SID output protection

MIDIbox SID
1

just saw this

“”“”“An Audio Out and In can be found on the module. The function of the small transistor behind the SID Output isn’t to amplify the signal, but to save the SID chip from any damage - so, never bypass this protection! If you are not able to find a BC547, just take any other “general purpose NPN” transistor - take care for the pinning! The SID also provides an Audio IN which allows external audio signals to be mixed with the SID output and to be processed through the 12db multimode filter”“”

just wanted to see what some of the people on here thought of protecting an audio out of a sid chip. im trying to run a direct feed off sid #1 on a sid2sid board. i was using an old circuit i found from the commodore era. of a 1uf cap and a 470k resistor, however i was recomended Optocouplers however getting that right confused me.

im thinking of just duplicating the sid2sid’s    sid#2 output on sid #1 any thoughts?

2

Dejavu :wink:

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3

It’s just a buffering principle, you could use the very simple bipolar transistor (essentially a “current buffer” in my opinion) or a simple op amp buffer (voltage follower), or voltage amplifier.  Opto couplers would work, but there are a few more bits involved, i.e. the opto couple would be used to drive another transistor stage I would imagine (think of an old opto compressor).  A pair of 74HC04 inverters one into the other makes a nice simple non inverting JFET buffer, as long as the single doesn’t get clipped and it’s biased properly.

Just take the audio out of the SID into the simple transistor circuit for the easy option… you could in theory take several buffered feeds from the SID output before it’s actually loaded down too much.