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-   -   Aleph 30 - 1nF cap and Square Wave Shape (http://www.diyaudio.com/forums/pass-labs/123054-aleph-30-1nf-cap-square-wave-shape.html)

N-Well 14th May 2008 02:25 PM

Aleph 30 - 1nF cap and Square Wave Shape
 
Hi,

I've juste built an Aleph 30. It sounds great. I use it in an active system, below 300Hz.

There is only one thing I noticed on square wave at 10kHz on 8ohm+1.5F load: there are oscillations superposed , without the 1.5F, no oscillations but a slight overshoot on the rising steep.

So I have one question about the 1 nF cap. that is on the original Aleph 30 schematic between the output and the drain
of the left mosfet of the differential 9610 pair.
I've use BrianGT boards and this caps is not present at all.

What's its purpose and is it that critical ?

Have you experienced similar oscillo Traces with this cap as well N ?

nwell

MEGA_amp 15th May 2008 01:47 AM

2 Attachment(s)
The only 1nF I see on the Aleph 30 circuit is C7 which is in the Aleph current source. The other 1nF thats in some Alephs is to prevent oscillations due to longer traces in the commercial board. This is not necessary with BrianGT's boards as it is fairly compact.


This pic is from an Aleph 2, the Aleph 30 schematic does not have it:


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