Chinese mic mod fun!

[Rybow]

Disclaimer- No tubes or transformers were used in this project.

Anyone still there?

Well, I just finished my first capsule replacement on a chinese mic, and I thought I'd share some thoughts and files with everyone. The mic is an Apex 435 LDC which has a schoeps style circuit. The capsule is an RK-47 from http://microphone-parts.com/.

My goal was to mod a cheap mic cheaply so that it didn't sound as cheap. The mic is around $70 or so new. My particular one is actually my first ever mic that came as part of a 3 mic pack. It has sat in a drawer for years now because it developed some rumbling issues. Unfortunately this means I don't have a stock mic for a comparison, but hey, good is good. I remember liking it

So this is step one for me, which is just replacing the capsule in the mic. Step 2 will be some capacitor changes and checking the FET bias, as well as damping the body a little bit. There may be a step 3, which will be replacing the circuit with a km 84 or even an mk 319/219 style circuit, but I may leave that for a time. I'll put up some pictures once I get into it to replace those caps.

The recordings were made in my little basement studio. I just used the pre's in my apogee ensemble. I do have a pop filter up for the spoken word. It's the metal variety. Its dorky, sorry, I was just riffing. Acoustic guitar had the mic on axis, about a foot back, pointed at where the neck joins the body. Not my best playing, but I think it gets the point across. I hope to do some electric guitar recordings very soon with this mic, and maybe some female vocals. No EQ or anything.

http://dl.dropbox.com/u/11106120/Acoustic%20guitar%20RK%2047.aif
http://dl.dropbox.com/u/11106120/Spoke%20word%20RK%2047.aif

So far, I really like it. I am not going to say it's my "go to" mic, but I think it has the potential. I am just a hobbyist type, so my mic locker does not contain any crazy gems, just solid work horses. This mic does fill a niche for me, especially when it comes to sibilance as I can be pretty sibilant. Of course, the big test will be how it sits in the mix. Guess I have to finish a song soon.

Let me know what you all think!

 

[Ptownkid]

Disclaimer- No tubes or transformers were used in this project.

Anyone still there?

Haha, that made me chuckle.

 

[abechap024]

Coolness. Audio samples are always nice! The sound seems quite smooth on the vocals.

 

[reanimatorstudio]

http://www.groupdiy.com/index.php?topic=42836.msg532958#msg532958

 

[pucho812]

Disclaimer- No tubes or transformers were used in this project.

that made me sad.

 

[Rybow]

I know, I know. I am looking at trying to shoe horn a transformer in there. One step at a time.

Ptown- I always try to lead in with a joke!

Abechap- Smooth is the word I would use for sure. I also notice that cheaper LDC's have something weird in the mids that I don't really hear in this capsule. No hyped highs as well. The samples aren't scientific at all. I just threw up the mic and pressed record. For $89, the capsule is a steal in my opinion. I'll post some more samples once I get some circuit mods done.

reanimator- Good info in that thread! I've done a quick read over it, and will do some more when I get into the circuit part. Always wanted to learn more about mic circuitry. Although I pretty much plan on just replacing a few choice ceramic caps with polystyrene/polypropylene types of the same value. I think the capsule swap has taken care of any harsh/hyped high frequencies.

Pucho- Sorry man, I'll get to work on that right away.

 

[tchgtr]

It claims to be a dual-diaphragm capsule, but it seems like you are using it in cardioid only for this. Yes?
I like your samples (especially the vocal one! I do some VO work and found it helpful), and might try one of these for a Nady 1050 replacement.
You might also consider the Oktava MC012 circuit. It's very simple and sounds good, and Gus recently suggested a LP filter addition for LDC mics. I put this circuit in a MXL 2001 with the stock capsule and so far like it a lot with the filter.

 

[abechap024]

Yes for 89$ bucks its the most attractive option I've seen.... Thanks for the link! Anyone know how they compare to say...a peluso?

 

[pucho812]

no worries capsule seems like a steal.

 

[Rybow]

Yes it is a double sided capsule, so can use it in a mic that does omni and figure 8. The Apex 435 is a cardioid only in its stock form, so that's how I have it wired. I was going to look in to modding an Apex 480 in the future which would give me omni and figure 8 polar patterns. For now, I just have an extra side on the capsule in case I need it. I am glad you like the samples! I hope to put up a few more once I finish everything.

I haven't looked at the mc 012 circuit yet, and I have been doing a little reading on filtering. I'll look into that circuit as well if another chinese mic crosses my bench. I was thinking about grabbing a cheap MXL mic to tinker with down the line.

I would love to hear some comparisons with the Peluso capsules. I was considering the CEK 89 before I finding out about the RK 47 that I used. A lot of people have used them and loved them. I would also like to hear if anyone has used Dave Thomas's C12 type that he sells for $95.

Hey Pucho. Capsule is certainly a good deal. I should have bought 2.

 

[mista min]

But it's only 3 micron

I want a 6 micron k47 clone ;(

 

[jordan s]

Interesting. I was looking into this capsule for my Apex 460 mods. I looked at the frequency response chart and lost interest. It's got a high mid bump and a jumpy high end roll off. I considered that this could sound harsh. You mic sounds pretty decent though.

 

[Rossi]

It sure doesn't look like a Neumann K47 response. If I had to guess, I'd say the diaphragm tension is too low.

But it doesn't look like a good measurement, anyway; there's a lot of ripple.

Here's what a healthy K47 equipped U47 looks like (my own measurement):

 

[Rossi]

It does sound good, though, from what I can tell listening to the soundfiles on (unfamiliar) headphones.

I still have some Dale capusles and a Gefell M7 left, but might actually get one of those capsules, just to see what they're like.

 

[Rybow]

Maybe I should change the title of this thread as it is more about comparing this capsule than various chinese mic mods.

Would the mics circuit play a part in smoothing that top end ripple? I looked at the measurements of Michael Joly's capsule as well as Peluso's CEK 89, and they both have some ripple up there as well. I would expect a harsh top end response to look more like distortion. For me, this capsule solves 2 problems. Hyped highs, and a big peak in the sibilant range. The mid range peaks are quite broad, and also in the presence range, which suits me just fine as I mainly do rock/metal type music. Anyway, here is the measurement that came along with my capsule. I'll post some more samples after the capacitor changes. I am also looking very hard now at the royer tube mod.

By the way, has anyone used the simplified gyraf km 84 schematic to mod their mic? It looks like all you need to do is adapt the DC board in the original mic, and replace the audio board with this circuit. I have been pouring over the Meta for more info, but it appears that a lot of the build info has expired.

 

[Rossi]

Oh, I was actually commenting on the quality of the measurement, not the capsule itself. Most of the ripple you see is probably due to the measurement method.

However, I've noticed in my own measurement of various mics that the lesser capsules do show more ripple than high quality capsules (the capsules themselves not the measurements). That may be due to production tolerances, for instance in the way the holes in the backplate are drilled etc. Another source for such ripple are sound reflections in the head basket.

I've built various mics, both LD and SC with circuits based on the KM84 circuit (there are full versions on the web as well). It is a good sounding circuit for LD mics as well; the Oktava MK-219/319 circuit is not that different. Note that R2 is wrong; the correct value is 47k. Most LD cardioid only capsules will do fine without a DC converter board. You do need a decent 7:1 or 10:1 transformer, though.

 

[Rybow]

Thanks for the info Rossi. I do have the full KM 84 schem, although the resolution is not great. The schem I posted looked to be just the audio path for the KM 84 circuit, and that's why I was wondering about using the existing DC board to provide the voltages. I was also thinking that I might be able to get a higher capsule polarization voltage using the existing DC board. I have read that 65V is a good voltage to have for LD capsules, but I don't know how much of a difference it makes. The full km 84 schem is not that complex though, and looks easy enough to do p2p. I was looking into a cinemag transformer for the mic.

For now though, I am just going to upgrade the circuit. Just ordered some parts from mouser including some additional 2SK170 fets. I figured I would breadboard a little test jig, and then switch them in and out to get a good bias. Of course I'll check the one in there first.

 

[Rossi]

You can use the DC board for 60V polarization voltage (60V is the usual value for most capsules); you can't use it for the FET drain voltage as the current capabilities of a typical dc converter are way too low.

So I'd recommend building the full KM84 circuit, and when you get it to work properly you can use your DC converter board for the polarization voltage.

 

[bezen4uk]

Hi Insomniaclown,
2SK170 is not quite good choice for KM84 circuit due to very high reverse capacitanceof this FET. It's better to try 2N3819 or BF245 - both FETs available at mouser.

 

[jordan s]

According to Joly, this freq response chart of his MJE-K47 style capsule is unsmoothed. Looks a lot smoother than the microphone-parts.com capsule. I wish he sold the capsules separately.