looking for "Bogen MM-S Mic preamp Module" Schema

hi folks, I just won an e-bay auction for 6 Bogen MM-S mic preamp modules and I need a schematic for them so I will know how to hook them up....i guess I"ll need to build a PSU for them so i will need to know the supply voltages and what the pin connections are ...(i believe they have a card type of interface simular to a PCI card)....

i looked all over then net for one and all I could find were the preamp specs.....

here are the specs that I found.....

MMS
The transformer-balanced, low-impedance microphone pre-amplifier shall be a Bogen Model MMS, or equivalent. Input sensitivity for rated output (100mV) shall be 250mV, and maximum gain shall be 52dB. The frequency response shall be 20Hz to 20kHz, ±1dB, with distortion less than .3%, and noise floor of -75dB. It shall have screwdriver-adjustable low- and high-frequency cut filters providing an action of -3dB @ 400Hz and @ 5kHz, and a separate gain control with an adjustment range of 25dB.
The module shall be capable of providing phantom power to a condenser microphone, enabled by means of a printed circuit board jumper. Screw terminals shall be provided for microphone connection.



I know these probably aren"t the best Mic preamps but I got them for cheap ($1 for all 6) and I need a little color in my recording chain so i figured these might add a bit of transformer Mojo and seem like a good project......

thanx for any help you can give.....


Cheers

You should edit the thread title to read "Bogen" instead of "bogden." People are probably wondering who this bogden company is. :green:

Those specs are confusing at best. They seem to be mixing measurements with: "Input sensitivity for rated output (100mV) shall be 250mV" Input sensitivity and output level expressed together this way is silly, and doesn't say anything useful. At first glance I read it as the output is smaller than the input; 250mV in = 100mV out. :? Then I realized they are specifying sensitivity without enough data to place it in context.

This page lays it out, scroll to "Preamp Input Overload":
http://www.rane.com/note148.html

The point I was going to get to is that Bogen gear of the era these are likely from was designed for low level microphones, and tend to overload very easily. You will probably need to rethink the circuit values to lower gain and increase input overload threshold if you want to use it for anything more than a fuzz box. But for the price you paid, who cares. It could be a fun project, or a rad distortion effect.

thanx....I guess i made a typo....

yes I know the Specs don"t really make any sence, I think they might have been Translated from another language in which case i think there meaning gets lost in translation.....

I know the specs aren"t very good , especially then noise specs But i was thinking of maybe swapping out the transistors for newer lower noise Ones (i believe it is a discreet design) plus re cap them....At the very least i can use the transformers for another project......

I guess I"ll wait till they show up and then I"ll figure out what i will do with them.....

I"ll post back with more info when they show up.....

Cheers

hi, well my preamp modules showed up, They look to be in very good condition and i was also able to get in contact with bogen and get the pinout info .....

these modules run off of 24v DC single supply and have old NE5532 op amps in them and produce 24v Phantom power for condenser mics...the inputs are transformer coupled but the outputs are unballanced and don"t have an output cap....

So here is my question , since there will be several volts of DC offset because of the single supply Should i add a ouput cap? and what value should i use??


Thanx

yes, add an output cap...these were probably part of a p.a. mixer and not meant to drive a line out...show some pics--I used some bogen input trafos in a g9 with much success.

Those modules aren't that old - somewhere from the early 1990's and meant to be used with a 150 to 600 ohm mic. Transformer input, standard 5532 gain stage. You should be able to trim the offset , but I would still use a cap on the output. Don't expect miracles from the input transformer; they aren't anything stellar.

Since there will be several volts of DC offset because of the single supply should I add an ouput cap?

Click to expand...

Are you sure there isn't one allready?

You should be able to trim the offset.

Click to expand...

You trim a 12 V offset, right? :wink:

Samuel

You should be able to trim the offset.

Click to expand...

You trim a 12 V offset, right? :wink:
Samuel

Click to expand...

Brain is dead today. Quite right you are.

Well there is no Offset trim on these modules and no output cap, there is a 10uf from the output to ground but no output cap......

These are probably from a PA or mixer so they probably had an output cap in the summing stage.....

What would be a good Cap value for the output cap ?? I have seen anywere from 220uF to 470Uf used on the outputs of NE5532 opamps so is 470uf cap a good choice??

Thanx