Update. - Al Sekela - Planar Speaker Asylum

Update.

Posted by Al Sekela (A) on October 16, 2006 at 13:45:46

In Reply to: Re: Perhaps you do not understand how these amps work. posted by morricab on October 15, 2006 at 07:45:59:

I spoke with Mark about your questions. His intent with the Glacier web site comment was that the amps do not use global feedback in the audio domain, and that all the stages are direct-coupled. The only capacitors used are in the power supply filters and the output low-pass filters.

These amps (including switching amps in general) use some form of digital control of the dark time, which is the time between one polarity of output transistor turning off and the other polarity turning on. Ideally, this time would be zero. However, due to the differences in available power NMOS and PMOS channel characteristics, including changes with ambient temperature variation, passive setting of the dark time results in too much distortion if it is too large, or the risk of output transistor destruction if it is too small and goes negative.

Thus, one could call this control a form of feedback. However, it is not applicable to the analog domain, and does not relate to the output impedance versus frequency characteristic.

The Raptor amp output impedance is specified at 50 milliohms (I may have been incorrect in another post), and actual measurements stay below 25 milliohms over the audio band.

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Follow Ups Full Thread

Topic - Amp shootout for Maggie Tympanis - results - stellar1 16:10:26 10/07/06 (16)

Control of Maggies - Al Sekela 21:16:04 10/07/06 (14)

Re: Control of Maggies - morricab 08:35:09 10/11/06 (13)

To be clear, - Al Sekela 11:56:02 10/11/06 (12)

Re: To be clear, - morricab 06:44:10 10/12/06 (11)

Don't know about output impedance versus frequency. - Al Sekela 16:47:07 10/12/06 (10)

Re: Don't know about output impedance versus frequency. - morricab 16:49:13 10/12/06 (9)

Re: Don't know about output impedance versus frequency. - morricab 01:49:49 10/13/06 (0)

I found it . It says "NO FEEDBACK-No coupling capacitors . . . - Alan G. 20:50:14 10/12/06 (7)

Re: I found it . It says "NO FEEDBACK-No coupling capacitors . . . - morricab 01:48:03 10/13/06 (6)

Perhaps you do not understand how these amps work. - Al Sekela 09:30:54 10/14/06 (5)

Re: Perhaps you do not understand how these amps work. - morricab 07:45:59 10/15/06 (4)

Update. - Al Sekela 13:45:46 10/16/06 (3)

Al please ask Mark to - GL 15:57:22 10/16/06 (1)

Correction: ADC/DSP/DAC.. - GL 16:00:29 10/16/06 (0)

Re: Update. - morricab 14:14:17 10/16/06 (0)

What they mean when they say an amp maintains control of the speakers" ... - andyr 16:51:28 10/07/06 (0)

Follow Ups

Update. - Al Sekela 13:45:46 10/16/06 (3)

Al please ask Mark to - GL 15:57:22 10/16/06 (1)

Correction: ADC/DSP/DAC.. - GL 16:00:29 10/16/06 (0)

Re: Update. - morricab 14:14:17 10/16/06 (0)

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