M-AUDIO Midiman AudioBuddy Mods

[bxt403]

I've been in the market for a cheap mic preamp that is or can be equipped with a NE5532 for my summing bus.  Ideally- it'd go before a racked stereo HL Studer 961 channel strip for stereo EQ adjustments (that's equipped with Signetics 5532s).  The rest of the equipment in the signal chain is also equipped with Signetics 5534s or 5532s but the preamp needs to be consistent sounding with the Studer channel strip. 

The only option I've found (without spending upwards of $400 CAD) is the M Audio / Midiman / M-Audio Audio Buddy that can be modded with the JRC/NJR SIP equivalent of the 5532 after finding a post on the Tape Op message board https://messageboard.tapeop.com/viewtopic.php?t=38520  that describes modding one but has a dead link to the picture and lists:

"change the red circled caps to 47uf/50v or higher (63v if you can fit them)
change the blue circled caps to 22uf/25v
change the yellow cirled caps to 100uf/25v
change the green circled caps to 470uf/35v or higher"


There's another website that deconstructs the Audio Buddy at http://www.audioimprov.com/AudioImprov/Preamps/Entries/2012/7/21_Reflections_on_the_lake.html

The Ed Anderson post is missing the photograph so I'm wondering which values go where.

W.r.t. the  Audio Improv website:

It seems the Audio Improv site missed the 2 x 100uF 25V capacitors (it lists 16 but there are actually a total of 18 electrolytic capacitors in the unit).

Are the "red" 47uF 50V or 63V caps the 4 x 10uF 50V  Phantom Power capacitors?  The Tape Op post says not to touch the four phantom power capacitors so I wonder where else a 47uF 50V capacitor might help.

Are the "yellow" and "green" values unchanged: where the "yellow" 100uf 25V are the 2 that aren't mentioned on Audio Improv and the "green" are the 4 x 470uF 35V for the +/- 15V supply derived from the 9VAC wall wart?

That leads me to conclude the 8 X 10uF 50V  (that's 4 per channel) are the "blue" 22uF 50V electrolytic.

If someone has the original picture or can clarify if my assertions are correct: that'd be great. 

The only mods I plan on implementing (thus far) are replacing the audio signal op amps to 5532s and changing all the capacitors to Nichicon UTT or 5000 hour UPW capacitors (that are the same as the original values installed).

It'd be great if someone who has the original picture can verify which values go where (with respect to the Audio Improv site). 

Thanks.

 

[bxt403]

I just finished the capacitor replacement (of all of the electrolytics with Nichicon UTT and 5000 hour UPW series) and of the four signal op amps (2 x NJM4580 at U2 and U6 for the mic and DI input & 2 x NJM4560 for the output at U1 and U3 were all replaced with 4 x NJM5532). The labeling for some of the capacitors and ICs is harder to find (especially U3- as the silkscreen overlaps with a nearby resistor's solder pad so you can only see part of the "3" as the "U" is covered by solder). The other hard to find silkscreens are either underneath components or overlapped with the silkscreen of a nearby part.

Taking apart the enclosure isn't too bad but I noticed there's Loctite for the bolts for the upper holes for the XLR input connectors. Some isopropyl alcohol and scraping the gunk off with a toothpick seemed to work with some elbow grease but it took me around fifteen minutes to half an hour to remove the nuts for the XLR.

The circuit board build quality is excellent but I'm a little floored with how good the mic preamp sounds with the upgraded parts (although the capacitors are still being broken in and are the same values as they were originally). I'm guessing the Ed Anderson values will help but given there haven't been any replies- I'm fine with the values M-Audio went with.

I've listened to my iPod 5.5 through a dock and to a CD player (through the DI input and through two JDIs into the XLR inputs, respectively). Plus- I wasn't aware the Apple iPod dock actually uses the convertor from the iPod 5.0. I'm a pleasantly surprised how clear and detailed everything is (thus far: without the capacitors having been broken in yet) but still can't believe that I paid around $100 for everything. I'm looking forward to trying it out on my summing bus.

 

[bxt403]

The preamp is still being broken in and it’s sounding smoother. 

In the mean time:  I came across the “$5 preamp” from the T.I. INA217 datasheet:  there are two 47uF 60V at the input XLR (before the preamp).

The datasheet for the THAT 1512 has a microphone preamp schematic with two 22uF  (no voltage  value) at the input. 

My educated guess is the 47uF  “red” ones are the two 10uF 50V at the XLR input (before U2 or U6)

Then the two “blue”  22uF 25V ones must be a 10uF 50V one after the mic op amp (U2 or U6) and another 10uF 50V before  the output stage (U1 or U3).  Since there’s no phantom power, I’m guessing it’s why 25V was used instead of 50V.

 

[bxt403]

After doing some research it looks like what I was actually looking for (w.r.t being something cheap compared to the SSL 9K) is the Green Pre (which is apparently based on part of the preamp section from the AMEK Mozart RN module but is  (according to a Gearslutz post) part of the module that WASN’T designed by Mr. Neve.

For the price (compared to the cost of the  SSL 9K)- the Green Pre seems to be comparable for a fraction of the price.

Don’t get me wrong: for the price (around $100 CAD for everything)- the modded AudioBuddy takes the least amount of effort but the result is only comparable to preamps like the FMR RNP; Rane MS 1B  or 1S (which is still good from a dollar to sound quality perspective).

The only other option I’ve found that’s in the ballpark of the SSL 9K or Green Pre (w.r.t. sound quality) is the Focusrite Green.  Still: the Green Pre looks to be best value (but doesn’t seem to be available any more as a kit or fabricated PCB).  So then is the Green Pre actually based on the Focusrite? 

Note that my research indicates the Mozart RN preamp section and the Focusrite Green only seem to be related to Mr. Neve tangentially (in that he appears to have designed neither).

 

[PRR]

The AudioBuddy was a fine $50 stereo preamp.

I ran one for years in a concert hall.

It has *real* design limits. Input hiss is high, input stage gain is fixed and high. I took a long look inside and knew there was no practical fix. In my specific case, high-output condensers over the front row, putting the mikes on -10dB pad was an excellent compromise for the background noise (the space was next to Rt18) and the acts we did (viola didn't clip, the loud jazz bands didn't mind).

I could see replacing a failed cap. But the ART stuff rarely fails, because their parts are not crap. That does sometimes force circuit simplifications to meet a BanjoWorld price goal; ART has learned this is the only way for a small outfit to stay in business.

Some of the small B-ringer $99 mixers (don't know which) have much better preamp topology, ala Greene. An old one may even be hackable.

 

[bxt403]

The thing is (regardless of how silly it appears)- I’m trying to “emulate” an SSL/Studer summing stage. The preamp doesn't need to be quiet- just consistent enough with my SSL DSP, Studer channel strip, and GSSL. My other preamps sound great but I need something that’s consistent with the rest of the gear on my output bus.

I’m using SSL’s Native with a passive combining network for the time being and am certain something like the Focusrite ISA Two or Focusrite Green 1 are probably my best (and most expensive) options. Otherwise I’ll need to rack a Calrec, Studer, or SSL module that’s equipped with two mic preamps. In hindsight: a stereo Studer channel that also has the stereo mic input option would've been the ideal choice.

All the options are still too expensive when all I need is something that will provide just enough “consistent” gain before a stereo EQ module.

To put it into perspective of a virtual API signal flow: I’d be using the Universal Audio Apollo with the API Vision plug-in on every channel. The analog output would have a CAPI ACA into an API 5500 into an API 2500.

I found a used Green 1 (and although it's tranformerless- it uses Phillips/Signetics surface mount 5532s in the signal flow) but I haven't been able to compare the Green 1 to the modded Audio Buddy.

Considering the total price- the AudioBuddy is still an excellent value. The parts (aside from the electrolytic capacitors & op amps), and especially the circuit board appear to be of extremely high quality (and there was no damage when I was desoldering components using leaded solder- which might not have been the case if I used silver solder).

The time it takes to mod (it took me around half an hour to an hour)- I’m uncertain if there are any other options that are as cheap and easy (that have or can be equipped with the 5532). The nice thing is that I can still use the Audio Buddy as a mic pre into SSL Native and the Green 1 as my summing amp.

 

[bxt403]

I noticed the Audio Buddy is now being sold as the Lynep Audio Dual Mic Preamp on eBay.

I bought (and modified) one. The circuit board is less sturdy than the M-Audio Audio Buddy but is still high quality.

All the Audio Buddy mods work with the Lynep but the included AC adaptor seemed to cause oscillations when I tested a phantom powered capacitor microphone (with the Audio Improv phantom power mod installed). Everything worked fine using an Audio Buddy power adaptor (and with a new one from a local electronics parts store).

I also noticed the LEDs are too bright (compared to the original Audio Buddy). Replacing the 1kOhm resistors connected to each of the green LEDs (at R39 and R40) to 10kOhms dimmed the two green LEDs to be less bright than the ones on the Audio Buddy. The four red LEDs are slightly brighter than the ones on the Audio Buddy when R28, R29, R48, and R50 are changed to 20K. In order to match the brightness of the green LEDs with 10kOhm- the red LEDs should probably around 25K (albeit 20k is still an improvement over the stock 1k values).

I should note that I swapped out U1, U2, U3, and U6 with NJM5532s but my Sony MXP 290 came with (and still uses) RC4558s and the Sony MXP 29 uses the 4580.

Knowing the the NJM4580L and NJM5532L are still being made- both are viable options that will yield a different sound.

Still- as the LynepAudio/AudioBuddy already comes with the NJM4580Ls at U2 & U6 and NJM4560LDs at U1 & U3; the most efficient and significant improvement might actually be from changing U1 & U3 to NJM4580Ls.

Conversely- one could also change all of U1, U2, U3, and U6 with NJM4558s (and even go as far as changing U2 & U6 with 4558Ls and U1 & U3 with 4558LDs).