t.bone SC140 - Mods

[irfrench]

Hi all,

I've been lurking in the other forum areas for a while and have finally strayed here.

Obviously this is my first foray into mic-DIY, and as such I thought it prudent to get a bit of practice in before moving on to the more involved stuff (C12/ELAM and U67 are on my to-do list).  I've had a pair of Thomann.de SC140s kicking around for a while, and while I like them as they are (if not, they are a little peaky) they seem like good donors for modding.

I have seen a few posts regarding this mic, and in particular outlines of mods by M.Joly that I'd like to implement as practice.

The first is to modify the head basket, as I understand it the more open basket will help control HF peaking (good for my wants).  I intend to cut away the strip between the slots and therefore open it up a bit.  Hopefully, if I am not too ham-fisted, I should be able to re-use the mesh inside as it looks pretty easy to remove.

The second thing I intend to do is replace the caps with non ceramic varieties. Are WIMAs good to go for?  A kind soul shared this schematic but unfortunately I cannot remember where or who.  Sorry.  From photos of his board, the mics were populated with SMDs.  I've looked over the boards and as far as I can tell they share the same schematics with differences between device types.

C1 = 153 = 15nF
C2 = 333 = 33nF
C3 = 22uF 50v
C4 = 22uF 50v
C5 = 104 = 100nF
C6 = 1uF 50v
C7 = 333 = 33nF
C8 = 333 = 33nF
C9 = 471 = 470pF
C10 = 332 = 3.3nF
C11 = 102 = 1nF
C12 = 102 = 1nF
C13 = 104 = 100nF
C14 = 153 = 15nF
C15 = 153 = 15nF
C16 = 100uF 50v
C17 = 153 = 15nF
C18 = 153 = 15nF
C19 = 6.8pF
C20 = 27pF
C21 = 333 = 33nF

Q1 = 2n5401
Q2 = 2n5457
Q3 = 2n5551

Here's the board

I can see quite clearly that the 'orange' caps are ceramic, I guess that the 'mint' caps are also ceramics?

I intend to document the process including samples of the differences it makes and compare alongside the other half of the 'stereo set'.

If anyone has any suggestions, things to avoid, things to definitely try etc that'd be great.

Thanks,
Ian

 

[ramshackles]

Hiya,
I've been considering using a pair of these to implement a km84 circuit. I haven't got the mic's yet, but I knocked up a PCB layout for the km84 circuit - really just to help me lay it out on a bit of breadboard.
The CM-2510 trafo should work well for the circuit, provided it can fit the mic...
http://cinemag.biz/mic_output/PDF/CM-2510.pdf

Can you give an idea of the size of the dimensions of the PCB in the t.bone? Is it easy to remove?

Do you know if it possible to get other capsules for the mic aswell? (omni...)

 

[MatthisD]

PCB is 108mm x 11mm and easy to remove, quite sure that cm2510 will not fit inside. BV107 does fit if positioned in the centre as it is in the KM84 between two PCBs.

 

[ramshackles]

Thanks.
Yes, the cm2510 is 17 by 24mm. I can't find the BV107 anywhere...I suppose it is not still available?

 

[MatthisD]

My mistake PCB is 108mm x 16mm

According to this post it is available:
http://www.neumann.com/forums/view.php?bn=neumann_mictec&key=1353514140&pattern=bv107

 

[ricardo]

There's a number of Golden Pinnae myths in what you propose eg

• The mesh in the slots has little or nothing to do with the HF peakiness
• NPO/COG ceramics are the BEST capacitors you can find if their value/voltage suits.

I won't comment further but instead recommend ...

You do your mods one step at a time on ONE of your pair so you can compare the results of each mod.  That way you can check if you are fooling yourself.

 

[johnR]

There's a number of Golden Pinnae myths in what you propose eg

• The mesh in the slots has little or nothing to do with the HF peakiness
• NPO/COG ceramics are the BEST capacitors you can find if their value/voltage suits.

I won't comment further but instead recommend ...

You do your mods one step at a time on ONE of your pair so you can compare the results of each mod.  That way you can check if you are fooling yourself.

I think he meant cutting out the pieces in the middle of the pairs of slots, which IIRC is what MJ does. That is likely to alter the HF response and I suspect it will alter
the directivity too (possibly towards hypercardioid).

I agree completely about C0G/NP0 capacitors being excellent. Medium and high K ceramics like X7R and Z5U (or any other X, Y or Z type) will distort due to piezoelectric effect, but C0G/NP0 does not do this.
I recommend reading Cyril Bateman's articles on capacitor sound (can be found with Google) which compare the distortion characteristics of different capacitor types.

 

[ricardo]

There's a number of Golden Pinnae myths in what you propose eg

• The mesh in the slots has little or nothing to do with the HF peakiness

I think he meant cutting out the pieces in the middle of the pairs of slots, which IIRC is what MJ does. That is likely to alter the HF response and I suspect it will alter
the directivity too (possibly towards hypercardioid).

I was referring to removing the mesh in these slots too.

There IS an effect on HF response but it is unlikely Ian will notice any difference unless he can do accurate anechoic measurements against a reference measurement mike.  It certainly doesn't affect 'HF peakiness'.

Similarly for directivity.  Its affected in a VERY small frequency range.  Hence I

.. recommend ...

You do your mods one step at a time on ONE of your pair so you can compare the results of each mod.  That way you can check if you are fooling yourself.

Who is MJ?

 

[HellfireStudios]

If the mic is anything like an MXL in dimension, the CM-2510 will fit, but it is not easy to implement. The transformer will take up the area just above the XLR. Also, the PCB has to be cut with a notch in it to make room for the laminations. A little hot glue to hold it all together and your good to go.

-James-

 

[Khron]

irfrench, you're welcome, i was the one that traced the schematic  ;D And you most likely found it on the micbuilders Yahoo group

I ended up replacing the whole PCB with one i DIY'd. Since the capsule is actually polarized with -48V (relative to ground / the casing), and since (as far as i recall, it's been a couple years since then  ;D ) i couldn't squeeze a Schoeps-style circuit in there (using through-hole parts), along with the oscillator for the polarisation voltage, i decided on a "hybrid" circuit.

I "transplanted" the oscillator SMD parts, and i pretty much copied the Oktava MK-012 circuitry Tweaked a couple resistor and cap values, 2SK170BL FET, 2SA970 BJT (low-noise, and the highest gain i had available in my parts box), 1nF polyester input cap, 1uF polyester coupling cap, two Rubycon YXF 47u/50v power filter caps, two Panasonic FC 22u/63v coupling caps.

What i CAN confirm, is that the mic still works ;D Haven't really had the chance to "really" test it though, but i'm planning on buying another pair, so i'll be able to test all four combinations at once (stock/modded capsule with stock/modded electronics). I've got a couple friends in town (one with a studio, one with a PA company) who've agreed to some test-sessions, so... Fingers crossed

 

[irfrench]

All,

Well it appears that I haven't been notifying myself of my own threads. Good start - Genius.

Khron - thanks very much for the schematic, and for confirming who created it, I hate not being able to credit. 

I haven't had chance to get around to modding mine yet as I've been really busy using them (typical?)!  I'm guessing I'll give them a going over when it is winter (who wants to record drums in churches/church hall/village halls when its Freezing!?).

In case anyone is thinking about modifying the element casing (a la MJ) I thought it would be helpful to say that I emailed Thomman about buying the capsules only - they were more than happy to do so at about £20/mic+delivery.  It has definitely made the idea of screwing one up a little easier! 

Cheers Ian.

{must click on notify... must click on notify... }

 

[Khron]

Nice call on the capsules-only thing Good to know there's always a "backup" ;D

I managed to eliminate those "beams" with a Dremel-like mini-drill (mine's a Proxxon) on a stand, with a 0.8mm or 1mm drill. Granted, the ends are (still) a bit jagged, but should affect the response far less than the enlarged vents, methinks.

Upon doing some more reading, it seems i *might* have to make sure the silicon parts are biased properly, but that's just a "finishing touch".

Either way, i'm looking forward to getting another pair of these mics, for the above-mentioned purposes. Plus, with a pair on overhead duty, the other two may well take up ride and hat spot-miking duties  :

 

[irfrench]

Notify works!  ;D :

I think I'll try the 'beams' mod and see if my cloth-ears can hear a difference, it'll be fun(!?).

As for the remainder of the circuit - I'm guessing with the the pad/LPF switches it'd be a pain to get a new board in there that takes advantage so modding (along with the inherent chances of ruining the PCB!) may be the best way forward.

I'd love to hear how you get on with this - I am completely green with mic circuits - as the mics are really quite usable as they are any mods would/should/could make these a real bargain (if they aren't already?).

I've ended up using these for OH duties a few times (for me it really depends on the cymbals and HATS being used) but also on acoustic guitar (it suited/helped balance the mid-heavy tone on one particular instrument).  If more can be brought out of these (aka 'improved') I'd be delighted.

Cheers,
Ian
8)

 

[Khron]

If needed / requested, i just might be able to get off my lazy arse and snap a few pictures of my questionable(?) handiwork so far ;D

You've got a PM

 

[Geraldo]

Hi all,

I've been lurking in the other forum areas for a while and have finally strayed here.

Obviously this is my first foray into mic-DIY, and as such I thought it prudent to get a bit of practice in before moving on to the more involved stuff (C12/ELAM and U67 are on my to-do list). I've had a pair of Thomann.de SC140s kicking around for a while, and while I like them as they are (if not, they are a little peaky) they seem like good donors for modding.

I have seen a few posts regarding this mic, and in particular outlines of mods by M.Joly that I'd like to implement as practice.

The first is to modify the head basket, as I understand it the more open basket will help control HF peaking (good for my wants). I intend to cut away the strip between the slots and therefore open it up a bit. Hopefully, if I am not too ham-fisted, I should be able to re-use the mesh inside as it looks pretty easy to remove.

The second thing I intend to do is replace the caps with non ceramic varieties. Are WIMAs good to go for? A kind soul shared this schematic but unfortunately I cannot remember where or who. Sorry. From photos of his board, the mics were populated with SMDs. I've looked over the boards and as far as I can tell they share the same schematics with differences between device types.

C1 = 153 = 15nF
C2 = 333 = 33nF
C3 = 22uF 50v
C4 = 22uF 50v
C5 = 104 = 100nF
C6 = 1uF 50v
C7 = 333 = 33nF
C8 = 333 = 33nF
C9 = 471 = 470pF
C10 = 332 = 3.3nF
C11 = 102 = 1nF
C12 = 102 = 1nF
C13 = 104 = 100nF
C14 = 153 = 15nF
C15 = 153 = 15nF
C16 = 100uF 50v
C17 = 153 = 15nF
C18 = 153 = 15nF
C19 = 6.8pF
C20 = 27pF
C21 = 333 = 33nF

Q1 = 2n5401
Q2 = 2n5457
Q3 = 2n5551

Here's the board

I can see quite clearly that the 'orange' caps are ceramic, I guess that the 'mint' caps are also ceramics?

I intend to document the process including samples of the differences it makes and compare alongside the other half of the 'stereo set'.

If anyone has any suggestions, things to avoid, things to definitely try etc that'd be great.

Thanks,
Ian

Hi there! I´d like to to the Joly mod on my SC140 as well. Unfortunately Michale Joly hast stopped his modding activity and I can´t get any information about what to do. Did you finally do the modding? Which parts did you exchange and which one did you use instead? What about the improvement? Is it worth the effort? Do you have any documentation or do you know where to get it? Would be happy about any help!

Thanks a lot in advance and best regards!
Gerald

 

[Khron]

Well, i designed and etched my own pcb's, and while i can't comment much on the "sound" (which should be a non-issue), what i can definitely say is that the MK012 type circuit is considerably less sensitive than stock. That might be useful for loud(er) sources, but i definitely haven't compared noise levels or anything.

If anything, the consistency of the capsules is so-and-so at best, but take that with a grain of salt too. I've yet to embark on the daunting project of measuring all my mics, but i haven't noticed much difference in the capsule responses, before and after removing the "rail" in the middle of the vents.