Console signal flow, input cards, general discussion on API styled DIY mixer

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boji said:
No greater compliment than to create inspiration. It's what put me on the path, so thank you!

Push buttons are Wellbuying (Well Buying?) ML series. Not the easiest to source since Rapid and Mouser stopped selling 4 pole. :/

PM sent.

Many thanks for the datasheet. I had forgotten you are using illuminated buttons. Not sure if I want to go that way right now but definitely a good way to see at a glance what buttons are pressed and I now have a utility supply on the backplane so it is a definite possibility.

I see you have squeezed quite a few into your module. How far apart are they?

Cheers

Ian
 
abbey road d enfer said:
That's correct. Console mfgrs that use them have light-conducting knobs custom-made. :(

There was a thread here about this a wile back. I tried to find it but it remains elusive.

Cheers

Ian
 
I see you have squeezed quite a few into your module. How far apart are they?

14.25mm for aux/slot and 12.25mm for group/pgm
jlvM7fM.png


 
boji said:
14.25mm for aux/slot and 12.25mm for group/pgm
jlvM7fM.png

OK and the caps are about 6mm diameter? so there is a decent gap between them. I was thinking of about 12.5mm spacing so looks like that is possible.

Cheers

Ian
 
Not entirely sure at the moment as they widen slightly at the base to about 8.6 so the hole ought to be 8.75mm Perhaps add another 0.05 to ensure faceplates can be slightly adjusted without cap rub. I can break out the micrometer later tonight.
 
boji said:
Not entirely sure at the moment as they widen slightly at the base to about 8.6 so the hole ought to be 8.75mm Perhaps add another 0.05 to ensure faceplates can be slightly adjusted without cap rub. I can break out the micrometer later tonight.

I have found it all too  is easy for there to be slight differences in the alignment of adjacent push buttons due to slop in the PCB holes when soldered in. This small angular error,  magnified by the length of the switch snout, can easily cause a switch cap to rub on the side of its front panel hole. I don't rememeber the exact number but I think I ened up leaving something like 0.5mm all the way round to accommodate it. With the number of buttons you have, maybe some sort of jig is in order to holes the switches in the right place while they are soldered in.

Cheers

Ian
 
due to slop in the PCB holes when soldered in.

Yessr. The WB's come slightly crimped every other pin to keep it in place when flipping around to solder. I imagine it also centers them a bit.
 
boji said:
Yessr. The WB's come slightly crimped every other pin to keep it in place when flipping around to solder. I imagine it also centers them a bit.

That is good. The ALPs ones I used on the EZTubeMixer design had straight legs.. Not so good. I think the slightly crimped legs are called snap-fit.

Cheers

Ian
 
Moderators, if you want to move this outside of drawing board, into mixers/monitoring systems, I'm ok with that.
 
Hey Boji,

Going over Jeff's 2SLA cards, I noticed the 82pF cap in the feedback stage of the first opamp. Your schematic has 62pF here. I went and looked at the 536 schematic scan and it looks like it might have actually been 82pF where some of it didn't scan or was rubbed off. Anyway, worth looking at I guess (???) I noticed Jeff's 312 schematic has a 120pF here but that's hardwired for mic gain staging

I'm also bumping to ask a couple questions.
1. What value for those input protection diodes for the line in circuit?

2. This shunt arm resistor from the negative input of the second stage 2520 can be changed I gather to set volume of the second 2520. In Jeff's cards (2S LA) he has a 15K resistor here which is in series with an optional pot that connects to the (+) of the 47uF. (See pic. I think I drew it right)
Anyway, is there an all around good value for that cap (the 47uF w/ 20K shunt originally) if I turn that shunt resistor into a volume pot?

I see maybe what Jeff was getting at with the 15K series resistor. Makes it easy (I think?) to use a rev log 10K pot and be in the right territory with it rolled all the way down at 10K + 15K =25K. But then, to be more exact, why not use a 10K series resistor. Hmmmmm So, as you rolled the pot up, less resistance for the shunt resistor and more volume. Maybe you'd not need more than what 15K would provide. I'll have to experiment to see.
 

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2. This shunt arm resistor from the negative input of the second stage 2520 can be changed I gather to set volume of the second 2520. In Jeff's cards (2S LA) he has a 15K resistor here which is in series with an optional pot that connects to the (+) of the 47uF. (See pic. I think I drew it right)
Anyway, is there an all around good value for that cap (the 47uF w/ 20K shunt originally) if I turn that shunt resistor into a volume pot?
The value of the cap depends on the minimum value that can take the combination of the resistor and the pot. Since the pot is supposed to possibly go to zero-ohm, only the resistor must be taken into account.
You can use the trusted formula C=1/R.2.pi.F
F being the expected -3dB response. However, good practice used to say to use at least 10x this value, but distortion optimization suggests 50-100x for electrolytic caps.
 
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