Aleph 60 mystical resistors

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Here're my last questions before I can buy all the stuff for my Aleph 60 and start the building process :D

1) What are the values of R1 and R8. There's only an * on the schematics?

2) R19 = 5622 = 5.622k = 5.62k ?

3) R21 = 1501 = 1.501k = 1.5k ?

4) On the Aleph 2, there was a thermistor in the power supply (plus the one to the ground). Why is this thermistor missing? Will the amp power up smoothly ?

5) Same question regarding the missing capacitor between C20 and Q4 (Aleph 60)?

6) Is it OK to use 5% 3W resistors?

Warning: I'm short on sleep and cross-eyed as a result...
but I think R19 is more likely to be 56.2k
I used the Panasonic 3W resistors from Digikey; they're 5% and work just fine.
The thermistor is to slow inrush when you first turn the amp on. Feel free to put one in if you like. Either way, be sure to use a fairly hefty switch. If all else fails, buy a double pole switch and wire the two sides in parallel. The next step after that is to put a 600V .1uF (some people say .01uF) cap across the switch to suppress the spark as the switch makes or breaks contact. If you really want to guild the lily, build a slow start circuit or use a Variac to bring the thing up.
The cap can be added if you like. It's there for stability. I changed my mind about ten or twenty times as I was building my amps, eventually deciding not to put it in...but I hedged my bets by making a place for it on the circuit board, and bought the caps anyway just in case I decided to put them in late some Saturday night. Mine are stable, but then I run them into a very tame load--both pairs are pushing purely resistive drivers. If I were using electrostats or something really freaky, I would consider using the cap.

I think it should be a bit more wide.
Only on that areas, where the current is higher, than normal. You can check in the schematics easily (FETs drain, source and power resistors, output, etc).

I would go up to 120-150mils, or even more...
Especially at drain, source and power resistor and out areas.
But, it is depend on you, of course.
In construction I would use 70um copper FR4 (hard to get it)
But the normal (35um) is the most popular.
Do not go down to 17.5um FR4.

I post now my version (NOT final) of Aleph 3 pcb.
I am working on it to get a little bit shorter signal path, but it have to look nice also. So, I have criterias...
This is some kind of mix from Kristijan-k and my ideas.



  • aleph_3_v1_0.jpg
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