KM84 DIY Body & PCB kit – CLOSED

[Fuzz Face]

Got my kits and transformers and couldn’t be more excited. Really great job on the kits and build doc. Thanks so much!

 

[iturnknobs]

Ha! I'm glad. Are there any other comments on the different transformers?  so far I've read AMI t8 sounds like the original (but $120!), Cinemag's have good low end, but are darker than original, and Haufe made a round of the originals, but are they still available? How do the 3U gtz 84's sound? any thoughts?

I don't want to bash someone's product, but you might want to steer away from the Haufe trafo. Mine, along with others are literally falling apart. AMI is expensive, but that won't happen with their product. Dennis at AMI is fantastic and will help to his full ability. David at Cinemag was so helpful, he deserves a raise. These are the things I have learned throughout this project and over the years of DIY.

 

[TillM]

I don't want to bash someone's product, but you might want to steer away from the Haufe trafo. Mine, along with others are literally falling apart. AMI is expensive, but that won't happen with their product. Dennis at AMI is fantastic and will help to his full ability. David at Cinemag was so helpful, he deserves a raise. These are the things I have learned throughout this project and over the years of DIY.

I must say, that the difference between my mic with the Haufe Transformer and the other one with the cinemag is nearly zero.

 

[jrmintz]

I must say, that the difference between my mic with the Haufe Transformer and the other one with the cinemag is nearly zero.

Wow, that's unexpected. The difference between the Cinemag and the AMI is not subtle.

For anyone who's interested here is a comparison between my first DIY KM84 with the Cinemag transformer and also with the AMI: https://www.dropbox.com/sh/z4hcoqk8nprezza/AACrOkfG3ztepQpGmk3azS1ca?dl=0

 

[Potato Cakes]

Wow, that's unexpected. The difference between the Cinemag and the AMI is not subtle.

For anyone who's interested here is a comparison between my first DIY KM84 with the Cinemag transformer and also with the AMI: https://www.dropbox.com/sh/z4hcoqk8nprezza/AACrOkfG3ztepQpGmk3azS1ca?dl=0

Are those with the same preamp gain settings? Besides the level difference, even on my not 100% Macbook Pro speakers I the difference is very much quite discernible.

Thanks!

Paul

 

[craigmorris74]

Yes, thanks for posting those clips.  The acoustic clips are a little tough to compare because of pretty big performance differences, and it does sound like the AMI is driving the mic pre harder than the other two.  When level matched the AMI is darker than the KM84 or the Cinemag on acoustic.

But still good stuff. I think I'm hearing different signatures of the transformers.

 

[craigmorris74]

Double post, sorry.

 

[jrmintz]

Are those with the same preamp gain settings? Besides the level difference, even on my not 100% Macbook Pro speakers I the difference is very much quite discernible.

Thanks!

Paul

Yes, same preamp settings. It's a Neve 1064 with the EQ bypassed. It's hardly a carefully controlled scientific comparison, but it gets the point across.

 

[Potato Cakes]

Yes, same preamp settings. It's a Neve 1064 with the EQ bypassed. It's hardly a carefully controlled scientific comparison, but it gets the point across.

I agree. Even if you matched the levels to where it seems more like the same volume so one doesn't suspect they are being given the old HiFi salesman trick, one could still tell a difference in the frequency response. No need for anechoic chambers and white lab coats when it's that apparent.

Thanks!

Paul

 

[duantro]

I got my pair together and had to bias by ear, as my old  tek 465b scope looks to have died. I used these on drum overheads this weekend, and they sound really huge and great. Thanks a ton for offering  this.

 

[maarvold]

I recorded a 24-96-Wave comparison on acoustic guitar of my 2 well-matched Neumann KM84's vs 2 builds of the DIY KM84.  Couldn't be happier.  If you want to check it for yourselves, download here:

https://www.dropbox.com/s/evvmsf7d1wpns6y/Test%20DIY-Neumann%20KM84s.zip?dl=0

 

[fripholm]

I recorded a 24-96-Wave comparison on acoustic guitar of my 2 well-matched Neumann KM84's vs 2 builds of the DIY KM84.  Couldn't be happier.  If you want to check it for yourselves, download here:

https://www.dropbox.com/s/evvmsf7d1wpns6y/Test%20DIY-Neumann%20KM84s.zip?dl=0

Thanks for the comparison. I can't open ProTools sessions, so have to listen to the WAV files directly.

Audio 1_01.wav
Audio 2_01.wav

KM84_Red SN 51518Run 1.wav
KM84-Brn SN 32547 Run 1.wav

KM84-Brn SN 32547  run 2.wav
MC KM84 w C3 Is 1.5 uF run 2.wav

KM84 w 100 uF C3 -C4 run 3.wav
KM84-Brn SN 32547  run 3.wav

The file names doesn't make it obvious which ones are the DIY mics and which ones aren't. I'm noticing "Audio 1" and "Audio 2" are sounding dull compared to the rest. So, as long as this was not supposed to be a blind test, which one is which?

I'm also noticing a very narrow stereo field when two pairs are panned hard left and right. How was the placement of the mics?

 

[craigmorris74]

I recorded a 24-96-Wave comparison on acoustic guitar of my 2 well-matched Neumann KM84's vs 2 builds of the DIY KM84.  Couldn't be happier.  If you want to check it for yourselves, download here:

https://www.dropbox.com/s/evvmsf7d1wpns6y/Test%20DIY-Neumann%20KM84s.zip?dl=0

What transformer did you use for your builds?  EDIT- See its the Haufe BV107.  Thanks!

 

[maarvold]

Actually, the one with MC in the name is an AMI T8; the one with MA (me) in the name is Haufe. 

 

[maarvold]

Audio 1 & Audio 2 weren't meant to be included--sorry. 

The ones with SN (serial number) in the name are real Neumann KM84's.  SN32547 is the Control mic; the rest are considered Test mics and are compared, one at a time, to the Control.  This is all explained in the ReadMe file I included; Unfortunately, it looks like my neatly-formatted file got a little weird-looking, but all the info is there and readable, in spite of the formatting. 

I included the Pro Tools session in case it makes things more convenient for some.  But the files can certainly be played directly in any DAW. 

A narrow stereo field is the whole point--see the included JPG.  Perfect mono would be even better, but the mics can't occupy the same physical space at the same time, so we have to settle for very close together. 

Thanks for the comparison. I can't open ProTools sessions, so have to listen to the WAV files directly.

Audio 1_01.wav
Audio 2_01.wav

KM84_Red SN 51518Run 1.wav
KM84-Brn SN 32547 Run 1.wav

KM84-Brn SN 32547  run 2.wav
MC KM84 w C3 Is 1.5 uF run 2.wav

KM84 w 100 uF C3 -C4 run 3.wav
KM84-Brn SN 32547  run 3.wav

The file names doesn't make it obvious which ones are the DIY mics and which ones aren't. I'm noticing "Audio 1" and "Audio 2" are sounding dull compared to the rest. So, as long as this was not supposed to be a blind test, which one is which?

I'm also noticing a very narrow stereo field when two pairs are panned hard left and right. How was the placement of the mics?

 

[fripholm]

Audio 1 & Audio 2 weren't meant to be included--sorry. 

The ones with SN (serial number) in the name are real Neumann KM84's.  SN32547 is the Control mic; the rest are considered Test mics and are compared, one at a time, to the Control.  This is all explained in the ReadMe file I included; Unfortunately, it looks like my neatly-formatted file got a little weird-looking, but all the info is there and readable, in spite of the formatting. 

I included the Pro Tools session in case it makes things more convenient for some.  But the files can certainly be played directly in any DAW. 

A narrow stereo field is the whole point--see the included JPG.  Perfect mono would be even better, but the mics can't occupy the same physical space at the same time, so we have to settle for very close together.

Aaahhh, now that you say it - there's a Readme included... d'oh  :-[

Guess a closer look would've helped. Everything makes sense now, thanks!

And while we're at it. I used my KM84 builds as drum overheads for a live recording I did about two weeks ago. The following folder contains a short snippet of the show. One file is the full stereo mix and one is just the two overhead mics without any processing:

https://www.dropbox.com/sh/7fkb22jw6d57jrs/AABONPgqjcGg4Y0ZDSqwBf2Fa?dl=0

As I intend to use the mics mostly as drum overheads, I replaced the 4pF cap with a 22pF as a permanent pad. Otherwise the mics are overloading all the time with most drummers.

 

[TwentyTrees]

Thanks for sharing the results of this test Maarvold - illuminating!

Audio 1 & Audio 2 weren't meant to be included--sorry. 

The ones with SN (serial number) in the name are real Neumann KM84's.  SN32547 is the Control mic; the rest are considered Test mics and are compared, one at a time, to the Control.  This is all explained in the ReadMe file I included; Unfortunately, it looks like my neatly-formatted file got a little weird-looking, but all the info is there and readable, in spite of the formatting. 

I included the Pro Tools session in case it makes things more convenient for some.  But the files can certainly be played directly in any DAW. 

A narrow stereo field is the whole point--see the included JPG.  Perfect mono would be even better, but the mics can't occupy the same physical space at the same time, so we have to settle for very close together.

 

[Lamont Replevin]

I ordered two kits--finished one of them, biased it, it sounds dope. Clear, full, gorgeous, inspiring.

Problem! When i was biasing the second one i was careless and neglected to shut off the phantom power while turning the screw on the trim-pot. Aaaaand i must have short-circuited the whole thing with the screwdriver and fried something. I am pretty inexperienced, so i'm not sure how to diagnose what i blew up and so forth. The tip of the screwdriver must have just drifted to the next component... Anyway I think i may have blown the JFET because i get total continuity between the gate and source/drain with no power applied. I would heartily appreciate any tips on how to trouble-shoot the circuit. What else could i have blown? Am i right that continuity in the JFET means it's borked? Please use small words! I am not too bright, but very enthusiastic and appreciative.

 

[Potato Cakes]

I ordered two kits--finished one of them, biased it, it sounds dope. Clear, full, gorgeous, inspiring.

Problem! When i was biasing the second one i was careless and neglected to shut off the phantom power while turning the screw on the trim-pot. Aaaaand i must have short-circuited the whole thing with the screwdriver and fried something. I am pretty inexperienced, so i'm not sure how to diagnose what i blew up and so forth. The tip of the screwdriver must have just drifted to the next component... Anyway I think i may have blown the JFET because i get total continuity between the gate and source/drain with no power applied. I would heartily appreciate any tips on how to trouble-shoot the circuit. What else could i have blown? Am i right that continuity in the JFET means it's borked? Please use small words! I am not too bright, but very enthusiastic and appreciative.

This has already been addressed in the official build thread. Head over there and check it out.

Thanks!

Paul

 

[Lamont Replevin]

Thanks, Paul--I see it now.