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<div>Excuse my heresy, but with the SID chips being so valuable, ... are any of the many clones (I think "workalikes" is probably a more suitable term) worthwhile? And do they come with any buffering or protection?</div>
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<div>GB</div>
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<div>------ Original Message ------</div>
<div>From "Ben Stuyts via Synth-diy" <<a href="mailto:synth-diy@synth-diy.org">synth-diy@synth-diy.org</a>></div>
<div>To "Antti Pitkämäki" <<a href="mailto:antti.s.pitkamaki@gmail.com">antti.s.pitkamaki@gmail.com</a>></div>
<div>Cc "SDIY" <<a href="mailto:synth-diy@synth-diy.org">synth-diy@synth-diy.org</a>></div>
<div>Date 7/30/2025 3:32:21 PM</div>
<div>Subject Re: [sdiy] SID output protection?</div>
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<blockquote cite="B464F723-6986-434B-A0A1-7C8F68C3C485@stuyts.nl" type="cite" class="cite2">
Hi Antti,
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<div>On 30 Jul 2025, at 21:20, Antti Pitkämäki via Synth-diy <synth-diy@synth-diy.org> wrote:</div>
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<div>So it seems I can just leave the original 10k/1000pF lowpass filter there for not-too-trebly-sound and forget about the original transistor buffer, going instead for the opamp buffer with protective diodes and the output resistor.</div>
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Yes, please do. The op-amp buffer costs next to nothing, compared to the rare and expensive SID chips.</div>
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<div>Thanks for all the help and links, I'll go through the information contained in them and let's see if I manage to come up with decent solution. I know it's not difficult, this is just not my field of expertise :P</div>
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<div>BTW, here is another SID output protection circuit:</div>
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<div><a href="https://csdb.dk/release/?id=150177">https://csdb.dk/release/?id=150177</a></div>
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<div>It is based on diodes without any active parts.</div>
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<div>The series-diode D1 doesn’t make much sense either. It could influence the sound (not sure about the output voltage levels involved), but it is definitely a non-linear device. In my opinion, it would make more sense to connect the D1 between the top of
D2 (anode) and +12V (cathode). That way, anything over +12 V is shunted to the 12V rail.</div>
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<div>And then loose the zener. Do not use zeners for this. Use a decent TVS (and check its datasheet where it actually starts clipping). The 12 V zener isn’t much of a protection. It is:</div>
<div>a) slow</div>
<div>b) not really 12 V (look up the data sheet)</div>
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<div>In all, I would ignore that circuit.</div>
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<div>If you settle on a circuit, feel free to post the schematic here for a go-over. There are lots of experienced designers here with solid opinions.</div>
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<div>Ben</div>
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