Great River MP-2 , info, schematics & discussions

[Gustav]

[quote author="pstamler"]I second everybody's remarks: thank you, Dan, for your generosity.

Gustav, or someone...how about putting on the Gerber something like "©2007 Dan Kennedy; non-commercial use only"?

Peace,
Paul[/quote]

Unfortunately, I have no idea how to do that. Could someone else add it to the file perhaps?

Gustav

 

[Orleanska]

It's all about sharing...

[/img]


thank you!
regards
Denis

 

[clintrubber]

[quote author="pstamler"]Gustav, or someone...how about putting on the Gerber something like "©2007 Dan Kennedy; non-commercial use only"?[/quote]
The DK-mentioning might be dangerous perhaps ? As in: look, it's a true genuine GR-product ! (after 'they' have removed the "non-commercial use only")


Something else: the bank of 680 uF caps.
Since they're anti-series already, how about polarizing them with a high-valued resistor to the neg. supply rail ? (connecting the bank in the centre where the '-'connections meet)
Don't want to tamper with the original design but it seems a nice opportunity.

Regards,

Peter

 

[clintrubber]

[quote author="matta"]Here is a review of the ORGINAL MP-2: http://mixonline.com/mag/audio_great_river_electronics/[/quote]
[quote author="mixonline"]Besides the ability to get from maximum to minimum settings easily, this continuously rotary control offers one other hidden advantage: The two settings on either side of the control's "6 o'clock" position set the input to +14 dB unity gain, although this is not marked or indicated on the front panel.[/quote]
Sorry, not enough tea yet, I don't get this. What's the idea here ?


And some more about the gain-switch:
for the #22, #23 & #24 positions there are two resistors in the gain-switch-pdf.
The legending might suggest they're to be put in series but for a logically continuing increase in gain for those positions they're to be put in parallel.

Might prevent eventual confusion.

BTW, I don't understand the note in the pdf either; there are three sections with two resistors but the note mentions two positions. Still not enough tea here :wink:


Regards,

Peter

 

[Whizard]

This is fantastic!
Dan - thank you!

 

[okgb]

The stop pins that prevent the switch from spinning around ,

i left them out of mine so they work like a mute position between the
highest & lowest gain settings [ there is the danger of going from lowest
to highest gain but it never happens for me . ]

Although not recommended one could also use reverse log 2k pots
[ if the fraudulent group order ever came in ! ] in place of the gain
switches

This one is for free

Turning knob to the right "gives" more ..........................almost always
works ! try it out for yourself !

Along with fader high , too much , fader low , not enough fader in the middle almost always works

 

[clintrubber]

[quote author="Dan Kennedy"]I've still got a pretty good pile of the FET's too, we'll figure out a way to get them out as well.

There isn't anything exotic, so feel free to substitute stuff.[/quote]
For convenience I've quickly grabbed the relevant datasheets:
(thank you datasheetarchive.com etc)

http://home.hetnet.nl/~chickennerdpig/FILES/datasheets/MP-2_semiconductor-datasheets.zip

Everything should be there, apart from the regulators, 1N4148 & some other diodes. I'll have a further look at the BJTs for equivalents (if needed; no idea how easy the original types are obtainable).

Bye,

Peter

 

[chrissugar]

Very good idea Peter. :thumb:

chrissugar

 

[Ptownkid]

What's the part number for the switch, I don't see it in the BOM

 

[okgb]

I believe this is the correct switch #

Elma 04 2 1103-s where s may mean special order ,
although i think it is a standard switch because a friend
ordered some from a place in the U.S. [ 20-25.00 ? ]

Again for those who want to save money the 2k c pot
should do .

regards Greg

 

[Ptownkid]

do you mean 04-1103

http://www.elma.com//Admin/ProductionFiles/ProductTypeI18NFile/264/Type_04.pdf

And what is a 2k c pot?

 

[DrFrankencopter]

I think the s in the Elma switch is for shorting....

I've got 4 of these preamps in my studio...with Jensen 117's (I think that's the model) for input transformer. I love them...great preamp, clean, plenty of headroom, plenty of detail.

Big Kudo's to Dan for releasing this to the Lab! :guinness:

Cheers

Kris

 

[Ptownkid]

according to the datsheet, they are shorting by default and show no s in the part number.

 

[okgb]

A=Audio or log , B= linear , C= reverse log ^a.f.a.i.k.

As marked on a switch from Dan

Elma 07.00
04 ^then sticker scratched 1103-S

On a recent switch from u.s.

Elma 0806

04-1103-20

i bought a couple of these and they seem exactly
the same except for slightly longer shaft and they fit the mini pcb

Eventually i will have a couple gain switch pcb
with sm resisters to give to someone

Also quote from Dan " You can get Cinemags from Tom at cinemag.biz, the CMMI-5C for inputs is virtually identical to the JE-13K7 " less dough

I have used two of the Lundahl 1538 XL which i like and gotten a couple
of the Cinemags for my quad

 

[TomWaterman]

Dumb question - what are the comparators doing in the PSU? I didn't look too hard yet...

Oh and THANKS DAN THIS IS VERY VERY COOL!
:thumb:

-Tom

 

[okgb]

the comparitors act like peak l.e.d. drivers , they actually glow a little at first before you it hit them hard instead of just flashing at you , they work on both the positive & negative sides of the waveform .

Perhaps they were a refinement after Dan had been producing the preamp boards ? and why mess with something that works eh ?

regards Greg

 

[Dan Kennedy]

Hi guys,

The Elma's should be shorting, some of the custom number was the shaft length, some the extra gold on the contacts, but in reality, just about anything will work.

The LED drivers are just or'd comparators on pos and neg peaks with some kludged pulse stretching.

 

[Ptownkid]

so in other words, 1x24, shorting, 2 deck

 

[DrFrankencopter]

Should be a single deck switch.....

Cheers,

Kris

 

[ruairioflaherty]

Just going to clog up the thread with some thanks for Dan, yet again I'm blown away by the spirit and generosity of this place and those who support it,

cheers,
Ruairi