looking for a DIY mic pre schematic....

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thajeremy

thajeremy

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I recently found out that one of the engineers where I work is into electronics...and also a pretty good drummer.....After finding out about his electronics experiance, we began discussing the DIY mic pre's that I had seen here on the board and we decided to build one. My job was to find the plans and bring them to work where he would look them over and start gathering parts....only thing is that I can find the plans I was looking for....I remember seing plans for a DMP3 and thought that would be a good one to start with since I remember reading that it was rather easy...at least for someone who is familiar with electronis. I have been using the search function but have not been able to find the schematic that I was looking for....anyone have any suggestions? or even schematics for other simple pres that we can start with?

thanks guys
 
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i think some peeps on here have made the green pre (maybe minion?) another awesome project could be to rack and connect a power supply to some raw yamaha pm1000 modules.
if you get ambitious you could do the gyraf 1176 or ssl clone.
i believe you can get schematics, etched pcb's, rack faces and other diy goodness over at the prodigy pro forums (i've visited, but don't rememeber the exact address and am clueless w/ diy electronics)
 
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At the JBL website they have some schematics for some nice sounding pre's that are very simple to build. They are transformer based, thus, going to have a certain "character" to the sound produced.

I would pass on the Yamaha PM 1000 modules. They are "claimed" to be a "class A" design, but not really, and frankly, they aren't all that interesting sounding in my opinion. Is it better than many budget pre's of today? Probably. Is it worth spending a lot time and money on? NO!!!
 
minion gave me some excellent resources and information for the green pre stuff.

+kudos to him.

i've been putting it off now, i sourced out my parts but i got some other projects sitting around that i want to finish first.
 
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The PM 1000's are indeed a transformer coupled, class A, single ended , discrete preamp. All of those terms are used to describe the type of circuit, not the quality..you can have bad sounding class A devices and great sounding Class AB devices ..Neve 1081 ring a bell? They sound better than most prosumer junk but not as good as real high end gear. The EQ on the strip is a passive, inductor based design that sounds pretty cool. They run on 44 volts dc so they have way more headroom than modern IC based lowend mixers and pre's that generally fall in the 12-18 volt range. They can be had pretty cheap so racking a pair is good practice before you delve into anything too pricey. What kind of pre's are you looking to build? There are tons of schematics, kits and info at the Prodigy Pro Forum. The API 312 circuit is about as simple as you can get and could be thrown together by a knowlegable tech pretty quickly and easily....

Cheers,
Ray
 
Why set your sights so low?

thajeremy said:
SNIP! I remember seing plans for a DMP3 and thought that would be a good one to start with since I remember reading that it was rather easy...SNIP
Click to expand...

There are quite a number of mic pre schematics out there. Here is a collection:

http://www.prodigy-pro.com/forum/viewtopic.php?t=20038

I'm not sure if you want the resulting pre or if you are more interested inthe process of building the pre (for the experience or understanding). Here are some observations....

The amount of effort to build from a schematic is significant. I just built a preamp power supply from this JLM schematic

http://www.jlmaudio.com/ACDCVer2sch.pdf

It was quite a bit of effort and I really should have purchased the PCB from Joe Malone (JLM). Having the PCB would have reduced the build time by a factor of 3 or 4 at least. Plus it would have reduced the chances of errors.

The DMP3 is a nice pre (I have one) don't get me wrong. However the effort required IMHO to build one from a schematic is significantly greater than building a pre that you have a PCB for. JLM, SCA and others make nice mic pre kits. You can build the:

Baby Animal http://www.jlmaudio.com/Baby_Animal_Mic_Pre.htm

A JLM twin servo: http://www.jlmaudio.com/JLM99v.htm

Or any number of vintage clones from SCA: http://www.seventhcirclestudios.com/SCA/SCA.htm

Both of these sites have schematics.

So for a few dollars more you can have a killer preamp for the same effort. I should add that putting the pre in a box is near half the battle. This is where the kits come into their own....

Here are some photos of the 1) breadboarded power supply (+-24 V and 48V) 2) a Jensen 990 Discrete opamp 3) the 2 channels of Jensen twin servo I'm building on a JLM twin servo PCB.

Hopes this helps! :D
 

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I'm building 4 channels of JLM baby animals at the moment, the first two are up and running and they sound pretty fantastic, OEP input xformers and the JLM99V opamp, the other two will have Lundahl xformers and the JLM hybrid opamp. It's a bit more paint by numbers than your first post suggested you were after though.

I built a 2 channel green pre as my first DIY project, very nice!

DSC00502.jpg


http://1176neve.tripod.com/id10.html
 
evm1024 said:
The DMP3 is a nice pre (I have one) don't get me wrong. However the effort required IMHO to build one from a schematic is significantly greater than building a pre that you have a PCB for. JLM, SCA and others make nice mic pre kits. You can build the:
Click to expand...

Agreed. Great little preamp, but they're so cheap that building one would make no sense at all. If your going to build something, build something that you can't buy for a few dollars more. The SCA kits are a good way to end up with preamps that comes damn close to the real thing, where the real thing will set you back big bucks.
 
I will layout the costs with an API-ish 312..

Perfboard- 10$
transformers- 100-150$ depending on your tastes
John Hardy 990c opamp-60$ (or forssell 993 or JLM)
Assorted electronic parts (caps, resistors, potentiometer, diodes etc..) 20$
power supply pcb 13$ JLM Audio
power transformer, 24 volts ac, 500ma...about 20$
chassis....anything you can scrounge will work great..I like to use old 2 space EQ chassis' with balanced ins and outs..surf evilbay and you can get one for about 20$..use the key words broken or repair since you are not interested in how the eq works....Get a new aluminum faceplate made... as nice or lowend as you like.

Total: about 280-300$

Now you are playing with the big boys...

Cheers,
Ray
 
Jensen Transformers will send you a book full of designs. They will also sell you all the parts minus the case and power supply. I had built 6 dual op-amp/transformer isolated units built that are excellent - clean, quiet, tons of headroom, and transient response for days.
 
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