24ch API SUMMING MIXER DR-2402

Shorting - to ground at the end of the cable (just before the switch)? Advantageous contra jumpering at ACA outs?

Not really, connecting the - to GND on the ACA output should work too. The GND layout is not very delicate in this build, you can get away with a lot of messing around

Btw. I just saw I did it exactly the same way Jeff's schematic suggests...

Anyone else finish this yet. I am having issues with mine so far.

Yup.

what's the problem?

I have populated all the boards and all 28 2520 DOA's. Wired up 2 channel boards (Channels 9-24, I'm working from bottom to top). I've made the PSU also and calibrated the PSU to -/+16v

I power up 1 channel board and send a signal from my DAW to the mixer and no signal passes through the channels. Volume and pan pots do nothing, no led display. 5 mins into testing the channel boards the PSU Capacitors C9 and C10 keep exploding. This happens with any channel board I've tried and I only hook up 1 channel board at a time.

Always, when you first run some projects, use bulb serial with 230v power cords. When bulb lights, then soemthing is wrong,  when go off - is ok. On my 2520 boards from kit, i must replace 47pf, at 10pf, and vice versa(i dont forget nr, but they are side by side). Checkout voltage on power, You must swap +-, ...or capacitors voltage are 25v.

Shortly.

Looks like there are more of these available...  www.diy-racked.com

...if someone wanna make power supply inside mixer i have pcb for them https://groupdiy.com/index.php?topic=64859.0
plus vu meter, and inserts. Monts hole are the same as ACA, from Capi.

So that`s the insert board + vu buffers + PSU in one board that fits ontop of the aca/bo? Nifty!

I`ve just got my mixer back on my bench after packing my whole studio down and moving to another city (started my career as a commercial diver  8) ) Anyways, pondering on different PSU solutions, as some have reported the current usage of the 2402 is pushing the limit on a single 317/337, and have troubles finding a proper heatsink that matches the PSU pcb layout.

I`ve been thinking about the various JLM psu`s (Kraftwerk, Powerstation 5 and V6) or even going with the easy solution of using this:

http://collectivecases.com/?product=psu-cc-psu1

Altough the last one doesn`t really provide more current than the DR2402 psu.

What do you think?

Not necessairly. This psu provide 2x+-16V/2x1.6A(if i good reading),  LM317, and LM337 delivers 1.5A max. I think this is almost the same. Next time i do something like this(adjustable 1,2-32v,/5A) :

I'm wiring mine and am a bit confused with the ACA inputs/booster inputs and the main volume on/mute switch.

The 3 boards are summed into the ACA input. 
ACA main output to the master volume pot.
Volume pot wired to on/mute switch as in the manual but in stereo
Now this also split off to the booster inputs from volume pot as shown in the attached thanks to buckethead

Main output on booster to relay board.
Multi output on booster to meter buffing board.

Am I correct on all this?

Also on the meter buffering board, I see some jumped the front diodes and removed the 3.3k ohm resistor?  ???
Whats the purpose?

The Relay board is powered from where? Manual says psu but there isn't a dedicated 12V tab or do I just tap off of the 16V?

Thanks
Neil

So I got a partial schematic resembling the channel structure sans led-driver on the 2402/1602.



So if I am right, this would be a differential amplifier setup for unity gain because R1 = R2 = R3 = R4 (I am going by the designations in the article as explained here:

http://www.electronics-tutorials.ws/opamp/opamp_5.html



r3/r4 designations are reversed in the DR schem)

So I have a couple of questions:

1) According to the article you can change the amplifiers gain by adding resistors in paralell to r1 and r3.
What resistor values can I use for setting up a channel for say 6 or 12 db gain?

2) If the input is setup for unity gain, will the 1646 actually add 6db`s of gain to the direct output? Why would not a 1640 be used instead?

fragletrollet said:

So if I am right, this would be a differential amplifier setup for unity gain because R1 = R2 = R3 = R4 (I am going by the designations in the article as explained here:

http://www.electronics-tutorials.ws/opamp/opamp_5.html

r3/r4 designations are reversed in the DR schem)

So I have a couple of questions:

1) According to the article you can change the amplifiers gain by adding resistors in paralell to r1 and r3.
What resistor values can I use for setting up a channel for say 6 or 12 db gain?

Click to expand...

Read further down in that article -- your question is answered there. Use the Differential Amplifier Equation.  And you will need to work the math to convert voltage gain in decibels to the unitless gain. (Hint: 6 dB gain is a gain of two.)

2) If the input is setup for unity gain, will the 1646 actually add 6db`s of gain to the direct output? Why would not a 1640 be used instead?

Click to expand...

Well, if you use a differential receiver that attenuates by 6 dB (please, not "db's of gain"), then you're back to unity.

Hey Andy, thanks for chiming in!

If I solve the equation with relation to R1/R3, what values should I use for V1/V2 and Vout? I`ve tried solving with an arbitrary 1v for V1 and V2 to find Vout (and then turn it around to find R1 or R3), but not sure if the negative V1 should have negative prefix or not, being a phase inverted input...?

Vout=2000/2000*(1-(-1))
Vout=2v...?

Using +4dbu input signal:

Vout=2000/2000*(1.78-(-1.78))
Vout=3,56V...?

As you mention a gain of 6db is a factor of (almost) 2. So my Vout would be almost the double?

Vout=3,56*1,995262 = 7,1

R3=(R1(V2-V1))/(3.56*1.995262)

R3=(2000(3,56-(-3,56))/(7,1)=2005 ohm? What, in paralell with R3?


Geez. This is all probably wrong so any further guidance would be appreciated!

All the best,

Magnus

surely someone have the chops to chime in ?  8)

fragletrollet said:

Vout=2000/2000*(1-(-1))
Vout=2v...?

Click to expand...

20K is 20,000 not 2,000

Because R1 = R3 = R2 = R4, then the voltage gain for each amplifier is 1 (or unity gain)

Using +4dbu input signal:

Vout=2000/2000*(1.78-(-1.78))
Vout=3,56V...?

Click to expand...

4dBu is 1.228V not 1.78V

As you mention a gain of 6db is a factor of (almost) 2. So my Vout would be almost the double?

Vout=3,56*1,995262 = 7,1

Click to expand...

Taking what Andy said about 6dB being a factor of two (increase is 2x the voltage, decrease is 1/2 the voltage)

2 = R3/20K
2 = R4/20K

R3 = R4 = 40K
-------------------------------------
0.5 = R3/20K
0.5 = R3/20K

R3 = R4 = 10K

with your 4dBu input signal:
2 x 1.228V = 2.456V (10 dBu)
0.5 x 1.228V = 0.614V (-2dBu)

http://www.mycircuits9.com/2012/06/differential-amplifier-calculator.html
http://www.sengpielaudio.com/calculator-db.htm

Thanks so much!

So you could use a DPDT switch to switch between 20k and 40k for r3 and r4.

If you wanted to use a toggle switch for both the muting and the switching of the resistors for an optional +6db gain, looking like this in operation:

3 way toggle switch:
high position: +6db
mid position: unity
low position: mute

what I need is something like a dpdt (for the gain switching) and a spdt (for the mute)? So is that a 3pole 3 way switch? on-on-on?

Or one could integrate it with the volume pot, using a concentric pot with 1k log pot with a 2-position dpdt switch ? Bet that is a way more costly solution... if one were to even find the right product...