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Old 26th July 2007, 09:57 AM   #41
suzyj is offline suzyj  Australia-Aboriginal
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Some more measurements:

THD+N, 1KHz into 8 Ohms (80KHz bandwidth):

100mW: 0.0318%
200mW: 0.0214%
500mW: 0.0146%
1W: 0.0116%
2W: 0.0094%
5W: 0.0081%
10W: 0.0074%
20W: 0.0067%
50W: 0.0065%
100W: 0.0073%

I didn't go beyond 100W, as the heatsink was getting fairly hot, and I didn't want to cause any damage. I don't think the level of heatsinking it's got is really adequate for 100W, especially as I was only driving one channel.
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Old 26th July 2007, 10:00 AM   #42
PMA is offline PMA  Europe
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Hi Suzy,

how about distortion at 10kHz?

Regards,
Pavel
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Old 26th July 2007, 10:24 AM   #43
sandyK is offline sandyK  Australia
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Default ETI 477 article

Suzy
Do you still have the original published distortion figures for this relic ? How does the relic 's good channel compare to your new SMD 6000 ,distortion wise ?

Sandyk
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Old 26th July 2007, 11:46 AM   #44
suzyj is offline suzyj  Australia-Aboriginal
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ETI March '81, page 37 has a plot of distortion versus frequency. It claims the THD is a bit below 0.001%, at 1KHz, 10W.

My SMD version of the 6000 does 0.0013% THD, putting 100W into 8 Ohms at 1KHz (using the same generator and THD analyser), so it's about 10-15dB better, as shown in the following plot:

Click the image to open in full size.

I didn't have much time to measure it today. I'll repeat the exercise tomorrow at 10KHz, and do a frequency sweep at 100W as well.

I don't suppose anyone has an original 6000 that I can borrow to measure?
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Old 26th July 2007, 11:58 AM   #45
sandyK is offline sandyK  Australia
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Default ETI 477 article

Suzy
I will send an email to vhf man,to see if he is willing to part with his for a few days
SandyK
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Old 27th July 2007, 03:17 AM   #46
suzyj is offline suzyj  Australia-Aboriginal
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More numbers.

10KHz THD: (8 Ohm load, 80KHz bandwidth)

10mW: 0.0681%
20mW: 0.0613%
50mW: 0.0507%
100mW: 0.0382%
200mW: 0.0298%
500mW: 0.0265%
1W: 0.0278%
2W: 0.0294%
5W: 0.0303%
10W: 0.0305%
20W: 0.0306%
50W: 0.0300%
100W: 0.0530%

Frequency sweep: (50W, 8 Ohm load, 80KHz bandwidth)

100Hz: 0.0090%
200Hz: 0.0088%
500Hz: 0.0060%
1KHz: 0.0068%
2KHz: 0.0100%
5KHz: 0.0190%
10KHz: 0.289%
20KHz: 0.0205%
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Old 27th July 2007, 05:40 AM   #47
PMA is offline PMA  Europe
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Thanks for the 10kHz numbers. They are higher than those for 1kHz, as almost always. Still quite good result. It would be nice to know THD harmonic content as well, but you probably do not have a spectrum analyzer.
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Old 27th July 2007, 06:11 AM   #48
suzyj is offline suzyj  Australia-Aboriginal
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Alas none of our spectrum analysers go low enough in frequency.

fayef, I've had some luck diagnosing the problems with the right channel. It appears one of the output FETs has gone - a 2SJ49. If you look at the photo you posted up, you can see one of them has been running really hot, so has corroded more than the others.

It's also been oscillating, and has cooked the resistor in the HF shunt.
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Old 27th July 2007, 06:23 AM   #49
sandyK is offline sandyK  Australia
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Default ETI477 article

Suzy
I noticed in the photo that the 4R7 had overheated.
BTW, with the AEM 6000, years ago, I noticed the occasional edginess on one channel only. Eventuually, I found that one pair of Mosfets was not current sharing very well.Just replacing the one that wasn't drawing nearly as much current completely cured the problem.It wasn't faulty.

SandyK
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Old 27th July 2007, 12:09 PM   #50
feyef is offline feyef  Australia
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Quote:
Originally posted by suzyj
feyef, I've had some luck diagnosing the problems with the right channel. It appears one of the output FETs has gone - a 2SJ49.
suzyj,
I have a spare 2SJ49, shall I pick up the amp to repair it, or send you the part?
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