Great River MP-2 , info, schematics & discussions

[okgb]

I seldom use mine with the gain more than 1/2 way up
but you could experiement with input impedance
series paralell on the input xfmr and using the 50 % steel
output xfmrs for a little less clean [ wee bit ]
i don't think of it as clean but rather clear & neutral
in fact i just don't think about it , which is good , just record

the 1/4" in sounds good on bass too , it bypasses the input xfmr
nice gain

again for my quad i used Cinemags & Lundahl inputs and
Jensen & unbal for outputs

 

[okgb]

This is not really the order thread though , so
perhaps contacting ptown from his site would be better
that would keep this thread cleaner for questions

 

[okgb]

Thanks goes to Dan  Kennedy , smart & a nice guy as well
who was very generous in giving all the info freely
including the fets & inductors at no cost .

I tried to make the first page answer most questions

let me know if i need to add something to it

 

[muffy1975]

Hi gang,

can I use this and plug it straight into the mic pre PCB? After all what are the onboard Voltage regulators for???

http://www.audiomaintenance.com/acatalog/Transformers_and_Inductors.html

CA-18-VT31284 - Transformer: Mains 110-0-110 (pri); 20v-0-20v +48v (sec) Toroid 1U
Details: Click on image for more information
Part Code: CA-18-VT31284

It's made my Carnhill.

Do I have to use an an external PSU to get the 48v or something.

Kind regards

Michael

 

[Ptownkid]

You need to rectify the voltage first.

 

[muffy1975]

Ok Team,

so the mic pre pcb needs to see +22v and -22v DC?

Can I deliver those voltages from MNATS's little PSU that come with the dual 1176 of his? ( I have already built the REV A and REV 1176 ).

Now, I will have no 48v but I will have the other voltages (+/- 22v).


I am going to plug these voltages in as per this diagram.

http://www.nrgrecording.de/temporary/MP2%20Wiring1.pdf

This diagram is V2 and is correct I presume?

Will anyone build a dedicated PSU PCB for this project in the future?

Kind regards

Michael

( i don't fancy blowing this unit up, gosh I hope this diagram is correct ie: V2 Nrg )

 

[vgdb]

can I use this and plug it straight into the mic pre PCB? After all what are the onboard Voltage regulators for???

Do I have to use an an external PSU to get the 48v or something.

hi Michael,

You don't have to use an external PSU but just to conform to Dan's plans which use a diode bridge and a few condensers to rectify the current.
More simple, in the previous page of this post (n°23 for me, I don't know if it's the same for you), Anders (Sredna) posted a plan that is a simplified extract of Dan's plan adapted for using this kind of single voltage transformer. I directly applied it and it works perfectly well and is simple to realise without any printed circuit board.
Once again, thanks Anders !

 

[vgdb]

I am going to plug these voltages in as per this diagram.

http://www.nrgrecording.de/temporary/MP2%20Wiring1.pdf

This diagram is V2 and is correct I presume?
( i don't fancy blowing this unit up, gosh I hope this diagram is correct ie: V2 Nrg )

The pinout is ok. The problem is that you have to be sure what pin is pin 1 (top or bottom). To be sure : if you look at the Audio card Schematic Rev B, you'll see that Pin 1 of J8 is directly connected to one of R37's legs. Pin 5 of J8 is directly connected to pin 1 of J6. Just check with a multimeter on the board and you will find which is which. As far as I remember, the problem is that the pinout goes from top to bottom (1 to 5) on the diagram but 1 to 5 goes from bottom to top on the card... Check the continuity between J6 and J8 and R37 and J8 and you'll be sure!

Vincent

 

[Ptownkid]

Like he said, all you need is some simple rectifier circuit.

 

[muffy1975]

Thanks gang,

a simple rectifier circuit looks scary to me. I'm just good a following instructions, testing components and so far....being lucky ( 1176 REV A and Rev D, 6 G1176s and one GSSL so far....gone compressor nuts ;D)

Are you familiar with MNATS PSU board that he sells. It will put out a steady +24 and -24V DC

Will this not work? I know i will not have 48V but all the same.....

Thanks VGDB for helping me. How i wish i were living in the Paris suburbs. How cool.

Thanks P Town for your help too. Having a Great River will be a buzz.

Michael

 

[Kev]

Thanks goes to Dan  Kennedy , smart & a nice guy as well
who was very generous in giving all the info freely
including the fets & inductors at no cost .

just wanted to wave the flag once more for Dan
a true friend

and yes
for those that can remember
he was one of the original   Friends of Group DIY  

thank you Dan

 

[Ptownkid]

Firstly, yes, Dan is a true Gentleman and a friend to all DIYers.

Yes, you can feed those two voltages from the Mnats psu to the board, but you still need the +48V

That circuit diagram is nothing to be afraid of, and represents one of the most simple circuits you'll encounter. Maybe now would be a good time to use this to try and learn instead of looking for a paint by numbers solution. Grab some perfboard, or a breadboard, and few dollars worth of diodes and caps and give it a go!

 

[muffy1975]

Ok P Town,

you are right. I am going to go for it and build that rectifier. 6800uf caps must be HUGE.
Thanks for the encouragement. Thanks for the kit. I can do it :-[

XOX

 

[vgdb]

PtownKid is right. Well, if I was able to do it, I'm shure you can , with a little time and soldering !
It is worth the pain and attention and simple enough, for shure !

Vincent

 

[Ptownkid]

I'm glad to hear that Muffy, you can do it, I promise!

Feel free to e-mail me if you need some help along the way, but if you just look at the schematic and make your connections logically, you'll succeed.

I'll pm you my e-mail addy.

 

[vgdb]

Hello Michael,

If you just check this page on lundahl site : http://www.lundahl.se/pdfs/datash/1538_8xl.pdf

At the bottom of the page, you'll find the connection alternatives for the Lundahl 1538 & 1538XL. For a 1:5 connection (the one I used), you have to connect pin 3 to 2 and pin 4 to 1 on the transformer itself. Pin 8 is connected to either the chassis ground and the electrostatic shield of the transfo, so the two pinouts you propose are exactly the same.

Careful : on the schema, the pinout is viewed from top of the component (pins under). But, since it is asymetrical, there is no possible confusion....

 

[okgb]

the second version from this above posted link
to the lundahl site  http://www.lundahl.se/pdfs/datash/1538_8xl.pdf
tells everything follow it

with the primary taps in paralell
gives you the higher ratio of 1:5
wire it that way  , either will work
the second will give you a little " extra " gain
and better s/n

Btw as per Dan , you  can omit the pf cap & resister
on the secondary if using the Lundahl [ forget the numbers ]
not a problem if you leave it in either way

 

[muffy1975]

OK I get it now. I was looking at the top example on the page ( stupid ) 1+1:5

Example 3 is 1:5

Clearly the primary goes like this

pins 1 and 4 are tied and go to PCB +
Pins 2 and 3 are tied and go to PCB -
Pin 8 to PCB GND

The Secondary is

Pin 6 PCB +
Pin 5 to PCB -
Pin8 to PCB GND

I hope this is not miss information. Please say so if it is and I will delete the my post

NOW here is a question!!!!!

Can I use a carnhill output transformer???

Until the next time

Michael

XOX

 

[audiovisceral]

i have been considering making a pcb and getting just pcb mount ones...

however, you guys should still trade as I am not positive.

Did this ever get done? If not, do you have a picture of the Elna's wired up to show how it connects? I'm having trouble understanding how this comes together just from this thread...

 

[muffy1975]

Hi team...I'm back.

My second kit has arrived ( held for 2 weeks in UK customs...unreal )

A few more questions

1) do i need both 10r in the r47 and 20r in the r36? I ask cos I am missing both 10r resistors. does this 10r resistor need to be 1w or can it be 0.6w?

2) The heatsinks. Can I superglue these to the regs? Or do I need to separate them?

3) I have used a 30va 25v transformer. Will this be ok considering I have built the PSU listed in the past few pages?

Gosh I hope my home made pSU works. have followed the sychematic so we'll see.

Thanks PTown for these kits by the way

XOX