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Old 26th December 2008, 02:41 PM   #1711
Zen Mod is offline Zen Mod  Serbia
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Quote:
Originally posted by jazz
Hello and a late merry xmas to you all,

.....
Could somebody give me some advice on how to cure this, assuming it is bad? Could it be because of me using bc550 in stead of mpsa18??

........

did you tried both - 1nF between B&C of Q3 and Q8 , also 1nF between
Q4 C and respective output , same as 1nF between Q9 C and respective output ?
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Old 26th December 2008, 02:55 PM   #1712
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Hi;

39pF is way too low. I hqd to use 4n7 to get rid of oscillations.

4S is around 1/0,000004 Hz.........

William
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Old 27th December 2008, 11:37 AM   #1713
jazz is offline jazz  Netherlands
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Hi,

Thanks for the advice. I had a look at the parts bin and found some 1n8 and 6n caps. I used the 1n8 base to collector and 6n emitter to collecter. This solved the problem. I'm happy with this for now. In the final build I'll try some different values, go as low as I can and then backup a little for some margin.

Time for some listening and evaluation. piccie of the test setup attached.

Regards,
Joris
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Old 25th February 2009, 08:47 PM   #1714
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Default AX debugging

I have my Aleph-X v1.0 board with J505/9610 CCS (powered from a 3 amp +/-15v bench supply).

At this stage i want to verify that the board is populated correctly and that it's ok to install the power FET's.

For R48 ihave used a wire link and i'm reading 18.8 volts from that link to the negative rail - There is nothing across R23 and R25 has 8.6 volts across it.

R16 has 2.93 volts across it & R30 has 0.03 volts

Q5 has 3v on the gate, Q7 has 0v.

Could anybody point me in the right direction for where i'm going wrong please?
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Old 2nd March 2009, 06:57 PM   #1715
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hello everybody,
I'am a brandnew member of this amazing forum.
I want to buy two pcbs to built an aleph x amplifier.
There is anyone can help me please.
Many thanks.
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Old 2nd March 2009, 09:58 PM   #1716
labjr is offline labjr  United States
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Quote:
Originally posted by Wolfpako
hello everybody,
I'am a brandnew member of this amazing forum.
I want to buy two pcbs to built an aleph x amplifier.
There is anyone can help me please.
Many thanks.
I have some rev 1 PCBs that I never built. PM me if you're interested.
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Old 3rd March 2009, 04:37 PM   #1717
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Yes Iam, please mail me.
fran.sede@hotmail.com
Thanks
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Old 7th March 2009, 06:06 PM   #1718
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Default Progress

Ok - i found the fault - Q7 was dud.

Afterward replacing Q5/Q7 with a new matched pair i got 4.3v over R23 & R25 and decided to go ahead and connect up the main FET's.

So far so good in that i haven't killed anything yet, but i'm having some trouble adjusting the amplifier.

I'm using a variable PSU capable of 3 amps, but adjusting the bias with V2 is reducing the absolute DC offset but increasing the current draw until the PSU starts current limiting at about 2.8A.

R11 & R33 are changed out for 4k7 instead of 47k5

I'm struggling to get more than about 0.3 over drain resistors R5, 6, 40 & 41.

I'm also not totally convinced about the CCS created by Q6 - i'm only seeing 8.8 volts across a 9.1v Zener, have tried replacing the zener but no difference.

The inputs are floating, the outputs are loaded with a 7R resistor.

Any help would be greatly appreciated.
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Old 8th March 2009, 08:24 PM   #1719
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Default Current limiting is preventing it coming up correctly

The power supply going into constant current t=rather than constant voltage mode is causing the problem - if i wind Vr1 back far enough to shutoff one of the CS FETs completely then i can get 0.5v on the 0R22 drain resistors on the other other side of the circuit easily - i'll be building another power supply tonight.

I've been a little disappointed at the lack of any kind of response - is the Aleph-X an amplifier that nobody bothers with anymore or is everybody just into other things at the moment?
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Old 8th March 2009, 09:36 PM   #1720
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Hello Jason,
I'am Francisco from Madrid,I sill have not started my project,but
we can talk soon about it.
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