Great River MP-2 Mic pre DIY

[evm1024]

Almost there. I'm so close to getting this pre up and running. I did a little sheet metal work on a 1U box that had some video stuff in it. Gutted and added the switches and so on.

I need to get a Greenlee punch for the input XLR but that is not a show stopper. I should be able to do the wiring tomorrow and then power it up for a little testing tomorrow or Christmas.

Being snowed in (not really I've been driving all over in a beater subaru) or at least not at work has giving me time to work on it.

The excitement builds....

-Ethan

 

[Slowjett]

Ethan was that a kit

Ethan was that a kit? What do you think you have into the electronics cost and time wise?

-josh

 

[evm1024]

Ptownkid

These are from the first run from Ptownkid DIYPARTSSUPPLY.COM

2 PCB kits $160
2 switches $70
2 Cinemag transformers $150
JLM PS $25
Toroid $30
Case Free!

Total cost for 2 channels = $435

I built them as time allowed over the last year - perhaps 8 hours to stuff and solder the preamps and ps boards and do the metal working up to this point.

Add in some more time to think about what to do. But remember that time working a preamp like this adds hours to your life at least one to one.

List price in 1999 was $1250 for 2 channels. Todays price on the MP2NV (not the same as this one) is $2960....

--Ethan

 

[Slowjett]

Very cool. I was considering getting a Seventh Circle or a Five fish preamp kit, this however looks pretty cool.

-josh

 

[tmix]

I look forward to hearing how you feel it performs.

 

[RRuskin]

These are from the first run from Ptownkid DIYPARTSSUPPLY.COM

2 PCB kits $160
2 switches $70
2 Cinemag transformers $150
JLM PS $25
Toroid $30
Case Free!

Total cost for 2 channels = $435

I built them as time allowed over the last year - perhaps 8 hours to stuff and solder the preamps and ps boards and do the metal working up to this point.

Add in some more time to think about what to do. But remember that time working a preamp like this adds hours to your life at least one to one.

List price in 1999 was $1250 for 2 channels. Todays price on the MP2NV (not the same as this one) is $2960....

--Ethan

Assuming the Cinemags perform as well as the original spec'd Jensens, you will find this to be a stellar performer. My 4-channels worth get used more than anything else in my rack and I have quite a lot of vintage and upper crust units to choose from.

 

[evm1024]

It's Alive!

The Cinemag transformers are right up there with the Jensens and as with all transformers have their own sound. They are not very colored at all.

I got it all wired up and did the smoke test. No smoke! That's nice, real nice. I've still got to get a hole punch for the input XLR but till then I've just dressed the wires as neatly an is reasonable and did some testing on it.

Sadly my signal generator has lots of HF noise on it at low amplitude but this noise is beyond the passband of the preamp.

The scope shows a 39 mV 1Khz input signal and a 1.160 volt output. (preamp set to 30 dB gain.)

I plugged in a dynamic mic and "sang" into it. The cat left the room but the waveforms looked like they should. I've not run it into a recorder yet. I've still got the last 5% of cleanup, wire dressing and mounting those XLR to do.

I'm always happy when something works the first time!

Regards, Ethan

 

[evm1024]

How much commitment?

Very cool. I was considering getting a Seventh Circle or a Five fish preamp kit, this however looks pretty cool.

-josh

Hi Josh,

I think that the instrument amp based pre's sound much alike. Some differences but all in the same ballpark. The Fivefish (which I've never heard) prehaps represents the top 1% of instrument amp based preamps and would be a very nice pre and a DIY starting point. If you just want a pre of this type/sound then the DMP-3 gets you most if not all the way there. (unless you get the transformer based 5fish pre which colors the audio).

The 7th circle stuff is way cool and is a step above instrumentation amp based pre's. Weather it is the API clone or the Twin Servo you will get an outstanding pre. Good support and good kits. hard to go wrong.

The Great River pre is an outstanding pre that ranks up in the top 5% of all pre (people who want to quibble numbers should go to the end of the line. The number does not matter)

But it is also a bit more of a challenge in putting it all together. No company behind it. Just a bunch of DIY biffs and the designer willing to support them. (The artwork for the PCB came from Dan Kennedy so it is a proven PCB from Dan's production runs. We owe him a debt of gratitude).

Not saying not to do it. Just saying that is is not a kit and requires more commitment and skill to get it done. But because it is a proven design you can achieve success. You can learn a lot and have a great Pre afterwards.

Regards, Ethan

 

[mshilarious]

I don't wanna be mean, but at the resolution of the .jpg, the distortion on the unit could be 0.005% or 5%, and we can't really tell

 

[evm1024]

NP (no problem)

I don't wanna be mean, but at the resolution of the .jpg, the distortion on the unit could be 0.005% or 5%, and we can't really tell

You're not being mean, you are being an engineer

The photo is not an indication of distortion - in fact the trace width of this old scope is such that you might not see lots of things.

The photo is simply proof that it is working (not how well the bear dances but the bear is dancing!)

I'll get around to qualitative measurements later. Plus some sound samples.

Just consider it an "It's Alive" type of post.... And joy in the lack of smoke.

Regards, Ethan

Say, know anything about the Grace 101 design?

 

[mshilarious]

Say, know anything about the Grace 101 design?

No. But it seems to me that whenever somebody traces a discrete design, it gets spread far and wide pretty fast, so I don't know if anyone has done so . . .

 

[evm1024]

No. But it seems to me that whenever somebody traces a discrete design, it gets spread far and wide pretty fast, so I don't know if anyone has done so . . .

There is one post out there that has it as an instrumentation amp design. I'm trying to find out if that is true.

Thanks, ethan