MK7 - tube mic project

[zebra50]

What is the best noise floor that people have recorded on this thread.

Noise should not be a big problem. I haven't made a proper measurement on mine but it's quiet - certainly as good as or better than my Neumann Gefell UM57s and CMV563, and indeed probably as good as my room. That's using a clean teflon AKG C12 capsule.

 

[tardishead]

Yeh - I found a very low noise tube and voila quiet as a mouse.
I am using the modded TBone psu and it works really well.
Spent a few hours trying out the mic and I am really impressed. I have some Gefell, Neumann, AKG and other small tube condensors but no good tube large capsule mics. I have a U87 and this blows it out the water. I am using a K47c capsule from Beesneez which sounds great to my ears. The MK7 is definitely the most balanced mic I have. I hire a U47 often and this is definitely on the same vibe.
I am no singer but when I tried out the mic with some plate reverb through some headphones boy you could not stop me.
This mic will get a lot of love in my studio. Nice one Max!

Now all I need to do is fill in that dodgy logo and spray with some funky enamel.

 

[SIXTYNINER]

someone need nos vf14?

 

[12volts]

someone need nos vf14?

Please Sir. Sir, I could use 2 if they authentic 

 

[ECC82]

someone need nos vf14?

Please Sir. Sir, I could use 2 if they authentic 

Me too, indeed!  8) 

Kind regards

 

[Skylar]

I have been testing my MK7 build.
Long story short—I'm very pleased.





The power supply is Max's design, built p2p on a turret board.
               


I replaced R2 of the voltage divider (200K) on the 160V side to a pot for a wider range of B+ voltages.
           


I destroyed my Thiersch STW-7 red line capsule [accidentally], so I am using a Chinese 34mm until I get a re-skin.
The Chinese capsule sounds awesome, though. This is now my best sounding tube mic.



I used Harwin pins/sockets for the capsule connections, so that capsules can be swapped out without too much effort.
   


The whole thing is built into my EQU47 rough sample. I'm hoping to get a new, better sample body soon.
           


I socketed the output cap, so that I could test various sizes and types.
                   

 

[kato]

Skylar, looks great! Would love to hear your cap impressions.

Where did you get that awesome PSU enclosure?

 

[cooljuk]

That is one seriously beautiful build. Congratulations! Do elaborate on your cap comparisons, please.

 

[Skylar]

Skylar, looks great! Would love to hear your cap impressions.

Thanks, gents.
I am still testing caps & tubes, so I will let you know when I'm finished.

Where did you get that awesome PSU enclosure?

This was a prototype built by a shop in California. I was going to have them mass produced.
I wasn't really happy with the quality-to-price ratio [in mass production quantities], so I did not pursue this any further.
[The one-off cost was over $400, so not an economical solution for just a single enclosure]
More details here

 

[tommypiper]

Skylar, great, thanks for sharing.  Where did you get your PS handle?  I've been looking for one like that for a while...

 

[Skylar]

Where did you get your PS handle?  I've been looking for one like that for a while...

http://www.phonekings.com/

 

[ioaudio]

 

[riggler]

Skylar,

What is the transformer housing? That's pretty cool!

 

[Skylar]

Skylar,

What is the transformer housing? That's pretty cool!

I guess I don't understand your question. Which transformer are you referring to—the one in the mic or power supply?

 

[plumsolly]

I believe that is a paper-in-oil cap. Best, Ben

 

[Skylar]

I tried the following output caps...


0.51uF Russian PIO



0.47uF Russian PIO green meanie



0.22uF Russian PIO green meanie



0.22uF WIMA polypro



0.15uF Orange Drop Polypro


These are just what I happened to have in my parts drawers.

I found that not only did these caps I tested have an effect on the lows but also the highs.
I tended to like the larger values better.

I liked the 0.51uF PIO best.
The 0.51 cap resulted in a noticeably smoother high end while providing a solid foundation.

I've heard a lot of people talk about certain microphones sounding "more real,"  "closer," or even "larger than life".
It wasn't until I put that silver 0.51uF PIO cap in there that I really experienced that type of performance from a microphone.
I feel very excited about this mic!

The WIMA sounded quite good, but produced brighter highs than I care for, but some people might prefer that.
I'd like to hear what a larger value WIMA would sound like...I would probably like it.

The green meanies were okay, but the WIMA and the silver PIO were noticeably better to my ears.
The 0.47uF green meanie was better sounding than the 0.22uF.

The orange drop was probably the bottom of the list, but, again, I would like to hear a larger value like 0.5uF.


I did my preliminary listening tests with vocals only, in several styles...speech—proximity test—country, pop, & rock vocals.
Once I settled on the 0.51uF cap, I tested acoustic guitar.
The bottom end was overpowering and boomy.
I then switched the preamp from Jeff's VP25 (API) to a Neve BA283-style (tweaked gain stages), and then the acoustic really came to life—sounded fantastic.
So, don't forget the importance of the preamp when testing these things.

 

[Skylar]

I almost forgot...

I tested tubes also.

I only had a Zaerix and two Telefunken EF86s.

I could not tell a difference between these tubes.
Because I only have one mic to test with, I couldn't record the same performance through multiple test mics;
I had to do the take, swap tubes, and try to replicate the original performance as close as possible, then compare.
The sound characteristics were so close that I could not discern whether any differences I was hearing were attributable to different tubes or different performances.

The effects that the capacitors had, on the other hand, were immensely easier to discriminate.

My conclusion is that the capacitors had much more impact on the sound than switching between these two brands of tubes.

 

[madriaanse]

Wow, that's a pretty cool writeup! Thanks for posting.

How are you doing with the mic body project?

Best,

M.

 

[Kingston]

I did a similar shootout with some tube preamps recently and I can agree that PIO caps win in every conceivable scenario and seem to be completely indispensable when voicing gear. It could be generalised that the sounds you found from those caps apply to all output transformer coupling scenarios, and for interstage coupling, too. For feedback caps they also make improvements, just less of it.

Those "green meanies" have a real name: K42Y-2. An equally good choice would be its other "K4-something" brothers, like K40Y-9. They are all good, and amazingly cheap.

But polyprops certainly have their place. Wima MKP4 for example, give an impression of more detail, but it's actually some type of distortion in the high mids. Perhaps you should have tried bigger orange drops. They sound great, but not as detailed as PIO. Just that the 0.15uF cuts way too much bass, and obviously "lose" to the other caps in this shootout.

One last thing to try, 1uF (huge) PIO cap. It will make the mic amplification flat to the very low bass, but might not work so well with certain capsules, and also removes the thinner "vintage" sound. Might also resonate with the transformer inductance, creating a bass bump.

 

[madriaanse]

Interesting. Who sells these PIO caps in the USA?

m.