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[soapfoot]

If the recent K870/K67 capsule I installed in one of our three U67s is any indication, then the 2013 capsule could be very good indeed. I bet Klaus will have the first-hand experience to know for sure.

[Uwe]

Neumann does maintain an interesting forum specific to their products, and with many interesting threads regarding vintage Neumann products. On their forum home page is an interesting link for inquiries about manufacturing dates for microphones produced before 1990. Through that contact you could find out that this specimen was one of the last five M49c produced in Berlin and delivered to Japan in March of 1974. I also got confirmation that the capsule has been replaced with an original Neumann K49 of very recent (2013) production, and with the standard protective top bumper removed in the interest of authenticity. (It is not required under the large head basket of the M49.) The wire from the capsule's center electrode should be rerouted, as it is currently touching the the rubber stand-off, possibly leading to handling noises. The pictures further suggest the plastic base of the head assembly should be more clear and transparent and might benefit from careful cleaning. According to the factory experts, all other parts, including the housing, basket, type label and their assembly look completely original for the confirmed 1974 pedigree.
Congratulations on this exceptional find, and many good recordings!

[klaus]

Thanks, Uwe.  Nice bookend, to the thread, and to the M49 model, too!

[brightmillion]

Thanks Uwe, for the detailed history of my mic! I really appreciate your research and knowing the details from the factory made me a confident buyer. The mic is now in my happy hands and I am excited to get recording!  Having a history of this particular mic makes it that much more fun to own and a great story for studio comers, whether they want to hear it or not..!
I am going to burn in the tube for 48 hrs to see if there are any strange happenins with the tube and then check out the power supply to see if I should get it adjusted. I'll upload some pics of the power supply (i think its original). I'll post back with my findings and first recording impressions!
I'm going to then look into the  "cardioid only" mode per Klaus' recommendation since I doubt I'll use it for anything but cardioid.
Thanks again for everyone's input and help 

[J.J. Blair]

Intersting.  So, by in 1974 they had stopped using the Bosch output cap in C5, and started using what looks like a wet tantalum cap, with a .69µF value? 

[klaus]

Say what? 0.69 mfd? Where do you see that?

[Uwe]

First page, picture below the one showing the type label... But not to worry, it is indeed an original aluminum electrolytic (not tantalum, as they were not be available for the necessary voltage rating).

[klaus]

The "10.69" below the "1µF" is the manufacturing date of the cap: October 1969.
Besides, there is no standard cap available that as a .69mfd value.

[J.J. Blair]

Oh.  Duh.  That makes much more sense.  Something tells me that cap doesn't sound so good!

On that note, are the output caps in U67s electrolytic or tantalum? 

[klaus]

They are polarized electrolytics- Siemens mostly.

[brightmillion]

Oh.  Duh.  That makes much more sense.  Something tells me that cap doesn't sound so good!

On that note, are the output caps in U67s electrolytic or tantalum?

J.J. - what do you mean by "Something tells me that cap doesn't sound so good!" ?
because of the date or type?

[J.J. Blair]

I have never heard an electrolytic cap that has sounded close to as good as either a paper and tar Siemens cap or a film cap, when in the transformer coupling position.  And yeah, you could guess that a 44 year old electrolytic cap probably isn't in the best shape, either! 

[Uwe]

J.J. can you provide a technically correct and logical explanation why one type of capacitor in an audio circuit should sound different (inferior) to another? Can you supply credible proofs (data, measurements, graphs) to support such emotional opinions?

[soapfoot]

I'll pipe in.

Cyril Bateman's excellent (though a few decades old) tests and measurements (complete with a thorough methodology that you can replicate yourself) expound on the subject at length.

http://www.scribd.com/doc/2610442/capacitor-sound

[boz6906]

Uwe has asked one of the Eternal Questions...

I'm also interested in the "sonic" differences between capacitors.

"Capacitors have unwanted inductance, resistance, and dielectric absorption. Different materials and manufacturing techniques produce varying amounts of these unwanted parasitics that affect a component's performance."

One parameter that may relate to sonic differences is dielectric absorbtion:

"Briefly, dielectric absorption has been revealed as a major source of distortion in audio circuits. Film dielectric type capacitors, particularly polystyrene, have very low dielectric absorption and for this reason are preferred in audio circuits."

Another effect that I think may affect sonic performance is the amount of "smearing" between voltage and current caused by the dielectric phase angle:

"When a capacitor is used as a series element in a signal path, its forward transfer coefficient is measured as a function of the dielectric phase angle, (theta). This angle is the difference in phase between the applied sinusoidal voltage and its current component."

http://www.reliablecapacitors.com/consider.htm

The link above also tries to explain the theory behind the use of "bypass" caps.

Of course, the best test is listening...