Aleph J illustrated build guide

[VDO]

Middle...

 

[VDO]

... And right side.

 

[Zen Mod]

I hope 6L6 will chime in to check orientation of parts

in meantime - double check is there any difference to working channel , same as possible shorts or cold solder

I hope you mount them on heatsink , prior to testing

 

[VDO]

Hi Zen Mod,
I will check again for mistakes.

What i do not get is why none of the mosfets work.

Thank you for helping out.

Regards, Vranc

 

[grimberg]

What transistors did you use for Q2, Q3 and Q4?

 

[sandyhooker]

j176 as input

say that you need at least 2+2 per channel

3+3 even better , and then still weak FE , comparing to 2SJ74BL

nota bene - measuring Idss and adequately setting of CCS on top of them is a must

edit - what you need to look for is xconductance of parts used

I have 100 j176 ready to put through matching (idss) process. plan to put three in parallel(total of six) per channel. CCS output must then be increased ,correct?
Current through input must reflect 80% common idss through each device????Need your help on this issue. Thank you.

 

[wengtech]

at last,
my long time delayed aleph J is done.

with passive volume min.
bias 400mV and dc offset is 0v.
temp is 60 degree celcius.

boxed into temporary case











nothing fancy here
and luckily it is done without any problem
no hum or hiss or speaker thump on turn on/off (without spk protector)

well, first impression with this aleph j was a bit clumsy
but the detail and other goodness can be feel directly
so i think, the component need to be break in for a while.

thx to papa, zenmod, and 6L6

next project: to mate aleph j with pumpkin.

 

[Zen Mod]

I have 100 j176 ready to put through matching (idss) process. plan to put three in parallel(total of six) per channel. CCS output must then be increased ,correct?
Current through input must reflect 80% common idss through each device????Need your help on this issue. Thank you.

pretty much yes

 

[VDO]

I use bc550c for Q3 and Q4. Q2 is a bc560c.

(In fact, the last bc560c in the store, as they said that the 560 is obsolete and can recommended the bc559c as a replacement).

 

[grimberg]

They don't look like the ZTX devices, that's the reason I asked. Based on the pictures you posted and the data sheets, they appear to be correctly installed.

 

[VDO]

I gave it special attention, as the pin layout is reversed compared to the Ztx450/550.

 

[Zen Mod]

BC bjts on both pcbs?

did you took care of pinout ?

flat side of BC is same as rounded side of ZTX, pointed to you , regarding pinout

edit : I didn't saw two last posts

 

[VDO]

I just put in a different pair of 240s for the ccs-side. Just to check if that was the problem; it was not. It would have been quite a coincedence, all 4 mosfets defect, but as they came from the same source, i gave it a try.

Maybe i will pick up some bc550 tomorrow to see if that is the problem...

 

[VDO]

Btw: also soldered all joints again. There is always good news: my soldering is getting better ��

 

[ticktock]

and luckily it is done without any problem
no hum or hiss or speaker thump on turn on/off (without spk protector)

congrats !!

temp is 60 degree celcius.

devices or heatsink?

nothing fancy here

if it's not fancy, your quad inductor PSU is at least classy

 

[wengtech]

congrats !!

thanks just lucky.
a very silent amp, basically.

devices or heatsink?

on heatsink
a bit hot i know, but this is temporary
will move into better case and heatsink soon

if it's not fancy, your quad inductor PSU is at least classy

nahh.. it's only 2,2mH 1.6mm each
a friend build the aleph j psu with 3H 2.2mm inductors (weighted 7kg each)
now that is classy

 

[VDO]

Hi,
I hope some one can give some pointers...

I have rebuild the faulty channel of the AJ and the CCS is getting warm now. The other mosfets are still cold. What further alarms me is the fact that the Jfets get very hot.

The orientation of the bc560c/550c is the right way around.

Where should i look, apart from shorts and other building mistakes?

 

[Zen Mod]

we really need some measurements

inputs grounded , no dummy load on output

 

[VDO]

I will do so today.

Do you have any suggestion on to what/where to measure?

And, just to be sure: inputs grounded... does this mean inputs shorted, as the minus input is connected to GND (unbalanced config)?

 

[Zen Mod]

here we go again ........

yeah , inputs shorted to gnd


regarding measurements , go back in thread , pick any of schematics used in troubleshooting , and read related posts