the effective power of the amp is developed across the output tubes that lower resistance.I guess this brings me to the last point which is that no matter what method of speaker coupling is used, it is still doing essentially doing the same thing, be it a transformer in a SE amp or a bank of tubes in an OTL. As to which is the best method, I would suspect each is prone to certain vagueries.
Thanks,
Rodney
Rodney, hi. Yup, you got it. There is a certain magic that can be had with OTL in the right set up with the right speakers. I am a fan of the OTL notion. I have heard them do wondrous things. The reality is that in the "real" world there is always a downside to every upside. It is only opinion, born of experience, that any time you tie together a whole bunch of output tubes you are creating a situation where the signal can be degraded: micro subtleties, the edge on transients, etc. Think about any dynamic devices tied together to perform as one. You can do it, but something may be lost or fuzzed up in the process. The Futterman scheme runs the audio through a whopping capacitor at the output to block the B+. The Circlotronic does not. Cordially.
OTL and horns :-O
Mmhhh, I don't know. You might want to use SS for lower power consumption instead; pretty much same sonics though...
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