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Post by Martin John Butler on Mar 8, 2017 23:04:50 GMT -6
Ok, I know.. here I go again, but... this cost $599, before you shop for any discounts. Give it a few months and I bet you'll see it sold for a few dollars less now and then. I've used a KM84 a lot the last couple of years. Bob was right, it's a surprisingly good vocal mic too, you just need a really good pop screen.
This is absolutely in the same class as the KM84. I'd much rather keep the time I saved by not building, and pay a little more for something already proven that's guaranteed.
If it's anything like the KM84, I bet that even though it's an SDC, it would be damn good for vocals too.
I haven't tried this myself yet, but I may have one to try soon. I'll post some files if I get one.
Occasionally, I've thought about how good the KM84 might be with a large capsule, but mics are tricky business, and theory goes right out the window when you use it.
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Post by jcoutu1 on Mar 9, 2017 8:39:49 GMT -6
Ok, I know.. here I go again, but... this cost $599, before you shop for any discounts. Give it a few months and I bet you'll see it sold for a few dollars less now and then. I've used a KM84 a lot the last couple of years. Bob was right, it's a surprisingly good vocal mic too, you just need a really good pop screen. This is absolutely in the same class as the KM84. I'd much rather keep the time I saved by not building, and pay a little more for something already proven that's guaranteed. If it's anything like the KM84, I bet that even though it's an SDC, it would be damn good for vocals too. I haven't tried this myself yet, but I may have one to try soon. I'll post some files if I get one. Occasionally, I've thought about how good the KM84 might be with a large capsule, but mics are tricky business, and theory goes right out the window when you use it. Martin, start a new thread about this. I don't want to clog this one up with my drool.
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Post by svart on Mar 9, 2017 9:04:43 GMT -6
Hey Dave, long its been a long time since we chatted. Question for ya, with the emitter circuit you are talking about is the capacitor in the audio path? I am assuming it must be some sort of coupling cap? BTW, I am mixing a record next for a client that was tracked with all of your mics plus a SM7. I listened to the tracks already and they sound really good. They used one of your 87 style mics on the vocals and they sound really great. I'm thinking that yes, it would need a coupling cap. "Class A" means a constant current is being drawn regardless of signal, and therefor having a directly coupled transformer would saturate the primary to some degree. You'd need to AC couple it to avoid DC across the primary, or you'd need a split/gapped core like the older Neve output transformers.
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Post by adamjbrass on Mar 9, 2017 9:21:26 GMT -6
The Bock Audio iFET nails this with the "V" mode
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Post by Martin John Butler on Mar 9, 2017 9:34:45 GMT -6
Welcome to the forum adambrass ! I looked up the bock iFET, and it's $2,150.
It's funny, the same friend who loans me his KM84's has two U47 FET's. I tried them both on female vocals, then my vocal, and they flat out sucked. The Blackspade UM-17R I had at the time, (with the same basic capsule style) killed it. So, a beautifully made big fat vintage Neumann FET mic doesn't necessarily make for a good vocal mic.
Does anyone have some idea why the KM84 circuit with a large capsule would make for a better mic than the U47 FET ?
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Post by dandeurloo on Mar 9, 2017 11:51:32 GMT -6
Historically 47 fets have always kind of been the last mic used because it wasn't all that great. So it got used on outside kick alot. They have a different polar pattern and lots of other mics seem to win over it on lots of instruments. I don't hate them, but I would rather have a good km84 over fet 47 for lots of instruments.
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Post by Martin John Butler on Mar 10, 2017 9:17:26 GMT -6
Me too ! What's unexpected is the KM84 is a good vocal mic, worthy of a listen for compatibility with a particular vocalist.
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Post by jeremygillespie on Mar 10, 2017 9:50:27 GMT -6
The FET47 can work well on certain vocalists.
Listen to the Soundgarden Superunknown album - its all a FET47 on Chris' vocals.
I'm sure he would sound great on anything at that time though.
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Post by adamjbrass on Mar 13, 2017 7:32:28 GMT -6
I only mentioned the Bock mic [not out of price, or Famed U47 Fet heritage] but....because it specifically has a KM84 style amplifier, with the large K-47 capsule. This gives an interesting tone.
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Post by Ward on Mar 13, 2017 12:23:41 GMT -6
Welcome to the forum adambrass ! I looked up the bock iFET, and it's $2,150. It's funny, the same friend who loans me his KM84's has two U47 FET's. I tried them both on female vocals, then my vocal, and they flat out sucked. The Blackspade UM-17R I had at the time, (with the same basic capsule style) killed it. So, a beautifully made big fat vintage Neumann FET mic doesn't necessarily make for a good vocal mic. Does anyone have some idea why the KM84 circuit with a large capsule would make for a better mic than the U47 FET ? That's because you already have a balanced sounding voice. The U47 is the BOMB.COM for someone singing hard rock, screaming, or nasally in any way. For the same way it treats voice, it also excels on kick drum, bass guitar cabinet, tuba, trombone and other applications needing more 'kick' or 'punch'.
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Post by Martin John Butler on Mar 13, 2017 17:32:15 GMT -6
This makes me wonder why Neumann hasn't put something like this together, or have they, and they didn't like it?
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Post by aamicrophones on Mar 13, 2017 18:12:17 GMT -6
Hi Dan, its good to catch up again.
In the Emitter follower circuit there is one more capacitor between the FET and the Silicon transistor compared to the U87. However, it could be dc coupled but then you loose the opportunity to utilize the capacitor value as a HP filter as we do in our microphones.
You could dc couple the 2 stages and then switch a smaller capacitor in place of the 22ufd output transformer coupling capacitor but its roll-off curve would change a bit depending on the loading of the following microphone preamp.
If you have a U87 pre-1988 then it will have a 200 ohm/5:1 and a 50 ohm/10:1 option.
After, 1988 the U87AI has a transformer with a 7:1 ratio and the higher polarization voltage which produce 3-4db more output from the capsule and a subtle rise in the upper midrange.
The emitter/follow allows the circuit parameters to only require a 2:1 transformer not the 5:1 or the 7:1 of the later U87ai. The difference in loss between a 2:1 to a 5:1 is 8db and 14db between the 2:1 vs the 10:1.
After the dust settles the U87AI has nearly 6db less headroom than the original U87 set to 50 ohms but the older U87 will have nearly 6db less output level.
So, this gives the emitter follower circuit 8-14db more headroom than the single fet circuit. I find the single fet circuits works really well in the KM84 but SD capsules put out less level than a LD capsules.
The single FET circuit also requires selected high gain fet's. WE lower the gain in the first FET stage by about 10db-14db compared to a U87 or U87AI. The medium gain 2SK170 FET's have a smoother gain curve.
We even use the emitter follower circuit in our CM1084 pencil microphone just like AKG did in the C451e SDC microphones.
Both AKG in the original C414eb used tantalum capacitors as did Neumann. The ESR of a tantalum is twice as good as the best electrolytic. However, they have life span of 15-20 years in my experience.
We have found tantlum's in U87's that have shorted and cause the circuit to fail. Bad tantlums will usually start to sputter and pop before they completely fail. We recently found one in a 70's microphone measuring about 1K ohm when they should measure infinity.
In our CM47fet the circuit has a traditional older U87 front end and polarization circuit. There is a 1meg and a 220pf capacitor in parallel creating de-emphasis for our AK89 (87AI type capsule).
We polarize the capsule from the phantom supply at the same voltage as the original U87 which is somewhere around 37v. In the U87AI Neumann uses a DC to DC converter and polarizes the capsule up at 60v.
We use a similar dc to dc converter in our CM87 as the U87AI as we want the FIG 8 pattern but we don't use de-emphasis with its larger 35mm AK67 capsule which has no rise in the responsee until 7khz where its up 2db and then is up 5-6db at 12khz.
So, our CM87 sounds about 1/2 way between the original U87 with the lower polarization voltage and the new "brighter" U87AI but with the headroom of a C414eb.
I have a pre-1988 U87 set-up in the studio that I just changed from 200 ohms windings to 50 ohms for a client. In 200 ohm the output of the U87 was overloading his vintage console and he doesn't like the sound with the pad engaged.
So, it will give him an output level closer to a SM7 than a U87AI without having to use a pad in the console or a pad on the microphone.
Cheers, Dave
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Post by dandeurloo on Mar 13, 2017 19:01:50 GMT -6
I believe the missing low end depth of the Microphone-parts KM84 circuit is caused by the output transformer. I sent it to Dave Hill at Jensen Transformers to run it on their Comtran system to quantify it. Jensen is now making replacement transformers for common Neumann mics, I'd love to get one to replace this one, I suspect it would solved the sonic issues I have. I found the same thing with the one I just put together. It sounds pretty good. I have a Redline capsule in it so the capsule is not the problem. Overall it sounds good. It does lack low end and I feel it is also lower output then it should be. I noticed the original KM84 has a higher ratio transformers. I need to try a few different transformers with this mic. I have a feeling that will help a lot.
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Post by aamicrophones on Mar 13, 2017 19:13:57 GMT -6
I believe the missing low end depth of the Microphone-parts KM84 circuit is caused by the output transformer. I sent it to Dave Hill at Jensen Transformers to run it on their Comtran system to quantify it. Jensen is now making replacement transformers for common Neumann mics, I'd love to get one to replace this one, I suspect it would solved the sonic issues I have. I found the same thing with the one I just put together. It sounds pretty good. I have a Redline capsule in it so the capsule is not the problem. Overall it sounds good. It does lack low end and I feel it is also lower output then it should be. I noticed the original KM84 has a higher ratio transformers. I need to try a few different transformers with this mic. I have a feeling that will help a lot.
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Post by dandeurloo on Apr 11, 2017 12:40:43 GMT -6
As a update to earlier in the thread about the MP's 84 kit. It sounds ok stock. It does lack low end so I modified the circuit and that helped but it still was missing low end.
I ended up putting in a better TX. That helped a lot and smoothed everything else out. Now, I have a really nice extra mic. It is a little light in the low end but what is there is more then enough and will make a great mic.
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Post by Roswell Pro Audio on Jul 30, 2017 22:59:46 GMT -6
This is an older thread, but some misinformation has been posted here that I'd like to correct.
The MicParts "T-series" microphone kits that John linked to at the beginning of this thread are indeed based on Neumann's KM84 circuit. We adapted it for large-diaphragm capsules. We made several upgrades to the original design; the result is not a straight copy of Neumann's circuit.
Jim Williams was not involved in the adaptation or parts selection for this circuit. We did work extensively with Jim when we licensed his transformerless circuit, which is based on MXL's version of the Schoeps design.
Regarding Jim's comment that the transformer circuit is thin in the bass, I would respectfully disagree. Further, I will share a relevant measurement: the circuit's -3dB point is 30Hz. Given that the primary intended application for this circuit is within a vocal microphone, the 30Hz rolloff has not been a problem.
Further, if any of my customers for this kit had ever complained about the bass response, I could point to a single component change that would address it. (Note: it's not the transformer.) But we haven't had a single comment about bass response, other than one guy on Youtube whose capsule had failed. (Yes, we replaced the capsule.)
The transformer that we use is custom wound for my circuits, and is made in the US. It was selected in part because it delivers superior low-frequency distortion performance than any of the off-the-shelf transformers we tested. We tested about six transformers, some with much larger core sizes, from all the popular brands. The custom unit delivered the best overall performance. We use it in this "T-84" circuit and in our tube mic circuit.
Regarding Dave's comments about the AA microphones, and specifically the idea that using a 2-stage circuit to lower the impedance in advance of a lower-ratio transformer is somehow superior: there are certainly lots of ways to solve this problem. Audio design is all about tradeoffs. We happen to like the sound of the single-stage circuit with our custom transformer. It has higher 2nd harmonic distortion than a 2-stage (emitter follower) circuit, and higher 2nd harmonic than our transformerless circuit too, by design. That's why it sounds amazing on vocals and other moderate SPL sources.
I believe a good mic locker has a lot of contrast in it. If you want clean and pristine, build the transformerless mic. If you want some vibe and color for your next vocal mic, build the transformer-coupled mic. They don't sound the same, and they're not supposed to. My transformer mic circuit was designed to capture rich harmonics. We make these kits inexpensive enough that customers can afford to build purpose-specific mics. And we have some really impressive results, e.g. when Greg Wells posted to Twitter that my T-12 microphone sounds like a $5000 microphone.
If versatility is your key consideration, we have other options. E.g., the S3-87 kit gives 3 patterns and a 10dB pad with a very clean, low-distortion circuit. Adjust the in-circuit EQ to taste (via socketed EQ cap -- no soldering required for the final voicing/tuning step) and you'll have a fantastically versatile mic with plenty of headroom and neutral tonality. Voice it anywhere between a U67 and a TLM103 (referring to the high-frequency response here, not the distortion characteristics). Or if you want more color, use a K47 capsule (with or without in-circuit EQ -- your choice).
I don't generally have time to follow the forums, so if anyone has followup questions about the DIY kits from micparts.com please contact me directly. I'm easy to reach, and happy to help.
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Post by johneppstein on Aug 2, 2017 14:54:00 GMT -6
Microphoneparts capsules are WAY too expensive. It's standard chinaware, available on Aliexpress for 70% less Are you certain? Is it standard Chinaware, or has it been through a hand selection process? Let's see - IF it's hand selected, and if only 1 out of 3 capsules makes the cut (not an unreasonable assumption), then that pretty much explains the 70% difference, with a few cents left over to cover the labor of testing. Not saying one way or the other (not in a position to know), but it's something that definitely be taken into consideration.
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Post by Deleted on Aug 2, 2017 15:01:37 GMT -6
Microphoneparts capsules are WAY too expensive. It's standard chinaware, available on Aliexpress for 70% less Are you certain? Is it standard Chinaware, or has it been through a hand selection process? Let's see - IF it's hand selected, and if only 1 out of 3 capsules makes the cut (not an unreasonable assumption), then that pretty much explains the 70% difference, with a few cents left over to cover the labor of testing. Not saying one way or the other (not in a position to know), but it's something that definitely be taken into consideration. You bring up a good point, John. On one hand, since you can get these same style caps that look identical for about $40-$50 each on Ebay, theoretically you could buy 3 of them for about the price of an MP capsule and hopefully have at least one good one. I think for some, the vetting MP does on their stuff is worth it for peace of mind, but I can see how an adventurous and knowledgable DIY'er would be happy rolling the dice.
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Post by johneppstein on Aug 2, 2017 17:11:05 GMT -6
Are you certain? Is it standard Chinaware, or has it been through a hand selection process? Let's see - IF it's hand selected, and if only 1 out of 3 capsules makes the cut (not an unreasonable assumption), then that pretty much explains the 70% difference, with a few cents left over to cover the labor of testing. Not saying one way or the other (not in a position to know), but it's something that definitely be taken into consideration. You bring up a good point, John. On one hand, since you can get these same style caps that look identical for about $40-$50 each on Ebay, theoretically you could buy 3 of them for about the price of an MP capsule and hopefully have at least one good one. I think for some, the vetting MP does on their stuff is worth it for peace of mind, but I can see how an adventurous and knowledgable DIY'er would be happy rolling the dice. Well, you could buy 3 and end up with 3 bad ones, too. The chances of getting that 1 out 3 good ones is a lot better when you buy a hundred lot to select from than if you just buy 3. Averages like that only really work well when you have a large pool to draw from. And you'd BETTER know your Ebay seller or you might just gets the rejects from somebody else's selection process. I learned that the hard way. Hope is a fine thing, but I've learned not to put too much money on it. I'd rather pay extra to somebody I trust and know what I'm getting.
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Post by aamicrophones on Aug 2, 2017 19:01:39 GMT -6
Hey Dave, long its been a long time since we chatted. Question for ya, with the emitter circuit you are talking about is the capacitor in the audio path? I am assuming it must be some sort of coupling cap? BTW, I am mixing a record next for a client that was tracked with all of your mics plus a SM7. I listened to the tracks already and they sound really good. They used one of your 87 style mics on the vocals and they sound really great. Hi Dan, just found this post. I probably missed it as we were at my grandson's graduation from his avionics course in the Canadian Airforce and assignment to the 424 Search and Rescue squadron. When we returned we were busy on finishing up our CM800T prototype and getting organized for the Summer Namm show. We had a great show and was busy on our return filling orders. Here is the KM84 schematic with the high gain 2N3819. So, there are 4 capacitors in the audio chain. C3 is used to trim the gain of the fet by about 4db. if it is removed there is 4db less headroom. C1 couples the capsules voltage change into the fet so it can be amplified. The 4.7ufd across the 3.9k resistor will also change the gain and LF response. I have repaired several Neumann's with failed 4.7ufd tantalum capacitors but the ESR of a tantalum is twice as good as a electrolytic. C2 couples the audio output of the fet into the 7:1 ratio output transformer and blocks dc from magnetizing the transformer. C4 is also a tantalum and can also fail in older KM84 microphones. With the original C414/C451 emitter follower circuit there is a capacitor between the FET and the output transistor and we use three switchable capacitors to give us a variable HP filter. Notice no small feedback capacitor is required to trim the gain as we have 12db less gain in the first stage from the medium gain 2SK170. We also bypass the R9 with a 22 ufd to ground which optimizes the gain and LF response. The output transformer is coupled from the emitter of the transistor through C4 to the output transformer which has a 2:1 ratio. The CM1084 has one more coupling capacitor in the audio chain but does not need the 4pf negative feedback gain trim capacitor. I am not sure how you could implement the output circuit without a capacitor driving the transformer. If you let DC get to the transformer you will magnetize it in one direction. The only circuit I have seen without a coupling capacitor is the Schoep transformerless circuit. I suppose a Shoep circuit might drive a 1:1 ratio transformer and give you better common mode rejection. Cheers, Dave
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Post by jakeharris on Aug 2, 2017 21:03:44 GMT -6
Are you certain? Is it standard Chinaware, or has it been through a hand selection process? Let's see - IF it's hand selected, and if only 1 out of 3 capsules makes the cut (not an unreasonable assumption), then that pretty much explains the 70% difference, with a few cents left over to cover the labor of testing. Not saying one way or the other (not in a position to know), but it's something that definitely be taken into consideration. It's 2017. Chinese output operates at 0 to 10% rejection rates, not 60-70% as you're suggesting. And that 10% rejected, you can sell off as 'b-stock' for half-price, and still turn a profit. You never need to take a hit when starting this high. It's. all. mark-up.
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Post by Coil Audio on Aug 3, 2017 13:50:13 GMT -6
Are you certain? Is it standard Chinaware, or has it been through a hand selection process? Let's see - IF it's hand selected, and if only 1 out of 3 capsules makes the cut (not an unreasonable assumption), then that pretty much explains the 70% difference, with a few cents left over to cover the labor of testing. Not saying one way or the other (not in a position to know), but it's something that definitely be taken into consideration. It's 2017. Chinese output operates at 0 to 10% rejection rates, not 60-70% as you're suggesting. And that 10% rejected, you can sell off as 'b-stock' for half-price, and still turn a profit. You never need to take a hit when starting this high. It's. all. mark-up. "0-10% rejection rates" LOL - are we talking about fidget spinners here? Respectfully - You. Are. Mistaken.
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Post by Deleted on Aug 3, 2017 14:44:15 GMT -6
You bring up a good point, John. On one hand, since you can get these same style caps that look identical for about $40-$50 each on Ebay, theoretically you could buy 3 of them for about the price of an MP capsule and hopefully have at least one good one. I think for some, the vetting MP does on their stuff is worth it for peace of mind, but I can see how an adventurous and knowledgable DIY'er would be happy rolling the dice. Well, you could buy 3 and end up with 3 bad ones, too. The chances of getting that 1 out 3 good ones is a lot better when you buy a hundred lot to select from than if you just buy 3. Averages like that only really work well when you have a large pool to draw from. And you'd BETTER know your Ebay seller or you might just gets the rejects from somebody else's selection process. I learned that the hard way. Hope is a fine thing, but I've learned not to put too much money on it. I'd rather pay extra to somebody I trust and know what I'm getting. Yeah, I think I got lucky last time I tried. A while back I got an Ebay alert that one of the WGT double-sided 87 style capsules had dropped in price to something stupid like $20 (they normally go for $45) so I figured what the hell. I only needed one good side for a cardioid mic I was tinkering with and one side did sound a bit better than the other, actually good enough that the mic is a near sonic match for my 416 shotgun mic that I use all day. Made me think about getting a Heiserman or some other high quality capsule to replace it, but for $20, I definitely feel like I got my money's worth and the mic sounds pretty good. Worst case scenario, I have a tester capsule I can use for my frankenstein projects or even throw it into a modded MXL and toss it up on Ebay for $200.
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Post by Martin John Butler on Aug 3, 2017 15:11:09 GMT -6
I've been working on my comparison of the KM84 and the Soyuz 0-13. For the sake of the video, and for fun, I used them both as vocal mics. First, all due respect to Bob Ohlson, the KM84 is no U47, 67, 87, etc. It is surprisingly good when you compare it to the $200- $400 Chinese made mics, in fact, it much better, but that said, it's OK as a vocal mic, and that's it. Perhaps in some circumstances like a truly great vocalist at Motown, in a great sounding room with a great band and great engineers something really good can come of it, but it doesn't quite hold up to my $600-$800 mics.
Now, I hate to say it, the Soyuz 0-13 sounds WAY better as a vocal mic, though it too doesn't quite compare to the big LDC's. So I wouldn't get too excited about an LDC with a KM84 circuit. When I post the results of my review, you can judge for yourself.
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Post by wiz on Aug 3, 2017 15:16:03 GMT -6
I've been working on my comparison of the KM84 and the Soyuz 0-13. For the sake of the video, and for fun, I used them both as vocal mics. First, all due respect to Bob Ohlson, the KM84 is no U47, 67, 87, etc. It is surprisingly good when you compare it to the $200- $400 Chinese made mics, in fact, it much better, but that said, it's OK as a vocal mic, and that's it. Perhaps in some circumstances like a truly great vocalist at Motown, in a great sounding room with a great band and great engineers something really good can come of it, but it doesn't quite hold up to my $600-$800 mics. Now, I hate to say it, the Soyuz 0-13 sounds WAY better as a vocal mic, though it too doesn't quite compare to the big LDC's. So I wouldn't get too excited about an LDC with a KM84 circuit. When I post the results of my review, you can judge for yourself. How far are you from the microphone (KM84) when singing into it? cheers Wiz
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