RE: ESLs and OTLs

Posted by Ralph (M) on January 31, 2014 at 10:51:01

In Reply to: RE: ESLs and OTLs posted by tyu on January 31, 2014 at 10:28:32:

The problem is not whether the feedback is on the cathode or grid.

It has to do with what frequency the feedback is no longer negative, but shifted in phase (due to time delays in the amplifier circuit) enough that it can act as positive feedback, causing the amplifier to oscillate.

This usually involves setting up some timing constants (capacitor/resistor networks) in the feedback loop, to sidestep the problem above. OTLs tend to have a lot of bandwidth and if this quality is ignored, oscillation will not be far behind. In this regard they have more in common with solid state amps than transformer-coupled tubes amps, as an output transformer limits the bandwidth.

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Follow Ups Full Thread

Topic - ESLs and OTLs - Ralph 12:27:38 01/30/14 (20)

RE: ESLs and OTLs - airheadair 20:18:32 02/02/14 (0)

RE: ESLs and OTLs - Caucasian Blackplate 22:45:25 01/31/14 (12)

RE: ESLs and OTLs - Michael Samra 15:12:35 02/02/14 (0)

Yeah, those 2-ohm ribbon speakers are ideal for an OTL - Lew 08:24:48 02/01/14 (10)

RE: Yeah, those 2-ohm ribbon speakers are ideal for an OTL - morricab 14:32:10 02/03/14 (6)

Moscode, or what? - Lew 12:58:40 02/04/14 (5)

RE: Moscode, or what? - morricab 09:42:50 02/05/14 (4)

RE: Moscode, or what? - Lew 06:48:32 02/06/14 (3)

RE: Moscode, or what? - morricab 05:19:08 02/10/14 (2)

Wow!!! - Lew 10:40:39 02/10/14 (1)

RE: Wow!!! - morricab 13:07:10 02/10/14 (0)

RE: Yeah, those 2-ohm ribbon speakers are ideal for an OTL - Caucasian Blackplate 15:50:05 02/01/14 (2)

What speaker is that? - Lew 10:09:32 02/03/14 (1)

RE: What speaker is that? - Caucasian Blackplate 10:20:42 02/03/14 (0)

Thanks for the analysis - Lew 10:52:13 01/31/14 (0)

RE: ESLs and OTLs - tyu 14:36:50 01/30/14 (4)

RE: ESLs and OTLs - Ralph 08:31:57 01/31/14 (3)

RE: ESLs and OTLs - tyu 10:28:32 01/31/14 (2)

RE: ESLs and OTLs - Ralph 10:51:01 01/31/14 (1)

RE: ESLs and OTLs - Banat 12:35:12 01/31/14 (0)

Follow Ups

RE: ESLs and OTLs - Ralph 10:51:01 01/31/14 (1)

RE: ESLs and OTLs - Banat 12:35:12 01/31/14 (0)

RE: ESLs and OTLs

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