Great River MP-2 , info, schematics & discussions

[Ptownkid]

Yeah, I think I'm leaning towards the Cinemags, what cinemags do you suggest for the output...I wasn't aware that there was an output xfmr.

 

[okgb]

Output is optional , totally fine without it but if you want a little more thick
[ and balancing ] than it does add it . the board in fact has outputs for both
and even if you use a transformer i recommend also adding the unbalanced out as well

On an earlier post i listed the Cinemag numbers which Dan recommended
as well as the lundahl , i can vouch for both and prefer the 1538 xl

Cinemag has some high nickle outputs

rregards Greg

 

[Ptownkid]

I can only find the input suggestions you made...

 

[okgb]

quite right , i'd have to dig up the output number , but i think there is some choice , How many high nickle 1:1 outs do Cinemag make ?
not critical , just as much for color , just don't skimp on the input

regards Greg

 

[Ptownkid]

If we're talking about the cmo series, there's a bunch and I don't know fark all about xfmrs.

 

[Bluzzi]

We could ask David Geren at Cinemag for suggestion if were stuck.

I'd prefer the Cinemag as well. I will be using an output transformer myself (also Cinemag).

jim

 

[okgb]

O.k. , Dan recommended Cinemag out CMOQ-1H

Adding the xfmr is not like you suddenly think thats better , i went years
with my first one unbal out , 100ft runs and then added two to the quad
and decided that two channels were enough [ having two bal 2 unbal ]

Still a nice option to have and the Cinemags should be reasonable money
to do that [ group buy ? , i'm in ]

 

[Ptownkid]

Ok, since cinemag is in the states, an american is going o have to organize the group buy. If I bring a box of transformers from the US into canada, it's gets hit hard with duties.

 

[Bluzzi]

[quote author="Ptownkid"]Ok, since cinemag is in the states, an american is going o have to organize the group buy. If I bring a box of transformers from the US into canada, it's gets hit hard with duties.[/quote]

I used to import for my business a long time ago and transformers were already almost duty free because of the Free Trade agreement between US and Canada. Are you sure you are bringing them in under the correct classification?

If you use a carrier to do the duty brokerage you will almost always pay duty as they do not give a damn what to classify them as.

If you get the papers filled out right by Cinemag they should pass no problems.

Let me know if I can help.

jim

 

[Ptownkid]

Well, if you can find a code that we can get em in by...i'll tackle it.

 

[okgb]

They will call them duty free , but charge taxes & handling fee ,
still better than UPS , but a point person in the country of manufacture
is still best .

Another Cinemag grp buy for a few other models too ?

did we burn out the person who did it last time ?

Anyone brave enough ?

Adding general info here to make it easier to find

Adding some info here so it is easier to find

power xfmr requirements = An off the shelf 30va 22 + 22 transformer will power this up fine
you don't need to build the supply in the schematic , although it is nice with o/l l.e.d. drivers

Suggested input Xfmrs
Cinemag CMMI-5C 150:3750
Lundahl 1538 XL 1+1:5
Jensen JT-13K7 1:5

Outputs Cinemag CMOQ-1H
Or Jensen JT-11-BM

Any 24 pos. shorting switch may be used for the gain control , although not recommended a 2k2 reverse log pot may be used to get the pre working until you find a switch

Finding the value for R46

R46 is determined by putting a FET in the circuit, then adjusting
for minimum output offset. This value drifts some with temperature, so
I try to adjust for <.5mv when the circuit is warmed up.

just power the board up, it already has the feedback resistor, and put
a 2K or so pot in for R46, adjust for minimum, let things warm up some
more and readjust. After 15 minutes or so I'll take the pot out of the
circuit, measure and replace with a fixed resistor of the closest 1%
value and then retest for warmed up minimum offset.

It takes a little while, but it's something you can walk away from in
between tweaks.
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

 

[Bluzzi]

Looks like 4% tariff. It hasn't moved in many years. Let me keep looking, I may find another tariff.

jim

 

[AudioJunkie]

Just for clarification: What all is going to be available in the kit? Boards, critical parts than Dan was sending (maybe gain switches)? That's all I really need. I'd like to use Lundahls myself, and don't mind sourcing the standard stuff (caps, resisters, etc) myself.

Daniel

 

[Ptownkid]

The first round will be kits only, which will include

PCB
All on board parts (including the 2sk389)
XLR connectors
1/4" Connector
Toggles

with the option of buying the elma rotary

There will be PCB's available by themselves in the future. As for the 2sk389 and the inductor's, they will not be included with pcb only orders. You can try Greg (OKGB) or get the Linear systems part LSK389, which will require bending leads as it comes in a different package and then sourcing a 18uH inductor.

There's a good possibility that if there's enough people interested, that I can get the lsk389 and ship it with the pcb only orders when we get there.

 

[Bluzzi]

Ptownkid,

I don't mind buying the whole kit form you but when you say XLR I am worried they are PCB mount only. I really would prefer to mount my own.

Will they be PCB mount only?

I'll probably will start with 2 full kits including Elmas. What happened to the transformer(s)?

Also I thought you were getting the inductors and Fets from Greg? I thought from an earlier post that he was just passing them on to you at no charge to include in the kits? Did I misunderstand something?

Really looking forward to this project happening.

jim

 

[Ptownkid]

The XLR connectors are NOT pcb mount, they are Neutrik NC3FD-L-1 and NC3MD-L-1

Yes, the inductors and the fets are in the kit, but when I get around to offering PCBs by themselves, there will be no more fets and inductors.

As for the transformers, it's not all that economical for anyone for me to import such a heavy and taxable item into Canada, only to send 90% of them right back to the states.

 

[hejsan]

Hi, do I have to order in this thread to get kits, or will you put an ad in the black market?

thanks,
hejsan

 

[Ptownkid]

I will put a posting up in the black market tomorrow with prices and all the info.

 

[okgb]

Yes the inductors & fets were passed on to Ptown , No charge
Courtesy of Dan

And he's quite right , the transformers only make sense IF someone in the U.S. is willing to do a grp buy [ and i would say open that up to a few other models too and i'll be in ! ]

Otherwise any 1:5 type input xfmr [ Don't skimp on this part ] and you can skip the output should get you started fine .

I have plently of extra inductors but very limited supply of the fets ,
the 1/4" jack needs to be a switching type eh !

Wheeeeeeee !

 

[Bluzzi]

OK, the transformers make sense. No worries. Actually this way we can pick what we want. I may just go for Jensens.

Also lets note we will need a Power Supply. The JLM ones are handy and maybe we can do a group buy as well. Not to save money on the units but maybe the transport and also iit would make it easier for JLM.

jim