Thought on OTL tube amps

Its very difficult to compete with OTL in harmonic richness for any solid state amplifier. I admit it. We are doing our best but its difficult.

I went down a similar path 25 years ago. It got a lot easier when we got rid of the feedback. All I can suggest to anyone who has not tried the same is, make sure all your ducks are in a row- run the most linear circuit you can and put it on a speaker that allows you to hear the results without tonal issues. Only then can you see if you really want to go back.

OTLs don't run hot unless, like any other amplifier, they are biased to do so. Heat and good sound happen to go hand in hand; sure, you can get an amplifier that does not make a lot of heat to sound OK but again its the sort of thing that once you try using a little more bias and thus making more heat, you may not want to go back.

Afc, getting rid of the output transformer has nothing to do with hum.

There are several advantages to getting rid of the transformer: wider bandwidth and lower distortion. One advantage that most people don't think about is the fact that because the output transformer steps voltage down, in an OTL that translates to less gain needed. This is why its possible to build an OTL that has only one stage of gain.

The claims of longer tube life with sweep tubes may be true, but not particularly because of the voltages used. The voltages used in an OTL are so low that even conventional audio tubes would have a long life if that tube could work in an OTL.

As a user of OTL's for over 20 years, and now an Atma dealer, I might add that anyone who has heard Atma-sphere amps over the years, should try and here Ralph's latest designs.

As fantastic, detailed, quick and lifelike as they always were, they have simply reached a new plateau with the latest versions.

I just recently added dampers to the output tubes ( I have had dampers on the input tubes for years) I was surprised at the improvement yet again.

I am currently using the Zero autoformer with 4 ohm speakers.

Great tube OTL amps I think are they way off the audio merry go round.

Yes they need to be paired with appropriate speakers (the Zero increases the lot of compatible speakers) but once the amps are chosen, one may now look elsewhere in the system to make improvements, confident that the amps are making much of the potential in the signal.

" using an autoformer I think I will use my tube amp with built in transformers"

Totally agree, provided its high quality amp

I just had my Atma-sphere MA1's updated to the latest 3.1 version (from 2.2) plus all options available have been added.

I have got to share that the current upgrades are a revelation for this amp. Wow does this amp now sing. So rich and glorious with state of the art transparency. The stage depth is jaw dropping and the images so 3D and real.

This is my first OTL amp or amp from Atma-sphere and I am taken back now realizing what I have been missing. This latest generation simply outclasses the 2.2 by a wide margin.

Yes, I am pleased to say the least. I have owned many a tube amp and this one has all of that wonderful warmth, bloom and weight combined with SET-like intimacy.