grantb
Junior Member
Posts: 97
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Post by grantb on Apr 3, 2021 15:03:07 GMT -6
84 group buy is on over at gdiy. I just impulse bought a pair. Anybody else jumping in?
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Post by johneppstein on Apr 3, 2021 15:23:51 GMT -6
84 group buy is on over at gdiy. I just impulse bought a pair. Anybody else jumping in? Very interesting. Wonder if my soldering hand is up to it? |
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Post by jerrypbury on Apr 3, 2021 18:51:15 GMT -6
I just picked up 2.
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Post by svart on Apr 3, 2021 20:15:38 GMT -6
Hmm. Would have much rather had someone make bodies that can use km84 or km184 capsules
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Post by gouge on Apr 4, 2021 1:01:16 GMT -6
Serrano posted picks of an 84 clone on their facebook page.
Fingers crossed.
Agree with svart diy would be more interesting if it took neumann capsules.
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Post by mulmany on Apr 4, 2021 12:59:49 GMT -6
These sound good. I have a pair from the first run.
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Post by bram on Apr 6, 2021 13:40:40 GMT -6
Also have a pair from the first run which sound great. I use them frequently on drum OH. We had Haufe make a small batch of the original transformers as well. Have not had an opportunity to compare the capsule and off axis response with the real deal.
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Post by mcirish on Apr 7, 2021 9:47:13 GMT -6
I just ordered 2 kits and two transformers. I wonder how long it will be before they ship?
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Post by Calvin on Apr 7, 2021 11:05:33 GMT -6
Decided to check this out. Bought a single kit and transformer. Can't go much wrong at those prices, and I could really use another small diaphragm condenser mic. If it sounds anywhere close to an 84, so much the better.
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Post by avgatzeblouz on Apr 8, 2021 11:50:26 GMT -6
Hmm. Would have much rather had someone make bodies that can use km84 or km184 capsules Absolutely agree. Still waiting. |
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grantb
Junior Member
Posts: 97
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Post by grantb on Apr 8, 2021 12:16:08 GMT -6
It certainly seems doable if the Warm mic is in fact a fit for the original capsule. Just get the body, xlr cap, and internal connector bit from their factory and spin up a board.
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Post by avgatzeblouz on Apr 8, 2021 13:43:07 GMT -6
It certainly seems doable if the Warm mic is in fact a fit for the original capsule. Just get the body, xlr cap, and internal connector bit from their factory and spin up a board. It is not a fit. It was rumored at beginning and ended up not being compatible. |
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oong
New Member
Posts: 11
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Post by oong on Apr 12, 2021 20:14:26 GMT -6
I ordered a pair! I've been waiting for registration approval over a year though. Maybe they recognize S.Korea as a spam country.
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Post by cserrano on Apr 19, 2021 20:05:43 GMT -6
Serrano posted picks of an 84 clone on their facebook page. Fingers crossed. Agree with svart diy would be more interesting if it took neumann capsules. It is in the works, for sure! Stay tuned! The DIY KM84's sound good but I and several others have reported issues picking up RF noise. So if you aren't able to get away from cell phones or wifi equipment, they may not be usable. I found the culprit of the RF noise and it's actually very complicated to get rid of because the issue is with the structural parts and how they connect to the circuit. |
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grantb
Junior Member
Posts: 97
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Post by grantb on Apr 19, 2021 21:31:29 GMT -6
I found the culprit of the RF noise and it's actually very complicated to get rid of because the issue is with the structural parts and how they connect to the circuit. I would love it if you wouldn't mind expanding on this a bit, even if the problem isn't easily fixable. |
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Post by cserrano on Apr 20, 2021 5:26:55 GMT -6
I found the culprit of the RF noise and it's actually very complicated to get rid of because the issue is with the structural parts and how they connect to the circuit. I would love it if you wouldn't mind expanding on this a bit, even if the problem isn't easily fixable. In short, I couldn't actually eliminate the RF noise from the DIY KM84. I am close to certain that the issue comes from the method of connecting the XLR jack to the circuit. I think the issue has to do with with not enough shielding/isolation, but I didn't see way to resolve this because the XLR jack is soldered directly to the circuit. Perhaps that method of connecting the XLR jack was chosen because they wanted to make the body a little shorter? Not sure, but if so it would appear to an electronic compromise that is creating the RF noise, just to make the body a little shorter, which is only cosmetic. The Neumann KM84 achieves its compact size by using two boards, one of top of the other. But with the DIY KM84 it's a single flat PCB, which makes it longer. All this is to say, if your DIY KM84 is picking up RF noise, it's unlikely that you will be able to get rid of it. |
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Post by svart on Apr 20, 2021 7:42:46 GMT -6
I would love it if you wouldn't mind expanding on this a bit, even if the problem isn't easily fixable. In short, I couldn't actually eliminate the RF noise from the DIY KM84. I am close to certain that the issue comes from the method of connecting the XLR jack to the circuit. I think the issue has to do with with not enough shielding/isolation, but I didn't see way to resolve this because the XLR jack is soldered directly to the circuit. Perhaps that method of connecting the XLR jack was chosen because they wanted to make the body a little shorter? Not sure, but if so it would appear to an electronic compromise that is creating the RF noise, just to make the body a little shorter, which is only cosmetic. The Neumann KM84 achieves its compact size by using two boards, one of top of the other. But with the DIY KM84 it's a single flat PCB, which makes it longer. All this is to say, if your DIY KM84 is picking up RF noise, it's unlikely that you will be able to get rid of it. The KM184 also suffered from RFI and their solution was to piggyback a second PCB with nothing but ground layers over the traces of the first PCB. I have never investigated the fix or why they simply didn't use a 4 layer PCB with ground layers on the outer layers. Maybe they did after the fact. In either case, I do these kinds of things all the time for my RF work. What's intriguing is that the body of the mic should be good for around 60-70dB of shielding, which is plenty to reject radio, so it's not a true ingress issue. Shielding doesn't work if it's not the lowest impedance conductor to ground/return. I'd suspect the way the ground is (or not) attached to the XLR shield for the source of the problem. |
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grantb
Junior Member
Posts: 97
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Post by grantb on Apr 20, 2021 9:54:49 GMT -6
From a quick look at the docs it seems like the ground connection to the body (and capsule) is only through the friction tab on the side of the XLR to the bottom ring and then bottom ring to body. A poor connection in these places will only be exacerbated by the fact that bare brass corrodes as soon as it touches air. I wonder if polishing, cleaning, and deoxit on these connections will improve the situation, and if so for how long? Electroplating the body?
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Post by svart on Apr 20, 2021 10:42:18 GMT -6
From a quick look at the docs it seems like the ground connection to the body (and capsule) is only through the friction tab on the side of the XLR to the bottom ring and then bottom ring to body. A poor connection in these places will only be exacerbated by the fact that bare brass corrodes as soon as it touches air. I wonder if polishing, cleaning, and deoxit on these connections will improve the situation, and if so for how long? Electroplating the body? It's a good place to start looking. Oxides between dissimilar metals can form diode junctions that rectify RF into audible noise. At that point, the body is not acting like a shield, but as an antenna. A bit of scotchbrite pad to clean up the brass and a little white dielectric grease might help. I think the KM184 fix also had a copper finger to the body. I'll have to open mine up and take a look. I have one non-fixed and one fixed mic to look at and compare. |
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Post by kcatthedog on Apr 21, 2021 4:41:00 GMT -6
The Warm prototype did take the Neumann capsule, but then they switched it for the production run: guess Neumann rattled some sabres ?
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ericn
Temp
Balance Engineer
Posts: 15,940 
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Post by ericn on Apr 21, 2021 19:30:33 GMT -6
I would love it if you wouldn't mind expanding on this a bit, even if the problem isn't easily fixable. In short, I couldn't actually eliminate the RF noise from the DIY KM84. I am close to certain that the issue comes from the method of connecting the XLR jack to the circuit. I think the issue has to do with with not enough shielding/isolation, but I didn't see way to resolve this because the XLR jack is soldered directly to the circuit. Perhaps that method of connecting the XLR jack was chosen because they wanted to make the body a little shorter? Not sure, but if so it would appear to an electronic compromise that is creating the RF noise, just to make the body a little shorter, which is only cosmetic. The Neumann KM84 achieves its compact size by using two boards, one of top of the other. But with the DIY KM84 it's a single flat PCB, which makes it longer. All this is to say, if your DIY KM84 is picking up RF noise, it's unlikely that you will be able to get rid of it. Good luck man! Very glad to see your trying to take this on, I just hope you can resist the temptation to go with generic metal work like everybody else has. |
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Post by svart on Apr 23, 2021 7:47:37 GMT -6
Here's a pic of Neumann's RFI "fix" for KM184. They placed another PCB with solid ground plane over the backside traces of the primary PCB and added copper fingers to reduce the impedance to the mic body. In further layouts it would be advantageous to move to 4 layer boards with ground on the outer layers and possibly a pad for a copper finger. Places like JLCpcb don't increase the price much at all to go from 2 layer to 4 layer.  |
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Post by mhbunch on Apr 23, 2021 8:57:15 GMT -6
Damn I must have gotten lucky - no RF issues at all in the pair I built. I didn’t know that was a problem people were having.
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oong
New Member
Posts: 11
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Post by oong on Apr 25, 2021 20:42:22 GMT -6
Here's a pic of Neumann's RFI "fix" for KM184. They placed another PCB with solid ground plane over the backside traces of the primary PCB and added copper fingers to reduce the impedance to the mic body. In further layouts it would be advantageous to move to 4 layer boards with ground on the outer layers and possibly a pad for a copper finger. Places like JLCpcb don't increase the price much at all to go from 2 layer to 4 layer. View AttachmentThink I can try that with some veroboard. Really informative. Thanks!! |
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Post by mcirish on Jun 18, 2021 14:10:25 GMT -6
I believe I have all the parts now. Anyone complete one of these and have a comment on them?
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