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Old 15th December 2006, 04:26 PM   #21
flg is offline flg  United States
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Babowana, in both Ls, the square waves only "overshoot" at the low freqs. The rising edges begin to get rounded at higher freqs. The "overshoot" and rounding, does look realatively symetrical...
Also, I do not have the feedback resistor bypassed with the 10p C as Nelson sugests in ZV9 (it should make the square with look better). I beleive this will only help the high end though and in the opposite way??? I can try a C though. I also think varying the gain/feedback might be worth a try
Fuling, That 800VA Toriod is the biggest thing I have in Toriod... I tried lowering the Iq a little (25%) when I saw that but I saw little difference
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Old 15th December 2006, 04:39 PM   #22
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I would increase the 470uF to the greater than 1000uF

Anyhow, very good
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Old 15th December 2006, 04:56 PM   #23
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I think you'd be much happier with an air-core choke. I sure am. To keep the resistance down, I use my amp in the mids and up. This allows me to use a smaller choke.

I'm going to put my amp under the scope today.

I'd like to know more about PC based analyzing software.

You're having fun and sharing an excellent tail with the rest of us. That's what I call priceless.

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Old 15th December 2006, 06:12 PM   #24
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So John, I guess your weather is clearing up out there? Perfect DIY weather though Ha???
Yes, I guess I'm having fun...
At lunch I think I figured out some of my problem, I think...
In all my excitement to bench test, I don't have some of my typical stuff on this amp. I'm powering it with my 'ol standby rack mount switcher. Well I generally have 5-10mF of C on my boards right near the output transistors and I don't have a board for this one... So, I figured out while at lunch, I am probably seeing the transient response of my 'ol standby switcher supply in the output response of the amp??? I was a little hesitant to call it "overshoot" cause it's not quite overshoot looking and it just transfers from overshoot to rounding of the leading edges of the squarewave across the frq band???
I can look at the supply line first(shame on me) or, I'm going to hang a big cap or two on the switcher output, with a film or two, and see what the output looks like then??? I'll bet it gets right back in line with what it should look like...
First I gotta take Mom and go visit dad in the Hospital... Congestive heart failure and emphasema...
Ho Ho Ho Buddy
I'll get back to ya on the PC based Audio Anal Software
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Old 15th December 2006, 06:20 PM   #25
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Babowana, Yep, I thought about that too And, that C kepps the amp on a real slow turn on too. But that power supply thing sounds more likely an important thing to correct first... I really have no idea what that supplies out Z, or transient response is
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Old 15th December 2006, 07:30 PM   #26
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Well, I doubled up on the cascode refrence bypass (2 x 470uF) and I added a 22,000 with a film to the choke input No change in the square wave response
Actually, the waveform is not exactly symetrical??? See below???
I can look around "the playroom" a little more for another xfmr... Or, I have a Lincoln arc welder transformer in the basement???
I can also switch to a resistive load and see what happens with that
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File Type: png waveform.png (7.9 KB, 153 views)
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Old 15th December 2006, 08:40 PM   #27
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Resistive load; good thinking.
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Old 15th December 2006, 08:45 PM   #28
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I think the best inductor in this circuit would be an iron cored one with airgapped core. Hammond has a few that would work, Id go for >150mH.
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Old 15th December 2006, 08:49 PM   #29
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Yes, Hammond had some with High DC current specs. They are $50+US though. Do you have a specific part number? Are we thinking about the same type???
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Old 15th December 2006, 09:47 PM   #30
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I dont remember the part numbers, but I know there are one or two in the 193-series that should be suitable for this kind of job.
Ive messed around a bit with inductor loaded amps and its a great way to get serious power out of single ended circuits.
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