OTL Asylum

OTL, Output Transformerless Amplifier User Group.

Use this form to submit comments directly to the Asylum moderators for this forum. We're particularly interested in truly outstanding posts that might be added to our FAQs.
You may also use this form to provide feedback or to call attention to messages that may be in violation of our content rules.

You must login to use this feature.

Inmate Login

By default, logging in will set a session cookie that disappears when you close your browser. Clicking on the 'Remember my Moniker & Password' below will cause a permanent 'Login Cookie' to be set.

Moniker/Username: The Name that you picked or by default, your email. Forgot Moniker?	Examples "Rapper", "Bob W", "joe@aol.com".
Password:	Forgot Password?
	Remember my Moniker & Password ( What's this?)

If you don't have an Asylum Account, you can create one by clicking Here.

Our privacy policy can be reviewed by clicking Here.

Inmate Comments

From:
Your Email:
Subject:

Message Comments

Original Message

RE: From what I understand the Zero's...

Posted by Lew on May 15, 2017 at 16:14:39:
Chris, You and a few others are the ones taking the purist stance. I have no desire to argue the point except to say what I said. Yes, the Zero is a kind of crutch to improve the match between an OTL and a typical low impedance speaker. That doesn't bother me. Most people who have employed zeros with their Atma and other OTL amplifiers report that they are happy with the pairing. I was too, until I found a way to modify my speakers to raise both their efficiency and impedance curve such that I no longer needed to use the Zeros. As you know, too, there are also ways to reduce the output Z of many OTLs, by adding NFB, that also might do the job and obviate the need for Zeros. It depends upon which is the lesser of two evils. It's all good, so far as I am concerned.

I would maintain though that a well designed autoformer, like the Zero, used at a 2:1 impedance ratio (I never went above 2:1; the Zeros permit up to 4:1, I think) is in fact likely to give wider bandwidth and lower distortions compared to a true audio output transformer as found on most OTC amplifiers, driving the same speaker, for reasons noted. If you want to say that an autoformer-coupled OTL no longer fits the strict definition of an OTL, I would not argue with that.

One other small point, the Zero is placed at the speaker end of the path from the amplifier outputs, not at the amplifier end, for whatever difference that makes. You might say it acts on the speaker. But I don't want to go there, either.