PCBs for scalable DIY Neve style summing mixer possible feeler

[Potato Cakes]

So I did this sorta. Kind of a blend. API meets Neve.
Check out
https://groupdiy.com/index.php?topic=62302.0I used 990s and app DOA's to keep in line with the 24v needed for the Neve boards I used for summing. Ian Thompson Bell (former Neve tech) pretty much walks me through everything

Where did you end up with your bus resistor values? I have been reading Ian's info for his DB25 passive summing, but it is for balanced connections whereas I will be summing unbalanced signal from the NV circuit.

I'm going to try to meet with the guy doing the board layouts next week. I just need to compile my notes before then.

Thanks!

Paul

 

[Rocinante]

15k I believe but let me check my notes. It might be 47k but I do remember I had to play around a bit and got help. I created a junction board to send the signals to the main, aux, metering and monitor outs that I would be happy to send you for ideas and for you to mess with. I also created a back plane to fit the API type input cards.

 

[Rocinante]

I was off. It is either 10k or 4k7. I'd have to open it up to know which. I think 10k offered better noise but I am not 100% what I chose.

 

[Potato Cakes]

Copy that. Since this is a scalable design to be used with a summing amp of the builders choice, there will be some level of bus resistors computation that will fall on the end user. 10k is one of the values I want to try for my initial build. This is to be a DIY project, so the builder will have to know or do testing to find out what the input impedance of their summing amp is and proceed accordingly.

Thanks!

Paul

 

[Potato Cakes]

Tomorrow I am scheduled to meet with the PCB designer with all of my drawings and get the ball rolling on getting these boards made. Here's where I've ended up:

- VTB9045/46M or EA-10468 on board foot print with user selectable jumpers for preferred series/parallel winding configuration. You can also use these same pads to wire a mute.
- on board switch for Mono/Stereo. Can be wired off board or wired to a pan control.
- trimmers for feedback gain and attenuation, which can be wired off board for level control
- expansion input from additional boards
- sized to fit two boards (16 channels), summing amp, output transformers, and PSU in a single rack space enclosure. This will depend on size of output transformer, summing amp PCBs, and number of front panel controls used

Is anyone else interested? I do not know the price at which to sell these at this point. I can't it would be more than $50 USD but no promises.

Thanks!

Paul

 

[Rocinante]

Why not design them yourself or have one of us work with you?  Eagle is a great program and can be learned relatively quickly. I have the full version as i use it a lot but you can download the free version which is still very good

 

[Potato Cakes]

Why not design them yourself or have one of us work with you?  Eagle is a great program and can be learned relatively quickly. I have the full version as i use it a lot but you can download the free version which is still very good

I did try to learn for myself a while back and I was very frustrated at the learning curve as nothing that I was doing from the tutorials seemed to translate to some of the simple circuits I wanted to make layouts. And since I'm fairly involved in a number of things I am trying to finish/accomplish, farming this part out is best. The guy I've been using is very good and boards I get from the Gerbers he generates are correct the first time. Plus, he's great to work with and I do wind up learning from him on each project, so I don't mind paying for that. For me, right now, trying to add learning how do my own PCB would be a bridge too far. Maybe someday...

Thanks!

Paul

 

[Rocinante]

I get that. I hardly have time to type this. I'm intrigued to see what you come up with.

 

[Potato Cakes]

So after a long wait, I'm nearing getting boards made for this project. Each board will have eight channels of BA283NV circuits that can be adjusted with a trimmer for driving each circuit and setting the output gain individually. Kinda like when calibrating each track tape machine based on what was to be recorded on said track was a thing. You could also wire this to a pot if so desired. There is also a footprint for either an Ed Anderson 10468 or Carnhill 9045M transformer for each channel. All the channels got to a L/R summing network (odd = Left, even = Right). There are connections for injecting an external L/R pair of something (more summed channels, effects, etc) into the LR summing network. connections are made either the board mounted DB25 or the mirrored header connection. There is a break away board that contains toggles switches for the relays that changes each pair to either stereo or mono along with a dual color, common cathode LED for indication.

You will need a pair of summing amps to complete the project.

I did try to make this so 16 channels (2 boards) with summing amps and PSU could fit in a 1U chassis, but this might be a bit of a stretch. The main board is approximately 8"x9", so 16 channels self contained in a 1U case is possible if the enclosure is deep enough to accommodate the extra bits needed to complete this. You can also connect the summed output to a pair of external preamps. It's DIY so you're only limited by your imagination.

You can run this circuit safely up to +48V if you want. I have been doing this for all of my current custom Neve type builds, but for this project it may cause complications depending on the summing amp you want to use. Obviously, the usual +24V is totally fine. I just wanted to make it known that a wider range of PSUs can be used without needing additional regulation, drop resistors, etc.

Some people expressed interest in this earlier but I don't know if the excitement has completely fizzled. I have to get some made for myself, so the question is who would be interested some of these boards?

Thanks!

Paul

 

[zero]

Interested!!

 

[Fsharpminor]

I am interested as well!

 

[Potato Cakes]

Design is complete. Before I send off to get the boards made, I wanted to get a show of hands to see who would want one or more of these. I can sell them for $75 a set (main and front panel PCB). The main PCBs are 9.8"x8" so it's a fairly sizable board, hence the slightly higher cost.

 

[fragletrollet]

...connections are made either the board mounted DB25 or the mirrored header connection.

If only the DR-2402 pcbs had this (and pcb mounted pots too whilst one's at it), the build would have been so much faster.

Interesting project you have going on! I can't really commit to buying pcb's right now as my backlog is huge enough as it is, and I'm doing something similar with my AML 1073 Line preamps going into the 2402.

Best of luck, following thread

 

[JMan]

I'm interested! It's 8 channels to a board?

 

[Potato Cakes]

Correct. Each board is 8 channels and can be scaled for a larger channel count in increments of eight.

Thanks!

Paul

 

[MidnightArrakis]

Paul:

May I - STRONGLY - suggest that you have your PCB Designer output your PCB design project as an "ODB++" file >> INSTEAD OF << the standard GERBER files and an Excellon N/C Drill file!!! The reasoning is.....GERBER files are merely "non-intelligent" ASCII text files that essentially contain no useful information, other than directing a photoplotter on how to create a film image. However, an "ODB++" file >> IS << an intelligent data file that not only contains - everything - necessary to have your PCB fabricated, > BUT ALSO, < contains all of the intelligence necessary (including the net names) for the PCB fabricator to perform all of the electrical testing of the PCB's (you are having your PCB's tested, right?), as well as all of the information necessary for a PCB assembly shop to program their "Pick & Place" equipment in order to place the components onto the PCB's!!! To put this in another way.....using an "ODB++" data format file will - SAVE YOU MONEY - in your PCB setup and fabrication costs in the long run.

In assuming that your PCB Designer is using some relatively recent PCB layout program, then there should be an "ODB++" output available to select. If, for whatever reason, the software that your PCB Designer is using does - not - have an "ODB++" file output available, you could.....if you wish.....send your PCB CAD file to me and I will gladly create one for you and send it back to you. I have the full-blown CADENCE/OrCAD "PCB Editor" Release 17.4 PCB Design software package ($3,000+) and I am able to import CAD designs from: Altium Designer, Eagle, OrCAD (older), PADS and PCAD.

Should you insist upon using GERBER as an output file format, then at least use the - RS-274X / 2.3 - format. Your PCB Designer should know what all of that means. If they don't, well-l-l-l-l-l-l-l-l-llllllll..........

I have been designing PCB's for well over 20+ years and I am only trying to pass on some information that would help you out. Should you have any questions about anything, feel free to give me a shout, OK???

JBW

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[Potato Cakes]

JBW,

Thanks for the information. The guy I'm using does work for many top tier audio companies. I've worked with him on several projects and each time the boards came out correct the first time and I also enjoy working with him as a person. I do appreciate the heads up with OBD++ files.

Thanks!

Paul

 

[MidnightArrakis]

JBW,

Thanks for the information. The guy I'm using does work for many top tier audio companies. I've worked with him on several projects and each time the boards came out correct the first time and I also enjoy working with him as a person. I do appreciate the heads up with OBD++ files.

Thanks!

Paul

Paul:

You are most welcome for the information. I'm just trying to help out here!!!

I guess what I am trying to get at is.....while your PCB projects may have come out "perfect", you really have no idea what the PCB fabrication shop may have had to go through to provide you those "perfect" boards!!! And by that, what I mean is.....about 15-years ago when I was working with a leading video electronics firm that was using a certain well-known PCB design software program, we would layout our PCB's and then view the GERBER files with the software's built-in GERBER viewer, check things out and everything would be "fine". Until one day.....I brought in and installed the GERBER and N/C Drill file editor that I use here-at-home and this GERBER editing software runs nearly $4,000!!! So, it ain't some Internet "FREE" program, OK???

The instant I loaded in a set of GERBER files and an associated N/C Drill file that had already been sent out for fabrication, everybody looked at my monitor and exclaimed.....WHA-A-A-ATT THUH F-F-FUUUUCKKKK??? --- Each layer of this board had its own "0,0 datum point", which meant that instead of ALL of the layers being aligned and registered one atop of another, each layer of this PCB was placed all over the screen everywhere, apparently randomly placed!!!

I then proceeded to load-in and check several other sets of GERBER files from already existing PCB's and.....to everyone's horror!!!.....THEY WERE ALL THE SAME WAY!!! HOW COULD THIS BE??? All of these PCB's CAME BACK "FINE"!!!

What it took in order to discover these errors was an "independent" GERBER and N/C Drill file viewer/editor program separated from the PCB CAD software for these errors to be seen. The PCB CAD-system's built-in GERBER viewer was tied to the same database as the PCB layout software was, so even though the PCB layout software was outputting randomly placed "0,0 datum points" on each layer, it all worked out on-screen because everything was referenced together. Since my software had nothing to do with PCB layout software package, it was showing "the reality" of what was being outputted and it wasn't pretty!!!

Long story short --- Upon calling our PCB fabrication shop I then come to find out and was told that the - job - of the PCB fabrication shop is to provide you with a working board.....PERIOD!!! The General Manager of this company proceeded to tell me that the most all of the GERBER and N/C Drill files that they receive from their customers are actually fairly well "screwed-up" and it is - THEIR JOB - to do whatever it takes to provide their customers with working boards.....>> only they - don't tell you - that your data files are messed-up!!! -- They just fix them -- and send you working boards.

The point of all of this is.....since the manner of output from an "ODB++" file is - completely different - than what a set of GERBER and N/C Drill files are, the PCB CAD-system is going to correctly output "good data" and then you really are "GOOD TO GO"!!! For me.....my PCB output files will always be "ODB++"!!!

So.....what PCB design software program is your PCB Designer-buddy using again??? THANKS!!!

JBW

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[Potato Cakes]

JBW,

Again, I do appreciate your insight, but let's keep this thread focused on the subject. You're more than welcome to send further correspondence regarding manufacturing PCBs to me personally.

Thanks!

Paul

 

[dacapitan]

Watching this thread. Definitely interested.