Tenor 75 OTL vs SET amps

I owned the Tenor 75 watt OTL's for 3 years (2001-2004).....on Kharma Exquisite 1D's.

it's going to be more linear than any SET I have heard. and will have more power with than many SET's if you find the right speaker but......there are a few things to consider. the early Tenor OTL's (the one's I owned) would grenade easily. mine did ignite a couple of times and took out ceramic mid range drivers on my Kharma's. after 2005 there were new owners of Tenor and they re-worked the circuit and it is more stable. so make sure you get an example that is newer spec. then get a relatively efficient speaker with an easy and flat impedance curve. lastly they get really hot. so prepare to deal with lots of heat.

it's one of my all time favorite tube amps, but needs considerable care in speaker matching.

Mike Lavigne said:

I owned the Tenor 75 watt OTL's for 3 years (2001-2004).....on Kharma Exquisite 1D's.

it's going to be more linear than any SET I have heard. and will have more power with than many SET's if you find the right speaker but......there are a few things to consider. the early Tenor OTL's (the one's I owned) would grenade easily. mine did ignite a couple of times and took out ceramic mid range drivers on my Kharma's. after 2005 there were new owners of Tenor and they re-worked the circuit and it is more stable. so make sure you get an example that is newer spec. then get a relatively efficient speaker with an easy and flat impedance curve. lastly they get really hot. so prepare to deal with lots of heat.

it's one of my all time favorite tube amps, but needs considerable care in speaker matching.

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Nothing like living on the edge .... were there reports of other amps of such vintage having similar flare ups?

Jazzhead said:

Nothing like living on the edge .... were there reports of other amps of such vintage having similar flare ups?

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well......I had been the first to put together the Tenor OTL and the Kharma in 2001 which is a story in itself (I've posted before on WBF)......involving some current WBF members. the match was one 'made in heaven' as the character of both products was super synergistic. Kharmas had a first order crossover, were relatively easy to drive and very coherent, direct and musical, which matched the attributes of the Tenor.....and that match was a very sexy sound. so many followed my discovery and put together various Kharma speakers with Tenor OTL's. then these beautiful amps revealed their nasty nature and so I was not the only one who had issues. then Tenor designed their 300 watt Hybrid mono blocks......which turned out to be worse yet. that adventure bankrupted Tenor and it was not a pretty picture.

a few of us got stuck holding the bag on those amps.....then the assets of Tenor were bought and the company was re-formed and they cleaned up the engineering and re-launched the products and they have been solid since.

getting back to your original question, OTL tube amplifiers are inherently volatile since there is no protection for either the driver or the tube from any issue. transformers tend to smooth out tube to driver issues. which is why OTL's need a relatively flat impedance curve. sharp dips cause the tube to be stressed directly.....which can be a 'bad' thing. bad = smoke + sparks + tube/driver popping.

so, yes.....other OTL's have had more than their share of 'events' over the years. early Tenor OTL's more than some others. the trade-off with OTL'S is that it has a more pure sound and is more linear than the typical tube amp with transformer. it's why the best sounding conventional (non-OTL) tube amps have very expensive transformers. it's the limiting factor to the sound, and eliminating it is a good thing for the sound.......until 'bad' things happen.

there are exceptions; the Atma-sphere OTL's seem to be quite stable.

btw; my personal sonic compass/reference is rooted in my memory of the Tenor OTL and then how the darTZeel captured and built upon what I liked about the Tenor OTL. so this subject is near to my heart.

Mike Lavigne said:

.and that match was a very sexy sound. so many followed my discovery and put together various Kharma speakers with Tenor OTL's. then these beautiful amps revealed their nasty nature and so I was not the only one who had issues. then Tenor designed their 300 watt Hybrid mono blocks......which turned out to be worse yet. that adventure bankrupted Tenor and it was not a pretty picture.

a few of us got stuck holding the bag on those amps.....then the assets of Tenor were bought and the company was re-formed and they cleaned up the engineering and re-launched the products and they have been solid since.

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Hello Mike, allow me to add that the reason why Tenor at the time, this is over 10 years ago, went bankrupt was a direct consequence of wanting to go the last mile in customer service. Effectively, by attending their customers by repairing the broken units free of charge and a whole product recall action associated to that, stretched the funds so much they needed a new capital injection which was done by Jim Fairhead, still current owner and CEO.

As you write, the 'new' Tenor amps (again existing for 10 years since the above happened) work flawlessly and Tenor Audio Ltd. has shown to be very responsive to any customer feedback since I am serving as an audition centre for them in Europe.

Regarding the OTL, I have tested both the 350M and 175S power amps with my Rockport Avior speakers and they do both flawlessly, although the Avior has anything but a flat impedance curve! My previous Lamm 1.2 Reference were struggling a lot more in comparison. Of course the current models are only OTL on the input stage and solid state on output stage, making them effectively a hybrid design, but successfully so I dare to say.
The true OTL is not made anymore by Tenor although they still do have some units on their shelves that have been fully upgraded to do away with their flaws. So, if anyone is interested in the SOTA for OTL, they can still investigate the Tenor option in all safety! Please PM me if you want any further information.

Now, as I also normally have the Aries Cerat Concero 65 true SET amps, I can compare the current Tenor models with the Aries and then we enter another world. In brief, if you need a lot of power because you have a really big room or very very demanding speakers, Tenor is the way to go, in all other instances I would choose for Aries Cerat Concero. Worthwhile mentioning that even my Rockports are easily driven by the Conceros as their massive current reserve handle the impedance and phase swings very solidly, in combination with a true SET sound.

Best,

Mike Lavigne said:

there are exceptions; the Atma-sphere OTL's seem to be quite stable.
btw; my personal sonic compass/reference is rooted in my memory of the Tenor OTL and then how the darTZeel captured and built upon what I liked about the Tenor OTL. so this subject is near to my heart.

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Hi Mike,

Agree with Atma-Sphere. I've always liked the Tenor rooms at shows. Quite a testament to DZ to compare its attributes to OTL.

flyer said:

Hello Mike, allow me to add that the reason why Tenor at the time, this is over 10 years ago, went bankrupt was a direct consequence of wanting to go the last mile in customer service. Effectively, by attending their customers by repairing the broken units free of charge and a whole product recall action associated to that, stretched the funds so much they needed a new capital injection which was done by Jim Fairhead, still current owner and CEO.

As you write, the 'new' Tenor amps (again existing for 10 years since the above happened) work flawlessly and Tenor Audio Ltd. has shown to be very responsive to any customer feedback since I am serving as an audition centre for them in Europe.

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as I was right in the middle of it back then I would agree that efforts were made to help customers both by the failing company as long as they could, and then later by the new re-formed company to some degree. you could get your 'failed' 300 watt mono blocks (by the new company) upgraded and fixed at a considerable price likely fair based on cost and the new price point of the new Tenor products then. what had happened was that they (original principles) 'bet' the original company on the success of the new Hybrid amplifier, then could not get it right. the lesson being financing expansion of a high end audio company based on new technology yet to be sorted out is not a good idea.

in any case since 2005 Tenor has been solid and successful and I did not mean to cast any doubts on current Tenor products, which I still think highly of.

Regarding the OTL, I have tested both the 350M and 175S power amps with my Rockport Avior speakers and they do both flawlessly, although the Avior has anything but a flat impedance curve! My previous Lamm 1.2 Reference were struggling a lot more in comparison. Of course the current models are only OTL on the input stage and solid state on output stage, making them effectively a hybrid design, but successfully so I dare to say.
The true OTL is not made anymore by Tenor although they still do have some units on their shelves that have been fully upgraded to do away with their flaws. So, if anyone is interested in the SOTA for OTL, they can still investigate the Tenor option in all safety! Please PM me if you want any further information.

Now, as I also normally have the Aries Cerat Concero 65 true SET amps, I can compare the current Tenor models with the Aries and then we enter another world. In brief, if you need a lot of power because you have a really big room or very very demanding speakers, Tenor is the way to go, in all other instances I would choose for Aries Cerat Concero. Worthwhile mentioning that even my Rockports are easily driven by the Conceros as their massive current reserve handle the impedance and phase swings very solidly, in combination with a true SET sound.

Best,

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I wonder (1) can the original Tenor OTL's still be 'fully upgraded' to updated safe circuitry?, and (2) how does the Aries Cerat OTL compare to the Tenor 75 watt OTL in performance? (I'm guessing that the price delta is considerable).

It is possible to get a new pair of Tenor OTL power monoblocks that has all the corrections brought to it so you buy in safety. The conditions for upgrading an older model are not known to me to be honest, I would need to inquire myself with Tenor.

I have not (yet) compared the Aries Cerat Collatio (an OTL 20W in stereo amp or 80W in mono config, check http://aries-cerat.eu/products/amplifiers/collatio-series which also explains the common 'historic' issues with OTL-designs and how Aries worked around that ) with the Tenor OTL 75 Wp. Pricewise the difference of the 20W version is effectively substantial and in favor of the Aries Cerat but for a different power rating although we all know that output power is only one of various factors determining the ability to 'drive' a loudspeaker adequately.
The Aries Cerat Collatio in mono version, basically twice the cost of the stereo version, is more expensive than the Tenor OTL of which only a very limited numbers are in existence as far as my latest update goes (i.e. dating from last summer so that is an important disclaimer...).

Merry Christmas to you all!

bonzo75 said:

So what about Aries OTL vs Aries SET?

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Mike Lavigne said:

(2) how does the Aries Cerat OTL compare to the Tenor 75 watt OTL in performance? (I'm guessing that the price delta is considerable).

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Well the big issue with making such a comparison is the nature of OTL is highly restrictive in terms of speaker options to use case. If you can get similar performance without going OTL why go OTL?

But should a comparison happen I don't imagine that it would be fair giving the Aries Cerat design is the first Single Ended OTL design and also has no feedback. But given the diminutive 20W of power at idle it pulls 1200W from the wall. Another potential deal breaker for many as that amount of heat in the summertime would be quite the challenge.

I was very tempted to introduce this design to the US market, but given the challenges in speaker options, power consumption, etc it will remain a mystery.....

Believe High Fidelity said:

Well the big issue with making such a comparison is the nature of OTL is highly restrictive in terms of speaker options to use case. If you can get similar performance without going OTL why go OTL?

But should a comparison happen I don't imagine that it would be fair giving the Aries Cerat design is the first Single Ended OTL design and also has no feedback. But given the diminutive 20W of power at idle it pulls 1200W from the wall. Another potential deal breaker for many as that amount of heat in the summertime would be quite the challenge.

I was very tempted to introduce this design to the US market, but given the challenges in speaker options, power consumption, etc it will remain a mystery.....

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Just FYI, transcendent sound introduced a SET OTL before Aries but it had 1.5 watts on a good day . They now have SET OTL monos with 12 watts.

morricab said:

Just FYI, transcendent sound introduced a SET OTL before Aries but it had 1.5 watts on a good day . They now have SET OTL monos with 12 watts.

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Then we'll just say first no feedback SE OTL

Wow... that is just not true.

flyer said:

Hello Mike, allow me to add that the reason why Tenor at the time, this is over 10 years ago, went bankrupt was a direct consequence of wanting to go the last mile in customer service. Effectively, by attending their customers by repairing the broken units free of charge and a whole product recall action associated to that, stretched the funds so much they needed a new capital injection which was done by Jim Fairhead, still current owner and CEO.

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That is just not true. It was all due to the ineptitude and greed of Francois Lamay. He intentionally left customers hanging and deliberately took orders and shipped products he knew were not ready for consumer use. He lied and cheated many people. You can try to spin this all you want, but I know the truth.

This is certainly no implication on Michel or Robert. Both are straight up guys.

Believe High Fidelity said:

Then we'll just say first no feedback SE OTL

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Go with the Berning 211/845!!

OTL, SE, plenty of power and reliable.

egidius said:

Go with the Berning 211/845!!

OTL, SE, plenty of power and reliable.

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Berning is not a SE OTL design. It is a 60W PP OTL design

A very good amplifier though I agree

sorry!

Believe High Fidelity said:

Berning is not a SE OTL design. It is a 60W PP OTL design

A very good amplifier though I agree

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..I stand corrected. I was probably overcome by the enthusiasm for my Berning Q'z ;-)

bonzo75 said:

I got an interesting feedback from someone who own the KR VT-6000, Silvaweld OTL 100 Reference, and New Audio Frontiers 845.

For speakers below 90db, he preferred the Silvaweld-KR-NAF.
For speakers over 99 db, he preferred NAF-Silvaweld-KR

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I have owned the Silvaweld OTL 100 Reference monos and on Acoustats the sound was shocking...NHB (thanks darTZeel) transparency and dynamics. However, they were a B*ç"h to keep biased properly and the HEAT!!! When the bias went off then the sound got...weird and somehow disjointed sounding...tune it back and MAGIC! My room went up by more about 10 degrees C in a few hours.

I am also quite familiar with the NAF 845 having heard it in a number of configurations and it is a very good amp but does not have the transparency of the Silvaweld...even into high sensitivity speakers. It is also warmer and rounder sounding...preferred by some but to others coloration. I would call it a mild coloration that does not cover over too much but is there nonetheless.

KR is less transparent than the Silvaweld, no debate there on my part BUT it sounds more cut "from the same cloth" from top to bottom and this coherence was a key factor for me. It is more neutral than the NAF, just as transparent and with better bass and equal or better dynamics, but especially better dynamics for speakers in between 90 and 99 db (the range your guy neglected to mention but where an increasing number of speakers fall). Also, it is important to note that the KR-VT6000 was a push/pull amp and not a SET, so it will not have the same properties as a SET KR. The KR from that generation that was the über model was the VT-800 MK. That was a great sounding amp (and very rare too!).

bonzo75 said:

I got an interesting feedback from someone who own the KR VT-6000, Silvaweld OTL 100 Reference, and New Audio Frontiers 845.

For speakers below 90db, he preferred the Silvaweld-KR-NAF.
For speakers over 99 db, he preferred NAF-Silvaweld-KR

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Did he explain why?

Did he express a preference ordering which includes NAT or Jadis or VTL amplifiers?