MXL 603 -> KM84 Replacement PCB

[Migs 31]

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.

Good morning,
Happy Easter Monday!

To answer your question:
I'm still fully satisfied with my choice of transfo. Even at loud volumes the mic holds his ground with no distortion/audible saturation. EDIT: The transfos I used at the end were Neutrik NTE 10-3 on a 7:1 setting output, so: Blue= + Black= -

The only place to watch out for, is at the junction of the Capsule - R1 & C1. That is, from my understanding, where you could overload the Neumann circuit at High SPL. There is a cap, C2 with a value of 4pF (C3 on the first Neumann schematic) in conjunction with rest of the network which is responsible for "how sensitive" for lack of better words, your mic will be. Over simplification I know, if someone wants to phrase it better please do. And with two caps- C2 & C9 that can be put in parallel thanks to S1, we obtain a -10dB? PAD on some of the KM models.

I use the NTE4 and the NTE10-3 on other SDC builds. But you'll have to find a way to glue them/hold them tight on the KM84 PCB.

Graeme's PCB's are well designed & easy to populate. Before you start soldering I advice you place the caps/resistors etc in their spots and check for height/size clearance. Height/size, caps available & trimmer were a bit problematic for me due to the body I was using (Apex180). Do not place the 10K step trimmer on top like me, put it underneath like Graeme .

Hope that helps.
M

 

[solowiej]

Fantastic! Thank you so much Migs. I ordered a pair of NTE4 trannies.

 

[bdamiano]

Great thread. I've been doing my own LDC KM84-ish boards for several footprints and finally got round to re-drawing it for the pencil mics. The first one worked perfectly right off the bench. I managed to lay the transformer down flat (with < 1mm of board around the edges, but I see this board puts it in on its side with the laminations going through the board. Never thought of that! (I guess rev 1.02 will be coming soon )
I built the first one with a cheap China tranny (because I didn't expect it to actually work) and a Mic Parts Capsule. I have CineMag 5722w's and AMIs in stock so I will build a "real" one soon.
Capsules are the big problem here. I've ordered a 3U to try but it is taking forever to arrive. In the meantime the MP capsules are great but the pricing is tough. Any other options? What has been the typical delivery with 3U for you folks who have used them?

-Bob

 

[Ricardus]

Capsules are the big problem here. I've ordered a 3U to try but it is taking forever to arrive. In the meantime the MP capsules are great but the pricing is tough. Any other options? What has been the typical delivery with 3U for you folks who have used them?

I don't recall exactly, but mine showed up within 3 weeks. I think a little less.

 

[GraemeWoller]

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.

I've never used the NTE4, but I'm not sure it'll fit in there based on the dimensions I'm seeing. Maybe someone else could confirm?

The MT811 looks the right size, but I don't know about tonal characteristics so that's another "someone else might know".

The CM-5722 6.9:1 ratio is a better match for a KM84's BV-107 than the CM-13113's 9.5:1 ratio.

 

[GraemeWoller]

Great thread. I've been doing my own LDC KM84-ish boards for several footprints and finally got round to re-drawing it for the pencil mics. The first one worked perfectly right off the bench. I managed to lay the transformer down flat (with < 1mm of board around the edges, but I see this board puts it in on its side with the laminations going through the board. Never thought of that! (I guess rev 1.02 will be coming soon )
I built the first one with a cheap China tranny (because I didn't expect it to actually work) and a Mic Parts Capsule. I have CineMag 5722w's and AMIs in stock so I will build a "real" one soon.
Capsules are the big problem here. I've ordered a 3U to try but it is taking forever to arrive. In the meantime the MP capsules are great but the pricing is tough. Any other options? What has been the typical delivery with 3U for you folks who have used them?

-Bob

They're a fun circuit to build with, aren't they! Yeah, the sideways approach works well with such a small amount of space to work with, so it'll be worth you trying that I think, Bob.

 

[bdamiano]

I've never used the NTE4, but I'm not sure it'll fit in there based on the dimensions I'm seeing. Maybe someone else could confirm?

The MT811 looks the right size, but I don't know about tonal characteristics so that's another "someone else might know".

The CM-5722 6.9:1 ratio is a better match for a KM84's BV-107 than the CM-13113's 9.5:1 ratio.

I tried some of the Analog classics Trannys and they had identical characteristics to the yellow Ali-express low cost transformers. Then I peeled the White analog classics label off and realized why. Boy, did I feel dumb

 

[solowiej]

I tried some of the Analog classics Trannys and they had identical characteristics to the yellow Ali-express low cost transformers. Then I peeled the White analog classics label off and realized why. Boy, did I feel dumb

Holy Samolies.

Got a link to the Aliexpress part?

 

[GraemeWoller]

I tried some of the Analog classics Trannys and they had identical characteristics to the yellow Ali-express low cost transformers. Then I peeled the White analog classics label off and realized why. Boy, did I feel dumb

I make it a point to feel dumb once or twice a day to keep my skills up...

Someone needs to do a shootout with the circuit and try all the different options to see what the differences are. Not me though, I value my sanity (such as it is).

 

[Flatpicker]

Holy Samolies.

Got a link to the Aliexpress part?

Just google "T-13 transformer aliexpress" or "U87 transformer aliexpress". They all appear to be of the ASTDS brand, whoever that is.

 

[Drosselmeier]

Just google "T-13 transformer aliexpress" or "U87 transformer aliexpress". They all appear to be of the ASTDS brand, whoever that is.

IMO T-8 transformer for KM84 schematic.

 

[bdamiano]

Here's the instagram post I did when I uncovered the analog classics transformer. I didn't intend the tear the label just like that, but it sure turned out extra funny Anyway, on the left is the ali part. On the right is the analog classics.
I've been offering my customers a choice of CineMag 5722w or AMI Tab-funkenwerk T12. I know the T8 is probably a more suited transformer but it's also $30 more and the ratio of the T12 is close enough (6.25:1). They sound really nice - a bit more color and harmonic distortion than the CineMag. I keep some of the Yellow cheap-os around just for testing the fit in new board layouts.

 

[SparkleBear]

I built my km84 with the cm5722 and another with the yellow t8. I find those Chinese t8 pretty decent sounding. At least In this design…cm5722 sounds more hifi though. But the gritty sound of cheaper traffo was charming imo.

 

[Chrisfromthepast]

Here's the instagram post I did when I uncovered the analog classics transformer. I didn't intend the tear the label just like that, but it sure turned out extra funny Anyway, on the left is the ali part. On the right is the analog classics.

What price are you paying for the aliexpress t-8?
I have found the gzt/3u to be excellent for my builds and the price is comparable to the aliexpress prices I’ve seen. Its like really low prices, so it seems the same but GZT is less likely to change specs mid stream and disappoint you later.

 

[craigmorris74]

I built my km84 with the cm5722 and another with the yellow t8. I find those Chinese t8 pretty decent sounding. At least In this design…cm5722 sounds more hifi though. But the gritty sound of cheaper traffo was charming imo.View attachment 107914

did you record any comparisons? Would love to her if you did.

 

[SparkleBear]

did you record any comparisons? Would love to her if you did.

I don’t have direct comparisons available right now unfortunately. I could make some in June when I’m home from tour.

Cm5722 with 3u was close to spot on with the Neumann I have on hand. Neumann was a bit sweeter with the transients but the overall was sooooooo close.

 

[bdamiano]

did you record any comparisons? Would love to her if you did.

Here is a shootout between a Chinese T8 and a Tab-Funkenwerk T12. This is in a LDC build with K47-style capsules (Getwins).



See the description for a guide to what is playing when. The CN is definitely much brighter and thinner. For a while I was offering them as a "low cost" option to my customers, but then I thought "what's the point?" - we're not doing this to save money, we're doing this to have great mics - so I stopped offering it. These days, I'm mostly using CineMag 5722w's although I really like the extra color from the AMIs too.

 

[bdamiano]

Cm5722 with 3u was close to spot on with the Neumann

That's awesome. I have a batch of 3Us on the way. Looking forward to trying them out.

 

[chappyclark]

A bit of odd question: Can anybody recommend a good replacement for the Mogami wire in the 603/991 mic bodies? I've accidently burned a few of these and would like to replace. I've tried what seems a 24 G wire from a mic cable but these wires are very stiff and a bit hard to work into place.

 

[Chrisfromthepast]

Are these the wires that connect the first gain stage to the phase splitting stage by hopping over the capsule polarization circuit?
If so, maybe try a different donor mic cable. Harvesting an inch or so from a nice mic cable seems to work for me. If you don’t have enough donor cables to choose from, you aren’t hoarding enough IMHO. JOKES
Alternatively, could you more thoroughly clean your hole with solder wick?

EDIT:
I completely misremembered this circuit, but found one as a reference.
The wires im thinking of are these bodge wires that don’t even have pads of their own, but solder to the legs of other components. Are these the ones you’ve burned?