M-audio Sputnik (Capsule and Transformer modding)

[useme2305]

hi, i'm new! 

i recently obtained two m-audio sputnik tube mics for REAL cheap. i know you guys build your own kick-ass tube mics but i'm not at that stage yet and i'm really damn poor.

so i'm thinking about changing the capsule and replacing the output tranny with the C12 tranny which i heard was a suitable mod for this mic.

i haven't ordered any of these parts yet as i'm totally unsure if this is even possible for me. i'm a total beginner. my only projects so far have been numerous guitar pedals based on vero layouts, a few Bo Hansen DIs, some Classic API pres including the DOAs and some tube amp repairs and mods without really knowing what i'm doing but always having been successful.

so yesterday i tried to measure the polarizing voltage of the Sputnik to see if any mods have to be done to the circuit for the capsule swap.

12V in Cardioid
40V in fig Eight
and less than 1V in Omni 

that doesn't sound right to me. is it? what might i be doing wrong? or is the Sputnik just a really shitty mic after all?

maybe i should just build a G7 or an MK47. what do you recommend?

 

[pasarski]

You can't measure polarization voltage at the capsule with a regular multimeter because of the high impedance, you have to measure before the big bias resistors. I would just swap the capsule and if the diaphragm sticks to the backplate then work on the voltages.

 

[tchgtr]

But wait! I just removed the capsule from a M-Audio Nova, and it was a pretty nice capsule, being amplified by not-so-good circuitry. I put it in a modded MXL 9000, and it sounds much better than the original (K67-type) capsule that was in that mic.
I would imagine that M-Audio used a similar, or better capsule for the Sputnik, so maybe you don't need to replace it, just improve the electronics. Starting with the transformer might be a good idea,
Does your capsule have a white ring around it like the photo below? If so, this is not a bad capsule. I don't want to stop you if you want to spend $300 on a nice handmade capsule, but these are not so bad.
Could you post pictures of the insides of one of the Sputniks?
Thanks.
The Nova body will now be used to make a multi-pattern Royer circuit. It's very sturdy, and well-built.

 

[useme2305]

thanks for the replies, guys. i'll take pics of the capsule in a minute.

 

[tchgtr]

I'm more interested in pics of the guts. Might be able to give you better upgrade ideas from those. I'll bet the capsule is fine, if it has the white ring. We are actually thinking about a group buy on those (or at least something very similar).

 

[useme2305]

alright, here are the pics of the guts and the capsule.
https://picasaweb.google.com/useme2305/MAudioSputnikGuts

the capsule seems to be the same as the one in your mic.

M-Audio Sputnik Capsule

 

[tchgtr]

  OK, what's not to like? Wima mkp caps, looks like an M-Audio relabeled miniature tube, and a pretty standard PSU.
Your capsule is the dual version, and what we are hoping to purchase in the group buy (see the "Anyone Tried These...." thread below).
  Capsule upgrades will cost a lot to get better than this, though you could try a Chinese C12 clone, but that's a waste of time, if you ask me. Your time would be better spent checking out the transformer, but it might be OK, too. Do you like the mics as they are?
  It's hard for me to see which cap is connected directly to the transformer. If it's an electro, shame on them. THAT would be the something to look into, but I can't imagine them making that mistake, since everything else seems to be well done. However, on my Nova, they had an electro on the output, so who knows?.
  I think this mic looks like it was well thought out, tho smarter folks on this website might differ.
  I tried to improve the circuit in my Nova, before deciding it was not worth it. It is not as well-designed as this. I'm glad I tried the capsule in another mic, as I think it's pretty good for Chinese stuff.
  A good deal on a pair of these? I think you did OK, unless you just don't like the sound.

 

[useme2305]

hey thanks for looking into it. i would like to find out about the cap problem you mentioned in m-audio mics.

i like the mics' sound. they are extremely detailed. i actually altered my fingerpicking technique because of this mic cause it made my resting fingers of the picking hand on the guitars body audible. those tiny movements.

the thing is that i think that these mics are not really suitable for M/S in their current state. that's why i'm thinking about a capsule swap.

 

[tchgtr]

  OK, do you think they aren't good for MS because the capsules don't sound the same in figure 8 mode? If so, I feel your pain. The whole reason I replaced the capsule in my Nady 1050 was for this very reason. Used a Chinese C12 clone from a group-buy here, and I am very happy with the results.
  However, if they sound the same on at least one of the mics, you should be in business. Just use the unmatched one as the cardioid mic.
  To figure out the cap issue...a schematic would be great. If you find one, please post it here, and I will be happy to look at it.
  What we wanna do is figure out the last capacitor (most likely the last component) in the signal chain before the transformer. If it's one of the electrolytics...no good.
    So, look at the wires coming into the mic from the transformer enclosure at the bottom of the mic. It looks like they are labeled (I see one that says "B+" and one that says "low"). Trace them back into the mic circuit, and see what caps they connect with. You can forget "B+"; that's the voltage going in to power the tube.
    I'm hoping that big blue electro near that end of the circuit board is not connected to the xfrmr. Probably not, but I can't read it's values.
    If it's that red Wima going from side to side, all is well. You can try a different type of capacitor, (as well as the Wima in between the two 1G resistors...the first cap in the chain), but a waste of time, IMHO, especially since you might damage the delicate PCB. Others may disagree.
  Never had a chance to play with one of these, but it looks fairly well done.
  I'm certainly no expert, but after three years watching this place, I have come to understand that 99.9% of what the truly knowledgeable people around here say is absolutely true. Be careful not to ruin a good mic (or two) from mod-lust.
  To have capsule improvement, you would have to spend 200-300 dollars or more per mic, but those capsules do sound great. However, then you have the chance of damaging something as you change them.

 

 

[useme2305]

none of the six wires except for the B+ one go into any of the three electrolytic's positive lugs.  8)

EDIT:

but one wire labeled "HI" from the transformer goes to the positive lug of C8 (16V 330uF). it's a red wire coming from the transformer...not a wire going directly to any of the seven pins on the output xlr.

 

[tchgtr]

  OK, I found a thread on GSltz you may already have seen, about changing the transformer. I see the guy from JJ tries to get someone to confirm whether the coupling cap is polypro or not, but nobody even responds to that.
http://www.gearslutz.com/board/geekslutz-forum/603884-m-audio-sputnik-transformer-upgrade.html
  From what I see in the photos there, the "hi" wire is most likely the output from the mic. However, in those photos, that wire is brown. It looks like the "low" wire connects directly to ground ("BO") on the back of the PCB.
If that 330uf cap is your output coupling cap, and electro.....eeeewwwwww!
Why would they do that, after putting all those other nice caps in there?
If this is indeed the case, you can try replacing C8 (which does seem to commonly be the coupling cap in many schemos. Perhaps someone with more experience than I can explain why that is. Maybe because everybody is copying the same circuit?
What value? What's the biggest polypro or film cap you can get in there? Maybe 1 or 2.2 uf....

 

[tchgtr]

When I replaced the 10uf coupling cap in the Nova wth 2.2 film, it seemed like the designers had used that electro cap to stunt the hi end a bit, and replacing it just made the mic too sibilant, whereas it had been simply OK before.
Hopefully, it's not the same case with this mic. It doesn't seem like it to me, with the other components used. My advice is to find a schemo, and/or search for other threads where folks have been thru this before us. I imagine you have already done a fair amount of this...

 

[pasarski]

(Unless it's a unusual circuit) I don't see how a cap rated for 16V could be a transformer coupling cap? 160-400V and 2-10uF would make more sense to me. Also (unless it's a unusual circuit) the WIMA's are too small, so the coupling cap is most likely one of the electrolytes.

 

[tchgtr]

Ah-finally someone with more smarts than me.
What Pasarski said...

 

[useme2305]

hexy thanks for clearing that up. i'll look into it tomorrow morning and check the values.

 

[hazmatstrat]

The 16v cap is most likely for the cathode bypass or the final stage of filtering for the heater voltage. I have not seen this mic in a while however the Wima may bypass the electrolytic transformer coupling capacitor and is used as the high pass filter on the switch.

The main Improvements that can be made to this mic is to change the transformer coupling capacitor and the transformer. 1uf  works fine in this mic and the AMI T14 adds wonderful tone and smoothes the response very well.

The power supply is a standard GT/ Sterling and has some nice Rubycon capacitors in them.

8) 8)​

Jim Jacobsen
JJ Audio

 

[useme2305]

repost of my geekslutz post from earlier today:

after hearing the samples i'd say the mod definitely gets rid of the grittyness of the mids. tames them quite a bit.

can anyone confirm that the Tab T49 doesn't fit in the Sputnik?
i guess one could stuff it in there with the original metal can removed?

also, has anyone replaced that suspicious cap with a polypropylene one?
if yes, which cap exactly needs to be replaced?
i found some suitable 1µF polypropylene caps that i'll be ordering some different values of. i have two sputniks. so i will be able to do lots of testing...maybe even post some comparision clips here.

i just need to know what values i should order. i guess some different makes of 1µF (mallory, xicon, tubular film etc.) maybe some 2,2µF ones too?

edit:
after some thinking i came to the conclusion that C6 (160V 10uF) is the decoupling cap. just not sure what values to order along with a 1uF mentioned earlier by hazmatstrat.

 

[timguitartaylor]

Hey guys...I also have an MAudio Sputnik which has NEVER worked right. I sent it back to MAudio twice, and they claimed they could find nothing wrong. I took it to guitar center and they confirmed it was definitely not working right, and we sent it out for repair. It sat at the repair facility for 8 months before I finally gave up and had them send it back to me. I would like to get the Mic working, and according to the repair facility the  problem is the Capsule. They felt it was blown. I am happy to replace it, but an unsure as to what the dimensions of the capsule are. I dont want to buy capsules that are wrong, and I could really use some good advice here. I am not a microphone expert, but having tried MAudio twice, and one of their authorized repair facilities for the third time...I would like to try to fix this thing, or find someone who CAN. Thanks.

 

[useme2305]

why not jut get one of the RK capsules from the whitemarket?
http://www.groupdiy.com/index.php?topic=49141.0
they'll all fit. you'll just need to find a way to mount it...but that shouldn'T be too hard.

 

[Cgaines]

What will changing the coupling cap do? Filter high frequencies?