the endless U67 M269 comparison question

Is it completely insane to try an AC701K in a U67 with appropriate power supply?  I haven't found an example of anyone trying it, only endless commentary about the sonic differences (or not) between the two models. 

At a glance the circuit differences appear to do with variable pattern, or not, unless you're talking about the M269C cathode bias version.  One resistor value difference in the calibration input. 

AC701K in a socket adapter, correct PSU voltages?  Why not?  Curious.  Someone must've done it. 

Why not? It should work.
Filament voltage is different, +HT is different and tube bias is different.
But with some minor changes it should work fine.
I am interested if it is worth all the effort.
A collegue of mine compared a U47 with a VF14 tube with a U47 with a 'modern' tube.
He said: "if you want to hear it, there is a minor difference, but I doubt if you would hear it in a mix".

I did not know there was a M269C cathode biased version. I found a M367
https://reverb.com/item/13508372-two-neumann-m367-m269-u67-ortf-a-mythical-vintage-microphone-that-works-like-on-the-first-day

120VDC B+ vs 210VDC

I think you can use a few different tubes as long as the gain is in a good range.

I would guess the 701 would be less microphonic than a EF86. I do wonder if part of the tube sound is microphonic tubes, caps etc. adding to the sound.

5840 is close to EF86 in triode mode what one is liked better?

Is this why solid state often sounds different?

I would normally dismiss these things as cork sniffing that vanishes in context, but I've found the differences in EF86's within the U67 circuit to be stark, not subtle at all. 

I agree EF86s do sound different in microphones

Tests I hope to get around to doing
Transconductance at the circuit design points
Gain in the circuit connected to a cable and preamp input
etc.

A well known 'microphone specialist' states that the microphone cable can make a (big) difference too.
Any thoughts about this?

It's kinda like listening to noise floors on headphones.....they seem intolerable many times until you listen at normal levels on speakers. 

Anyone look at the link? there is a schematic in the pictures

I am guessing the cathode biased 269 is the M367

Gus said:

Anyone look at the link? there is a schematic in the pictures

I am guessing the cathode biased 269 is the M367

Click to expand...

Looks like it. 

If you have an AC701K on hand (or can get one), why not.  More than a few folks have said they prefer the M269 so it'd be interesting to know what you think. 

I've never seen an M367 in black.  Actually, I've only ever seen a single one in the flesh,  Dan Alexander had one for a while at the old Coast Recorders in S.F. 
I'd sure like to own that pair on Reverb. 

RuudNL said:

A well known 'microphone specialist' states that the microphone cable can make a (big) difference too.

Click to expand...

Do you mean the microphone historian? 

abbey road d enfer said:

Do you mean the microphone historian? 

Click to expand...

I mean the man who can hear the difference between Belden 3344 ("a match made in heaven"), Doefler-made German Broadcast cable ("sibilance"), Gotham GAC 7 ("tight bass, pleasant dry") and modern Neumann cable ("little bit of mid-range congestion"). 

RuudNL said:

I mean the man who can hear the difference between Belden 3344 ("a match made in heaven"), Doefler-made German Broadcast cable ("sibilance"), Gotham GAC 7 ("tight bass, pleasant dry") and modern Neumann cable ("little bit of mid-range congestion"). 

Click to expand...

Yes, the same one that can hear the effects on group delay of cathode bias, when he can't hear the effects of the cardioid arrangement.