I have just purchased the latest Sound Lab M1

Sure is a interesting thread; for me it is pretty simple on the OTL definition; If the input signal flows only off the output tubes and goes to the speaker output jacks then to me the amp is OTL; if there is a transformer in the path it is not OTL.

Hey Allan, let's not be condescending toward one another. I see this thread going nowhere (and far off topic, by the way) due to differences in perception and arguing semantics. A transformer is a transformer; you contend there are none, at least in the audio frequency band. It's not a matter of understanding, it's a matter of definition.

In the end the only thing that counts is the sound. I hope Winston, the originator of this discussion thread, is able to pursue some of the amplifiers suggested and recommend that he contact the respective retailers to audition the candidates in his system to make an informed purchasing decision.

Well my friend Jocelyn, he's the guy that mod's the Acoustat's in Quebec Canada uses a Plinius S-250MK1V on his Acoustat's Spectra 6600, and it's the best sound i have heard in 40 years and i have heard quite a few, i have been attending the Montreal S.S.I. audio show for over 20 years so i know how a good system sounds.

PS: just google MrAcoustat Flickr you will see pictures of my Acoustat's 1+1s and the Acoustat's Spectra 6600s the small one weighs 200 pounds each the big ones 600 pounds all metal frames.

This was interesting. I think Dave is a genius and Ralph is right there with him. But as a degreed engineer I have to say that Allans assertion that
"A transformer is a transformer, a audio output transformer is something else" is ahem..., how to say... Ridiculous. I don't care what band a transformer is designed to handle; it is a TRANSFORMER. This to me is like saying a car that has a CVT (continuously variable transmission) is direct drive (i.e. A hub motor) because it does not use a standard slosh-box :). Bunk, it has a transmission.

I personally think the Berning amps are ingenious and I like them, but the schematic clearly shows a transformer in the circuit that audio signal passes through via a carrier frequency on its way to the output...that's a transformer hence it is not an OTL. A rose by any other name (rf transformer) is still a rose (transformer).

Now I get what Davis is saying, he is making a distinction between a typical iron/steel core transformer with kilometers of wire vs a very small air core transformer. I also understand Ralph, in the strictest since no matter how you write it, describe it, obfuscate it..., a transformer exists in the output of the Berning amplifiers. My Graaf amplifiers have NO transformer of any type in the output..., hence they are OTL amplifiers.