DB25 summing PCB - MK2??

The last batch of 50 DB25 boards has nearly gone so I have ordered yet another batch. I am selling lots of these but not hearing about many completed projects. Where are they all going???


Cheers

Ian

New batch of boards arrived this morning. I got 100 this time so hopefully they will last a bit longer.

Cheers

Ian

I only got mine today, But I'll be using them as the input interface for a Neumann V475 summing project.

Hi

I'm racking up 8 stereo Midas XL3 modules. I was thinking of using DB25 for the patchbay because of space constraints. I will also probably need 2 summing amps. One for the 16 aux outs and another one for a stereo master output. My idea was to etch boards for right angled DB25s to make connections easier and avoid having to solder the cables directly onto the DB25 connector (been there before).

My questions are:

-Can I use your PCBs without a summing amp (just as a connection platform for the Ins and Outs)
-If I use your PCBs to create a summing amp for the aux master sends, how do I know what resistors etc to use? Would you have a schematic for that?
-Finally, are your PCBs' print compatible with any right angled DB25 or should I buy a specific brand/model? If so do you have a Mouser part number by any chance?
Thanks

Cheers
Sono

sonolink said:

Hi

I'm racking up 8 stereo Midas XL3 modules. I was thinking of using DB25 for the patchbay because of space constraints. I will also probably need 2 summing amps. One for the 16 aux outs and another one for a stereo master output. My idea was to etch boards for right angled DB25s to make connections easier and avoid having to solder the cables directly onto the DB25 connector (been there before).

My questions are:

-Can I use your PCBs without a summing amp (just as a connection platform for the Ins and Outs)

Click to expand...

Yes,you can. As you can see in the PCB layout below, all the active pins are brought out to a set of 0.1 inch pitch pads (J7) for just this purpose. You can common the screens together and connect them to J6.

-If I use your PCBs to create a summing amp for the aux master sends, how do I know what resistors etc to use? Would you have a schematic for that?

Click to expand...

This document should give you all the information you need:

http://www.ianbell.ukfsn.org/EzTubeMixer/docs/db25/db25config.pdf

-Finally, are your PCBs' print compatible with any right angled DB25 or should I buy a specific brand/model? If so do you have a Mouser part number by any chance?

Click to expand...

I don't know about ANY right angled DB25 but there does seems to be a lot of identical ones from different manufacturers. THis one will work:

http://uk.mouser.com/ProductDetail/HARTING/09663516512/?qs=%2fha2pyFadujRDvANzSkZy%252baCkRAnLId48BeSHMrPKrQzY%252bEm7AJisQ%3d%3d

If you check out the manufacturers drawing you will see the distance between the two PCB fixing holes is 47mm. You will find lots of other manufacturers who makes ones the same.

Cheers

Ian

Thanks a lot,  Ian 
Cheers
Sono

I'm trying to find DB25 connectors for cable (solder cup) on Mouser and these seem to come in different bits (connector, screws, shell, locks, etc). I'm trying to figure out if these parts are sold separately or what.

Can someone with a little experience with DB25s tell me if I need to purchase anything else than this, since there doesn't seem to be an "accessories" link anywhere and the data sheets don't seem to mention anything either (OR I need to get some sleep):

Mouser part number 617-09-67-225-5604

btw I want to build a 8xTRS/DB25 snake

Thanks for the help
Cheers
Sono

It is very confusing, I have ordered the wrong connector a couple of times.

If it helps:

Shells are the part you put the DB25 connector into on the cable.  Some vendors (FCI) also refer to the Screen as the shell.
Screen - the metal part around the pin connectors
Screwlocks or Screw Locks are not used consistently they are also called Jackscrews they are the bolt with the female thread on top, just google jackscrews.  You will see that the jackscrews are used to refer to the female AND the male parts.  The male parts used with the shells, and the female parts used with the board mount connectors usually.
Harpoons are board mount solder in mounts that attach a connector to a board
Peg and Pin-In-Paste are other terms for board mount connectors.  Harpoons clip in so you can solder them.  Pegs are flush with the bottom of the PCB but can still be hand soldered.  Pin in paste leads are also pretty flush with the bottom of the PCB but I could solder them by hand easily.  Peg and Pin in paste are meant for wave soldering, but work fine on D-SUB 25 connectors for hand soldering.
right angle - for board mount connectors means the pins and sockets are mounted geometrically parallel to the surface of the PCB
DSUB DB D-SUB D-Subminiature These are used (incorrectly) interchangeably with and without hyphens.  (to be precise the DB (and DA, DC etc) spec refers to a "shell or screen size" but have you ever heard anyone call a 9 pin VGA connector a DE-9? (not I). ( DB refers to the 25 pin screen/shell size), http://en.wikipedia.org/wiki/D-subminiature


Also, be aware that DB25 connector jackscrews use various thread sizes.  4/40 and I think M2.5 usually, but you should check and check what you want.

Also the "screen" is mentioned that is the metal shell around the 25 pins, sometimes it is isolated from the screwlocks, and sometimes not.

And often the spec sheets are unclear as to whether they come with the jackscrews or not, etc.  It is not really set up for us "onesy twosey" purchasers.  But don't worry, if they come without they can be ordered separately.

And the connectors are spec'd for the number of connections and unconnections (Mating cycles) they support.  The best ones seem to handle 500 cycles, and have machined pins and/or receptacles .... depending on how you use your snake you might want to pay attention to that spec.

Also... The high reliability line from FCI and Kycon are some pretty nice connectors, but if you want really cheap and dimensions etc don't much matter (for you they don't if you are making cables - solder cup, etc) there are a lot of other sources (chinese, surplus, etc).

*edited to add more detail*

Bruce
Thanks a lot for the input

Hi all,

I recently bought two db25 summing pcbs from Ian. I'm looking forward to building it, but its the first project I've done that doesn't have total hand-holding instructions. I had a few noob questions before I get started:

On the board, J6 screen is already connected to the ground pins on the db25 channels correct? And I would just wire J6 to my ground without having to wire individual grounds on the db25 or anything?

Also, what watt rating should the resistors I use be?

Thanks!

Pascau said:

On the board, J6 screen is already connected to the ground pins on the db25 channels correct? And I would just wire J6 to my ground without having to wire individual grounds on the db25 or anything?

Click to expand...

You should treat J6 just like pin 1 on an XLR - it should be connected  directly to the chassis (at the connector if possible). Whether you actually need  to do this depends on the DB25 connector you  buy. On some types, the fixings that hold the connector to the board are connected via the connector body to the shell which is then screwed to the chassis. The more economical connectors have plastic bodies so this connection does not exist - instead you use J6 to make the connection from the screens to the chassis.

Also, what watt rating should the resistors I use be?

Thanks!

Click to expand...

0,125W (eighth watt) or 0,25W (quarter watt) resistors will be fine. I generally use MR25 types:

http://www.spiratronics.com/data/5600.pdf

To work out the connector values you should read this:

http://www.ianbell.ukfsn.org/EzTubeMixer/docs/db25/db25config.pdf

Cheers

Ian

Great! Thanks very much Ian!

Ok I finished building my summing mixer and need to trouble shoot. Got two DB25's connected loaded with 10K resistors. They are then going to a twin line amp entering M- (cold from DB25),  M+ (hot from DB25) and L- (cold from DB25), L+ (hot from DB25). I have wires connecting L-,L+ and M-, M+ to L-,L+ and M-,M+ respectively near the transformers (missed this the first time around) The transformers are Cinemag CMMI-10PCA's. I have also connected with wires T01-->IN1 and T02 --> IN2. The outputs of the twin line amp are going to Carnhill VTB 2291 Transformers. How should the transformer be wired? 2400ohms:150ohms?

Bonsaimaster said:

The outputs of the twin line amp are going to Carnhill VTB 2291 Transformers. How should the transformer be wired? 2400ohms:150ohms?

Click to expand...

You should wire the VTB2291 2400:600

Cheers

Ian

Several people have asked me if it is possible to tweak the DB25 PCB so that you can switch pairs of inputs between a single stereo input and two mono inputs (panned centre I assume). There is no easy answer to this but the simplest scheme is shown in the schematic below:



Two inputs (1 and 2) are shown. Input 1 is normally assigned to the left channel and input 2 to the right channel via 10K resistors R1H, R1C, R2H and R2C. These resistors are in the normal channel hot and cold positions marked on the PCB.

For mono operation switch S1, (which is a four pole double throw toggle switch) connects each channel also to the opposite bus - so Input 1 is connected also to the right bus and input 2 is connected also to the left bus. The resistors to do this would normally be the M1H, M1C, M2H and M2C resistors. However, on the PCB these are connected straight to the inputs and we want them to go via the switch S1 so we need to stand these resistors on end on the PCB and wire them to the switch. The inputs for the switch can come from the unconnected end of the appropriate mono reisstors or they can come direct from J7.

The switch S1 is shown in the stereo position. Notice how in this position the two mono resistors are shorted together to maintain the bus impedance.

As I said, this is the simplest solution I can think of. Its only downside is that the gain is 3dB too high when inputs are switched to mono but that is easy to fix in your DAW. I can think of no easy way of avoiding that without using a switch with a huge number of poles.

Cheers

Ian

Hey Ian,

that's a great approach! !

Which leads me to an other short question.
Do I have to short "+" and "-" if the input isn't connected, to keep maintain the bus impedance constant?

Cheers!

Dr_J said:

Hey Ian,

that's a great approach! !

Which leads me to an other short question.
Do I have to short "+" and "-" if the input isn't connected, to keep maintain the bus impedance constant?

Cheers!

Click to expand...

Yes you do.  That's the one real downside of passive mixing. It is OK in a mixer where all the bus inputs are driven but a bit of a pain in a stand alone unit.

Cheers

Ian

HI Ian,
how are you? How are you fixed on these boards? I could use 5 of them, let me know 

thanx
T

tonycamp said:

HI Ian,
how are you? How are you fixed on these boards? I could use 5 of them, let me know 

thanx
T

Click to expand...

Yes, I still have plenty in stock. Drop me an email with your order and delivery address and I will send you a Paypal  invoice.

Cheers

ian

Up and running. Sounds great. 16 channels in. Collective case with DB25's cut out and custom front panel. Thank you Ian for all your patience. Great stuff!