OFFICIAL ioaudio MK67 build and support thread

[chunger]

the "good" E80F that I found so far was Amperex.  I think they all came from the same factory in Holland, no?  Valvo, Amperex, Zarex, Philips, etc.

 

[micaddict]

Oliver wrote this on the Neumann forum:

The E80F was only made by Valvo and was sold by the Philips mother company here in the US under the Amperex brand name as 6267.

Now that would suggest they were all made in Hamburg (yes, owned by Philips, anyway).

But AFAIK, the E80F was invented by Philips and only made in Heerlen (Holland).
A Dutch tube seller told me this, too (I'm Dutch myself BTW).
And this site suggests the same:
http://www.hupse.eu/radio/tubes/E80F.htm

Also, 6267 would be the equivalent of the EF86.

Anyway, if you have a clean one in hand, there should be a code.

 

[MicDaddy]

I have 1 out of 3 quiet tubes so far which makes it essentially a $60 alternate tube.  I have not tested them in studio yet against the Amperex and Telefunken EF86's, but am burning in a couple to prepare.

Chung can you talk some on your method of testing?  It might be helpful to describe a method of test that we can all perform similarly and do some correlation. 

 

[chunger]

I have 1 out of 3 quiet tubes so far which makes it essentially a $60 alternate tube.  I have not tested them in studio yet against the Amperex and Telefunken EF86's, but am burning in a couple to prepare.

Chung can you talk some on your method of testing?  It might be helpful to describe a method of test that we can all perform similarly and do some correlation.

Nothing particularly scientific.  . . put the tube in, trim to proper voltage,  and listen to see if it sounds like a microphone or a hurricane   Most of the ones I've tried so far sound like a hurricane.  48 hours burn-in could change the story on some of these so I mark them "noisy - 0 hrs" and move on to the next tube.  Just an initial sorting.

 

[kidvybes]

Oliver wrote this on the Neumann forum:

The E80F was only made by Valvo and was sold by the Philips mother company here in the US under the Amperex brand name as 6267.

...Henk, I believe that Oliver referenced 6084 as the Amperex variant for the E80F...the 6267 is, as you said, an EF86...

...my experience with Amperex 6084/Valvo E80F is that adequate burn-in quiets all the NOS samples I've employed or distributed to my associates (8-9)...this became the tube of choice for the popular Stellar CM-6 mic,  in which,  due to it's very simple and clean-sounding plate-follower circuit,  any excessive tube-generated noise would be easily heard and recognized as problematic...

...the only noisy ones I've been made aware of were purchased as pre-used/pulls, not NOS variety...

...also, important to keep in mind, the true E80F tubes are long-body tubes...I've seen numerous tubes, similar in size to the EF86, that are branded as E80F as noted in this list of fake tubes: http://www.jacmusic.com/nos/images/Fakes/
...I would steer clear of any "E80F" of that variety for obvious reasons...

...if anything, I find the E80F/6084 to be less problematic than EF86/6267 tubes, which are readily plentiful, from several manufacturing sources with varying construction quality and inconsistent performance characteristics...

 

[micaddict]

...Henk, I believe that Oliver referenced 6084 as the Amperex variant for the E80F...the 6267 is, as you said, an EF86...

He does say 6267 here (twice), but going by heart he probably mixed them up. Unfortunately, we can't ask him anymore. 
But it wasn't the point anyway.

http://www.neumann.com/forums/view.php?site=neumann&bn=neumann_archive&key=1015804332

Dennis, I know no man (even including the maker probably) who has tested that Stellar CM-6 as much as you have. And if you say the E80F works great in that circuit, I believe that 100%.
Also, when Oliver spoke, I listened.

There are a couple of things I wonder about, though. Perhaps I should hush before I have actually tried a couple myself, but hey, why not share my ponderings.

Firstly, there's the midrange magic and character aspect. The EF86 is not a perfect tube. Ask a tube guitar amp lover and he'll probably tell you it's too microphonic. And that's just one example. On the other hand, this pentode to many is an incredibly musical sounding tube, for some reason or other. And I would agree. It oozes character. I have a U67, but also a Gefell that wears an EF86. Although those are very different mics, their basic character and midrange richness are very similar. It's like a warm bed. Velvet comes to mind, too. This is not a thing you can easily measure and show in a plot BTW.
Interestingly, Christian Whitmore mentioned (low) midrange when he compared the E80F to the EF86. He said he heard less in the E80F.  If this is true to begin with (the guy does have good ears, mind) then this doesn't have to be a bad thing, of course. As a matter of fact, the same sort of holds for U67's sister M269. The latter wears an AC701 and it is considered to be a superior (allround) mic to the U67, by quite a few people who have used both.
Poctop started his U67 build threads a couple of years ago and while he was at it, he also did the M269. He fitted his own mic with a, more affordable, 5840 subminiature, though. What we found in his build threads was that the M269 clone indeed sounded more open and bright than the U67 clone (more "hifi" if you will), but also had little less oomp, guts and syrup (my own words). But that was the M269-c version (self biased). Interestingly, when he did the -b version (fixed bias, like the U67) the differences were smaller. Still, I don't believe you could ever make a 5840 or AC701 tube sound like an EF86.

Secondly, if the E80F is such a great tube for the U67, then why didn't Neumann pick that one in the first place? Yes, it was a relatively expensive tube. But the mic itself was much more expensive. And if you could fit such a high quality studio mic (a technical marvel and state of the art piece in 1960) with a superior tube that lasts a lifetime to boot (!), then why didn't they?

Darn, now I really must try one myself ...

Anybody here who could send me a ... um ... stellar example of the species? 


Henk

 

[kidvybes]

...Henk, I believe that Oliver referenced 6084 as the Amperex variant for the E80F...the 6267 is, as you said, an EF86...

He does say 6267 here (twice), but going by heart he probably mixed them up. Unfortunately, we can't ask him anymore. 
But it wasn't the point anyway.

http://www.neumann.com/forums/view.php?site=neumann&bn=neumann_archive&key=1015804332

...yes, I see Henk...that's odd that he would make that mistake more than once...in the proceeding post from the same thread, he sets the record straight,
"E80F made by Valvo were sold here in the US under the Amperex brand as 6084."

http://www.neumann.com/forums/view.php?site=neumann&bn=neumann_archive&key=1015290588

...in reference to the CM-6, it should be noted that this particular mic was designed to deliver a very "clean, clear, airy, detailed and shiny" tonality, shy of any "color" or "mojo"...so in this application the E80F suits the mic's voicing very nicely...but in a mic circuit that delivers a bit more "character" such as the U67, while it may work fine, the E80F may not enhance the desired effect...so, it really becomes a matter of personal preference...

...frankly, in my own experiments with tubes over the years, I find it difficult to make generalizations about certain tube variants, as I've heard both excellent and poor examples of the identical variant, in the same mic circuit...so, when I recommend a tube, I always try to add the tag,  "YMMV"...as with anything audio, we all hear differently and our preferences skew in different directions...what looks perfect on a sonic graph,  doesn't always translate well to the ear,  and vice versa...

...Brian Fox will argue that the 6922 tube is the best choice for the 47 circuit, while Oliver favored the EF800 and Max the dual 408a configuration...you say "to-may-to'' and I say "to-mah-to", but in the end, if it sounds good, it is good!...wishing you more musical blessings!

 

[kcatthedog]

hey cat5,

could we track  or could you spill the beans on which which tube specifically performs in which DIY build ?

If I made the mike and had inconsistencies I would suspect my build, if you notice it, I conclude the tube is performing differently and or begin affected by its operating environment( the mike).

Perhaps, an electronic table could be created and kept at Group DIY or studio 939 site ?

 

[Category 5]

Ah Kcat, that would be very subjective and I am the least qualified.  I simply try as many as I can get my hands on and nite what I hear.  Since everyone's tastes are different it's probably avoid idea to try on your own.  Obviously try tubes that are known to behave in the circuit.

For instance. I find a huge improvement in the 50s era 6072 in the C12.  Others hear no difference between those and current issue 6072s aside from noise characteristic.  It's in the ear of the beholder I guess.  My listening tests were night and day. 

 

[kcatthedog]

ya fair enough; like u and me with the BLA microclock with apollo

u should get my cap this week !!!

 

[MicGeek]

Just finished building my first one.  When the pad is off, I get all high end and no lows, when it's on I get all lows and no highs.  Strange.  I'll be troubleshooting this weekend.  The build looks real pretty tho.

 

[ioaudio]

Hi Ben,

re-check the wiring - that should be the culprit - check all the connections between switches, acryl-part and pcb.

-Max

 

[MicGeek]

Hi Ben,

re-check the wiring - that should be the culprit - check all the connections between switches, acryl-part and pcb.

-Max

Well, i checked and rechecked and still had the problem.  So, i built the second kit and it worked beautifully.  Then I went back to the first one, took it back apart and rechecked again.  There must have been something touching because when I put it back together again, it worked. 

Now, I've got two working and beautiful sounding U67's.  Thanks Max and Chung, you guys rock!

-Ben

 

[ioaudio]

Thank you, Ben!

 

[chunger]

Initial comparison of the Eric Heiserman HK67 against the current production Neumann K870 capsule is yielding a very similar general timbre.  So the "ballpark" tuning seems correct.  Used as a pair in drum overheads in our room, these have become the go-to microphones.  The capsule differences to our ears are not yet significant enough to determine a specific mic preference (left and right side) in that application.

As drum tracking is one of our main activities, this is a significant development for me.

Further testing on different sources and in omni and figure 8 modes to come.  Those should sniff out the sonic differences more clearly.

 

[tskguy]

That's great news Chung!

Always good to hear my capsules sound like the ones I am trying to reproduce  ;D ;D

 

[mica]

I have a 230K resistor and i want to test the PSU without the mic attached. Can i do that using the 7pin XLR only (like the C12 build)

 

[ioaudio]

Yes, should bring you in the ballpark - fine tuning should be done with the circuit/tube in place.

-Max

 

[mica]

Im stuck at 200V with the 25K trim turned all the way. Ive done the psu like described including the fix to get the voltage up. (Im in DK at 220V and using the 200V version of the psu)

Any ideas?

 

[ioaudio]

Lowering the value of R5 should bring you there - you can install another 15K resistor in parallel (=7,5kOhm).

-Max