Aleph J illustrated build guide

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#4,302
JSA1971 said:
I would seriously consider buying the back panel kit if you’re thinking of using one of the chassis (4u/5u) from the Diy store. It has the rca input connectors, speaker terminals, power switch AND all the mosfet mounting screws and washers needed. I don’t believe it has the split washers though which you’d need to source separately.
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Many thanks for the advice guys, unfortunately I had already got the 4u chassis without the back panel kit but managed to source the IEC socket ok although I must admit, I've never seen a dual fused inlet before and it does concern me slightly! Does 2.5a slow blow sound ok for Aleph J with 500VA transformer 240v? (and DIY audio soft start) I was thinking of using a larger fuse on the neutral side.
Quick question as I am planning to populate my boards tomorrow, should R8 be a 500R pot as per the BOM or a 1k fixed resitor?
 
#4,303
R8 should not be a 500R pot. The BOM I looked at indicates a 2K pot.
It is nominally set to 1K to ensure about 8-ish mA current through the
front end jfets. (So the pot value should be greater than 1K)

I built mine with a 2K pot, set it at 1K, and never touched it since. If
I were to do it again, I would have just gone with a 1K fixed resistor.

Cheers,
Dennis
 
#4,309
JSA1971 said:
Just trying to help out, and trying to pay it forward. I’ve received a lot of advice and help with my projects, and am eternally greatful. My first build was in fact an Aleph J thanks to a little push from 6L6 (aka Jim) and Dennis Hui. I was petrified that the little knowledge I had wouldn’t be enough to get through the build, let alone a functioning amp. The help, advice and encouragement from the people on this forum from Nelson himself, 6L6, Zen Mod, Dennis Hui and Mark just to name a few is never ending and appreciated. Without the help I might not be sitting here as I type listening to my J. 😊
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Hear, hear.

Now back to the bench, I'm upgrading the PS to dual mono for my AJ.
Best amp I've ever heard as is; but if it can sound any better, I want to know it.
 
#4,310
mpa said:
Many thanks for the advice guys, unfortunately I had already got the 4u chassis without the back panel kit but managed to source the IEC socket ok although I must admit, I've never seen a dual fused inlet before and it does concern me slightly! Does 2.5a slow blow sound ok for Aleph J with 500VA transformer 240v? (and DIY audio soft start) I was thinking of using a larger fuse on the neutral side.
Quick question as I am planning to populate my boards tomorrow, should R8 be a 500R pot as per the BOM or a 1k fixed resitor?
Click to expand...

The fusses should be the same value, 2.5A slow blow is fine for 240V.

If you use dual diodes (the fast switching/soft recovery types) and you have a large capacitor bank and you decide to use thick&short wires (and you already have a 500VA transformer) the fuse may have to be increased to 3A...or more... see how you'll go.
 
#4,311
mpa said:
, should R8 be a 500R pot as per the BOM or a 1k fixed resistor?
Click to expand...

Omit the pot, use the 1K. The Zener is actually what's setting the current, the pot, if installed, can only made very small changes if desired. As others say, you set it to 1K and be done, so why even bother with the $4 pot when a $0.05 resistor does the same job. 🙂
 
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