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

[ruffrecords]

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]

Hey Abby. I looked up Alps SUN and only found non-illuminated. Interested in what you've seen.

That's correct. Console mfgrs that use them have light-conducting knobs custom-made.

 

[ruffrecords]

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

 

[boji]

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

 

[ruffrecords]

14.25mm for aux/slot and 12.25mm for group/pgm

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

 

[boji]

Yes, caps in photo are roughly 6mm. CAD shows the WB brand clear caps which are roughly 8.5mm .

 

[ruffrecords]

Yes, caps in photo are roughly 6mm. CAD shows the WB brand clear caps which are roughly 8.5mm .

That is pretty big. What size clearance holes do they need?

Cheers

Ian

 

[boji]

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.

 

[ruffrecords]

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

 

[boji]

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.

 

[ruffrecords]

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

 

[boji]

Lil' update, nothing special. Trudging through necessary terminations of panpots. 22 to go  :'(

 

[boji]

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

 

[abbey road d enfer]

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

I would suggest you start a new topic there. Maybe then we could move some posts to the new thread.

 

[JW]

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.

 

[abbey road d enfer]

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.

 

[JW]

Thanks Abbey. So for the input protection diodes? Would 1N4007 be sufficient?

 

[abbey road d enfer]

Thanks Abbey. So for the input protection diodes? Would 1N4007 be sufficient?

Actually, the way this protection scheme works, the diodes see a maximum PIV (Peak Inverse Voltage) of about the sum of the power rails, about 20-40V, so you can use any 400x diode.

 

[JW]

I believe those 33K resistors off the pan pot should be 3.3K