Dfrigovt, consider this fact, Atma-sphere has been manufacturing OTL amps since 1980, Joule since the early 90's, Transcendent since the mid 90's. The others I really don't know, but the Tenor is certainly more recent and the Berning which uses a completely different approach, was brought out I believe in 1996.
There were major considerations of owning such an amp in the past. The Counterpoint SA-4 and NYAL amps are really the only ones that contributed to the bad reputation of this design often because folks used them with the improper load. Harvey Rosenberg was very defensive of his design and was adamant that most of the problems were caused by audiophiles not paying close enough attention to this.
I am not trying to sell you on anything. If you like tubes I would say that a OTL is no more maintenance than a regular tube amp. The tubes should last a long time on the above mentioned amps. The outputs on the Joule the 6C33C are projected to last over 5 years. I believe the Tenor uses the same output triode. Audio Research 6550's are recommended for replacement every 2,000 hours, cost per tube is similar, about 30-40.00 each to replace. The Atma-sphere tubes are even less. The Transcendent's are about 20-30.00 each. Atma-sphere even less. I have not heard of ONE incident of catastrophic failure of either speaker or amp with the above designs. The advocates of these designs are speaking from experience. My guess is that Marakanetz is not but purely from an engineer's perspective based on what COULD happen with such a design from a purely theoretical viewpoint and how a transformer would act as a buffer in the event of failure. His concern seems to be about DC at the input of the speaker without a capacitor to act as a buffer. I can't speak for all the designs but I know the Transcendent uses fuse protection but is direct coupled. I'm sure the others have addressed this. Maybe someone else can offer input to Marakanetz's concern regarding this with the other amps. If not call the manufacturer and ask. Knowledge is king, misinformation is of no benefit to you or anyone else reading this thread. Get the facts.
Jud Barber has been working with tubes since the 50's, and also is an engineer. Bruce of Transcendent is an electrical engineer. Ralph I don't know. I think their experience and success with the reliability of their products would qualify them to a greater extent than someone providing theories as to what COULD go wrong and making absolutely erroneous remarks about replacing tubes regularly. The same for Atma-sphere. This design is mature and refined. See if you can find any horror stories about Atma-sphere amps blowing up.
The point is this as it is with anything audio, it is up to YOU to find out to your satisfaction the reliability of these amps. The users of current OTL amps disagree adamently with the naysayers who probably don't own or have NEVER owned an OTL amp. First thing you need to do is listen. The newer designs DO work to 4 ohm loads but as stated above, the OPTIMAL load is 8 ohms or higher. There are many speakers that qualify. Talk to the manufacturers'. Jud of Joule, Ralph of Atma-sphere and Bruce of Transcendent will give you the low down of the do's and don't for their respective designs. Each of these designs are considerate of the past failures that has led to the current reputation (by some) that OTL's are somehow still unreliable.
There were major considerations of owning such an amp in the past. The Counterpoint SA-4 and NYAL amps are really the only ones that contributed to the bad reputation of this design often because folks used them with the improper load. Harvey Rosenberg was very defensive of his design and was adamant that most of the problems were caused by audiophiles not paying close enough attention to this.
I am not trying to sell you on anything. If you like tubes I would say that a OTL is no more maintenance than a regular tube amp. The tubes should last a long time on the above mentioned amps. The outputs on the Joule the 6C33C are projected to last over 5 years. I believe the Tenor uses the same output triode. Audio Research 6550's are recommended for replacement every 2,000 hours, cost per tube is similar, about 30-40.00 each to replace. The Atma-sphere tubes are even less. The Transcendent's are about 20-30.00 each. Atma-sphere even less. I have not heard of ONE incident of catastrophic failure of either speaker or amp with the above designs. The advocates of these designs are speaking from experience. My guess is that Marakanetz is not but purely from an engineer's perspective based on what COULD happen with such a design from a purely theoretical viewpoint and how a transformer would act as a buffer in the event of failure. His concern seems to be about DC at the input of the speaker without a capacitor to act as a buffer. I can't speak for all the designs but I know the Transcendent uses fuse protection but is direct coupled. I'm sure the others have addressed this. Maybe someone else can offer input to Marakanetz's concern regarding this with the other amps. If not call the manufacturer and ask. Knowledge is king, misinformation is of no benefit to you or anyone else reading this thread. Get the facts.
Jud Barber has been working with tubes since the 50's, and also is an engineer. Bruce of Transcendent is an electrical engineer. Ralph I don't know. I think their experience and success with the reliability of their products would qualify them to a greater extent than someone providing theories as to what COULD go wrong and making absolutely erroneous remarks about replacing tubes regularly. The same for Atma-sphere. This design is mature and refined. See if you can find any horror stories about Atma-sphere amps blowing up.
The point is this as it is with anything audio, it is up to YOU to find out to your satisfaction the reliability of these amps. The users of current OTL amps disagree adamently with the naysayers who probably don't own or have NEVER owned an OTL amp. First thing you need to do is listen. The newer designs DO work to 4 ohm loads but as stated above, the OPTIMAL load is 8 ohms or higher. There are many speakers that qualify. Talk to the manufacturers'. Jud of Joule, Ralph of Atma-sphere and Bruce of Transcendent will give you the low down of the do's and don't for their respective designs. Each of these designs are considerate of the past failures that has led to the current reputation (by some) that OTL's are somehow still unreliable.