VOGONS


Reply 20 of 23, by Tronix

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After a year, a small update here. A user from one russian old-hardware forum trace the new PCB and recently I soldered it. Started checking without an amplifier:
P90713-200103.jpg

Digital f***n noise still present, because SAA1099 has an open-collector PWM output, which we pull-up to +5V power rail and collect all the interference. So, i make new +5V analog path with help 78L05 linear regulator from +12V, as is done in many sound cards:
P90811-125954.jpg

The interference is all gone! The sound immediately improved and became clear. Finaly, replace 78L05 TO-220 package with TO-92 and mount ampliefier. Sound quality still good without noise. Waiting for variable 10k resistor....
P90901-075436.jpg

Last edited by Tronix on 2019-09-23, 04:02. Edited 1 time in total.

Reply 21 of 23, by digger

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Great job!

We can't have enough retro sound card projects going on. 😀 I'll continue following your progress with great interest.

Reply 22 of 23, by Fagear

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Tronix hello. I've implemented your circuit in "CMS" debug block for FMonster.
I can send you blank debug board if you are interested.

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New BIG soundcard: FMonster.
Covox Sound Master replica
Innovation SSI-2001 replica & DuoSID.
My audio/video collection.

Reply 23 of 23, by maxtherabbit

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Tronix wrote on 2019-09-22, 19:16:
After a year, a small update here. A user from one russian old-hardware forum trace the new PCB and recently I soldered it. Star […]
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After a year, a small update here. A user from one russian old-hardware forum trace the new PCB and recently I soldered it. Started checking without an amplifier:
P90713-200103.jpg

Digital f***n noise still present, because SAA1099 has an open-collector PWM output, which we pull-up to +5V power rail and collect all the interference. So, i make new +5V analog path with help 78L05 linear regulator from +12V, as is done in many sound cards:
P90811-125954.jpg

The interference is all gone! The sound immediately improved and became clear. Finaly, replace 78L05 TO-220 package with TO-92 and mount ampliefier. Sound quality still good without noise. Waiting for variable 10k resistor....
P90901-075436.jpg

Is this project still alive? Are the EDA files for the board shared publicly somewhere?