Oh definitely had experience of that. A guy laid out the A/D and amplifier section of an avalanche photodiode array underneath a MAX232 and then wondered why the analogue signal was packed with crap, but randomly packed with crap. Taking the board out of the case and just eyeballing it, yeah, righto...Moral being, don't let the digital electronic guys route your sensitive analogue circuitry...![[-X]( "Shame on you")
I do recall someone had made micropower voltage source using a TL081 and used that to provide power to the analogue section. The LM324 and LM386 aren't very good at PSRR I vaguely remember it being 50-ish dB. A more expensive op-amp would help a lot with noise, but, of course, limiting the amount unnecessary inputs carrying noise to the circuit is good too.As noted before in a topic, it would have been better if the audio circuitry had been on one corner of the board, fed with its own supply rails and ground. And with no all round the houses all the way across the board audio input tracks.
On the B+ they missed a chance there, but because of feature creep, the chance to disconnect the amplifier from the analogue in was replaced with a chance to make the analogue in into analogue out...Given how few 1MHz bus devices actually use the audio connection, Acorn would have been better off having a link/jumper shunt to err, shunt out the "audio input".
You know, the very last place I'd want to be using the speaker output, after it has gone through that shitty circuit twice and then down a ribbon cable. Might be good for de-tuned, old skool electronic music?Statistics: Posted by maniacminer — Tue Mar 26, 2024 4:35 pm