Great River MP-2 , info, schematics & discussions

[vgdb]

Hi vgdb!

I would say that the MP-2 (in kit form) is a medium level project.

Hello Sredna,

Thanks for encouragements. Soldering is not a problem for me. My only concern would be debugging if there is a hidden "electronic" problem. But so far, I had luck that those debuggings didn't need too much electronic competence (and I hope I will improve my electronics knowledge with time...).
So, I will try to build this pre as soon as I can get an answer from Ptownkid. At the moment, he doesn't seem to take care of this post, neither of his site mails...

What about the PSU for this GR MP-2 ? Did you build one ? If yes, did you use Dan's schematics or what ?

Thanks again (danke schön!)

 

[vgdb]

I'm french

it's ok nobody's perfect...and you're not alone! 

the green pre is really basic to do, even more if its a kit!
the gr2 will cost you more in part (output tx) than the green who is transformerless!

Hi diyfanatic,

As far as I heard, it seems to me that the preamps I prefer are those using transformers, it seems to sweeten the sound ? The transformerless amps I have already used are very good but sound a little bit agressive. This is the reason why I thought a class A preamp with transfos would provide more "sweetness"...
And the cost for the GR MP-2 seems to be reasonable...
But as from now I didn't hear any of these pres so it is not a founded point of view... This is why I asked my question!

I heard your production, if they are recorded with DIY material, that's very encouraging (tell me which pres you use ?)

Merci beaucoup  for your answer!

 

[Ptownkid]

Hey Vgdb

There's a lot of documentation to help you get through the MP-2 project. As long as you take your time and check components as you go, you should be fine.

The psu doesn't have to be anything special, as the power regulation is contained right on the board itself. If it helps, I can probably get s simple psu together for you.

As for the costs, you need the following outside of the kit
- Switches (Elma 1x24)
-Input transformer (output is optional)
-simple psu and power transformer
-case
-knobs

BTW, your english is perfectly fine!

 

[Sredna]

@ Vgdb

One problem with debugging the MP-2 is that the PCB is double sided, slightly
harder to desolder. (for me at least)
If you're careful with the poulation of the PCB and check everything twice, you'll have no problems as this is a proven design!

I would also consider the MP-2 as a rather "clean" preamp suited for acoustic/klassic music, think "neutral".
It might not give you the "colour" that you seem to look for...

The PSU is easy. I used the one from Dan's schem but without the peak circuit.
To get the 48V for phantom I used two capacitors as in the SSL 9k preamp PSU. (search for that!)
I'll try to draw a quick sketch when I get time...

By the way, ptownkid is not more responsible for this thread than you and me.
He just happen to sell a kit for this project. But as he already pointed out, this thread
already holds a lot if information.

Good luck,

Anders

 

[vgdb]

BTW, your english is perfectly fine!

Thanks you, Ptownkid. You know, it takes me some efforts and time to write in english!

- As far as I understood, I will begin with commanding 2 kits and 2 switches on your site, as recommended.
- As I told in a former post, I am a beginner in electronics, so if you have recommandations for a good PSU that suits for Europe, your help will be welcome.
- Do you know addresses or where I should search for I/O transformers ? The only address I found in my first searches is Edcore WSM 15k/600 for output and MX series (1 or 2 ?) for input, but it seems not everybody appreciates these transformers, I am a novice on this particular point... People seem to privilegiate the Lundahl transfo for input, but I haven't found it at the moment and I don't know if the price is "reasonable"...

Thanks a lot for your help and great job, it seems, on this project.

Best regards

 

[Ptownkid]

I think most people used the cinemag transformers and they can be purchased directly from cinemag.

 

[okgb]

I highly recommend the Lundahl 1538 XL 's
i have a quad with both them & the cinemags and maybe
because i started with the Lundahl's i prefer them
Also went years without using the output xfmrs , which
may add a slight color but i consider these pres
just plain solid & smooth , not bright or warm or whatever
you just plug in and never worry about it
i use mine mostly for classical [ and choral ] and then next
for Drum overheads makes a decent bass D.I. as well .

Don't know that i would think of it as a beginner project though

 

[vgdb]

plain solid & smooth , not bright or warm or whatever
you just plug in and never worry about it

Thanks okgb for your advice.

Smooth is the exact word I was missing. I have a very good Swedish pre (Line Audio is the maker) at the moment, very neutral. but I find it a little bit aggressive sometimes (especially when recording voices), even if this can be corrected with EQ-ing.  I would like not to worry about the sound and I miss the smoothness which is, I think, a characteristic of very good preamps...

Don't know that i would think of it as a beginner project though

I hope I can face the difficulty... maybe with a little help some of these days when the kit arrives... I just passed the command on diypartssupply when your reply arrived !

Thanks a lot to you and everybody who answers on this post. It really impress me and makes me feel confident !

 

[Sredna]

Ok, here goes:

It's easy to breadboard as all regulation is made on the preamp PCB.

I have a very good Swedish pre (Line Audio is the maker)

Funny that you mentioned that, I use their CM2 and CM3 microphones.

/Anders

 

[vgdb]

Hello Anders,

Thanks a lot for your schema. As far as I can see, you're drawing late ! This is of course a big help for me. I will go and see my local retailer for choosing the right type of capacitor (I see the 680 uF is not polarized, I suppose it's not the same type as the others). I think I can't go wrong with your plan.

Funny that you mentioned that, I use their CM2 and CM3 microphones.

Really, that' funny ! I already have 2 Oktavas MK-012 and I am wondering if I take 2 other ones or give a try to the CM3 (I asked for a quotation in a swedish shop but still, I'm not shure!). Your advice would be welcome! In my opinion, the Line Audio 8MP (I have the older OMP version) is really a great preamp, especially for its excellent Quality/Price ratio. But as I told you, I find it a (very) little bit too harsh sometimes on my large diaphragm mic (Nevaton 416). I hope the MP-2 will correct that...

Once again, lots of thanks.

Regards,

 

[Sredna]

Late drawing = wrong drawing  :-\

The 680 uF cap for the phantom voltage is of course a normal electrolytic.
Drawing is now corrected.  ;D

You can get the CM3 for about 100€
http://www.jam.se/produkt/Mikrofon-och-tillb./A27116-Line-Audio-Design-CM3.jam
It has an electret capsule very similar to what sits in a Audio-Technica ATM 31 R.


/Anders

 

[vgdb]

Thank you Anders for everything.

With your schema I finally "understood" Dan's PSU schema. But at first when I read it, it looked like chinese to me (I don't speak chinese!).

Thanks also for the swedish link. Good night if you're still awake  .

 

[vgdb]

So Here it goes !

I received last week all the parts for building the supply, the box, the lundahl Xfrmrs and the week before I received your kits, Ptownkid.
By the way, thanks a lot for the good job and the quick sending of those parts.

I took some time reading this topic and now I'm checking the parts in the kit. I have a few questions less, that I am not shure I will find the answer by myself. Here they are :
- first , about the K389. I read in this topic the original is the 2SK-389 and there is also a K389 which would probably not share the same pinout. As far as I could see, mine are labelled "K389". I would like to be shure the board I have is corresponding to the pinout of this chip (7 pins in two lines, 4+3). Can you please confirm ?
- second, about the 1N5251. I checked all the other diodes which were labelled exactly as the Bom specifies. But for those D1 & D2 diodes, I find two little "cristal" diodes which are, as far as I can see, labeled "251B" or something like that. Do you confirm these are the D1 & D2 1N5251 diodes ?
- third, I couldn't find if there is a difference (and which one) between TN2E-24V which is specified on the BOM and TN2-24V (without the "E") which is the label for the two relays I have in the kit. Is there any difference or can I use them directly on my board ?
- just to finish : everything conforms to the BOM in your kit (thanks a lot, this is a great job!), except a (very) little point : I miss the two plastic "female" parts of the J6 and J8 connectors. I have the male part (to be soldered on the board), the 5 terminals to clip on the cables, but no plastic female connector to put those terminals in... This is for the two 5 pins connectors in one kit. Could you put those two little parts in an envelope and send them as a letter for me ?

Thanks for taking care about that.

And oh, by the way, may I add my thanks to the others for Dan who shared his design and experience in this topic ? I hope I will measure up!

Best regards,

 

[Sredna]

Hi!

- The K389 is the correct part. The one with different pinout has a different designation.

- I just built two kits and also noticed the diodes, I used the provided ones ("251B") and it works.
  Sometime the designations on very small parts are shortend. (like on K389 = 2SK-389)

- I didn´t notice the relay designation difference, mine are working. I can´t check now if they´re TN2E or TN2...

Best,

Anders

 

[Ptownkid]

All the parts are the right parts, and yes those are the right diodes.

I'll get the missing connector out to you.

 

[vgdb]

Hello Anders and Ptownkid,

Thanks for your quick and effective answers, as usual 8). I did not worry too much and supposed the parts were the right ones, but I wanted to be sure because there is enough "risk" with my little experience, not to cumulate with other uncertainties...

I'll get the missing connector out to you.

Tanks a lot, Ptownkid. I just would like to recall there are 2 of them.

Best regards,

 

[Ptownkid]

noted

 

[lsskmki]

Finished mine last weekend. I've recorded some tracks with it during the week and it seems to do it's job nicely. Maybe I expected these to have just a little more 'character' to them, but these are rather clean and that's good. I have other stuff I can use if I need more color.
The top end seems quite bright, but not in an ear piercing kind of way.  I think this is a sign of a very good preamp.

Thanks to Ptownkid for boards/kit. I think all parts were there and I was happy to notice the parts being great quality!
And huge thanks to Mr. Kennedy for giving people the chance to build these in the first place!

 

[vgdb]

Hello,

I finished one week ago my first GR MP-2 channel built with Ptownkid's kit, completed with a home-made power supply built on Anders (Sredna) schema provided in this thread.
I still have a very little hum I can hear at higher levels when "recording silence" (which I don't practice so often). This obsesses me a little, but the S/N ratio is still good enough for forgetting this (grounding ?) default when recording. I hope I can fix it.

As far as I can hear, the result is really good. Compared to my Line Audio preamp, the mids and highs are more subtle, airy and smooth. I did a few quick tests and the improvement is subtle, but makes the difference : the recordings sound "natural" and will improve my recordings. That's really cool!

Thanks to all people for encouraging me to start this project which made me learn a lot (even if I am still not able to understand the heart of this electronic. I hope I will one day). Thanks especially to Ptownkid and Anders for their direct support, thanks to Greg Boboski for starting and supporting this thread and of course, huge thanks to Mr Dan Kennedy for sharing his work and experience. I don't know the english for it but "chapeau bas" (hat down), M. Kennedy !

I will go on building the second channel. I will also try implementing the peak level / phantom power leds because I find it really useful.

To be continued...

 

[vgdb]

... Next step : the quad version !

I used the jack input with my classical guitar and it sounds wonderfull! I just passed command to PtownKid for two more kits to put in the box...
What a wonderful tool for making music !