Bearcat 412 Discrete Mic Pre Kits FEELER

FEELER!!

Bearcat 412 Discrete Microphone Preamplifier Kit:

PRE-ORDER OFFER!!! Please read full description

$1200 USD for full kit (EVERYTHING YOU NEED – except the audio transformers)  


YOU CAN CLICK ON THE PICS TO SEE THEM LARGER...









Hello, I have been using this forum for years but have never been an active poster.  My brother and I live in Montreal and have been building DIY projects both for my studio and with students and colleagues for about 5 years now.  I’ve done all sorts of projects from 1176s to IC mic pres, SSLs, Great River Pres, LA2As, API 553s & 325s, Twin Servos, Pultecs, DI boxes, summing busses etc.  This discrete microphone preamplifier is our most recent project.

This kit was designed specifically to mimic the behavior of the pre that it resembles and intended as a vehicle for teaching about mic pre-amp design and behavior.  In development, it was compared to an actual unit at every step of the process.  It was designed to be assembled by students and is simple and easy to put together. It should take someone with limited soldering experience only about 12 hours to fully assemble and test the entire project.

I have always supervised the assembly of the kits and so I do not currently have a manual, although one is under development. This kit was not designed to be marketed publicly but I have 10 additional units and I need some cash flow to continue prototyping some new designs I am working on.




It turns out its not much more trouble to make parts for 40 units rather than the 16 I originally needed. Eventually, we ended up building 10 more so there are 26 of these units out in the world: working well and kickin’ ass. 26 pretty much eats up my “friends and family network”.  I want to sell 10 of these in order to liquidate my investment in these and put that money into prototyping some future projects.

The unit is somewhat…um, well… “cosmetically derivative.”  It was never meant for public sale, though, even with it’s similarities, it does have it’s own style – particularly the attractive 8-segment VU meters.





It actually comes with more than what is seen in the picture...

The only thing you will need besides the kit are the Audio Input and Output Transformers.  We used the Ed Anderson transformers (EA2622 Input and EA2503 Output) available from Jeff at Classic API:

http://classicapi.com/catalog/index.php?cPath=21.  

These are the transformers we used to test and tune the response of the pre so I would recommend you go with them but I have also had good results with the Sowters which can be mounted in just fine.  I have not tested it with Cinemags but I am sure they would be great (the current 3124 uses a Cinemag input transformer). Still, I can’t guarentee they would fit because I haven’t tried myself. We will not stock the audio transformers because we would need to pay import duty on them to bring them into Canada.

BESIDES THE AUDIO TRANSFORMER, THIS KIT HAS EVERYTHING:

• 4x Bearcat 412 mic pre cards
• 4x GKL522 Discrete OpAmps
• 4x 8-Segment LED VU Meters (surface mount components pre-stuffed)
• 1x Ultra Low-Noise Suzlter-Borbely Power Supply Board
• 1x 48V Phantom Power Board
• 1x Over-spec’d Toroidal Power Transformer (110 or 220)
• 8x Knobs with color inserts
• ALL Panel Mount XLR connectors (pre-wired) and PEM - even an IEC
• Custom Made Steel and Aluminum Enclosure with all the holes pre-drilled
• The Beautifully Silk-Screened Faceplate with the BEARCAT logo
• ALL the hardware, switches, pots, resistors, caps, LEDs, connectors, and harness wiring








Remember, you can CLICK on the pics to see them in higher resolution







FEATURES:

• Minimum Gain (without Pads): +24dB
• Maximum Gain: +60dB
• Clipping Level: +32dBu
• EIN (20-20kHz, measured with +50dB of gain): -111dB
• 48V Phantom Power available on all channels with LED indicator
• -20dB input PAD
• 8 segment VU meters showing  -28 -18 -12 -6 0VU +6 +12 + 24
• Output Pad switch-able between 0, -6, -12, & -18
 **the output pad allows one to “push” the OpAmp and the Output Transformer harder without overloading your A/D converters.  


Here is the frequency response of the Bearcat 412 compared with that of another popular 4 channel mic pre:



If you notice the scale, you will see that there is about a ½ dB difference at 20Hz – otherwise the two curves are identical.   This VERY slight difference is the result of the EA 2622 and something we could not adjust for without changing the transformer.  Even with this slight difference, the tone and character of the pre and excellent and very representative.

I’m looking to get $1200 USD per kit.  I only have 10 kits to sell.

IF YOU ARE INTERESTED IN PRE-ORDERING THIS KIT, LEAVE A MESSAGE HERE.

We need capital to stock some of the more expensive components such as the Pots, Switches, Knobs and Connectors.  In order to sell these I need to collect at least some money in advance.  Most likely it will be about a 5 week turn-around depending mostly on the knobs but also the time to create a manual and part-out the kits to ship.

$1200 is less than other available kits for 4 channels of classic American mic preamplification.  Even with the additional cost of the audio transformers ($288 USD for the set from ClassicAPI).  It’s half the price of a comparable commercially available mic pre… And I SWEAR…  * to all that is holy *… this mofo sounds f’n fantastic.  It looks great, it’s easy to build, the VU Meters are pimp.  You WILL be satisfied or I WILL BUY IT BACK FROM YOU.

I should also say something about the PSU --  Power Supplies are surprisingly important in the overall performance of a piece of gear -- This is an Ultra-Low Noise supply that uses dual stage regulation.  After the first stage, there are noise-canceling, low input-offset-voltage OpAmps, followed by a second regulation stage that sets the supply voltage.  There is also a completely separate regulator for the VU Meter’s LEDs.  It is essentially a Sulzer Borbely design adapted for bi-polar operation and it measures better than any other power supply we compared it to (except our bench-top supply) in Noise-Filtering and Line-Rejection.





If I get enough response I will move this thread to he White Market and post a link to the store I just started at:

http://market.diyrecordingequipment.com/



Also, I have seen in the threads that 3nity has recently begun manufacturing his discrete OpAmp mic premap boards again as well.  You should check that out too:

http://www.groupdiy.com/index.php?topic=43484.0



I’m hoping that the market for these pres will not be over-saturated.  As I mentioned, I’m only really selling these off because I need capital to continue prototyping new projects.  I’m stuck under this investment and I really want to move forward with some projects this summer.

THERE ARE ONLY 10 KITS AVAILABLE!

This is just to see if there is interest.  I promise the units to the first 10 people who post HERE that they want to buy them and that they are willing to PRE-ORDER.  Once I have enough pre-order commitment to cover my parts costs, I will set-up the sale at http://www.diyrecordingequipment.com/ and begin assembling kits to sell.  Once again, my estimation is 5 weeks from collecting the funds to being able to ship.

Feel free to PM me or leave a message in this thread if you have any questions.

** We also have GKL522 OpAmps for sale in the WhiteMarket. Check them out here:

http://www.groupdiy.com/index.php?topic=44491.0



Cheers!

Robert-Eric

Looking at the pics here I think I could get some better shots.  Check back again - I will try to update the photos in the next few days.

Cheers!

REG

The built in "post output transformer" stepped pad is a KILLER touch!  I generally use inline pads on the outputs for that - I like this much better 

Looks like a very nice and easy to build project.  I recently picked up parts for the 3nity Access 312, so I'll have to pass - but this does look like a professional project none the less...

Your students must LOVE your class  ;D

8)

Thanks Randy!

Just to let y'all know, I've had 1 person commit so far.  That means there are 9 left.  After I get 3 or 4 more responses I will begin ordering parts.

=e

Randyman... said:

The built in "post output transformer" stepped pad is a KILLER touch!  I generally use inline pads on the outputs for that - I like this much better 

Looks like a very nice and easy to build project.  I recently picked up parts for the 3nity Access 312, so I'll have to pass - but this does look like a professional project none the less...

Your students must LOVE your class  ;D

8)

Click to expand...

No kidding, I've been lucky enough to be there for the prototyping, saw this project go form a gerber to this finished product. Always nice to see Eric put another awesome DIY into the world.



Giancarlo

Randyman... said:

The built in "post output transformer" stepped pad is a KILLER touch!  I generally use inline pads on the outputs for that - I like this much better 

Click to expand...

Could you explain how this is done?  Maybe with a schematic?

Absolutely, It’s just a T-Pad.  Which is basically a symmetrical voltage divider.  Same sort of pad that is used for the -20dB input pad.

Check it out here http://www.uneeda-audio.com/pads/

The Pad sits after the output transformer.  This allows you to push the op-amp and the transformer harder.  OpAmps will behave differently at different amounts of gain due to their inherent gain-bandwidth relationship.  This is a big part of why some engineers feel their pres have a “sweet-spot” in their gain-range.  The output transformer will also saturate a bit and have more distortion when more power is applied to it.  This gives a particular sound that can be desirable in certain applications.

Because many engineers these days use their mic pres straight into their A/D converters with no additional intermediate gain stage, they are locked into the clipping point of their converters which is, more often than not, much lower than the +28 dBu that the A.P.I 312 is capable of. 

Pushing the pre a bit harder gives a more aggressive sound and the pre handles transients differently when it is running near its limit.

You can easily build yourself a pad out of resistors and put it into an XLR connector but this pre puts the pad on a 4-position switch making it easier to try different gain combinations.

Cheers!

=e

Hey everybody!

Just a heads up that I updated some of the pictures.  They are still not uber-glamor shots but they'll give you a much better look at the details of this project.

I'm using picmatic to host so you can click on the pictures and see them full size.

enjoy,

=e

I'm really interested in this kit!  Are any still available?

still have them available?

I would like one kit???

+1 for me as well if still available!