"U67"-ish microphone

[RuudNL]

I suppose this will work. You may want to adjust the value of the 120 pF capacitor, depending on the capsule you use. (I have also used 100 pF and 150 pF. Higher value = less HF.)

 

[RuudNL]

I have tried your U67ish de-emphasis in a similar mic circuit but if I connect the 120pf after the output capacitor I get noise (probably from B+ because if I turn off the psu, the noise dissapears).

I have built several microphones like this, but never had this problem.
For AC, the signal at both sides of the output coupling capacitor should be (nearly) the same.
Isn't it oscillation?

 

[LevinGuitar]

I have built several microphones like this, but never had this problem.
For AC, the signal at both sides of the output coupling capacitor should be (nearly) the same.
Isn't it oscillation?

Maybe, have no idea how it work and how to get rid of it. It starts after some seconds. Even with a very small resistor of 40ohms the problem seems to solve

 

[Aleguitarpro]

I suppose this will work. You may want to adjust the value of the 120 pF capacitor, depending on the capsule you use. (I have also used 100 pF and 150 pF. Higher value = less HF.)

Thanks. I'll try and report.

 

[digizaemon]

If anyone wants to try my design: I have a few extra printed circuit boards available.
(The PCBs fit into Chunger's 'budget' SYT-5 body.)

Edit June 07: All PCBs found a new owner...

Hi Ruud

Can i try your design PCB?
Please Let me know

Best

 

[RuudNL]

Can i try your design PCB?

At the moment I don't have PCBs available, but I will try to 'dig up' the design, so you can copy it.

 

[digizaemon]

At the moment I don't have PCBs available, but I will try to 'dig up' the design, so you can copy it.

 

[Dimon]

At the moment I don't have PCBs available, but I will try to 'dig up' the design, so you can copy it.

Hello!
I did not find how to write to you in a personal. I admire your skill and professionalism in the field of microphone construction. If possible, please send me a photo of the printed circuit board (design) U67 and a list of necessary parts. I would love to make this microphone. Thank you. Sincerely with hope.

 

[abbey road d enfer]

Hello!
I did not find how to write to you in a personal.

For sending a PM (Personal Message), just left-click on the member's picture/avatar and then pick "Start conversation".

 

[Dimon]

For sending a PM (Personal Message), just left-click on the member's picture/avatar and then pick "Start conversation".

Thank you. I understand.
I have not yet fulfilled the conditions so that I can write in a personal. Ten days have not passed and there are no 10 posts, sorry).

 

[Drosselmeier]

At the moment I don't have PCBs available, but I will try to 'dig up' the design, so you can copy it.

yes sir, looking forward to it

 

[LevinGuitar]

I'm experimenting with different deemphasis and don't get what is the difference between connecting C9 to C5/R10 as it is in your schematic versus connecting C9 from the anode/drain to the backplate like the U87.
There is an audible difference but I can't choose what I like most, does anyone tried that?

 

[RuudNL]

There will be no significant difference.
The advantage of the situation as drawn in the schematic, is that there is no DC over the HF feedback capacitor, so you can use a low voltage type.

 

[Kaskelot]

Just for fun, I recently put together a "U67"-ish microphone.
It is a kind of mix between a U67 and a U87.
The microphone works as expected, sounds good and I don't hear any difference between this microphone and a U87ai.
Measured self noise is 2 dB higher than a U87ai. Not too bad, but maybe a better EF86/EF806 could improve this.
I used an original Neumann capsule that I had as a spare.
The microphone is powered from an existing tube power supply, delivering +120 V for HT.
De-emphasis is through feedback from the output. (15 KHz is 5.5 dB down referred to 1 KHz.)

For those who are interested: the schematic is in the attachment.

Just posted my upcoming project Tube microphone project with vintage M7 capsules after RuudNL using your schematic RuudNL and would be grateful for comments and if anyone has a parts list to share.
Thanks!
Robert

 

[Kaskelot]

Hi.
I think this is a great project.
I'm going to build this with a body without switches on it so I'm thinking to use REMOTE PATTERN from PSU.
I modded schematic. I don't know if it's ok.
I'd like to build it but I'd like to remove FILTER and PAD, too.

Could it work like this scheme attached?
To test it without feedback (to hear Flat capsule response) can I only wait to install C9 or with this pattern arrangment C5 need to be grounded to work without C9 installed?

Thanks

Hi
Any luck with the "Remote Pattern"?

 

[Kaskelot]

Just posted my upcoming project Tube microphone project with vintage M7 capsules after RuudNL using your schematic RuudNL and would be grateful for comments and if anyone has a parts list to share.
Thanks!
Robert

Just ordered some stuff and here is my parts list Parts list
Robert

 

[doqmemory]

I finally finished one of these, using a 797 Audio K67 and a 3U Audio GZT-87. It sounds great, very similar to my M269c clone using the same capsule, Moby's Bv12, and a 5718 tube.

Thanks for the great design, @RuudNL !

 

[doqmemory]

I improved my layout in the second one (bottom one), moving R1 to the switch PCB, as in the original diagram. Now no "crossed wires" on the backside!

 

[HerbertR]

I improved my layout in the second one (bottom one), moving R1 to the switch PCB, as in the original diagram. Now no "crossed wires" on the backside!View attachment 118567View attachment 118569

The more microphones I build, the more I come to the conclusion that point-to-point, Turet... is a lot less trouble than building with etched circuit boards.....Cheers

 

[OneRoomStudio]

The more microphones I build, the more I come to the conclusion that point-to-point, Turet... is a lot less trouble than building with etched circuit boards.....Cheers

...until you have to replace a part that has a leg that forms a bus. Desoldering gets messy fast. I'm a fan of PCBs myself.