Aleph-X builder's thread.

[moe29]

If you are following Grey's original schematic you would not use
the SST505 part. It is an optional biasing method for D1a/D1b.

Use D1a (1N5239B)

Put a jumper from pin 1 to 3 on Q12a.

Put a jupmer on J1a.

Jumper on R48 and R49.

Use a 3 watt resistor for R21 if you have it. If not at least of some
value at 3 ohms.

I'd also use the McMillan resistors at R46 and R47.

No need to use jumpers at C7, C10... they can just be omitted.


Hope this is of some help... me not being the final word on anything!,
other than i did get the thing to work sticking close to Grey's schematic.
You did pick a little bit of a sticky project for your first
effort! Also read the Aleph-X WIKI too, lots of great info there.

maybe someone else will chip in if i've lead you astray.

[koolscooby]

Thanks moe29

i've removed the sst505
jumpered q12a
removed jumpers on c7 thru c10
added a 2.2ohm 3w resistor on r21

so now...
only R49, r48, j1a, and q12a are jumpered
btw i do have the mcmillan resistors in r46+r47

now when i turn the amp on, and speakers are connect, they "blip"... then no more sound
if i shut it off again and turn it back on, same gig...

i'm still feeding it 1kHz @ +18dBm w/ a 0mv offset
signal gets to the board fine (oscilloscoped)

thanks in advance everyone

[moe29]

hmmm... it seems like you are going to need more help than i can
provide. I really wouldn't hookup speakers until you get readings
that varify the amp is working and is stable. It's difficult to trouble
shoot a circuit from afar. Often it can be something trivial that you
are overlooking. Maybe take a fresh look at it tomorrow.

by no means am i an expert in amp building... It took me a day or
two to get the circuit working, after correcting obvious errors, and
learning a bit more about the circuit. I wouldn't reccomend this
amp as a first time project, but since your in there bailing, keep up
the work... maybe a picture or some better answers from the
more learned will get you up and running

All the big guns seem to be off discussing loftier questions in
another part of the Forum, rather than lending their expertise here...

[koolscooby]

Originally posted by moe29

All the big guns seem to be off discussing loftier questions in
another part of the Forum, rather than lending their expertise here...

hehe, maybe so ...

well thanks much for the help ... i'm going through and rechecking schematic vs board vs values

[koolscooby]

ok well i decided to try something
before i omitted the c7-c10 jumpers, i got a steady signal out of the amp
then ijust had the blip
so i re-added the jumeprs there and i get a signal again, but
its still not turning the fets on ... upt o 5v and its not turning them on

[koolscooby]

question about output...

ok this telulex function generator feeds out a bnc, which i'm going to an F connector into rg6 coax...the pin inside the shielding is + and the shield is ground... i connected the ground to the - and the pin to + and i connected the SHD on the XLR connector to ground... this does and doesnt sound right

because the signal coming in isnt balanced... and i need a balanced signal
could this be why the fets arent turning on?

about ready to something!

[BDP]

before i omitted the c7-c10 jumpers, i got a steady signal out of the amp

Remove the jumpers, they are for frequency compensation. The 'C' designation is for capacitor. You have just coupled the signal from the differential pair to the outputs bypassing the output devices and disabled the output current sources.

There is no reason why you can't use current source Q12b. You would use it in place of jumper Q12a, but for now stick with what you have so we can get you going then you can switch back to the current source.

What is the voltage across D1a ( cathode is neg anode is pos) the stripe should be to the positive rail. What is the voltage across R17? What is the voltage across R24, VR2? What is your voltage across drain resistors R23 and R25?

The schematic I have is different than the board. I probably have an old version ( probably not the only one). J1a is drawn from R17 to ground and on the board R17 is connected to Q12 then to J1a or J1b. J1a goes to ground. J1b goes to the negative rail.

BDP

[tomchaoda]

Originally I was planning the parts for my Aleph 2. Then, I found out the Aleph X PCB GP and purchased 4 PCBs. I grew interests in the Aleph X and is planning to use my prepared parts, may be, to make the mono-blocks of Aleph X into 100W version. While my parts is coming (mono block cases is still month away), I made my own project notes. I would like to share with you all. All comments, corrections are welcome! You can refer my preparation notes at:

http://www.penguinlovers.net/audio/alephx_proj.html

Thanks,

Thomas

[koolscooby]

Originally posted by BDP


Remove the jumpers, they are for frequency compensation. The 'C' designation is for capacitor. You have just coupled the signal from the differential pair to the outputs bypassing the output devices and disabled the output current sources.

>> I just removed the jumpers
>> Hehe, i know that "C" is for capacitor... i'm not that noobish :-D


There is no reason why you can't use current source Q12b. You would use it in place of jumper Q12a, but for now stick with what you have so we can get you going then you can switch back to the current source.

>> Okay, im' still on a jumpered q12a pin 1 to pin 3

What is the voltage across D1a ( cathode is neg anode is pos) the stripe should be to the positive rail. What is the voltage across R17? What is the voltage across R24, VR2? What is your voltage across drain resistors R23 and R25?
Across, voltage

>> d1a, .17v
>> r13, .13v
>> R24, .04v
>> vr2, 0v
>> r23, .01v
>>r25, .03v
>>obviously, this isn't correct... something is awry
>> w/ the c7-c10 j's, i still got 9.1 v on d1a, now i dont [something is wrong! ]

The schematic I have is different than the board. I probably have an old version ( probably not the only one). J1a is drawn from R17 to ground and on the board R17 is connected to Q12 then to J1a or J1b. J1a goes to ground. J1b goes to the negative rail.

BDP

Thanks BDP :-D

[BDP]

Do you have a good ground to the PCB? If you measure from PCB ground to cathode of D1a you should have positive rail voltage. What is the voltage from PCB ground to junction of D1a and R17.

Is J1a in. Resolder your connections.

BDP