Aleph J Schematic

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#1,322
Thanks for the link, you beat me to it. 🙂

As for the board, I was envisioning the same basic layout as the F4, F5c, etc... The longer board with the outputs all on the lower edge.

Also, I would love to see R7 replaced with a trimmer pot, as that's where you will be able to dial out any DC offset on the outputs... Maybe put pads for a parallel resistor there as well...

J109's are basically impossible to get anymore, so most people will be using a matched pair of J74's... it would be handy if they were face to face so their cases can be zip-tied together for better thermal tracking.

Thanks a bazillion for the offer!
 
#1,323
Ok i fell flat with the second channel 🙂

Offset is (-)23.6Vdc😱
R7 - 36V
Q3 Vce-36V
Q2 Vce - 0V
Q4 Vce ~ 4 V
Z1 - 9.9V
R8 - 9.1V
All source resistors are around ~.56xV

Q5 & Q6 gets pretty hot (case temp of 70C after 5 mins)

So before i unmount the setup, anything that comes to anybodys minds pls.

I have used 2Sj74 & BC550/560 (have been careful with the pinouts 🙂)
 
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#1,324
Can I jump in and suggest right now, please fellers, that a new thread is opened for discussion of a new UMS Aleph J board design rather than doing it in here?

I'm interested in following if not contributing to the process and I think it would be a mistake to bury something that important in the 13?th page of an existing thread.

Much respect to craigtone for bravely volunteering ;P and all due respect to 6L6, and Mr dB.
 
#1,325
kroyin said:
Ok i fell flat with the second channel 🙂

Offset is (-)23.6Vdc😱
R7 - 36V
Q3 Vce-36V
Q2 Vce - 0V
Q4 Vce ~ 4 V
Z1 - 9.9V
R8 - 9.1V
All source resistors are around ~.56xV

Q5 & Q6 gets pretty hot (case temp of 70C after 5 mins)

So before i unmount the setup, anything that comes to anybodys minds pls.

I have used 2Sj74 & BC550/560 (have been careful with the pinouts 🙂)
Click to expand...

I dug up a old post from Zen it says

'so - voltage across R7 is completely dependent on input LTP's CCS (Z1, Q2,R8)'

So as of now Q2 seems to be the culprit as R8 & Z1 reads more or less ok
 
#1,327
whatever you have , between +/-18 and +/-28Vdc

be sure that steady dissipation of each IRFP150 is no more than 50W , with proper heatsinking

Pa sez that input Jfets (in that configuration) are pretty safe up to ....... +/-35Vdc PSU , if I remember correctly
whatever - I don't like regs in power amp supply , for my taste better solution will be to un-wind some turns of xformer secondary , if possible
 
#1,329
pls help

kroyin said:
I dug up a old post from Zen it says

'so - voltage across R7 is completely dependent on input LTP's CCS (Z1, Q2,R8)'

So as of now Q2 seems to be the culprit as R8 & Z1 reads more or less ok
Click to expand...

Change q2,q3,q4 but things are not right

ZD1-9.36V
R8-8.75V
Q2 Vce-13.8V
Q2 Vbe- 0.6V
R7-8.7V ?????
R16,17,18,19- 0.59xV
Q5,Q6 Vgs - 4.2V
Q7,Q8 Vgs- 8.1V ???
Q4 Vce-4.68V

One other thing the good channel has 0v across 5pF, while the bad one has 2.8v

I am confused
 
#1,331
Ok done..there. was a short on one of the JFEtS.

Both channels are working.

While these are early days with burn in and all,my idea was
J requires around 1.6v to drive it to 25W while F5 requires > 2V to drive it to 25W.

But all things being equal for the same setting F5 is louder? ??
My aleph is SE with -ve input grounded & all components as per published circuit
 
#1,332
New AJ boards,

many thanks to craigtone for his volunteer to do the job.
May I suggest some additional design proposals:

- Lead pitch for the use of 1/4W audiophil resistors as Dale or PRP
- Space for an - input foil capacitor as f.i. 1uF ClarityCaps PWA or ESA

Thank you

gku
 
#1,333
kroyin said:
Ok done..there. was a short on one of the JFEtS.

Both channels are working.

While these are early days with burn in and all,my idea was
J requires around 1.6v to drive it to 25W while F5 requires > 2V to drive it to 25W.

But all things being equal for the same setting F5 is louder? ??
My aleph is SE with -ve input grounded & all components as per published circuit
Click to expand...
In my build, Aleph J has more gain and sounds louder at similar input signal level compared to a standard F5.
 
#1,334
anilva said:
In my build, Aleph J has more gain and sounds louder at similar input signal level compared to a standard F5.
Click to expand...

To get the level of the F5 closer to the AJ, change the feedback resistors (R5 R6 R7 R8) from 100R to 150-220R in the F5 to increase the gain. (At the expense of feedback, but I have built one with 100R and one with 150R and I hear no difference...) 😀 😀 😀
 
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