Neumann U67 Clone : D-U67 Tube Microphone Build Thread.

update: so I swapped the capsule sides and it seems like that's my issue. Now in cardioid mode, there's significant less high end and about 20 db less.  :-\

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Let Ben know. He'll do you good.



Henk

Sorry this is probably a silly question but im new to all this audio DIY and dont have any experience with electronics but how hard is this to build (im doubting its newbie friendly) and are the PSU's compatible/switchable between the US and UK voltages?

Thanks!

Welcome!

If you're new to electronics, a tube microphone is not a starting project, I would say. Also, there's lethal voltage (!!!) in the PSU. And the U67 arguably has the most complicated circuit of all tube mics.

On the other hand, the D-U67 is not completely DIY, that is the schematic and layout are already done for you.
If you have a friend who knows what he's doing (!!!) or a good (!) technician in your neighborhood, you may be in luck. Otherwise, I'd do some serious studying and practising first.

i'm still buying parts for my U67..
for the Styrene 270pf /630V
i assume the Polystyrene Film "Tubular axials" 270pf axial at 630V is fine but i don't understand this :
feedback Capacitor Stryrene 80-160pf/630
does it mean i can buy anything from 80pf to 160pf/630v ?  :-\
sorry i'm not used to this and the justradios is not super explicit

micaddict said:

Welcome!

If you're new to electronics, a tube microphone is not a starting project, I would say. Also, there's lethal voltage (!!!) in the PSU. And the U67 arguably has the most complicated circuit of all tube mics.

On the other hand, the D-U67 is not completely DIY, that is the schematic and layout are already done for you.
If you have a friend who knows what he's doing (!!!) or a good (!) technician in your neighborhood, you may be in luck. Otherwise, I'd do some serious studying and practising first.

Click to expand...

I agree with this...I just finished this project last night and it's working great! With that said, I consider myself 'intermediate' I suppose and don't think there is anyway I could have done this a year or two ago before some of my other builds...not to mention the lethal voltage of course. Plus, although Poctop did a TREMENDOUS job getting this together, there isn't a 'definitive' build guide so you will do lots of referring to the schematic and confusing pictures, which, if you aren't comfortable with the schematic, will be terribly difficult.


On an unrelated note, I just showed the internals of my new U67 to an engineer friend of mine, and his first question was 'won't the tube heat up and melt these wires?' (referring to the wires connecting to the transformer). Is this at all an issue? If it was a concern, I feel like I would've read about it here already. Is there a danger of melting/burning wires or they touch or are too close to the tube? I 'burned in' my tube for about 8 hours last night, and nothing happened, so I assume it's fine, but still interested to know for sure.

Thanks!!

Thanks for the input chaps!

Ive been looking at a ton of stuff on groupdiy and im trying to think of what would easiest and most useful to start of with, i guess ill have to bug my dad and bro problem is im working out here in NY and there back in the UK 

Also just to recap on my other question, do i need anything special in order for these mic psu's to work in both the US and UK or is the voltages switchable on the psu?

Thanks and sorry derailing the thread a bit!

do i need anything special in order for these mic psu's to work in both the US and UK or is the voltages switchable on the psu?

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you need to use transformers with a dual primary that works with either 120v or 220v.

I would suggest starting with a project that 1) does not have dangerous voltages 2) does not have very expensive components for you to wreck as you learn
A microphone is a poor 1st project for both reasons.
I'd suggest a discrete preamp or compressor. Look at Classic API or Hairball audio to pick something out.

dgoszillai said:

i'm still buying parts for my U67..
for the Styrene 270pf /630V
i assume the Polystyrene Film "Tubular axials" 270pf axial at 630V is fine but i don't understand this :
feedback Capacitor Stryrene 80-160pf/630
does it mean i can buy anything from 80pf to 160pf/630v ?  :-\
sorry i'm not used to this and the justradios is not super explicit

Click to expand...

yes that mean the C17 the feedback capacitor can be from 80-160pf it can be tweaked a notch ,  but usually the stock value from nuemann is 100pf wich is what I supply in the styrokit .

Best,
Dan,

Finished my build...it's working great!!!!! So excited to record a project with it. I plan on powder coating the body this weekend. Here are some pictures;

2

3

MikeFFG said:

On an unrelated note, I just showed the internals of my new U67 to an engineer friend of mine, and his first question was 'won't the tube heat up and melt these wires?'

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Get out your Visa and max it out @ http://www.apexjr.com/ . He sells PTFE (Teflon) wire in various gauges and colours. He's also super nice to deal with.

The PTFE wire won't melt very easily which helps around heat sources and makes soldering in tight spaces easy. His wire is not terribly expensive so I've been stocking up with every build I do. I use it for everything and now have a good colour selection. I won't comment on the necessity of using it in your build since I did not use the AMI transformer but I use this wire everywhere I can now.

On an unrelated note, I just showed the internals of my new U67 to an engineer friend of mine, and his first question was 'won't the tube heat up and melt these wires?'

Click to expand...

in all my AMI build the Wire is close but does not touch the tube at all , but the tube will never generate that much heat to melt or even cause a problem i have been myslef using the mic for several several hours and nothing happened here too ,  this has never been an issue here from what i can tell,
just my 2 cents,  ,

if the tube would get hot at this point you would be able to cook an egg on the mic body 

Best,
dan,

One of two built, tested and working as it should.  Sounds great too.

Thanks to Dany for making it possible, and Max and Ben for the core components.  8)

poctop said:

On an unrelated note, I just showed the internals of my new U67 to an engineer friend of mine, and his first question was 'won't the tube heat up and melt these wires?'

Click to expand...

in all my AMI build the Wire is close but does not touch the tube at all , but the tube will never generate that much heat to melt or even cause a problem i have been myslef using the mic for several several hours and nothing happened here too ,  this has never been an issue here from what i can tell,
just my 2 cents,  ,

if the tube would get hot at this point you would be able to cook an egg on the mic body 

Best,
dan,

Click to expand...

Pretty much what I figured, but had to check.

Thanks again for this! I'm powdercoating mine 'black wrinkle' today. Should look pretty cool. And dammit, I'm probably going to have to build another one of these for the stereo pair!

I just did a really quick shootout test in the studio I work at with our U87 (I think it's a 'vintage' one? Definitely not the modern U87 AI) and I could hear a definite difference. Of course I'm biased, but the U67 sounded, I guess...clearer...more 'open' if that makes sense. The best way I could describe it is almost like I was using better converters. The U87 also sounded a bit more 'boxy.'

Edit:

Just so you know, I'm using the capsule from tskguy, the AMI T67 transformer and a NOS Telefunken tube.

MikeFFG said:

Just so you know, I'm using the capsule from tskguy, the AMI T67 transformer and a NOS Telefunken tube.

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That's an awesome combo! I bet it sounds stellar!

Dave

Received my capsules friday and finished my first of two 67's yesterday. After initial testing and a really long burn in period, I'm really happy with this mic! I expected an extended debugging period, but it worked first time I plugged it all in, thanks to Dany's great documentation. I'm building a stereo set with Beesneez capsules (matched!) and ioaudio transformers. I'll get started on the next one after some more testing this week. Mine is going up against two original u67's later this week

kpearsall said:

Received my capsules friday and finished my first of two 67's yesterday. After initial testing and a really long burn in period, I'm really happy with this mic! I expected an extended debugging period, but it worked first time I plugged it all in, thanks to Dany's great documentation. I'm building a stereo set with Beesneez capsules (matched!) and ioaudio transformers. I'll get started on the next one after some more testing this week. Mine is going up against two original u67's later this week

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Thanks Ken,
Can't wait to see your feedback on this marvellous testing you are planning to do ,
Best,
Dan,

Me too! Exciting

Hey guys, wanted to give an update on my capsule. I had it sent out to Ben, it was repaired and shipped back within a week! Sounds great now and performing like the other mic.

I'm still trying to lower some of the noise in my mics. I have that sorta wind/bubbling sound down there. I thought it may be the tubes at first but I replaced them with some low noise tele silver shield hilumins from the nos store, and the noise is still down there. I've been cleaning the circuit with alcohol which seems to be helping. Maybe it's just a matter of getting the circuit really clean? Has anyone else had any successful tricks to lowering noise? Thanks!