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This idea has been a bit of a contention between morricab and myself.So here's a photo. The class B amp is an Electro Voice A20C, which used the Wiggins Circlotron patent, in which a supported claim was there would be no spike or 'switching transient' at the zero crossing that would usually occur when a power tube went into cutoff (and its associated magnetic field in the output transformer collapsed, causing the transient in a manner similar to a spark coil in a car).
I inherited this amp years ago but got curious a few months back since I had read about this particular claim. EV made no bones about this and clearly pointed it out in the owner's setup guide. So I restored this amp- it needed new filter caps and quite a few of the original coupling caps had failed. The driver tubes have an interesting relationship to the output tubes in that they are 'bootstrapped' to drive the output tubes. The screen resistor of one power tube is also the plate resistor of the driver tube for the opposing output tube.
The first photo is the setup so you can see the connections. The right meter on the analyzer is showing about 35dB below 1 Watt and its set to 8 Ohms. The second photo is a closeup of the 'scope. The top trace is the amp and the bottom is the output from the generator.
Edits: 03/10/25 03/10/25
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Topic - A class B amp can have no zero crossing artifact. - Ralph 10:36:59 03/10/25 (67)
- The undistorted truth - 13th Duke of Wymbourne 14:43:15 03/16/25 (13)
- +1 nt - Ralph 10:16:37 03/17/25 (0)
- RE: The undistorted truth - morricab 08:49:38 03/17/25 (10)
- RE: The undistorted truth - 13th Duke of Wymbourne 16:58:25 03/18/25 (9)
- RE: The undistorted truth - Ralph 10:04:41 03/19/25 (2)
- RE: The undistorted truth - 13th Duke of Wymbourne 13:19:26 03/21/25 (1)
- +1 nt - Ralph 13:27:53 03/21/25 (0)
- RE: The undistorted truth - morricab 03:17:34 03/19/25 (5)
- Logical failure to due use of logical fallacy - Ralph 10:18:36 03/19/25 (4)
- RE: Logical failure to due use of logical fallacy - morricab 12:37:13 03/19/25 (3)
- Nonsense. - Ralph 12:45:27 03/19/25 (2)
- It's correct - morricab 06:11:59 03/20/25 (1)
- RE: It's correct - Rod M 09:59:44 03/20/25 (0)
- A royal summary, a princely proclamation... - peppy m. 06:26:55 03/17/25 (0)
- To be clear.... - AbeCollins 10:53:36 03/12/25 (21)
- RE: To be clear.... - morricab 01:09:33 03/13/25 (18)
- This post contains false statements and so muddies the waters. - Ralph 08:31:01 03/13/25 (16)
- RE: This post contains false statements and so muddies the waters. - morricab 08:09:32 03/17/25 (1)
- And that statement is false too. You just haven't been reading. nt - Ralph 10:16:12 03/17/25 (0)
- is this why QUAD has so many improvements since the 405 Ralph? - Story 08:45:46 03/13/25 (13)
- RE: is this why QUAD has so many improvements since the 405 Ralph? - Zombie 12:58:51 03/14/25 (0)
- Seriously? - E-Stat 11:04:11 03/13/25 (9)
- The LM301 has been improved over the years... - Ralph 12:49:44 03/13/25 (8)
- Why bother? - E-Stat 12:54:07 03/13/25 (7)
- :) maybe because you have the thing on hand - Ralph 12:57:09 03/13/25 (6)
- Ok - E-Stat 13:02:13 03/13/25 (5)
- Exactly! The 5532 is a better part. And that isn't how I want to spend my time :) nt - Ralph 13:32:22 03/13/25 (4)
- and what Mr Stat assumes is that replacement chips have not been tried - Story 16:37:11 03/13/25 (3)
- What that means - E-Stat 20:13:59 03/13/25 (2)
- why not insult people somemore - Story 05:28:31 03/15/25 (1)
- Current Artera amps - E-Stat 07:46:59 03/15/25 (0)
- Without more experience with the amps I can't say. - Ralph 09:19:48 03/13/25 (1)
- RE: Without more experience with the amps I can't say. - Story 09:31:29 03/13/25 (0)
- RE: To be clear.... - AbeCollins 07:17:59 03/13/25 (0)
- Its not off base but - Ralph 11:35:11 03/12/25 (1)
- RE: Its not off base but - AbeCollins 07:17:02 03/13/25 (0)
- RE: A class B amp can have no zero crossing artifact. - morricab 04:15:03 03/11/25 (14)
- I looked up some basics - Story 12:23:40 03/18/25 (0)
- If THD+N is at 0.00075 why should I care if it's notch distortion ... - Feanor 04:33:39 03/12/25 (9)
- Did you leave out a zero to the right of the decimal point :) nt - Ralph 09:15:02 03/12/25 (1)
- Not even that ... - Feanor 04:04:53 03/13/25 (0)
- RE: If THD+N is at 0.00075 why should I care if it's notch distortion ... - morricab 06:50:11 03/12/25 (6)
- I'm not disputing that necessarily - Feanor 04:34:13 03/13/25 (0)
- Nonesense, rubbish, etc. - Ralph 09:26:14 03/12/25 (4)
- RE: Nonesense, rubbish, etc. - morricab 01:34:26 03/13/25 (3)
- Your post contains false statements. - Ralph 08:57:05 03/13/25 (2)
- RE: Your post contains false statements. - morricab 08:08:30 03/17/25 (1)
- OMG ROTFLMAO nt - Ralph 10:19:29 03/17/25 (0)
- I never said anything other than a class B amp didn't have to have a zero crossing artifact. - Ralph 09:39:19 03/11/25 (2)
- RE: I never said anything other than a class B amp didn't have to have a zero crossing artifact. - morricab 01:58:36 03/12/25 (1)
- :) :) (-- that's someone laughing a lot. - Ralph 09:12:25 03/12/25 (0)
- We were discussing Solid state amps! And you missed the crucial measurement! - morricab 03:54:31 03/11/25 (9)
- :) Actually all I did was make the claim that a class B amp didn't have to have a zero crossing artifact - Ralph 08:40:09 03/11/25 (8)
- RE: :) Actually all I did was make the claim that a class B amp didn't have to have a zero crossing artifact - morricab 03:34:15 03/12/25 (7)
- And I explained how the Topping amp can be class B and not have a zero crossing artifact. - Ralph 08:28:58 03/12/25 (6)
- You didn't and have no idea what they did - morricab 12:52:32 03/17/25 (5)
- Your statement is false. - Ralph 14:13:48 03/17/25 (4)
- Wait! Are you talking about - morricab 23:51:21 03/17/25 (1)
- Yes, I was. The class of an amplifier is defined by - Ralph 09:09:59 03/18/25 (0)
- No, no, no - morricab 23:31:42 03/17/25 (1)
- Yes, yes, yes, I have... :) nt - Ralph 09:12:05 03/18/25 (0)
- RE: A class B amp can have no zero crossing artifact. - Tre' 18:45:48 03/10/25 (2)
- The Electro Voice A20C - Ralph 08:37:09 03/11/25 (1)
- RE: The Electro Voice A20C - Tre' 10:21:29 03/11/25 (0)
- RE: A class B amp can have no zero crossing artifact. - Story 14:41:01 03/10/25 (2)
- RE: A class B amp can have no zero crossing artifact. - morricab 04:05:57 03/11/25 (1)
- RE: A class B amp can have no zero crossing artifact. - Story 04:30:23 03/11/25 (0)
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