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Old 19th June 2003, 11:00 AM   #81
Netlist is offline Netlist  Belgium
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Quote:
Originally posted by panos29
Dear Netlist,
I am really happy that somebody took the time to measure the aleph-x as some time I did but the responce was minimal. However, I would like to ask at what power output levels did you take the measurements you post, and upon what kind of load(inductive, resistive, mixed etc)? Did you tried loading the output with 1-2uf?
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Don’t be disappointed about the response, this happens to anyone now and then.
I did have a look at your results and part of the answer is probably given here:
http://www.diyaudio.com/forums/showt...72#post179872.

The measurements were done with a resistive load, but I’ll try to add some capacitance.
Don’t you think 1-2uF is a bit much?
Some recent experiments learned that adjusting the bias to a certain point is quite important.( in my amp)
Here’s what I did:
I connected a sinewave 1Khz. Because my amp is not clipping symmetrically, the upper part of the waves clips sooner than the lower part, I increased the power till the lower part was just not clipping. Of course the upper part was already flat.
Then I started trimming the bias on both sides till both halves didn’t clip anymore.
The funny part is that there is only one point were the bias is optimal. Increasing it results again in clipping on the upper part. Also the lower part can be pushed much further without showing a flat clip line. It rather shows distortion, but clips much later, no matter what bias point I set.
It’s quite a hassle to remount a pot in place of the active current source regulator but it will have to be done.
All this is said by Grataku in earlier posts, but sometimes it takes a long time and much reading to fully understand what really happens in practice.

Measuring the power just before clipping gives 30.6Vac RMS with an 8ohm resistive (16 X 8R2 50W wirewounds in series-parallell) load: 117WRMS. It could be a bit inductive after all.

Hugo – back to the bench…
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Old 19th June 2003, 01:01 PM   #82
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Just to let you now...in case you get bored.
The battery has arrived

/Hugo
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Old 19th June 2003, 05:03 PM   #83
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Quote:
Originally posted by Netlist
Just to let you now...in case you get bored.
The battery has arrived

/Hugo

How about the thermistors to go with those?
What's the plan, 6/channel?
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Old 19th June 2003, 06:09 PM   #84
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Quote:
Originally posted by grataku

How about the thermistors to go with those?
What's the plan, 6/channel?
This is what I'm brewing for the moment.
Correct me if you see mistakes.
/Hugo
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Old 19th June 2003, 06:26 PM   #85
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Quote:
Originally posted by Netlist
Just to let you now...in case you get bored.
The battery has arrived

/Hugo

I noticed that Madrigal is using similar caps in their most recent amps.
http://www.marklevinson.com/image_li...=6&productID=7
http://madrigal.harman.com/image_lib...n/383PS_lo.jpg
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Old 19th June 2003, 06:40 PM   #86
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Quote:
Originally posted by Netlist

This is what I'm brewing for the moment.
Correct me if you see mistakes.
/Hugo

looks great to me....
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Old 20th June 2003, 02:12 PM   #87
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Quote:
Originally posted by Peter Daniel

I noticed that Madrigal is using similar caps in their most recent amps.
Can’t be bad then. Those amps look awesome. Can’t get enough of the pictures…
Quote:
Originally posted by Edwin Dorre
looks great to me....
Well then, the new PSU is up and working.
The hum is (almost) completely gone. When listening very close to the speaker, I can hear a very tiny amount of hum.
Measurements reveal 1.8mV AC. I definitely can live with this.
The voltage is now +/-30V. The AC meters on the variac show 1.9A on 227V.

Thanks again guys.

/Hugo
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Old 20th June 2003, 02:15 PM   #88
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So increasing capacitance eliminated hum?

Do you hear any difference in sound with new electrolytics?
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Old 20th June 2003, 02:33 PM   #89
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Peter
Before there were 4 caps, each 68.000µF. Total: 272.000µF
Now I have 6, each 47.000µF. Total 282.000µF

Making it a CRCRC filter does the main improvement.
The R's do the trick I believe.
Over the first caps I measure 355mV AC.
The second shows 81mV AC and the third 25mV AC. This results in 1.8mV differential AC at the outputs.
The sound, to me, is the same as before. There's no way to go back to the old setup to do an A/B test.

/Hugo
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Old 20th June 2003, 10:07 PM   #90
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Quote:
Originally posted by Peter Daniel



I noticed that Madrigal is using similar caps in their most recent amps.
http://www.marklevinson.com/image_li...mp;productID=7
http://madrigal.harman.com/image_lib...n/383PS_lo.jpg
Sorry Hugo for butting in, but I had to ask what the rows of metal pegs were sticking out of the PSU board in the Levenson amp?
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