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: SoundLab transformer MOD

Posted by Ralph on April 18, 2012 at 09:52:07:
The 1st drawing is the Acoustat. The 2nd is for Sound Lab.

The mods seem to follow two pathways. One is to remove the resistor as seen in the second drawing, along with the inductor, and change the cap value to 15-22uf. A lot of people remove the Brilliance control entirely.

The second path is to replace the HF toroid entirely with a new one that comes from Australia. So far from what I have heard with this mod there is no crossover at all for the HF toroid, but I suspect a cap of the right value in series with it will help out.

Either way the speaker is a lot easier to drive! Not only for OTLs, but people with transistor amps have reported the same thing, and in all cases it sounds better. Its not hard to see why- that resistor as shown in this example is a 40-watt device (some versions have 80-watt power ratings). It has to have that kind of power handling to survive- and the power to heat it comes from the amp. Take it out and the amp does not have to work as hard; sound quality is improved at all frequencies as a result.

The only issue with the 1st pathway is that the HF toroid should not have low frequencies applied to it else it could distort due to saturation. That is easily solved by simply decreasing the cap value, which has the added benefit of greater transparency. In some cases the cap is easily decreased as there are several in parallel and one can be simply cut out, in other cases the cap has to be replaced outright.