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anders.a 14th December 2005 06:10 PM

In the Aleph-X wiki about starting up it is recommended initially not to connect Q1, Q2, Q10 and Q11, then power it up to see that the diff pair and it's current source work properly, and that there are no surprises with the rest of the circuitry.
I was wondering what surprises I should look for. Heat? Any broken part? Voltage? Measuring any ware?

Also should I set AC current gain before I set absolute and relative DC or is it the other way around?

wuffwaff 15th December 2005 06:42 AM


if you are shure you connected and soldered everything correctly you can connect the fets before the first startup.

I would set the ac-current-gain after everything else (bias, abs-offset). You can leave out the ac-current-gain resistor on startup and first test the amp without the active current source. You can ook for oscillations etc.
Then connect the ac current gain resistor and determine what cap you need in the active current source (probably between 2n2 and 6n8) It is easier to use a pot first cause the ac-current-gain changes quite a lot with small resistor changes (in my amp 1k3 was around 60%, 1k37 was 50 or52%)


P.S. you canīt really set the relative offset although there are some changes when stting the bias. Here the input pair needs proper matching.

anders.a 15th December 2005 05:12 PM

Ac-current-gain resistors. Are you refering to R12 and R34?

wuffwaff 16th December 2005 06:31 AM

yes those are the ones.


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