latigid on

AOUT_NG Eurorack format

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I would like to re-route the AOUT_NG board for use in Eurorack systems. I imagine two stacked boards with a final panel of 6-8 HP.

 

The first contains PCB-mount 3.5mm sockets for CV 1-8, Gate 1-8 and DIN SYNC. I don't there's room for proper 5-pin DIN sockets. A DB-25 connector would be used to bring gates, DIN-sync and J19 from e.g. a MB-SEQ or a standalone Core for MIDIBox CV. I would think about simple emitter follower/common collector circuits to indicate "Gate On" states. LEDs could also be useful for CV indication, especially in negative mode. 

 

The second board would be a clone of the current AOUT_NG circuit (assuming that this is okay) except fitting onto a rectangular PCB. The power would come from the Eurorack buss, and would probably need extra filtering and/or optoisolation to keep digital noise out of the rails. Either sandwich-style or DIL connectors would bridge the two boards.

 

The benefits I can see are: easier power requirements for a MB-SEQ and a more useful layout of connectors for patching as part of a modular system. I already have a DB-25 breakout board that buffers and level shifts gates inside the SEQ enclosure.

 

Anyway, just a diving off point for further discussion. I firstly need a copy of the .sch file for the AOUT circuit, otherwise I will have to translate it from the .pdf diagram. I did try to contact Seppoman but he doesn't seem to visit here much any more.

 

 

 

 

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I think Seppoman is the only one with the schematic file in Eagle. Copying it from the pdf is probably the best option and not that much work i think.

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Your project sounds familiar. Here's how I approached it:
 
post-5877-0-41867800-1364762394_thumb.jp
post-5877-0-34519100-1364762386_thumb.jp
post-5877-0-71769800-1364699158_thumb.jp

 

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That's about it :)
 
I have some questions if you could: How are you powering the AOUT_NG board? If it's from the Eurorack power buss do you have any issues with digital noise crossover?
 
Do you find the DB-25 connector intrusive in any way?
 
Thanks for stopping by!

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I'm powering the aout_ng from my eurorack power (tiptop uzeus). I haven't encountered any issues with digital noise crossover. Powering the board with the eurorack power is a really clean solution since everything you need is already there. The db25 connector isn't intrusive on my setup because the module is located on the bottom left corner of my modular rack. The big connector and thick cable aren't covering up anything. I'm using a lpc17 and small buffer board to drive the aoutng over a 3ft cable. I found that the using the lpc17 was critical to getting reliable signals over that distance.

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Surprise Surprise, Seppoman is in the house and posting :)

 

I have uploaded the .SCH file to my server (the Wiki tells me that this file extension is not allowed...) http://www.seppoman.de/aout_ng/mbhp_aout_ng_r1.sch

 

The link is also added to the NG Wiki page.

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Thanks for the schem! I have added some filtering for the PSU (10 ohm resistors) and changed the trimming circuit. It's based on a design from http://www.bartonmusicalcircuits.com/dnq/ and uses an inverting amp stage (with additional low pass filtering, the idea of Seppoman) and a switchable offset/unity gain inverting mixer. Some connectors need changing, but this will be done in conjunction with the other board layout.
 
If somebody with a scope could measure the frequency of any digital noise/glitches that would help me design the LPF. 
 
Should the DOUT chain perhaps be terminated to stabilise operation?  
 
 
EDIT: I had the op amp inputs reversed, fixed now :)
 
Edited by latigid on

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Routing everything now, a good holiday project! 

 

Question: will any application make use of J2 (serial out) for chaining multiple modules? It seems unlikely so I would prefer to remove this connector. In this case, would it be better to terminate the digital out in some way (tied high or low)? 

 

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I like the circuit! :smile:

 

Could you please change J1 to the new recommended 2x5 header layout + a jumper which selects between RC1/RC2?

See also: http://www.ucapps.de/mbhp/mbhp_aout_mcp4822.pdf

 

Should the DOUT chain perhaps be terminated to stabilise operation?  

 

no, this shouldn't be required

 

 

Question: will any application make use of J2 (serial out) for chaining multiple modules? It seems unlikely so I would prefer to remove this connector.

 

It's supported by the MIOS32 AOUT driver, but not used by any application yet.

However, but this also means that it isn't unlikely that somebody would use such an option for his project.

 

 

would it be better to terminate the digital out in some way (tied high or low)? 

 

No, please don't terminate the signals.

 

Best Regards, Thorsten.

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PCB layouts without and with GND plane:

 

gallery_5453_5_78331.png

 

 

 

gallery_5453_5_15579.png

 

 

 

 

Routing was a bit tight for this format, but I think it works okay. 

 

I added a chip select line and put the DOUT signal on the same connector. Hopefully this is okay if somebody wants to chain more than one module. 

 

I isolated AGND and GND, and both top and bottom planes are connected. Is this a good idea? On the AOUT_NG PCB only the top layer is connected. 

 

 
 
Edited by latigid on

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The J1/J2 sockets are not "polarized" (no notch) - probably you decided this due to the missing space.

But I would prefer this against J2 - so, just remove J2 again to make place for a polarized J1 connector.

If somebody would like to chain multiple modules, he has to build an external adapter and solder it directly on the required pins.

 

 

I isolated AGND and GND, and both top and bottom planes are connected. Is this a good idea? On the AOUT_NG PCB only the top layer is connected.

 

to which ground are they connected?

I would use the digital GND for both planes.

 

Best Regards, Thorsten.

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The J1/J2 sockets are not "polarized" (no notch) - probably you decided this due to the missing space.

But I would prefer this against J2 - so, just remove J2 again to make place for a polarized J1 connector.

If somebody would like to chain multiple modules, he has to build an external adapter and solder it directly on the required pins.

 

Okay, I will not use my version in this way as the connections will be "sammich" style to another board. But I agree, polarised connectors make good sense. Unfortunately that makes the board bigger, but I needed to give proper clearance to the mounting holes anyway. So I moved the trimmers around and that leaves room for another connector: J2 for serial output. Can I please check pins with you because the AOUT_NG does not seem to match 1:1 with the newer Cores' J19?

AOUT    : Vs Vd CS SI SC
AOUT_LC : Vs Vd SO SC RC
AOUT_NG : Vs Vd SO RC MD (?, from wiki picture)
        : Vs Vd FS DIN SCLK (connections to DAC on schematic)

AINSER64: Vs Vd DI SC RC1
          Vs Vd DO SC RC2
           _____| |_____

CORE(32): Vs Vd SO SC RC1
          Vs Vd SI SC RC2
           _____| |_____

 

 


 

So, are these connections correct ?

 

CORE(32): 
Vs Vd SO SC RC1
Vs Vd SI SC RC2
______| |______

AOUT_EURO J1: 
Vs Vd DIN SCLK RC1   J3 chip select   
Vs Vd nc  SCLK RC2    RC1/RC2 => FS
______| |______  

AOUT_EURO J2: 
Vs Vd DOUT SCLK RC1                                                     
Vs Vd nc   SCLK RC2
______| |______

 

to which ground are they connected?

I would use the digital GND for both planes.

 

Best Regards, Thorsten.

 

Sorry for the confusion, there is essentially one ground (both top and bottom layers) but GND and AGND are connected only at one point on the board. There is a "bridge" for Vd and Vref to travel on. My question was: should this bridge be on both top and bottom layers?

 

Thanks! I'll keep chipping away at it.

 

 
 
 
Edited by latigid on

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Getting closer:

 

gallery_5453_5_19089.png

 

 

 

gallery_5453_5_119694.png

 

Data lines are okay?

 

 

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I never ordered the boards and instead made a THT MAX525 version, which works quite well. The DAC is expensive though. 

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I'm doing something similar, but I built a Eurorack case that has space between the two rows. I am going to mount a panel there with all the jacks, and mount the line driver receiver to the side of the case.

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What was the reason for changing to the MAX525?

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9 hours ago, jaytee said:

What was the reason for changing to the MAX525?

Hello

I guess max525 have better spec than tlv5630

Best

Zam

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C'est vrai. Also, most decent DACs are fine-pitch SMT, or at least that's what I thought at the time. Plus, there's already a MIDIbox AOUT, meaning no coding or config changes needed.

 

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