Aleph J illustrated build guide

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#8,202
IMG20220113153257_BURST000_COVER-01.jpeg

IMG20220113154156-01.jpeg

Almost done...
It is very very heavyweight!
Please help me set Iq and DC offset with these boards :cheers:
 
#8,207
peppennino said:
View attachment 1014642

View attachment 1014643

Almost done...
It is very very heavyweight!
Please help me set Iq and DC offset with these boards :cheers:
Click to expand...

First things first.

1: this is an extremely well designed circuit. It is very, very stable wrt bias and offset adjustments.
2: Expect a quite high minimum/initial Iq. Don’t be surprised if minimum is approx 1A. Don’t worry, have no fear. All is good.

Adjustments=very easy.

1: If you are unsure and cannot set the bias pot to minimum value, set it to mid position (12,5 turns from click).

2: Offset pot is really not that important, but mid position is fine.

3: One DMM across one of the source resistors, alternatively two DMM’s, one across each. I used one.

4: One DMM across speaker outputs, to measure offset.

5: Turn on, and adjust 🙂 Normally it is good practice to adjust a little, zero offset, and adjust more. It is probably a good idea here too. But I am not known for being careful, so I did not care too much about that with this particular circuit. Felt very safe to set up.

In 4U and using goop @ 0N85-9, I would target approx 35 watts dissipation per device for starters, and see how it goes - measuring temps at devices center pin/device body, sinks close to devices, and sinks in general as it reaches equilibrium.

35 watts @ 21V5 is a drop of 0V440 across source resistors 🙂

Iq @ 1A62 per device.

My amp in 5U has higher voltage rails @ 24 volts, and is biased at approx 1A75 and 42 watts dissipation per device. All chill. I could sleep on it.

Explained by a GH.

Edited to add: Give it 50-100 hours before passing judgment. It needs a bit of time to bloom 🙂 also, don’t expect too much sugar coating. Haven’t measured yet, but this one is low on distortion.

Mighty comments?

Hugz and kisses,
Andy
 
Last edited:
#8,209
Zen Mod said:
no load on output, inputs shorted/grounded

final setting with lid on (probe wires/crocs to DMMs outa case); wait, read, open, fiddle, close, wait, repeat
Click to expand...

Forgot those important steps. That said, and kudos to you Mighty, I could not measure a difference in offset with inputs shorted/not shorted. Also, when I after three days of use in listening position/in an open cabinet decided to verify/null out offset, it hadn’t drifted more than 3mV. A beauty 🙂
 
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