Very interesting. A few years ago I did consider something similar re digipots for remote volume control but couldn't see how I could get it to work electrically in the Self design. Will go back and rethink. Was also concerned that the non linear aspects of digipots would increase the distortion. Whist any effect would be minimal and totally inaudible but seemed a sin in a Self design. I also see you have what looks like a small switching UPS presumably for standby power. Notoriously noisy but again may make little difference in reality depending on what it's there for.
From my point of view, the original implementation surely has a touch of perfection. If you want to add a remote control or other things which require a microcontroller, you have to make a compromise. But I'm not a pro and others would surely be able to design things in a better way - starting with better test equipment.
Actually there is nothing to try as all multi-conductor cables should be twisted as it reduces pick-up and interference. That goes for AC power, interconnects (AC as well), digital and speaker cables as well. One exception is coax cables. Even in DC supply cables, twisting reduces self-induction.
The twisting ensures that both wires are on average the same distance from an interfering source and are affected equally, which helps canceling common mode later.
If you try to find it by listening, you wouldn't probably, depending on your equipment and ears. Above you mentioned you don't have proper measurement gear.
But this was only a hint, if you are happy by no means you should twist the wires.
Nevertheless, in case you had the appropriate equipment, it would be very interesting to see a comparison twisted vs. untwisted within the same build!
One idea which just came to my mind:
Shouldn't it be possible to replace the volume pot with LDRs?
It could be controlled using a rotary encoder or ir remote by an Arduino. This concept would be somewhat "less invasive" than my digipot approach and very good decoupling of analog and digital domains.
The principle with the Arduino controlled LDRs can be seen e.g. here: https://www.diyaudio.com/community/...olume-and-source-selection-controller.278667/
Maybe this passive attenuator could even be used without hardware modifications.
Just an idea.
Shouldn't it be possible to replace the volume pot with LDRs?
It could be controlled using a rotary encoder or ir remote by an Arduino. This concept would be somewhat "less invasive" than my digipot approach and very good decoupling of analog and digital domains.
The principle with the Arduino controlled LDRs can be seen e.g. here: https://www.diyaudio.com/community/...olume-and-source-selection-controller.278667/
Maybe this passive attenuator could even be used without hardware modifications.
Just an idea.
Ah, just noticed that @Zen Mod has developed an LDR attenutator, too:
https://www.diyaudio.com/community/threads/poor-serbian-man-optical-volume-control.134316/
Maybe he has some data on LDR performance?
https://www.diyaudio.com/community/threads/poor-serbian-man-optical-volume-control.134316/
Maybe he has some data on LDR performance?
Thank you for your input
Actually, I have been looking quite a while for measurements and couldn't find any. This somehow matches with your statement, unfortunately. Nevertheless, it would be great if there was any evidence for this "pretty terrible". Or could you maybe let us know in which way they are terrible? This would help as well.
Finally found something:
https://www.effectrode.com/wp-content/uploads/2020/05/silonex_optocouplers_application_notes.pdf
I agree with @jwilhelm that this idea should be buried
https://www.effectrode.com/wp-content/uploads/2020/05/silonex_optocouplers_application_notes.pdf
I agree with @jwilhelm that this idea should be buried
I haven't experimented with LDOs myself but what I've been reading is the linearity is poor from a control perspective and distortion is high.
A PGA2310 is an option for remote control. Another option is a VCA. I've got a couple THAT 2180s that I plan to experiment with. They probably aren't a great fit with this pre-amp though, they're high in H2 distortion.
A PGA2310 is an option for remote control. Another option is a VCA. I've got a couple THAT 2180s that I plan to experiment with. They probably aren't a great fit with this pre-amp though, they're high in H2 distortion.
ZM - frankly - newer was too much warmed for approach but relented under pressure of my dear friend to work on it
in time, we had good result, considering knowledge and everything else ..... but I knew that anything except ultimate solution*** is not going to suffice me in the end
anyhow, I pursued my other dream and I made it, nowadays known as Iron Pumpkin
LDR attenuator is, in the end, still resistive attenuator and not a thing giving me wide smile while I'm sleeping
***self-calibration procedure during start-up; demanding serious programming skills which I still doubt I will ever have; irrelevant - will not try it
best audio result is one which gives you widest smile and greatest amount of your foot-tapping
various ppl are obsessing about various things - some are investing 20kg of copper and caps for preamp, while having most crude pot in it .... and they're happy
I personally abandoned resistive attenuators completely, and it doesn't matter which sort is it - for my ears inductive attenuator properly made is superior to resistive attenuator properly made
but that's for my ears
various ppl are obsessing about various things - some are investing 20kg of copper and caps for preamp, while having most crude pot in it .... and they're happy
I personally abandoned resistive attenuators completely, and it doesn't matter which sort is it - for my ears inductive attenuator properly made is superior to resistive attenuator properly made
but that's for my ears