DB25 summing PCB - MK2??

[sharpeleven]

4 for me, pls!  8)

 

[johnnyscotch]

Hey Ian,

Great work on this, your timing is impeccable.

I have a question/suggestion. How hard would it be at this stage to add an option for "mono/center" channels? Would it be as easy as adding a couple of holes on the bus traces and a slightly alternate path like a Y off the resistor traces to line up?
Maybe even only a couple of them, not every one.
This may be a specific problem for me, and not applicable to anyone else.

I was thinking of building a 16x2 summing mixer with 4 mono/center channels. I can make do and mod the construction with these boards and make it work, just curious if that's something anyone else is interested in.

cheers!
Eric

 

[ruffrecords]

@Eric

I will have a look at it. One or two might be possible without too much trouble.

Cheers

Ian

 

[ruffrecords]

Here is a pic of the db25 board with mono capability. By re-arranging things a bit I managed to get all the resistors in so you can have mono on any or all of the 8 balanced inputs. I have arranged the resistor number so that you just use R1 thru R16 for normal alternate left and  right assignment. If you want a particular input to be mono then you also fit the resistor numbers plus 16. So if you fit R1 and R2 for input one, then fit R17 and R18 to make it mono. I also had to make the board a little bigger to get the shunt resistors in.

Thinking about it a bit more I realise the resistor numbers do not correspond neatly with the Tascam input numbers so I might go around and tweak all the resistor labels. Anyway, here's the current PCB layout.


Cheers

Ian

 

[Holger]

Nice idea, this should work for most people.

 

[johnnyscotch]

I love this place!

 

[ruffrecords]

I have changed the labelling of the resistors to hopefully make it more obvious which is which and also to reflect the Tascam input numbering system. So, for a regular alternate left/right assignment you just fit the resistors whose label begins with a letter 'R'. The second character is the Tascam channel number 1 thru 8 and the last character is either 'H' or 'C' to indicate if it is the hot or cold connection. So:

R1H is channel 1 hot
R7C is channel 7 cold

If you want to make any channel into mono then just fit the corresponding resistors whose labels begin with the letter 'M' (for mono). So:

M1H and M1C make channel one into a mono channel.
M4H and M4C do likewise for channel 4

So normally you would fit all the resistors beginning with the letter 'R'. For any channel you want to make mono you fit the corresponding resistors beginning with the letter 'M'.

Hope that makes sense.

Cheers

Ian

 

[MartyMart]

Great stuff Ian, next time I visit my Brother in "Saxlingham" I will buy you a beer or three !!
( if you are anywhere near Holt area ? )

Regards,

Martin.

 

[ruffrecords]

Great stuff Ian, next time I visit my Brother in "Saxlingham" I will buy you a beer or three !!
( if you are anywhere near Holt area ? )

Regards,

Martin.

That would be very nice. I live in Holt itself so you should be able to find me.

Cheers

Ian

 

[ruffrecords]

I got the REDD EQ PCBs today from the new supplier, Quick-Teck, that I am trying. The visual quality is very good so I am going to order some db25 PCBS from them. I'll do that later today so they should arrive in a couple of weeks.

Cheers

Ian

 

[erikb1971]

Two of those would make a 16 channel; passive summer right? In that case: would love to have 2!

 

[ruffrecords]

Two of those would make a 16 channel; passive summer right? In that case: would love to have 2!

That's right.  Two PCBs, a couple of db25 connectors, a handful of resistors, a couple of XLR connectors and a small box and you are done.

Cheers

Ian

 

[erikb1971]

Two of those would make a 16 channel; passive summer right? In that case: would love to have 2!

That's right.  Two PCBs, a couple of db25 connectors, a handful of resistors, a couple of XLR connectors and a small box and you are done.

Cheers

Ian

count me in for two then!

 

[tylerromo]

I'm entertaining the idea of doing a stereotype build when Don puts the finishing touches on his boards... And since the project looks like I'll have to shoehorn it into a reasonably sized enclosure, I'd be interested in a few of these with the intent to cut the board at the first set of pads just for soldering my cabling to. Any reason I shouldn't do that? maybe integrate one of those scored-lines to the board for a nice clean cut to accommodate whatever anybody is looking to do with it on a single board?

 

[helterbelter]

I got the REDD EQ PCBs today from the new supplier, Quick-Teck, that I am trying. The visual quality is very good so I am going to order some db25 PCBS from them. I'll do that later today so they should arrive in a couple of weeks.

Cheers

Ian

eeehhhhhhrrrr.... I obviously missed this. Am I too late to order 4 of these ?

greetings,
Paul

 

[ruffrecords]

I'm entertaining the idea of doing a stereotype build when Don puts the finishing touches on his boards... And since the project looks like I'll have to shoehorn it into a reasonably sized enclosure, I'd be interested in a few of these with the intent to cut the board at the first set of pads just for soldering my cabling to. Any reason I shouldn't do that? maybe integrate one of those scored-lines to the board for a nice clean cut to accommodate whatever anybody is looking to do with it on a single board?

I see no reason why you shouldn't do that. A single cut should leave all those pads and the screen pad intact. Unfortunately the PCB has already been sent for manufacture so it's too late to add a scored line.

Cheers

Ian

 

[ruffrecords]

eeehhhhhhrrrr.... I obviously missed this. Am I too late to order 4 of these ?

greetings,
Paul

I had a feeling this might prove popular so I ordered plenty. I'll put you down for four of them.

Cheers

Ian

 

[erikb1971]

Two of those would make a 16 channel; passive summer right? In that case: would love to have 2!

That's right.  Two PCBs, a couple of db25 connectors, a handful of resistors, a couple of XLR connectors and a small box and you are done.

Cheers

Ian

What would need to be done to upgrade that into something like this:

(and I mean the tube stage.. not the meter or switches...)

 

[ruffrecords]

Two of those would make a 16 channel; passive summer right? In that case: would love to have 2!

That's right.  Two PCBs, a couple of db25 connectors, a handful of resistors, a couple of XLR connectors and a small box and you are done.

Cheers

Ian

What would need to be done to upgrade that into something like this:

(see pic in previous post)

(and I mean the tube stage.. not the meter or switches...)

All you would need would be:

1. One of my Twin Line Amp cards with 1:10 mic input transformers fitted
2. A couple of VTB2291 output transformers
3. HT and heater power supply

The master level pot you could do on the secondary of the output transformers
I don't know about the channel assignment switches - have to think about them.

Cheers

Ian

Cheers

Ian

 

[erikb1971]

wow! Interesting!... anyone else in for a Poor Man's SSA-2B?