Great River MP-2 , info, schematics & discussions

[jdbakker]

[quote author="ruairioflaherty"]how many Elmas do you need? I think I might have 2 of the pcb mount units for the 33609 to spare. Let me know if two is enough for you and I'll take a look for you.[/quote]
Great! Two would be fine.

Thanks,

JDB.

 

[Ptownkid]

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

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

 

[okgb]

there should be a gerber for the pc switch mount
although it uses smt resisters

 

[Tungstengruvsten]

[quote author="okgb"]there should be a gerber for the pc switch mount
although it uses smt resisters[/quote]

...ah shit. really hoping for one like the 33609's have with vertical 1/4 or 1/8 watt...alot easier than soldering to the pins...but I do have them -

 

[Ptownkid]

That's why I'd make a new pcb, screw smt.

 

[Tungstengruvsten]

if those boards were available i'd buy 10 or more - they would be handy for many things! Hell I'd do 4 channels of this in a second if I didn't have to solder resistors to switches! It's so easy on a PCB...

 

[3nity]

Quick question guys.....
I'm a little confused....how to read mV on a DMM....
I need to read 5mV.

my meter has only mV, 2V, 20V or 200V scale...
Now in the 2V scale should i see: 00.5V or should i use mV and see: 00.5?

Sorry for the dumb question...

Thanks

 

[Bluzzi]

If you are in 2v or any volt scale and read 00.5v its 0.5v but if you are in mV scale and you read 00.5 then its 0.5 mV. Its that simple.

There are no dumb questions (only maybe dumb answers but were not politicians here so no worries)

Jim

[quote author="3nity"]Quick question guys.....
I'm a little confused....how to read mV on a DMM....
I need to read 5mV.

my meter has only mV, 2V, 20V or 200V scale...
Now in the 2V scale should i see: 00.5V or should i use mV and see: 00.5?

Sorry for the dumb question...

Thanks[/quote]

 

[3nity]

OKGB

Grounding scheme
As recommended by Dan
Run a heavy bus wire along the back of the i/o connectors - in Canada & U.S. the copper house wire fits perfectly into the XLR connector
Have the Chasis & PSU grounds meet at this point
Run the Preamp board ground [ including the psu ] to this point
Run the Input Xfmr screen & ground as well as any shielded i/o wire to this point , preferably between their respective i/o connectors .
Do not connect any of these grounds [ i/o & Xfmrs ] to the input side of the board

Where's the preamp board ground?
I'm using Lundhal 1538XL, wich pin is case? pin 8 is ground.
Should i connect the DI jack shield to that point?
I have a ground loop every time i hook up a mic i have a ground and gone when i touch the case.

Jorge.

 

[okgb]

the preamp ground is on the back pcb connectors ,
with the copper housewire will fit into the pin 1 hole of the xlr
then bend a rail to the last one to cover either 2 or 4
depending on how many channels you have , all grounds go
to this bus wire at the xlr connector

important if using shielded wire to or from the the input transformer
ground these at the busbar as well and leave lifted at the xfmr and the front connections of the preamp pcb .

the d.i. may be short enough to not need shielded wire , but pay attention
to whether the jack itself is grounded from the front panel or not
it only takes one extra connection for a loop

 

[3nity]

Here is my Wiring layout on the Great River...i have a steady hum.

Power supply is external.

 

[okgb]

the xfmrs show a ground symbol , is that a mistake
it's not grounded at two places right ?
Also is the 1/4" jack isolated from ground ?
test with a meter and trying lifting that ground .

the inputs & xfmr can have shielded wire but grounded only back at the
xrls , i had a hi freq buzz to one of mine , after a while i found that the
metal standoff to hold the input xfmrs was grounding it as well ,
cleaned up that and it WAS clean

 

[Bluzzi]

[quote author="okgb"]the xfmrs show a ground symbol , is that a mistake
it's not grounded at two places right ?
Also is the 1/4" jack isolated from ground ?
test with a meter and trying lifting that ground .
[/quote]

Hmmm...going back and forth with 3nity trying to debug my GR (these are mine he is working on).

The 1/4inch is where maybe I went wrong. Its been a while and I don't have it in front of me but I think I normalised pin 2 to pin 3! It should be terminating no? Its just a guess that maybe I did that thinking that it only needs Tip & Sleeve (Sleeve=GND, Ring Pin 2).

So what you are saying is that it should be terminating (Sleeve=Pin 2, Tip= pin 3 GND is left unconnected).

Jim

 

[okgb]

I mean that the 1/4" jack itself doesn't contact ground but is isolated
[ plastic washer , you know what i mean eh ? ]
the jack is a switching type where inserting will break the path from
xfmr to circuit for the 1/4" in ,
normally tip & ring connect when not used , the xfmr feeding the ring
and tip going to board input pin [ forget the numbers ] inserting 1/4"
caues the ring to be disconnected and the 1/4" becomes the input to
feed the circuit [ i'm sure you knew that but it has to be the right
kind of jack , switching and not connected to ground by the front plate

it needs a ground , but lifting it will tell
you if you have a loop .
I'll be out of town till sunday night , regards Greg

 

[Bluzzi]

That's the way I remember wiring it. For a minute I thought it might have been wrong. Still its a good idea to lift ground there if its lifted everywhere else (except 0v from Power Supply).

Jim

 

[3nity]

YEah sorry thats a mistake a i've made on the drawnings.
Actually the red is wired to the other side of the blue wire....and Jack inserted it breaks.....

 

[Bluzzi]

Lift ground on the connector to see of hum stops.

Jim

 

[3nity]

Still having some hard times with this....the hum is now gone.
But if i switch any relay hums comes and hunt me!! argh....

Any of you had troubles with switching?

Thanks.

 

[okgb]

the relay[ switches] have one common ground that runs back to the front
of the board on the same connector as the switches

 

[3nity]

Greg i have one problem here....the pad relay works fine in all pres....but engaging the phase in 2 preamps using lundhals produces a HUM...in the other with Cinemag 75101APC wired to 1:5 it just goes mute..??
No i'm thinking this....the relay switch phase in the transformer secondaries...but the secondaries on input transformers has a High and a Low...a preamp need to see a Low (ground reference) in parallel to the High...

Could this be the problem?