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Old 9th December 2002, 04:30 PM   #121
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Quote:
Originally posted by blank527
This is a little off topic but can anyone tell me what the heat dissipation of an aleph 60 is?
On page 4 in the manual it says 240Watts.
Later in the manual it says 200Watts.
On the specs page it says 220Watts of power consumption
I wrote all that. MuuuuHahahahaha....

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Old 9th December 2002, 06:11 PM   #122
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Talking Nelson's Evil Laugh (TM)

Quote:
Originally posted by Nelson Pass


I wrote all that. MuuuuHahahahaha....

Maybe someone from the forum lucky enough to be going to
the CES can make a recording of Nelson laughing
his evil laugh.

Dennis
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Old 9th December 2002, 07:06 PM   #123
ststone is offline ststone  United States
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I have this recording on file

MuuuuHahahahaha....
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Old 3rd January 2003, 01:58 AM   #124
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Default Aleph30 Distorsion

I Have distorsion quite easy to see on my Aleph30. Waveforms are ok at 1Khz, but a bump in the waveform can be see at soon as 10Khz, it is worse at 1Khz. Here the waveform, in 8ohms, at 10khz.

Any idea what can cause this distorsion and how can I remove it. One possible source, the AC gain feedback capacitor 220uf. I'm using a Panasonic FC type. Will it be better a Black Gate? What BG type?

Any suggestions?

Thanks.
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Old 3rd January 2003, 02:01 AM   #125
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Default Aleph30 Distorsion, next

Here waveforms at 1Khz
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File Type: jpg all three_1khz_small.jpg (22.5 KB, 1070 views)
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Old 3rd January 2003, 02:05 AM   #126
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Default Aleph30 Distorsion, My Setup

Here my Aleph30 on test
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Old 3rd January 2003, 04:37 AM   #127
JDeV is offline JDeV  South Africa
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Hi Algar_emi
I also noticed similiar distortion when I tested my A30, but discovered that it was my Scope's probe leads that caused it. I don't think that the type of capacitor you use will change this problem, although higher quality caps will sound better in certain cases. BTW, can you hear this distortion, how big is this signal, is it on both channels? Did you check for possible bad solder joints? I used standard type Nichikon and Rubycon caps on my A30 and standard type Elna caps for the PSU and they all sound very good singing together.

Hope you get the cause of your'e problem and can fix it.
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Old 3rd January 2003, 09:10 AM   #128
Henrik is offline Henrik  Denmark
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If You increace C8 from 10pF to say 20 pF You proberly would get rid of it the instabilit at the 10KHz squarewave, but on the other hand You also will lower the hig rolloff.
Try it out, but I think it is oky as it is.
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Old 3rd January 2003, 09:11 AM   #129
Henrik is offline Henrik  Denmark
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BTW really nice work!!!!
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Old 3rd January 2003, 02:04 PM   #130
Koy is offline Koy  Czech Republic
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I tell you the same as Henrik did. 20pF is not so much Dont afraid.
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Old 4th January 2003, 07:05 PM   #131
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Default Aleph30 Distorsion

The sound is very detailled, with a lot of air, but lean bass.
But all this only at low level. If I tried to crank to volume, the sound change and become congested.
I have a pair of acclamed Axiom 3Ti.
My preamp is a Bride of Zen.
The distorsion I mentionned is a higher listening volume, that why I think it explained th change in sound.
As described by others users, the aleph used the active Current source to increase efficiency. So, I think that the change in sound occurs when the active current source pull the amp in class A-B mode rather that pure Class-A. The Capacitor in the current feedback path is the on passing the AC and contributing, maybe, to the distorsion. By the way, both my channels are behaving the same.
Is a better FET matching in the Current Source could eliminate this distorsion?
I will tried to open the AC feedback an listen to it...
I'm waiting for any suggestions.
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Old 4th January 2003, 09:00 PM   #132
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Algar,

I never heard such behaviour even with a 75% ac-current gain setting. Can it be that your amp is clipping?

This could be the case if your ac-current gain is chosen too low (under 50%) and your speakers demand the current but don´t get it.

william
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Old 4th January 2003, 09:54 PM   #133
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When you deviate from the 50% figure for current gain
on the current source, you get more distortion at the
highest output, either because you are current-starved,
or because the current source is shutting off on negative
peaks. The cure in both cases is more bias.

Come to think of it, more bias is almost always the cure
for any limitations of Alephs.
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Old 5th January 2003, 12:08 AM   #134
Coulomb is offline Coulomb  England
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Quote:
Originally posted by Nelson Pass
When you deviate from the 50% figure for current gain
on the current source, you get more distortion at the
highest output, either because you are current-starved,
or because the current source is shutting off on negative
peaks. The cure in both cases is more bias.

Come to think of it, more bias is almost always the cure
for any limitations of Alephs.
Well we all have our Biases, some more than others.
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Old 5th January 2003, 05:17 AM   #135
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Default Aleph30 Distorsion

Thanks Mr. Pass for participating to the discussion.
My current biais is 0.5A, as per Aleph30 service manual.
I adjusted the AC gain to 50% one week ago using the procedure described in one of the thread. I changed R21 from 820 ohms to 1K and got a perfect 50% gain.
My supply is using a 18+18V, 500VA transformer and the same bank of cap as the original Aleph30.

I tried using 0.8A biais but my output DC offset increased from the actual 120mv to more than 300mv! So I put it back to 0.5A.
This DC offset is causing me also a lot of problem. My input FETS are well matched. The Current and Active FET are almost identical also, except for one of the Current Source One.

Can I try to balance my Current FET by tuning one of the 221 ohms gate resistor on the FET that is different?

Mr. Pass you mentionned that R8 can be used to adjust the offset. What are the typical values to use? Do I need to used both R8 at the same time, or they are indicated at two different places?

Thanks for any comments.
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