Great River MP-2 , info, schematics & discussions

[Matador]

Here are preliminary completed layouts.

Top of PCB:

Back of PCB:

 

[Ptownkid]

What lead pitch are the connectors?

 

[Matador]

What lead pitch are the connectors?

3.5mm.  They are from Phoenix Contact.

 

[Ptownkid]

Is it possible to make it 2.54mm?

 

[dmp]

If there is enough demand (and this board sounds fine and works) I would be happy to copy it to a 51X template.  However keep in mind I don't have neither any 51X gear to confirm the design, nor capabilities to make or design front plates so someone else would have to do that.

Awesome. If you don't want to do the gold fingers and edge connector, you could make the board work with the from Silent-Arts / ClassicAPI edge connector. It would just have to not exceed max length and width.
Or else perhaps someone would give you a 51x template that you could use???

 

[Matador]

Is it possible to make it 2.54mm?

That shouldn't be an issue.  Pheonix Contact makes a 0.1" version of the same screw terminals I normally use:  I'll just have to re-draw the components.

Is this to make it compatible with an adapter?

 

[Ptownkid]

No...it's to make it compatible with the thousands of 2.54mm terminal blocks I have...and TE mta-100 idc connectors

 

[Matador]

Ok here's another layout. 

I wasn't happy with how much back and forth I had to do across the board to go between the signals and the relays.  So I moved the relays over near the switches, and made dedicated routing channels for the input and output signals (along the top sandwiched between the +24V and -24V supplies).  All in all, the layout is much cleaner.

I also switched the connectors to 2.54mm (0.1") pitch.

Here's the top silkscreen (designators aren't positioned yet, but this gives a feel for component placement):

The top copper:

And bottom copper:

I feel this layout is also much more true to Dan's original board.  And I also routed it with no vias this time.

 

[pachi2007]

+1 for the 51X layout.
Awesome work Matador!

 

[baadc0de]

+1 for the 51X layout.
Awesome work Matador!

+2 here

 

[Matador]

Here is a 51X template I had put together some time ago:

However the dimensions were what I had gleaned from previous posts.  I could never find a detailed template in any official manner, and I don't have any boards in front of me to measure.

Does someone have a detailed dimensional drawing of the 51X format they can share?  Or better yet, an outline in DXF or Eagle format I can just use?

 

[Ptownkid]

http://www.groupdiy.com/index.php?topic=41919.0

 

[Matador]

If nobody has any opinions or feedback on the non-51X layout I posted above, I'll go ahead and have two copies made for prototypes.

 

[Ptownkid]

Get three...I'll chip in if needs be.

 

[okgb]

Where the opamp  ?  although simple , the 1/4" d.i. input does work well , I'd put in at the bottom though
so the cable doesn't dangle over the switches and cover them up . there's an l.e.d. for phantom power ?

 

[Matador]

Where the opamp  ?  although simple , the 1/4" d.i. input does work well , I'd put in at the bottom though
so the cable doesn't dangle over the switches and cover them up . there's an l.e.d. for phantom power ?

The 51X layout is simply a template.  It doesn't have any of the GRMP-2 goodies.

I don't want to invest a ton of time in layout if the new prototype board doesn't work.

 

[3nity]

Matador looks really impressive Tio.

It looks like the board is less congestionned.
Did you thought about a doing a version for Lorlins and not GRayhills??
I mean with a daughter board for lorlin and toggle switches for 48/pad/pol??

This would make the project more affordable and still be quiet fancy.

just my .002 cents.

 

[Matador]

Matador looks really impressive Tio.

It looks like the board is less congestionned.
Did you thought about a doing a version for Lorlins and not GRayhills??
I mean with a daughter board for lorlin and toggle switches for 48/pad/pol??

This would make the project more affordable and still be quiet fancy.

just my .002 cents.

Aye those are all possible.  If you notice the layout also has a spot for a Bournes 12mm rotary potentiometer for the gain control.  One could wire up a Lorlin with a daughterboard directly to the two pot connections.  Or even a cheaper Alpha or other pot will work (it's how I tested my original prototype).

I also have another daughterboard for a reference LM3915 design for VU metering.  You'll see the three holes at the front of the board are for mounting this board.  There's also a two pin header right in the middle for sending out to the VU meter right before the output transformer.

 

[Ptownkid]

Smart! Great work dude.

 

[okgb]

I would use the metering if it were there BUT I think every preamp could use a HPF
the ones on Jeff's VP 28 is good but ends up being 4 switches [ makes it versatile ]
if there was one switch and user determined 6 or 12 db slope and selectable cap
for the roll off or kness frequency [ by selecting parts values inside ]  that'd be usefull ,
I'll dig around for a circuit if you can fit it in .

the gyraf g9 simply switches caps into the audio circuit in line [ smaller the cap , less low end it will pass ]
I recall the pv tube mic preamp switched 2 aps in at two different places , I believe that will increase slope
of the knee for the HPF , just searching the internet now