Banzai's KM84 DIY Body & PCB kit build thread

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Whoops

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I have two kits from Banzai and will be buying the 3Us. Seems a lot of other people went that route. They are readily available and affordable.

I can let you know how they turn out, but won't have much of anything compare them against.

Thanks for your reply.
It would be great to do some comparisons on the different transformers.
GZT-84 seems cheap Chinese, have some doubts on how good are those.
3U Audio, although Chinese maybe it's good quality since they make some nice stuff.
Cinemag I can only say good things about them in general.

It's a shame that Moby doesn't make this transformer. Moby transformers are really high quality and he gives a lot of attention to detail and correct materials, that would probably be the best transformer for this project
 

shabtek

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It would be great to do some comparisons on the different transformers.
GZT-84 seems cheap Chinese, have some doubts on how good are those.
3U Audio, although Chinese maybe it's good quality since they make some nice stuff.
Cinemag I can only say good things about them in general.
that transformer likely comes from the same factory as the other parts
 

Whoops

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Is there any reason not to use electrolytics in place of the tantalum capacitors?

Some people swear but the sound of Tantalum caps on some circuits, like for example in Neve BA283 boards, some of that people are quite knowledgeable like Geoff Tanner (Ex-Neve).

These is just a consideration for you they're not my words

Does the original KM84 circuit use Tantalums?
If so I would keep it that way
 

maarvold

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Some people swear but the sound of Tantalum caps on some circuits, like for example in Neve BA283 boards, some of that people are quite knowledgeable like Geoff Tanner (Ex-Neve).

These is just a consideration for you they're not my words

Does the original KM84 circuit use Tantalums?
If so I would keep it that way
 

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kato

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Does the original KM84 circuit use Tantalums?
Most definitely! At least one appears to be directly in the audio path, possibly more.

But I think that component choice has more to do with the limited miniaturization technology of the time. Personally, I doubt I would be able to hear any difference. But I have this impression that tantalum is more likely to fail spectacularly, failing to a short and possibly damaging other components in the process. Not to mention the bad rap it has as a conflict mineral. I've mostly stopped buying tantalums whenever possible. (But I'm not naive: I know the cell phone in my pocket is full of conflict minerals and much suffering when into making it.)

I know sometimes tantalums are specified for their very low D.C. leakage. And if that's the case, I might opt for low-leakage electrolytics. But I lack the smarts to know that from looking at the schematic.

Thanks for chiming in. Anyone built these with electrolytics successfully?
 

Banzai

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Thanks for your reply.
It would be great to do some comparisons on the different transformers.
GZT-84 seems cheap Chinese, have some doubts on how good are those.
3U Audio, although Chinese maybe it's good quality since they make some nice stuff.
GZT-84 is made and sold by 3U Audio

that transformer likely comes from the same factory as the other parts
Nope. See above.
 

Whoops

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Not to mention the bad rap it has as a conflict mineral. I've mostly stopped buying tantalums whenever possible.

Totally understandable your reservation, I guess the problem is related to the War in Congo, but there's other sources of tantalum from other places in the world with no conflicts involved.
The problem is that when you buy a tantalum cap you dont know if the minerals come from Congo or any other place in the world.

And yes, our cellular phones, that the manufacturers try hard that we change every 2 years, even if we dont need to, are full of tantalum caps. Also our Laptops and a lot of electronics that we use everyday
 

kato

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Has anyone tried a different ratio output transformer, like the 4:1 ratio used in the Lulu? Looking at Graeme's investigation, it appears to be a dead-nuts clone of the KM84 with some cap value changes and a 4:1 transformer.

Seems like the 4:1 ratio would give a hotter output and possibly help with some of the noise floor issues inherent in the original design. Or is a transformer swap going to cause some impedance issues internally?
 

kato

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Seems like the 4:1 ratio would give a hotter output and possibly help with some of the noise floor issues inherent in the original design. Or is a transformer swap going to cause some impedance issues internally?

Don't mess with a classic formula dude.
Also, you don't know enough about what you're doing to be randomly swapping out transformers.
 

jrmintz

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I used AMI transformers in mine after trying the Cinemags, and I much preferred the AMIs. I have a pair of real KM84s and I would say the sound is indistinguishable with the AMIs. The only difference I noticed is that the pickup pattern seems tighter on the real KM84s. Apart from that I'd use one of Banzai's as a stereo pair with a real one any time.
 

kato

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Seems like the 4:1 ratio would give a hotter output and possibly help with some of the noise floor issues inherent in the original design. Or is a transformer swap going to cause some impedance issues internally?

I dunno man. Might as well try it. Take one for the team. Order one, try it out, and report back here.

Also, you're kind of a dick.
 

Zim

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Just finished building one of my two. AMI transformers and still have to properly bias the FET, but so far very much liking what I’m hearing.

i tried the 2nd capsule in the mic out of curiosity and there’s quite a significant volume difference between the two capsules, I’d never considered different versions of the same capsule having volume differences. Is this normal? (I assume it must be, as there are no other variables to account for it, other than one of them having spent more time in the mic). Do capsules ‘burn in’?
 

totoxraymond

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Just finished building one of my two. AMI transformers and still have to properly bias the FET, but so far very much liking what I’m hearing.

i tried the 2nd capsule in the mic out of curiosity and there’s quite a significant volume difference between the two capsules, I’d never considered different versions of the same capsule having volume differences. Is this normal? (I assume it must be, as there are no other variables to account for it, other than one of them having spent more time in the mic). Do capsules ‘burn in’?
I just finished my pair. I can only advise you to properly bias the mics before you try them. With the course of the 20k pot is large enough so the mic can be unusable.

Bias them, 😉

Thomas
 

Zim

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I just finished my pair. I can only advise you to properly bias the mics before you try them. With the course of the 20k pot is large enough so the mic can be unusable.

Bias them, 😉

Thomas
Yup, I’ll definitely be doing that - unless I’m missing something though, that wouldn’t have any effect on the difference between the capsules...

I’m talking about having tried two capsules on one body, and the capsule isn’t part of the biasing process so don’t understand how that would account for a volume difference between the two. Guess I’ll see how we go tomorrow.

(Not casting any aspersions on this mic btw - both capsules sound great already so far - just looking to learn)

cheers

Zim
 

rogs

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Interesting .... I've never had much time for those folk who buy fake 'Rolex' watches - or fake 'Neumann' microphones.
If you're parting with the kind of cash that overpriced 'Veblen' goods attract - then you need to know exactly what you are doing.
If you end up buying a fake, then clearly you don't know what you're doing, and you probably deserve to get caught out!

But there will always be those who can't resist a 'bargain' - and there will always be those prepared to make the bits and pieces to adorn those 'bargains', to make them look more expensive.
Golden rule applies ... if it looks too good to be true - it almost certainly is!

I wonder if it's illegal to actually sell those badges, or simply illegal to stick them on to mics , and try to pass them off as Neumann mics?
Probably different laws in different countries?...
 

JohnRoberts

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Interesting .... I've never had much time for those folk who buy fake 'Rolex' watches - or fake 'Neumann' microphones.
If you're parting with the kind of cash that overpriced 'Veblen' goods attract - then you need to know exactly what you are doing.
If you end up buying a fake, then clearly you don't know what you're doing, and you probably deserve to get caught out!

But there will always be those who can't resist a 'bargain' - and there will always be those prepared to make the bits and pieces to adorn those 'bargains', to make them look more expensive.
Golden rule applies ... if it looks too good to be true - it almost certainly is!

I wonder if it's illegal to actually sell those badges, or simply illegal to stick them on to mics , and try to pass them off as Neumann mics?
Probably different laws in different countries?...
I don't know how likely such IP theft could be prosecuted in a court of law, but it clearly is "wrong". If you have a shred of respect for intellectual property this should be unacceptable.

JR
 

rogs

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I don't know how likely such IP theft could be prosecuted in a court of law, but it clearly is "wrong". If you have a shred of respect for intellectual property this should be unacceptable.

JR
I agree - this should be completely unacceptable, but as we know there is some 'fakery' amongst almost all high priced 'premium' goods.
For example within the markets for paintings, handbags, watches, microphones -- the list goes on.
The stupid economics of 'Veblen' goods (where the price goes up, the more the price goes up!) is very attractive to fakers (understandably).

There is an argument that the more widely known the availability of 'fake' Neumann external parts like badges and bodies is, the more people might become wary of fakes?
 
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