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I just hooked up my Fourier Components Panthere OTL monoblock amps to my Essence 2-way speakers using Zero autoformers. And let me tell you, OTL amps are everything they are cracked up to be. I have had a number of push-pull tube and solid state amps but nothing has come close to the OTL's. Big dynamics, huge soundstage, lots of detail, presence of instruments and voices is uncanny. Highs are extended and clean. And the bass was better than I thought it would be--more prominent, maybe not quite as deep as with the SS amps, but also more clarity. It was a royal pain in the neck getting together everything required like the autoformers, finding tube locations, biasing the tubes, etc. It was also well worth it.
Follow Ups:
HI,
I think you hit the nail on the head so to speek.
OTL amps are just incredable and i will never forget the first time i heard one.
This was after listening to a push/pull made by the same manufacturer.
After 4 hrs of p/pull i was not prepered for the sonic onslaught of OTLs.
I noted a transparency that was as clear as water itself and the soundstage had real depth and clarity far beyond other types of amps.
Can't speak to commercial designs particularly, but my home brew dc coupled (as in -3db @ 1hz, reduced to unity gain @ 0hz - given that I've smoked a couple woofers in the past with it as is due to offset or motorboating problems upstream, I've never had much desire to run it flat to DC) high damping factor (> 100) balanced triode OTL has been my hands down reference for the last seventeen years now. Not expensive at all to maintain, either ...after all, there's hardly anything in the signal path but tubes and resistors. I still have half or more of the original tubes in it - even at the output stage - I just can't bring myself to replace some of the oldest 6AS7G's, even though their emission has surely dropped somewhat by now.
Hi.OTL topology removes the bottleneck - O/P transformer, the historic bottleneck to music nirvana. I always believe in this truth.
However, really good OTL-OCL amps are not easy to find & can be very
expensive to own or even to DIY properly.I travel thousand miles every year on business & I've tried whatever brandnames of whatever topology in the marketplace worldwide to audition the very best, from WE300B parallel SE to tube OTL-OCLs.
After years of auditioning, I still come up to my own sonic conclusion: OTL-OCL topology still wins. My best score so far is still Tenor 75WP 75W monoblock, retailed only for USD20,000 a pair three years back.
I tried its new 'replacement' model - a tube-transistor hybrid, just last November in Tenor rep's studio, I was NOT impressed at all. IMO, Tenor 75WP still the best so far sonically.
It used 3 mirror pairs of 12AX7s, 6H6P, 6H30P, driving only 4x6C33C, the infamous twin-triode O/P tubes previously used in Russian jetfighters. The circuitry is a balanced, quasi-Circlotron OTL-OCL topology with heavy-weight solid-state regulation throughout, which forms the backbone of Tenor, & which is always a crucial design for any good OTL amp, according to its designer, Michel Vanden Broek, audiophile converted microwave-aerospace engineer. For sure he is not
a Russian though he used all Russian triodes in his brainchild.Deep realistic soundstage, sky-is-the-limit dynamic range from subsonic to ultrasonic, yet so subtle & musical that its sonic presentation, IMO, outperforms any amps I've ever auditioned, be them
any other OTL brandnames, or transformered tubes, including the superb Japan Audio Notes silverloaded 300B SE power amps. It handles gracefully BCC mininature monitor-type - KEF LS3/5a as well as 6ft
500lbs monstrous Hyperlon of Rockport Technologies (USD90,000 pair). WoW!A word to those O/P iron die-hards, Michel is a DIY tube fan like you or me. He started his SE tube amps when he was 14. Surely he is no stranger to O/P irons. He has chosen OTL topology on technical & sonic ground which I fully second.
Good listening
cheap-Jack
Feb 1, 2005.PS: Bad news to OTL fans, I got the impression that Tenor Audio in Canada has recently moved out or even closed down as I can't
reach it any more with its phone no.Anybody can tell me whereabout is it now?
They ran into financial difficulties and have closed down. Everyone is waiting to see if they can reorganize and return in some form, but no definitive reports so far.Here's a link to an ongoing thread at Audiogon:
I found it interesting, Lew, that in talking with Ralph that he says the Tenor is based on a circuit Atma-Sphere explored at one time and then moved away from because Ralph never could overcome a coloration in that circuit. He says he hears it every time he hears that amp. You may also recall an interesting thread (was it on ASOG?) some time back in which a listening session after a show (CES?) was described. Chesky was using the Tenor 75s to show a new speaker they were introducing. Ralph invited them to compare to an M-60 after hours. As I recall the thread, it was said that Chesky ended up preferring the M-60 as more neutral and decided to show with it the following year. Dunno if the subesequent show ever occurred.
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I was not aware of the incident you mention, but I once queried Ralph about the Tenor, and he only noted that the circuit was adapted from one that had been published in the audiophile press back in the early 90s. He told me no more than that. While I have to respect the reviews of "gifted listeners", like Jonathan Valin, I have been skeptical re the Tenor, because it uses a 12AX7 input tube. Now I know that sounds like the highest form of snobbery and short-sightedness, but I just don't see how a 12AX7 can compete with a 6SN7, or any other of the best medium-mu triodes, as an input tube. And after all, most of the "flavor" of the amp comes from the initial voltage amplifier at the input. OTOH, I am told that the Tenor amp uses regulated hi-voltage supplies and that this may account for its ability to compete with Atma-sphere designs, which traditionally used unregulated supplies. But then in recent upgrades, Atma is now using regulated voltages on its HV supply, too, using the same one-chip regulator that Tenor uses. In fairness, I would have to hear the amplifier before I criticize it. So, I'm withholding judgment. One thing: the cost makes an MA2 look positively sensible, on a dollars per Watt basis.
If I'm recalling this correctly, the circuit that was published in the magazine was actually published by Ralph in explanation of what was going on in the new generation OTL amps he was producing. Ralph later moved away from that specific circuit to another design.
I definitely remember that thread and the fact that Ralph expressed relief after actually hearing the Tenors because he felt they were more colored than his own product and he had been a little concerned about them because of the runaway good press they had been garnering at that time, pricepoint notwithstanding.
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I'd be curious to know whether they are as wonderful as Jonathan Valin seems to think they are, particularly the 20W all-tube product. I'd be grateful for any informed opinions.
I had the Tenor 75watt amps in my system a couple of years ago. They did not sound as neutral as the Atmasphere MA1's and the highs were not as extended either. They had a pleasant sound but I would not necessarily known that they were OTL's - I thought the Graaf GM 200 which I owned for awhile was better. I was using stock Pipedream speakers at the time which are a fairly easy load - perhaps the rave reviews were with speakers that had a more difficult load and lower efficiency. I went the other way and reconfigured my speakers to be tri-amped with a relatively high impedence (12 ohms midrange, 18 ohm highs)- and the Atmaspheres really responded. The distortion goes down and the dynamic envelope is significantly increased.
I have one at one 15W OTL to which all my amps are compared.
(disclaimer: I am not promoting whatever brandnames in the marketplace. Just that I read posts regarding audition comments on the Italian Graff & American Atma-Sphere, which I've auditioned, I put in my own sonic impression of the Canadian Tenor as well.)Whoever wants to borrow the critics' opinion on the Tenor flagship
model: 75WP 75W monoblock, here are some of them:"The best stereo system I've ever heard: Rockport Technologies Hyperion loudspeakers+ Tenor 75WP OTL amp"
"Best buy"by Jon Valin, The Absolute Sound, June/July 2002.
I've auditioned this combination bigtime & agreed with Jon wholeheartedly."Sound open without being lean, full but without excessive warmth or any murkiness...pleasurable to the extreme but not ruined by obvious eupohony or coloration... absolutely nails the harmonic structure of instruments... Piano has the most correct atttack and decay"
"What more can I say? Seek a pair, but have your checkbook ready"
by Marc Mickelson, Soundstage June 2002.My way of auditioning any equipment is to listen its sonic performance before I start to read its specs & reviews. So no pre-bias whatsoever.
My first audition of this monoblock was three years ago. I started
by asking the attendant (a lady, incidentally) in the top sound boutique in town, to show me the best sounding amp available there. What a quasi-blind test as I didn't know what I would be given to listen!After three hours solid audition with my test CDs among other music programmes, I got to find back my jaw where I dropped it. Then I started to read the reviews the lady attendant gave me & then knew this is a 'something-else' of an amp made by a Belgian in Canada.
It is indeed a pity as learned from Rushton that the amps' maker is
in sort of financial insolvency. If really so, we audio fans will lose a golden opportunity of enjoying music reproduction to its finest.Good OTL listening
cheap-Jack
Feb 2, 2005.PS: I fully agreed what Marc Michelson implied in his review above
that really good OTL designs, like Tenor, does "not ruined by obvious euphony or coloration" that many output-transformered tube amps do.
Thanks for in the process correcting me on the power of the amp, 75W, not 20W. I am well aware of Jonathan Valin's rave review, but since he falls in and out of love regularly with audio components, especially amplifiers and speakers, I was looking for fresh opinions. Good to know that your experience was similar to his. What speakers do you use with the Tenors, or what speakers were playing when you auditioned them, if you do not own a pair? Is the schematic available anywhere?
Welcome to the club, rlawry. It's quite revelatory to experience the step-up in quality that the elimination of the output transformer begets. Simpler is, indeed, better.
Try driving your OTL with a passive pre like the Sonic Euphoria PLC. This uses an autotransformer as the attenuator and is stunning with my Transcendent sound OTL. I have heard several OTL's and they all sound wonderful.
Alan
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