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Old 4th May 2013, 12:33 AM   #1121
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Here are the tests with and without the EC buffer respectively. And a very strange peak (harmonic?) at 60KHz.

So as I expected, with such a simple circuit and fast transistors, frequency doesn't really impact performance even when the output is loaded by an IRF250 gate. My current listening amp is an IRF250 biased at 500mA. That has to do until I have an idea how I want to design my next discrete amp.
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Old 4th May 2013, 09:11 AM   #1122
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Maybe this 60kHz peak comes from a switching regulator. OTOH, the spectrum from post 1125 doesn't show this peak. Weird.
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Old 4th May 2013, 09:17 AM   #1123
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The chart in post 1125 doesn't show 60KHz. I think it may be from my CRT monitor. My resolution is 1280*960; 60Hz*960=~60KHz. But the peak is conspicuously aligned to 60KHz. I will investigate, eventually.
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Old 4th May 2013, 11:37 PM   #1124
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Hi keane,

To help me understand what you are measuring , is this EC stage part of a power amplifier or is it by itself. Is the EC stage loaded with 8 ohms ( could you confirm this) and what is the voltage level across the load.

Regards
Arthur
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Old 5th May 2013, 12:20 AM   #1125
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The EC stage is biased into class A at 10mA by a 1k resistor. So it is basically unaffected by any load impedance over 5k. Its output is fed into the gate of the IRF250 fireball (for speakers), which is its own construction. If I want I can bypass the buffer or I can listen to the buffer with headphones without the IRF250 amp.

I'm measuring the EC stage on it's own; I really am not very interested in the measurements of the IRF250 amp, so I haven't actually thought about measuring it.
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Old 9th July 2013, 06:09 AM   #1126
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I've posted here about the EC buffer, since I saw that others were going in that direction:

Mpp
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Old 19th January 2014, 12:07 PM   #1127
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Default Revival

Hi Edmond
I finally worked out feedback theory and probe technique sufficiently well to do a bit more on this circuit.
I would like to better understand some of the loops, especially the conditional stability.
I seem to remember that you eventually downloaded a copy of LTSpice.
Do you have this circuit as an LTSpice ASC?

Best wishes
David

Last edited by Dave Zan; 19th January 2014 at 12:09 PM.
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Old 19th January 2014, 09:08 PM   #1128
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Hi David,

Nice to see you have made progress. Regrettably, I don't have *.asc files.
>I seem to remember that you eventually downloaded a copy of LTSpice.
Yes, but I only use it as a schematic reader and not as tool for simulation.
Sorry.

Cheers, E.
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Old 19th January 2014, 09:50 PM   #1129
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Quote:
Originally Posted by Dave Zan View Post
Hi Edmond
I finally worked out feedback theory and probe technique sufficiently well to do a bit more on this circuit.
I would like to better understand some of the loops, especially the conditional stability.
I seem to remember that you eventually downloaded a copy of LTSpice.
Do you have this circuit as an LTSpice ASC?

Best wishes
David
Hello Dave,

It does not really matter if somebody does not use the same simulator that you do , you can still ask the questions as different simulators should give the same results provided all the models and the circuit are the same.

Regards
Arthur
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Old 20th January 2014, 12:18 AM   #1130
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Quote:
Originally Posted by PHEONIX View Post
It does not really matter if somebody does not use the same simulator that you do , you can still ask the questions as different simulators should give the same results provided all the models and the circuit are the same.
I know that Edmond had previous problems with inconsistencies between simulators that should produce the same results.
But mainly I just wanted to save the time to re-enter all of Edmond's circuit and models.
Plus eliminate the inevitable errors and discrepancies.
You followed this thread, do you have an LTspice version?

Best wishes
David
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