Topic: mic preamp chip upgrade for Beyerdynamic MV-100 pre

[teamakg]

if you need somewhere to host the before and after sound sample files let me know.  i can host them on my school site.  great speeds and lots of space.
george

[leegeddy]

the BurrBrown INA217 chips FINALLY arrived today after weeks of backorder.

when i desoldered the original Analog Devices SSM2017 chips, i added a low-profile DIP socket for each chip so i don't have to solder the new chips in. just need to push them in snuggly, and they can be removed easily w/o desoldering.

-interior of Beyerdynamic MV-100 w/ BurrBrown INA217AIP upgrade.


-BurrBrown INA217 (top left); Analog Devices SSM2019 (bottom left); low-profile DIP sockets (top right)


i'm going to try the modified pre out at few Claypool shows for some comparison.

marc

[dklein]

hey - this is a cool project.  It would be nice to hear something controlled where it's the exact same scenario except the chips.  I guess you could record stuff at home.  Or maybe take a signal from 1 mic, feed it to both left and right on the pre and have a different opamp on each channel.

[morst]

before i do the replacement, i'll record some test tones and some music with the stock mv100 and do the same for the modded version, all done with the environment controlled as best as possible.

bump for a cool thread?  I am now thinking about modding my MV100.  . . got samples?  are you happy with the mod?  any notable difference in sound that you can describe?

 

and +T for your industriousness. . . now that I can award tix! 

[leegeddy]

before i do the replacement, i'll record some test tones and some music with the stock mv100 and do the same for the modded version, all done with the environment controlled as best as possible.

bump for a cool thread?  I am now thinking about modding my MV100.  . . got samples?  are you happy with the mod?  any notable difference in sound that you can describe?

 

and +T for your industriousness. . . now that I can award tix! 

backatcha tom. +t

i started this project back in mid '04 and didn't save any of the test tracks. i have 2 mv100 and modded one and not the other and recorded the same material by blasting my stereo.

i don't represent that there is a night/day difference between the old ssm2017 vs the ina217 chips, as the ssm2017 IS/WAS a good chip....simply outdated and replaced by ssm2019.  the overall effect was lower noise and more clarity. again, said differences were not night/day, but noticeable.

on a different note, i noticed a large difference in s/n when i went from the fixed +20db gain down to ~7db.

marc

[§†∑∫åµÞ≥¥]

I have one of Marc's mod'd MV100's as well (Burr Brown chip) and think it sounds great -- tight bass, soothing mid's.... however, since I didn't have the unit before the mod, I can't comment on the difference in sound. It sounds better than the stock UA-5 though imo.

[Todd R]

i dont understand exactly how what he did to the box reduced the gain; i was hoping someone else would have some insight as to how marc did it and chime in. 

I modded my MV100 to have something like 11db-18db-29db gain rather than the stock 20-40-60 gain.  I did it 6 years ago or so and of course took no pictures or notes, so I don't recall the details too specifically.  You should look at the SSM2017 spec sheet (and/or the INA217 spec sheet) to get the specifics, but there is one pin on the SSM2017 that sets the gain level based on the size of the resistor (amount of resistance) on that pin.  So you will need to change the gain resistors to change the gain.  The spec sheet should have info detailing what level of resistor leads to what amount of gain.

The resistors are little surface mount jobbies, and can be seen in the pic above.  There are resistors for one channel below the red capacitors, and I think the resistors for the other channel are up in the top portion of the pic mixed in among the capacitors (double check all this, it's been years and my memory may not be that good).  You'll need to trace out the circuit (or find a schematic from Beyer) to find out exactly which resistors correlate to what.

The trick is, the design does not have 3 different resistors selected by each setting of the 20-40-60 gain switch.  Instead, it is something like this:  resistor A is selected as the gain resistor when the gain is set at 20.  Then the gain "resistor" for the 40 setting is actually Resistor A in parallel with Resistor B.  The gain "resistor" for the 60 setting is Resistor A in parallel with Resistor B in parallel with Resistor C.  It makes resistor size selection a bit of a pain.

FWIW, I was able to replace the surface mount resistors with regular axial thru-hole resistors, by cutting and shaping the resistor leads appropriately and soldering them to the surface mount pads.  Either way, use 1% tolerance resistors and hand match them so both channels get exactly matched resistors, otherwise the gain in one channel will be hotter than the other.

Good luck!

[kgreener]

fwiw i recall Chris Church recently saying he'd love to try modding an MV100:

http://taperssection.com/index.php/topic,80697.msg1075961.html#msg1075961

[Chuck]

The DMIC-20 uses the ssm2017 also. I have a DMIC-20 and I replaced the stock chips with INA217's. I might try the THAT chips to see if it makes a difference. The gain setting on those instrumentation chips is cool. The more resistance you put in that loop, the less gain you get. Just the opposite of how a negative feedback circuit works with op-amps. The effective max gain is around 60 db with a very low resistance value (tens of ohms) in that circuit.

[Todd R]

The DMIC-20 uses the ssm2017 also. I have a DMIC-20 and I replaced the stock chips with INA217's. I might try the THAT chips to see if it makes a difference. The gain setting on those instrumentation chips is cool. The more resistance you put in that loop, the less gain you get. Just the opposite of how a negative feedback circuit works with op-amps. The effective max gain is around 60 db with a very low resistance value (tens of ohms) in that circuit.

Ok, good to know Chuck.  If that's the case then my directions above are probably backwards.  That is, it sounds like the 20db setting would be Resistor A || with Resistor B || with Resistor C.  Then 40 gain is Resistor B || with Resistor C, and 60db setting is just Resistor C.  Again, don't assume my memory on the spefics is right -- trace things out and double-check.  But they definitely use a design that uses the resistors in parallel with each other, rather than 3 different and separate resistors for the three different gain settings.

[Chuck]

Here's the data sheet on the INA217. It includes a chart that gives values for the resistors that set the gain.