Neumann Vintage U87 Clone : Build Thread.

[Khron]

And not necessary to do another between RD and RBK?

Why would i have kept that piece of information obscured, IF it was essential?

 

[Potato Cakes]

Hello, Everyone,

Trying to wrap up a pair of M version PCB builds and I somehow forgot to order the 47uH inductors even though I remember clearly thinking I needed to make sure that I don't forget them since I did not have any on hand. The ones I do have laying around are 4.7uH. I noticed in the Version 16 schematic that L1,2 positions were sometimes bridged for certain versions. I am just wondering if using this low of a value will either create an undesired filter effect or if there will be insufficient EMI suppression.

Thanks!

Paul

 

[micolas]

Hello, Everyone,

Trying to wrap up a pair of M version PCB builds and I somehow forgot to order the 47uH inductors even though I remember clearly thinking I needed to make sure that I don't forget them since I did not have any on hand. The ones I do have laying around are 4.7uH. I noticed in the Version 16 schematic that L1,2 positions were sometimes bridged for certain versions. I am just wondering if using this low of a value will either create an undesired filter effect or if there will be insufficient EMI suppression.

Thanks!

Paul

Many times I didn't even put these inductors.

 

[Potato Cakes]

Many times I didn't even put these inductors.

Did you notice any unwanted effects such and RF interference when using a jumper instead?

Thanks!

Paul

 

[micolas]

Did you notice any unwanted effects such and RF interference when using a jumper instead?

Thanks!

Paul

In short, No.
I have never had any problems with RF interference although there is a local FM radio station nearby (which I personally founded in 1996 ) which has 100W power in the antenna. In addition, I live surrounded by dozens of wi-fi routers, and probably hundreds of switching sources of devices,several cable television networks and towers with mobile phone antennas.
In addition, I live in a block built over 60 years ago and the grounding of the electrical network is no longer efficient.

 

[Potato Cakes]

In short, No.
I have never had any problems with RF interference although there is a local FM radio station nearby (which I personally founded in 1996 ) which has 100W power in the antenna. In addition, I live surrounded by dozens of wi-fi routers, and probably hundreds of switching sources of devices,several cable television networks and towers with mobile phone antennas.
In addition, I live in a block built over 60 years ago and the grounding of the electrical network is no longer efficient.

Good to know. Thanks!

Paul

 

[joulupukki]

Where on this board would I measure to verify the polarization voltage?

 

[micolas]

Where on this board would I measure to verify the polarization voltage?

If you refer to the polarization voltage of the capsule: in point 6.
If you mean the jFET bias: at point D - drain.
Measurements are made against GND, with a DMM with sufficiently high input resistance.
Better post a clear picture of your PCB and have someone physically point out the measurement points for you.

 

[joulupukki]

Gotcha. Based on that I was able to measure it. I was trying out a small daughter board that would increase the polarization voltage from 48 to 60V but in my situation it didn't really make much of a difference (in terms of increasing sensitivity of the mic). I still have to crank my preamp way up before it matches my other microphones' sensitivity.

 

[micolas]

Gotcha. Based on that I was able to measure it. I was trying out a small daughter board that would increase the polarization voltage from 48 to 60V but in my situation it didn't really make much of a difference (in terms of increasing sensitivity of the mic). I still have to crank my preamp way up before it matches my other microphones' sensitivity.

The vintage version U87i has lower sensitivity than the current version U87ai, and than other modern condenser microphones, ie it provides a lower output level, the gain of the preamplifier will have to be increased.

 

[Khron]

increase the polarization voltage from 48 to 60V but in my situation it didn't really make much of a difference (in terms of increasing sensitivity of the mic).

https://repforums.prosoundweb.com/index.php/topic,36194.msg531542.html#msg531542

It's not just about the capsule bias voltage...

 

[joulupukki]

Right. Maybe I should restore this back to the stock D-87 circuit and just sell it off and build another Fuchs u87a? Or, maybe the ORS 87 ... did I see somewhere that someone had figured out how to get more sensitivity out of that build?

 

[Khron]

Or, maybe the ORS 87 ... did I see somewhere that someone had figured out how to get more sensitivity out of that build?

How big of a hurry are you in?

 

[micolas]

Right. Maybe I should restore this back to the stock D-87 circuit and just sell it off and build another Fuchs u87a? Or, maybe the ORS 87 ... did I see somewhere that someone had figured out how to get more sensitivity out of that build?

ORS87 is cardioid only.
If it is enough for your studio purposes, then you can easily convert D-87 into ORS87, using the same electronic/mechanical construction, (body, pcb, capsule),
giving up some components and connections.
You don't have to invest a cent more.

 

[joulupukki]

How big of a hurry are you in?

Not in a hurry. I’m just not impressed at all with the low output of the D87 and would like to improve it.

ORS87 is cardioid only.
If it is enough for your studio purposes, then you can easily convert D-87 into ORS87, using the same electronic/mechanical construction, (body, pcb, capsule),
giving up some components and connections.
You don't have to invest a cent more.

I’d do that if I’d get a good volume/sensitivity boost. Cardioid is the only pattern I’d use with the mic anyway. For now, it sits in the case doing nothing. I’ve got other mics that handle the other polar patterns.

 

[micolas]

Not in a hurry. I’m just not impressed at all with the low output of the D87 and would like to improve it.

I’d do that if I’d get a good volume/sensitivity boost. Cardioid is the only pattern I’d use with the mic anyway. For now, it sits in the case doing nothing. I’ve got other mics that handle the other polar patterns.

The ORS87 has better sensitivity than the D-87, in fact it is comparable to current condenser microphones.

It actually has comparable sensitivity to the U87ai according to @Wordsushi's benchmark tests:

View attachment Wordsushi U87ai vs ORS87 Levels.wav
https://groupdiy.com/threads/open-source-diy-mic-project-ors-87-stripped-down-u87.86814/post-1143094

 

[joulupukki]

The ORS87 has better sensitivity than the D-87, in fact it is comparable to current condenser microphones.

Sounds like that may be a good direction to go with this particular build then. I'll have to study up more on that circuit and see what I'd need to do to implement it on this PCB ... unless that's already been done somewhere.

 

[micolas]

Sounds like that may be a good direction to go with this particular build then. I'll have to study up more on that circuit and see what I'd need to do to implement it on this PCB ... unless that's already been done somewhere.

That's exactly what I was trying to explain to you.
You have already built the ORS87 in the D-87 circuit. You just have to give up some components, that is, break/modify some connections. Very simple!

 

[joulupukki]

That's exactly what I was trying to explain to you.
You have already built the ORS87 in the D-87 circuit. You just have to give up some components, that is, break/modify some connections. Very simple!

Probably simple for you.

I glanced through the ORS87 thread just now looking for schematics and there are a few variations posted out there. I think I must not understand enough how microphone circuits work yet to be able to deconstruct the D87.

 

[micolas]

Probably simple for you.

I glanced through the ORS87 thread just now looking for schematics and there are a few variations posted out there. I think I must not understand enough how microphone circuits work yet to be able to deconstruct the D87.

The easiest way is to draw the changes on the D-87 diagram (delete unnecessary components, parts and connections to transform into ORS87)