MXL 603 -> KM84 Replacement PCB

[chappyclark]

Thank you, thank you, thank you!!! A thousand times,
to Graeme for this project.

I got two of his PCB's and built them during the second lock down in Europe.
I could not source all the parts I wanted, so I had to improvise the with parts I could find. But the two mics sounded very very good to me. I used two APEX 180 as donors, slightly different insides to the MXL 603, but with a file and a bit of patience, Graeme's PCB's fitted just fine.

The result was day and night compared to the originals.

I have been recording a Kiwi (New-Zealander) artist, John McClean, in London over the past month & the MXL 603-KM-84's have been used over Guitars, Percs, Drums O.H. and even SNARE!!! (more on that a bit later).

And yes, I had to compare with a pair of Neumann's and other SDC's we had in the studio.
Result? Graeme's versions of the MXL603 KM-84 won (to my ears) most of the time.

I'm a very satisfied sound engineer/musician with these.
:0)
M

Curious as to how the NTE-4 transformer sounds compared to some of the other, more expensive transformers. Has anyone performed a comparison and care to share thoughts/findings?

 

[Rob Maxwell]

Thank you, thank you, thank you!!! A thousand times,
to Graeme for this project.

I got two of his PCB's and built them during the second lock down in Europe.
I could not source all the parts I wanted, so I had to improvise the with parts I could find. But the two mics sounded very very good to me. I used two APEX 180 as donors, slightly different insides to the MXL 603, but with a file and a bit of patience, Graeme's PCB's fitted just fine.

The result was day and night compared to the originals.

I have been recording a Kiwi (New-Zealander) artist, John McClean, in London over the past month & the MXL 603-KM-84's have been used over Guitars, Percs, Drums O.H. and even SNARE!!! (more on that a bit later).

And yes, I had to compare with a pair of Neumann's and other SDC's we had in the studio.
Result? Graeme's versions of the MXL603 KM-84 won (to my ears) most of the time.

I'm a very satisfied sound engineer/musician with these.
:0)
M

Interesting this. Can I ask what capsule you used? Rob.

 

[Migs 31]

Interesting this. Can I ask what capsule you used? Rob.

Hi @Rob Maxwell !

Welcome to this party.
To answer your question: I just used the capsules that came with the APEX 180's. It's just a standard Cardioid capsule, stock on those mics. Some people have gone to some lengths to buy other "better" capsules from different on-line shops or e-bay. Which I can understand, as a good capsule is VITAL, to the sound of the mic. Peluso, APEX 180's/185's, MXL 603's all share the same dimensions for SDC capsules (22mm diameter if I remember well/correct me if not) and same type of threads.

M

 

[SparkleBear]

AFAIK, the 603 is a more expensive donor as it has the transformer in the design. But perhaps you can use it’s transformer in your km84 diy? Not sure what the ratios are though…

 

[Ricardus]

AFAIK, the 603 is a more expensive donor as it has the transformer in the design. But perhaps you can use it’s transformer in your km84 diy? Not sure what the ratios are though…

Pretty sure the sacrificial pair of 603s I bought didn't have transformers.

 

[JW]

Couple of questions.

Graeme, do you have any of the bigger boards for sale that are on page 5? Are they for the bm700 or bm800 Chinese bodies?

Also, is there a bigger Cinemag that would be just as suitable as the little Km84 transformers? I'm building a couple of these into Bm700 bodies with K47 capsules.

 

[SparkleBear]

Pretty sure the sacrificial pair of 603s I bought didn't have transformers.

Ahh interesting. For some reason I thought that… jeeze they are pricy for that. I usually get a pair of 804 with shock mounts for under $100

What did you get the 603 for?

 

[Ricardus]

Ahh interesting. For some reason I thought that… jeeze they are pricy for that. I usually get a pair of 804 with shock mounts for under $100

What did you get the 603 for?

For this conversion.

 

[SparkleBear]

For this conversion.

Misunderstanding. What was the cost of your 603 donor?

 

[Ricardus]

Misunderstanding. What was the cost of your 603 donor?

Hmmm.... I think I paid $125 or so. Which is kinda nuts just to get a body (and a so-so road case), but once you use this circuit with the 3U capsules you have an amazing microphone.

 

[SparkleBear]

Hmmm.... I think I paid $125 or so. Which is kinda nuts just to get a body (and a so-so road case), but once you use this circuit with the 3U capsules you have an amazing microphone.

Its so true, I built my own design before I discovered Graeme's thread here. But I did mine with the same body but badged 804/991 and with the cardioid 3u capsules its a total game changer. Makes me not even want to bust out my vintage km84s anymore... these are just as good for most applications. I only miss them when i'm contending with a multi track session where the bleed might not be as nice coming in on the 3u. But its negligible tbh.

My boards are a slightly different layout it turns out... but we are using the same mother schematic from the holy sacred vault of Neumann, hallowed be thy name.

 

[fsalter]

Hmmm.... I think I paid $125 or so. Which is kinda nuts just to get a body (and a so-so road case), but once you use this circuit with the 3U capsules you have an amazing microphone.

In case anyone is looking for a cheaper alternative to the MXL 603 as a donor body, I just bought 2 Nady CM90's at 49$ a piece on Amazon, and they seem to do the job. I have'nt started the build yet, but the 3U capsule fits, as does the pcb.

 

[Ricardus]

In case anyone is looking for a cheaper alternative to the MXL 603 as a donor body, I just bought 2 Nady CM90's at 49$ a piece on Amazon, and they seem to do the job. I have'nt started the build yet, but the 3U capsule fits, as does the pcb.

Is the length correct? Will it require any more mods?

 

[chappyclark]

In case anyone is looking for a cheaper alternative to the MXL 603 as a donor body, I just bought 2 Nady CM90's at 49$ a piece on Amazon, and they seem to do the job. I have'nt started the build yet, but the 3U capsule fits, as does the pcb.

I had no trouble getting either MXL 991 and/or 603 for $30-35 bucks, used. Facebook marketplace, reverb, eBay, Craigslist are good places to look, here in the States.

 

[Cappy]

How would these be different from this build? SDC-84 Microphone Kit - Neumann KM84 Style

I did a pair of these mic parts km-84 style sdc’s and also did a pair of mxl-603s-schoeps style circuit conversions and used their capsules for all of them. I think these are the same parts as what’s listed here. Anyway, they all worked and sounded decently good, I used them a lottttt especially for live recordings at venues where I didn’t want to risk taking out my more expensive gear. I think they sound good but when I got a pair of real Schoeps CMC6-MK4 I realized why people pay much more for them. The level of detail is not even a close comparison. That being said, I do like the punch of the tx in the 84 clones. If your circuits do that thing then I would imagine they would be a really fun build and rewarding result for the people who build them. I do personally prefer my similar km84 clones to the schoeps style circuit with the same capsules. More fun and more flavor. Does your tx rattle loosely in your mic body though? The mic parts build does not include any instructions or parts for securing the tx in place, so it can move freely inside. If you shockmount it it’s not a big deal but this unfortunately has prevented me from clamp-mounting it onto an instrument such as the acoustic bass for fear of recording a rattle. Need to go back and figure out a way to secure that tx inside.

Wrap vinyl tape around it (horizontally around the PCB). It holds it in place well.

 

[chappyclark]

Just putting a feeler out for a drop-in replacement for the stock MXL 603 series PCB.

The MXL 603 is boring. It sounds boring and it is boring. It's a overly boring bright/brittle version of boring. It’s cheap for a reason.
The Neumann KM84 is not boring. It's awesome. It's got thickness. It's got iron. It's got thick iron. It's basically the opposite of the MXL, which doesn't have iron. It doesn't even have lead in it's pencil.
The MXL 603 KM84 replacement board takes the circuit from the KM84 and uses your old MXL as a donor body, capsule and XLR connector.

You're building a MXL 603 with mojo.

What I'm thinking is: I'll provide the PCB, the schematic, BOM, and a build guide, inc. postage to wherever you are for US$30 each. You get the parts and put it together, and BLAM! you've got a better sounding mic than you started with.
It's an easy DIY, and if you have the mics around you might as well make them better.

nb. This ain't going to work if you want to chuck it in a Banzai style body. The PCB is a different length, and the mounting is different at the XLR end. It's for MXL mojo, not other mic mojo.

Let me know if you’re interested, we'll need a few to make it worthwhile.

Graeme

Is this the correct wiring for the 3U GZT-84 transformer in the MXL->KM84 Rev B board?

RED wire -> G
BROWN wire -> R
YELLOW wire -> B
ORANGE wire -> Y

 

[GraemeWoller]

Yeah, that sounds perfect, Chappy.

 

[SparkleBear]

Wrap vinyl tape around it (horizontally around the PCB). It holds it in place well.

Better than vinyl tape is Kapton. It lasts forever and no residue melting. Good ol nasa hand me downs.

 

[solowiej]

I could not source all the parts I wanted, so I had to improvise the with parts I could find. But the two mics sounded very very good to me.

It's been a couple years since your post, but if you're still out there: Any issues at higher levels using the NTE4 transformer?

Anybody else have thoughts about the NTE4 or other trannies in Graeme's setup?
Cinemag CM-5722 seems most popular, then 3U GZT-84. What about this NTE4 or Cinemag CM 13113, or even the Analog Classics MT811?
I'm curious what people have tried, and any noticeable differences in character.

 

[gar381]

Graeme are these pcbs still available ??
interested in a pair.

Gary