Ptownkid
Well-known member
Shoot, I'll send the resistors...
Great River MP-2 , info, schematics & discussions
- Thread starter okgb
- Start date
Help Support GroupDIY Audio Forum:
Hey PTOWN,
don't worry about those resistors man. I'll get them. Can they be 0.6W Dude thanks so much for putting these kits together for us....
Has anymore compared these pres to the Focusrite ISA pres? Can wait to hear the Great River....
XOX
don't worry about those resistors man. I'll get them. Can they be 0.6W Dude thanks so much for putting these kits together for us....
Has anymore compared these pres to the Focusrite ISA pres? Can wait to hear the Great River....
XOX
vgdb
Member
muffy1975 said:
Hello Muffy1975,
Conforming to the Audio Card Schematic, R36 (20 Ohm 1Watt resistor) goes to pin 3 on the J7 connector. R47 (10 Ohm, not provided because not necessary, Dan says 20 Ohm output is better to his ears sooner in this post) is connected to pin 1.
So, if you leave R47 blank, you should use pin 3 and 4 on the connector (or more simple if you're not shure of the pinout : just verify you use the pin that goes to R36 by testing). If you do so, you don't need the R47 resistor.
By the way : before you connect your power supply, don't forget to verify with the audio card schematic which pin is which on the J8 connector ! As far as I remember, several people did connect it the wrong way (and burnt some components) because pinout goes in the wrong direction on the "wiring diagram" (even on v2) : pin 1 is indicated on the "top" of the diagram, but on the card, pin 1 is the "bottom" pin of J8 . You can very simply identify pin 5 on the J8 connector : it is directly connected to pin 1 of the J6 connector. Pin 1 of J8 goes to R37. If you check with a multimeter, you can't go wrong.
Cool,
no need for the 10ohm. thought so.
Can anyone help me with this PSU listed in the past few pages.
I have followed it using 6800uf caps, 680uf cap and 100uf 100v caps / 4007 diodes,etc and I have a 30va 0-25v 0-25v transformer. I have 85V on the phantom power and +42.7v and -42.7v. Have I wired the transformer wrong?
Thanks for any of your help Team GR
XOX
no need for the 10ohm. thought so.
Can anyone help me with this PSU listed in the past few pages.
I have followed it using 6800uf caps, 680uf cap and 100uf 100v caps / 4007 diodes,etc and I have a 30va 0-25v 0-25v transformer. I have 85V on the phantom power and +42.7v and -42.7v. Have I wired the transformer wrong?
Thanks for any of your help Team GR
XOX
0-25Vac is a bit hot.
0-22 is what I've always used.
You should be able to slog it down with some power resistors. I guess I would do it in the transformers secondary wiring.
0-22 is what I've always used.
You should be able to slog it down with some power resistors. I guess I would do it in the transformers secondary wiring.
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Wooooo,
It's Dan on the phone. Cool.
Yeah I couldn't get a 0-22v from my dealer. i can't see where all the extra volts have come from. What maths I'm gonna have to do to find the correct resistors? Am i gonna attach these to the 2ndrys? If I use 2w resistors am I looking at 200r on each 2ndry?
It's Dan on the phone. Cool.
Yeah I couldn't get a 0-22v from my dealer. i can't see where all the extra volts have come from. What maths I'm gonna have to do to find the correct resistors? Am i gonna attach these to the 2ndrys? If I use 2w resistors am I looking at 200r on each 2ndry?
Now I've trred 5w 220r and it made no difference on the secondaries. i put no resistors on the centre tap.
What value resistor will i need on each of the secondary wires from my 30va 25v transformer? And what wattage?
Thanks again
What value resistor will i need on each of the secondary wires from my 30va 25v transformer? And what wattage?
Thanks again
It won't make any difference until you put a load on the supply.
Makes me think a load on the 48 to hold it down might be needed.
How many channels will you be powering?
Makes me think a load on the 48 to hold it down might be needed.
How many channels will you be powering?
No on the superglue, heres a proper isolator link. You should get in the habit of using these isolators. Not sure what package type of regulator is used but I would think one of these should fit the bill.
http://www.aavidthermalloy.com/products/standard/access/kits.shtml
http://www.aavidthermalloy.com/products/standard/access/kits.shtml
Guys,
I read earlier in the thread that the MP-2 wants to see 36V. Now my PSU is gonna give 43v and 83v for the phantom which has got to be too much.
How can I pad down the voltage? What resistors would I need?
If at all possible can someone tell me ( if they know ) what each Mp-2 draws so I can get a local tech to figure out what resistors I may need. :'(
I know I should just get a 22v trannie but digikey want £12 for delivery which is a joke considering that's the same price as the trannie.
I am not plugging this PSU in yet. I love the thought of having an Mp-2 in my setup not a piece of toast. 8)
XOX :
I read earlier in the thread that the MP-2 wants to see 36V. Now my PSU is gonna give 43v and 83v for the phantom which has got to be too much.
How can I pad down the voltage? What resistors would I need?
If at all possible can someone tell me ( if they know ) what each Mp-2 draws so I can get a local tech to figure out what resistors I may need. :'(
I know I should just get a 22v trannie but digikey want £12 for delivery which is a joke considering that's the same price as the trannie.
I am not plugging this PSU in yet. I love the thought of having an Mp-2 in my setup not a piece of toast. 8)
XOX :
okgb
Well-known member
Generally speaking you want to feed the regulators a volt or two above
so they can regulate it down and hold it there
too much voltage and you're going to be drawing more current and disapating heat
bringing it down [ i believe ]
If you have an unregulated psu feeding the regulated mp2 boards then i'd say a volt or two
over is safe ,
throw a pot in line with the voltage to rough guess a value to bring it down ,
adjust it , connect the pre for a load and recheck it for a voltage dropping resister value
then get a larger watt resister for the job [ 1-2 watt ? ]
[ adjust the pot for the right value , check the resistance of the two terminals you used
measure that and get THAT value resister ]
hope that helps
so they can regulate it down and hold it there
too much voltage and you're going to be drawing more current and disapating heat
bringing it down [ i believe ]
If you have an unregulated psu feeding the regulated mp2 boards then i'd say a volt or two
over is safe ,
throw a pot in line with the voltage to rough guess a value to bring it down ,
adjust it , connect the pre for a load and recheck it for a voltage dropping resister value
then get a larger watt resister for the job [ 1-2 watt ? ]
[ adjust the pot for the right value , check the resistance of the two terminals you used
measure that and get THAT value resister ]
hope that helps
Just a question about psu: I have 2 boards to supply. Does a 14VA (2*24V) r-core transformer have enough power?
I've problems to find a r-core 30VA 2*22V transformer which could fit a 19'' 1U case.
Thanks for your advices.
Best of all.
Eric
I've problems to find a r-core 30VA 2*22V transformer which could fit a 19'' 1U case.
Thanks for your advices.
Best of all.
Eric
14va is fine.
The boards draw about 40ma each.
In a quick test with a 22v transformer and a variac to run it up some a 47 ohm resistor in each leg is about
right to drop the resultant dc at the filter caps to about 40 volts, which is fine for the 317/337 pairs.
You'll need 5w rated resistors, they'll get warm.
There are a lot of variables, this is a reasonable place to start.
Put a 20 ohm 2W resistor in the feed to the voltage doubler, this will drop it down some, you might want
to put a load across the filter cap at the output of the doubler as well, maybe 2.2K also 2W. This will help
hold it down too.
The boards draw about 40ma each.
In a quick test with a 22v transformer and a variac to run it up some a 47 ohm resistor in each leg is about
right to drop the resultant dc at the filter caps to about 40 volts, which is fine for the 317/337 pairs.
You'll need 5w rated resistors, they'll get warm.
There are a lot of variables, this is a reasonable place to start.
Put a 20 ohm 2W resistor in the feed to the voltage doubler, this will drop it down some, you might want
to put a load across the filter cap at the output of the doubler as well, maybe 2.2K also 2W. This will help
hold it down too.
Team Dan Kennedy and the MP-2 Interns,
Just got my Gloch. It was a case of point and shoot ( after I nearly killed myself with the home made PSU ).
Both channels worked straight away although one has a DC offset of 10mv while the other is 0.5mv.
Gosh they sound good.
Still pondering about the phantom power side. Do you think i should run a variable resistor across it and put maybe 250ohms on it as a starter? At the moment is chucking out 84v?
Thanks Dan for making this available for us all. What a joy. Can't wait to see how they perform next to the Focusrite Blue ISA and the UA 610 8)
Thankyou thankyou thankyou
XOX
Michael de A
Just got my Gloch. It was a case of point and shoot ( after I nearly killed myself with the home made PSU ).
Both channels worked straight away although one has a DC offset of 10mv while the other is 0.5mv.
Gosh they sound good.
Still pondering about the phantom power side. Do you think i should run a variable resistor across it and put maybe 250ohms on it as a starter? At the moment is chucking out 84v?
Thanks Dan for making this available for us all. What a joy. Can't wait to see how they perform next to the Focusrite Blue ISA and the UA 610 8)
Thankyou thankyou thankyou
XOX
Michael de A
team,
can anyone confirm whether or not I can use a Carnhill VT1847(1+1:1.7+1.7) or VTB 2281 (1+1:1+1)output transformer? How do you wire these things to the output?
here's the stinky link
http://www.audiomaintenance.com/downloads/carnhill_design_guide.pdf
Thanks
can anyone confirm whether or not I can use a Carnhill VT1847(1+1:1.7+1.7) or VTB 2281 (1+1:1+1)output transformer? How do you wire these things to the output?
here's the stinky link
http://www.audiomaintenance.com/downloads/carnhill_design_guide.pdf
Thanks
okgb
Well-known member
you'll need to compare the pin out info / specs
of the recommended ones vrs the one you mention
but yeah , why not
also don't forget they work totally without an output transformer
of any sort , your option
of the recommended ones vrs the one you mention
but yeah , why not
also don't forget they work totally without an output transformer
of any sort , your option
Well they 8) are both 1:1 style transformers
How do you connect them though? I know to take pin1 and pin2 of the output on the Mp-2 board but how do you connect those to the transformer and the transformer to the output XLR. Is there a diagram I could follow out there. I have searched and I've tried to find the way, but there's only one way and I can't find it. Dang.
Michael
How do you connect them though? I know to take pin1 and pin2 of the output on the Mp-2 board but how do you connect those to the transformer and the transformer to the output XLR. Is there a diagram I could follow out there. I have searched and I've tried to find the way, but there's only one way and I can't find it. Dang.
Michael
riggler
Well-known member
Hi!
Does anyone know the current draw and load resistance of each preamp card? I need it because I have a 25-0-25 transformer and need to calculate dropping resistors to get me to 22V.
Thanks!
Does anyone know the current draw and load resistance of each preamp card? I need it because I have a 25-0-25 transformer and need to calculate dropping resistors to get me to 22V.
Thanks!
call me crazy, but has anybody considered giving a 51x board for these a whirl as another kit option? after doing a couple pixel reference measurements on the guts of some assembled kits, it looks cram-able w/trafos (if just barely). couldn't you just add the phantom wheatstone/cap solution suggested by sredna, then resistively drop the 24V rails to 22 to save space over a third trafo?
