Aitos EV 903 250 watt OTL amplifier

Ron Resnick

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microstrip

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Never heard about it, but 6 x EL519 in an OTL configuration can not deliver 250W at 10 ohm. Even at 10 ohm 250W needs a lot of current.
 

Ron Resnick

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Oh no! Another OTL circuit design mystery? :mad:
 

microstrip

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audio.bill

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Also notice that the rated distortion is 0.25% at just 1 watt, so you can only imagine how high it must be at full power (whatever that may actually be) since they choose not to even specify it.
 

spiritofmusic

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Back to the drawing board, Ron?
 

Ron Resnick

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I do not know anyone who has heard, or even heard of, this Dutch amplifier.

I am hoping that someone is going to come up with a theory as to how the Alieno works.
 

morricab

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Never heard about it, but 6 x EL519 in an OTL configuration can not deliver 250W at 10 ohm. Even at 10 ohm 250W needs a lot of current.

Perhaps if it is running nearly all Class B?
 

morricab

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No. They are probably referring to peak power in some strange conditions that does not apply to audio.

Look at the specifications of the fabulous Technics 20A, an OTL that used not 6, but 10 similar power tubes per channel. http://audio-database.com/TechnicsPanasonic/amp/eaa-2007-e.html.

It sounded great with ESL63.

Also, these are monos and hte Technics is stereo. so it is really 12 for a stereo amp...nonetheless, it seems unlikely to get that much power.
 

morricab

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Also notice that the rated distortion is 0.25% at just 1 watt, so you can only imagine how high it must be at full power (whatever that may actually be) since they choose not to even specify it.

With the amount of feedback used they are probably pretty flat distortion-wise until clipping.
 

morricab

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Graaf GM200

The Graaf GM200 ran 16 PL504s to get 200 watts per channel. I think that this tube, based on the look and size, is probably similar to the one in the amp in question (EL519) in terms of plate dissipation and therefore power capability.

It is one of hte hottest running amps I have ever experienced...right up there with the Joule Electras and my old Silvaweld OTL monos (which had 4 6C33Cs per channel).
 

microstrip

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The Graaf GM200 ran 16 PL504s to get 200 watts per channel. I think that this tube, based on the look and size, is probably similar to the one in the amp in question (EL519) in terms of plate dissipation and therefore power capability.
(...)

Unfortunately it is not - the power and current ratings of the 504 are around half of that of the 509 and 519. It was one of the reasons why the great sounding GM200 become known for very low medium time between failures. :( Although it could deliver the power - it had a low output impedance, lower than most transformer coupled tube amplifiers, it could not do it safely, as it was exceeding the safe maximum ratings of the components. And Graaf advertised it as compatible with 4 ohm speakers, making things even worst. But I have loved its sound - a good friend still owns one in his collection.

The only true high power OTL I have experience with is the Atmasphere MA-2.
 

Ron Resnick

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This company never even replied to my message transmitted via their contact page.
 

spiritofmusic

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That’s a sad indictment of a lot of so-called high end companies.
Ron, one of your Golden Rules is provenance and experience. And yet you’re talking about this company, and other below the radar concerns in your amp search.
Why?
 

spiritofmusic

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Surely the best approach will be to stick with those companies that are tried and tested, the usual suspects, and those left-field candidates that have a solid provenance like NAT Audio. How many companies on your friend’s Mono And Stereo website are still in business 12 months later?
 

Ron Resnick

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You are correct! That is my general rule, for sure. :)

But I am determined to find a viable OTL option for the Pendragons. And the Einstein OTL is too low in power output.

The Alieno is very low volume but I have seen it and heard it, and Kedar has seen it and heard it, and there are several in the field. As long as the speaker protection circuitry is robust, I would take a chance on it -- if, and only if, we get a better understanding of its circuit design.
 

Ron Resnick

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That’s a sad indictment of a lot of so-called high end companies.

. . .

Marc, it is a sad indictment of exactly one high-end company: Aitos.
 

spiritofmusic

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Maybe when you’ve emailed several high end concerns, and a big minority don’t respond even to repeated requests for info, you’ll get my sentiment.
I can name Saskia tts, The Disc Rotator tts, Wheel Fi Horns, amongst others, that don’t even get the first contact right.
I think you’ll find many concerns promoted on Mono And Stereo don’t even exist months after exposure there.
 

microstrip

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(...) The Alieno is very low volume but I have seen it and heard it, and Kedar has seen it and heard it, and there are several in the field. As long as the speaker protection circuitry is robust, I would take a chance on it -- if, and only if, we get a better understanding of its circuit design.

I think that if we ever get such understanding we will find it is not an OTL in the usual sense ...
 

Ron Resnick

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Maybe when you’ve emailed several high end concerns, and a big minority don’t respond even to repeated requests for info, you’ll get my sentiment.
I can name Saskia tts, The Disc Rotator tts, Wheel Fi Horns, amongst others, that don’t even get the first contact right.
I think you’ll find many concerns promoted on Mono And Stereo don’t even exist months after exposure there.

+1. Now those are more data points!
 

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