Aleph-X builder's thread.

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homme_de_terre

Member
Joined 2004
Hi labjr,

actually I am in the need of two boards. It seems that I am a little late for group orders and I also could not find any Gerber files so far.
I have even considered point-to-point wiring.
Anyway, I would happily buy the boards for two mono blocks.
Drop me an email, in case you cold help me out. This is my first post, so I can't email.

Manfred
 
Jason Hubbard

Jason Hubbard

Member
Joined 2001
Regulated power supply

I had my AX up & running OK using a variac to bring the voltage rails upto +/- 15v (this is the "standard" AX, 15v & 4.5A total quiescent current).

I switched to regulators - in order to drop the voltage from the 18v transformer windings, so after the dual bridge rectifiers i now have 100,000uf, followed by an LT1083 regulator followed by a further 100,000uf. The ouputs are then connected to give me split rails & it all works OK.

I have the following questions;

Does the current draw of the AX vary much - I.e. "most" class A amps are considered to have a constant current draw, but in reality the current varies between 0 and 2Iq - with the AX being symmetrical does this rule also apply or is the current draw pretty well constant?

Should i consider parallelling LT1083 regulators to provide more current capability - i am pulling 4.5 amps and the device is capable of supplying 7.5 amps - would an additional device on each rail be beneficial?

I currently have the reservoir capacitors either side of the regulator - should i revise the arrangement to perhaps have say only 20,000uf before the regulator and put the 200,000uf after the regulator?
 
Jason Hubbard

Jason Hubbard

Member
Joined 2001
Regulated power supply

The power supply works just fine as it is and the device is operating well within manufacturers specs.

What i wanted to know was would an additional regulator give sonic benefits in that it would provide additional peak current capability if it were ever required? More to the point, will it ever be required? (i.e. will there be varying current requirements or does the symetrical nature of the amplifier pull a constant current?)

Are the capacitors best placed or would a different configuration yield better results?
 
C

commandercam

Member
Joined 2009
Can anyone help me understand the difference between the Aleph X and Aleph J-X? I want to build a pair of mono-blocks based on the Aleph design. Also, it seems I am a few months late (at least) for getting in on a group buy. Are any group buys planed for the future or does anyone have unbuilt boards they would sell?

Thanks!
Cam
 
S

scatterbrain001

Member
Joined 2007
noisefree said:
Hello,

hope there is any interest in this project – seems that I am the only one who tries it :-(

Here are some new details:

Have changed again some resistors with the result that the absolute and differential offset is very stable now:
I came to the decision to put in again the divider across the voltage reference and throw out the frontend loading resistors to ground – have found out that the divider only has the effect of a shifting ground (the supply voltages starts to become unsymmetric) in combination with this output to ground resistors (but I don’t know why this happened).
Also the trimmers have been scaled down: Abs. pot is now 20R and diff. pot 50R – both are 25 turn types.
I have implemented the resistor from FE to OS which I have also seen in the A75 article. (The A75 uses a combined feedback from output and front end.)
In the shown circuit below the feedback is not mixed and only comes from the OS. But mix mode can be realized when changing the 0R resistor to a higher value.
My main goal was to get a really good trimmable offset and this is done now and works very well - both offsets are adjustable to 1-3mV without a problem (but I can’t say if this resistor has a negative effect and how to dimension it!?) and the supply rails stay symmetrical.
The abs. offsets of the FE reaches values in size of +140 and +180mV - think that is acceptable (perhaps it can be reduced with a bit higher resistor value for the upper divider resistor)
Also new are the four resistors in the bias circuit connected to ground – it could be that they are not necessary - perhaps they bring a bit stabilization.
The two resistors which steal the voltage references some current in stand by mode are reduced to 270k which give a stand by output bias of only 26mA (2mA p-fet + 24mA SE-resistor)! That’s a consumption reduction to a tenth. The abs. offset goes down to -120mV and for diff. offset I get about 12mV.
However I need another possibility to throw away some open loop gain which is still to high.
Without the ugs output to gnd loading resistors the open loop gain raises again by 4dB.

Perhaps other people will try it out or have some ideas!???

Regards
Dirk
Click to expand...
Hi again, I did not put the 'quote message' in my last note, I would like to know if you have built or if anyone has built the schematic 'ax-sepp.pdf 'and also if PCBs have ever been made from it.

Thank You

scatterbrain001
 
J

jackies

Member
Joined 2007
Is the previous message a spam?
My fur crew?? :eek:
I'm reading this endless thread, as well as few other Aleph-X threads, and Aleph-X Wiki page is mentioned quite often, but alas, links are dead and I can't find the wiki page no matter how hard I look.. Could you kindly point me to it?
Your help will be greatly appreciated.
 
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J

jackies

Member
Joined 2007
Thanks for the answer!
I have another question though.. I have 16a rated schottky diodes, will that be enough for one channel of alepx-x with a reasonable amount of capacitance - circa 60-80 mf?
Or they gonna blow?
I'm a little confused after reading this thread - ppl seem to use everything from MUR08 to 35a bridges and I seen recommendations as hearty as 75a and 85a...
 
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M

mthoi

Member
Joined 2009
I am a newbie and would appreciate any assistance in troubleshooting my AX bias-ing problem. The schematics I followed was based on Blitz's AX2 V1.0 (100 watts) design.

After adusting V1 and V3, I have the following voltages across the bias resistors - R5 0.5V; R6 0.62V; R34 0.023V; R41 0.001V. V3 resistance measures around 80KR. Q1 is nice and hot but Q2, Q10, Q11 are stone-cold.

I suspect Q8 (MPSA18) may not be functioning properly since the voltage at collector = 22.98VDC, Vbase = 19.01VDC, Vemitter = 19.02VDC. The power supply is steady at +23.14VDC and -23.15VDC. I have replaced Q8 twice but the problem still remains.

Is there anything that I am overlooking? Any asssitance are appreciated. Reg.
 
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