Wow and kudos to you, jean_paul! 👍😎 That's a nice relay, muted, (stepped) volume, and selector switch all bundled on one PCB. It would be a boon to aspiring and even seasoned DIY'ers. Do you make them in volume, as per request process, or it's a one off creation? Had I know earlier, I would have ordered one instead of installing a LDR, Elma selector switch, (an currently no muting, not ideal) when I was putting together a classDAudio module as a project/DIY lkit.
"BTW I think a predefined power on/off sequence is silly. Stuff should be made to withstand human errors and be silent while switching sources. Volume should be low at power on. Possible with some decades known simple logic. The more expensive audio stuff is the less one sees such implemented. Incomprehensible and unacceptable. Just don’t buy or build hampered stuff. Grandparents, parents, kids, wife, dog, you yourself the morning after the night before: all should be able to use devices in a home without consequences." - Agreed! (Too bad that in the current the state of world - cuttings costs at any/most level(s) is mostly the norm. ahem, moi included 😢 due to budget constraints - LOL?)
'To err is human' and to AI being infallible - bosh!
"BTW I think a predefined power on/off sequence is silly. Stuff should be made to withstand human errors and be silent while switching sources. Volume should be low at power on. Possible with some decades known simple logic. The more expensive audio stuff is the less one sees such implemented. Incomprehensible and unacceptable. Just don’t buy or build hampered stuff. Grandparents, parents, kids, wife, dog, you yourself the morning after the night before: all should be able to use devices in a home without consequences." - Agreed! (Too bad that in the current the state of world - cuttings costs at any/most level(s) is mostly the norm. ahem, moi included 😢 due to budget constraints - LOL?)
'To err is human' and to AI being infallible - bosh!
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It is a 56 Euro Aliexpress item 😀 that I wanted to try out.
Relays are genuine Omron bistable types.
I just made a transformer board in the same color to go with it.
Relays are genuine Omron bistable types.
I just made a transformer board in the same color to go with it.
Have you tried make before break selector switch? The common switches are break before make. Another thing you could try that we used in military equipment is to load all your inputs, directly at the connector wit a 10K or so resistor that ensures that the output of the device you are selecting is at ground potential (or rather, it output capacitor is discharged).
Hello All:
Just thought to provide an update and maybe a closure on this loud pop issue.
As suggested by Mooley (Thanks, Mooley! 😎), only performed a partial (shortcut/workaround?) implementation...
1. Ordered enough 1uf film capacitors and 1Mohm resistors for six (RCA) inputs and two (RCA) outputs from HiFi Collective. (Those 1uf film caps are quite large. And, for some reason, this time, got dinged with brokerage/delivery fees from DHL!😢)
2. As for the partial implementation - only soldered 1 cap and two resistors as per the suggested values for each L and R input RCAs per Mooley's diagram (e.g., R1+C1+R4) only to the RCA outputs of the preamp and NOT to each input RCA NOR the 1 cap and 1 resistor to the selector outputs (C4+R7) prior to the 100k ohm pot/volume control (Note: the two outputs were wired in series (i.e., the positive of output one was already jumpered to the positive of output two and the negative/ground of output one was already jumpered to the negative/ground of output two)).
3. The loud pop when (rotary) switching the inputs no longer occurs/is an issue.🙂
4. The thought (good or bad?) to implement, the 1 cap+2 resistors, in this way was to stop all/any possible DC(?) from reaching the outputs. (Cheap fix?)
5. In my haste (and aging mind), totally forgot to measure for any voltage across the input selector pins as per Mooley!😱😴
Thank you all, for the suggestions/inputs!
Have a another simple question for Mooley, does the cap plus two resistors (in your circuit diagram) affect the (input and/or output) frequency response?🤔 Thanks.
Sincerely,
Kingsley.
Just thought to provide an update and maybe a closure on this loud pop issue.
As suggested by Mooley (Thanks, Mooley! 😎), only performed a partial (shortcut/workaround?) implementation...
1. Ordered enough 1uf film capacitors and 1Mohm resistors for six (RCA) inputs and two (RCA) outputs from HiFi Collective. (Those 1uf film caps are quite large. And, for some reason, this time, got dinged with brokerage/delivery fees from DHL!😢)
2. As for the partial implementation - only soldered 1 cap and two resistors as per the suggested values for each L and R input RCAs per Mooley's diagram (e.g., R1+C1+R4) only to the RCA outputs of the preamp and NOT to each input RCA NOR the 1 cap and 1 resistor to the selector outputs (C4+R7) prior to the 100k ohm pot/volume control (Note: the two outputs were wired in series (i.e., the positive of output one was already jumpered to the positive of output two and the negative/ground of output one was already jumpered to the negative/ground of output two)).
3. The loud pop when (rotary) switching the inputs no longer occurs/is an issue.🙂
4. The thought (good or bad?) to implement, the 1 cap+2 resistors, in this way was to stop all/any possible DC(?) from reaching the outputs. (Cheap fix?)
5. In my haste (and aging mind), totally forgot to measure for any voltage across the input selector pins as per Mooley!😱😴
Thank you all, for the suggestions/inputs!
Have a another simple question for Mooley, does the cap plus two resistors (in your circuit diagram) affect the (input and/or output) frequency response?🤔 Thanks.
Sincerely,
Kingsley.
This one?
The combined parallel resistance of the two resistors define the input impedance. That would be 235k here.
The cap and the right hand 470k define the response. 10uF and 470k gives a -3db point of 0.03Hz, a 1uF would be 0.3Hz and a 0.1uF would be 3Hz which is still perfectly fine for audio and lets you use a smaller cap.
The combined parallel resistance of the two resistors define the input impedance. That would be 235k here.
The cap and the right hand 470k define the response. 10uF and 470k gives a -3db point of 0.03Hz, a 1uF would be 0.3Hz and a 0.1uF would be 3Hz which is still perfectly fine for audio and lets you use a smaller cap.
Depending on what is parallel to the resistor on the right of course.
C4 was/would be the cause for plops probably as it was dangling in the air at the left side causing it to charge when switched.
Basic rules for fine operation:
- Always avoid the "2 cap in series" scenario.
- Always use an RC filter at inputs.
- Never leave caps floating.
- Build tidy and compact with short connections.
- Build the device in a metal casing connected to PE
C4 was/would be the cause for plops probably as it was dangling in the air at the left side causing it to charge when switched.
Basic rules for fine operation:
- Always avoid the "2 cap in series" scenario.
- Always use an RC filter at inputs.
- Never leave caps floating.
- Build tidy and compact with short connections.
- Build the device in a metal casing connected to PE
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Hi Mooley:
Sorry, not the one with the 10uf cap in series with the 2x 470kohms resistors (the other end of the resistors being tied/soldered to ground) but the 1uf and 2x 1Mohm (as per your suggested schematic). The exception/difference is that they are soldered to the output RCAs versus/rather them to each input (as per your schematic and jean-paul's RC filter recommendation). Not entirely sure if the way I did it affects the circuit and/or frequency response.
Hi jean-paul:
Thanks for the break down of the rules. (It looks like I broke the basic circuit rules, i.e., RC filter at inputs vs output(s)!)
Sincerely,
Kingsley.
Sorry, not the one with the 10uf cap in series with the 2x 470kohms resistors (the other end of the resistors being tied/soldered to ground) but the 1uf and 2x 1Mohm (as per your suggested schematic). The exception/difference is that they are soldered to the output RCAs versus/rather them to each input (as per your schematic and jean-paul's RC filter recommendation). Not entirely sure if the way I did it affects the circuit and/or frequency response.
Hi jean-paul:
Thanks for the break down of the rules. (It looks like I broke the basic circuit rules, i.e., RC filter at inputs vs output(s)!)
Sincerely,
Kingsley.
R1 loads the source directly but is so high it can be disregarded. The 1uF and 1meg give a -3db point of 0.16Hz which is extremely low. You could again decrease the 1uF to a 0.1uF and that still gives a -3db point of 1.6Hz
Where these parts are located does not affect the response they produce.
Where these parts are located does not affect the response they produce.
Thank you for the break down of the circuit placement, cap sizing, and -3db cutoff point, Mooley! (Ooh, would have been good to have use a 0.1uf cap as it's much. much smaller in size.)
You're welcome 🙂
There are lots of online calculators if you want to play around with this rather than getting the calculator out.
This is from Digikey:
https://www.digikey.co.uk/en/resour...lter?msockid=0997d283babd6470260cc7adbbbb6525
The way to work it out manually is by the first formula shown below and called 'fc' or cutoff frequency.
It's '1' divided by (2 * pi * the resistance * the capacitance) So 1/(2*pi*1,000,000*0.1E-6) which is 1.59Hz. Try is and see 🙂
There are lots of online calculators if you want to play around with this rather than getting the calculator out.
This is from Digikey:
https://www.digikey.co.uk/en/resour...lter?msockid=0997d283babd6470260cc7adbbbb6525
The way to work it out manually is by the first formula shown below and called 'fc' or cutoff frequency.
It's '1' divided by (2 * pi * the resistance * the capacitance) So 1/(2*pi*1,000,000*0.1E-6) which is 1.59Hz. Try is and see 🙂
Just tried it - that's a good tool/calculator, Mooley.
Those formulas for some reason, kind of look familiar (from college electronics but was a bit over my head/understanding at the time as I was preoccupied with other stuff - LOL. Alas, such is life when one looks back over it's course. 🤔😴)
Thanks.
Those formulas for some reason, kind of look familiar (from college electronics but was a bit over my head/understanding at the time as I was preoccupied with other stuff - LOL. Alas, such is life when one looks back over it's course. 🤔😴)
Thanks.