OFFICIAL ioaudio MK67 build and support thread

[Pip]

So finished the build and all powered up fine. Mic sounds great I think? What I mean is I have never really used a U67 before so have no comparison. My build is Beezkneez K6 capsule and Poctop PSU Board.

Here is the one thing I am not sure of. When I plug the mic into my preamp with the power off I get a buzz, nothing new for a tube mic, low but its there. then I power the mic on and all seems fine.  The ouput is a little low but nothing crazy. I am basing this on other mics in my possession and where the gain of my pre is. But when I kick in the pad the volume drops, a lot if you ask me.  The mic still works fine in all patterns etc...  But the buzz is now louder or I should say less masked. What might be wrong.

I have triple checked my grounding while listening to the mic all is as quiet as I can get it.  I have quadruple checked my wiring.  All my voltages are spot on and I have tried multiple tubes. Again the mic sounds fine but I really think I might have a problem. Is it possible C10 is hosed somehow?

Hi Pip , For the psu parts i am glad everything is right on , i have implemented a SHLF jumper to gnd lift the cable shield
you can try to remove it as it is on by definition ,
Best,
Dan,

Thanks but I will try it but I don't think thats  it. Alas I see a long trouble shooting session in my future. All components seem to check out in circuit next I will start to deconstruct and check all solder joints etc...

Sorry to quote myself but it seemed the easiest way to keep this a thread.

So all is good. It turns out that my test mic pre had developed a problem. Argh! I guess its always good to test your test kit eh?! Don't know what it is yet but switched to another of the same units as I own two and bingo problem gone. I also want to stress that I made double sure that the body sleeve was on correctly and that it was tight and making good contact. This mic was very agitated by close proximity to my soldering station!

Beesneez K6 sounds awesome! But I wonder if Chunger will make those Delrin spacers available as I need one too?

 

[maq3396]

Hi Chunger

Thanks for another great build guide!

I just want to clarify something before building myself into a deep hole.

You show a green wire that comes from the C1-C10 juncture of the HiZ portion and say that for direct wiring only one wire is needed but for turret builds two are required.

The remainder of the build pics show two wires- one to the switches and one to the capsule (as does the build illustration).

Am I correct in using the double green wires regardless of turret use or not?

Thanks
Mac

 

[maq3396]

For those of us that aren't fortunate enough to have a Shaggy in the neighborhood here is a 3D printed extension that performs a similar job to the 8mm delrin spacer used in Chunger's build.

I used a 3 x 8mm set screw to hold the printed part onto the rubber mount as a suitable length single bolt was not available. It works fine but a single screw would be desirable.

Cheers
Mac

 

[maq3396]

And assembled...

 

[sebastianzet]

Is there a place where i can just buy the COMPLETE kit all at once? it looks really confusing to buy all of the parts

 

[GlennZippy]

What are the chances  of seeing this PCB kit again?

 

[mica]

(NEWBIE ALERT)
So i made this build a couple of years ago and got it out of the basement recently to try it on some vocals.
It was quite noisy so i started by checking B+ voltage and it's 218V at the lowest setting on the 25K pot with the mic connected. I think i made all the corrections in the original guide, but how can i get the voltage down to 210V, and could the high voltage be the source of the noise?

EDIT: I can see i jumped R5 to get the voltage up from 205V to 201V originally. Maybe that was a mistake? Should i just put the R5 resistor back and can the voltage at B+ change over time?

Pic of the PSU:
http://soundz.dk/u67psu.jpg

Thanks to anyone who can get this baby back on track.

/Michael

 

[wmarden]

When are these kits going to be available again..?

 

[Greenie]

Wher can I buy the Alctron TPS-100 power supply?

 

[kingkorg]

Wher can I buy the Alctron TPS-100 power supply?

Should be the same thing.
https://www.thomann.de/gb/the_tbone_psu_sct_2000.htm
Or fancy variant
https://www.thomann.de/gb/the_t.bone_psu_retro_tube_ii.htm

 

[Greenie]

Should be the same thing.
https://www.thomann.de/gb/the_tbone_psu_sct_2000.htm
Or fancy variant
https://www.thomann.de/gb/the_t.bone_psu_retro_tube_ii.htm

Thanks...

 

[kinglok]

Not Sure if this thread is actively maintained but here's the problem I am having right now:

The U67 build was made way back in 2015. Capture installed is from Eric's HK67. Tube is E80F. It sounded so sweet and especially great for male voice recording.

But it just failed last month. No signal output at all. I thought it is the problem of PSU. So, I bought the PSU parts from studio939. Voltages with dummy load are good - B+ 210V and heater -6.3V.

However, connecting to U67 mic again, B+ rose to 230V (it can go higher before I unplug the power) and there's still no audio signal output at all. I even tried swapping tube from E80F into EF86. It's still the same. B+ rose to 230V and no audio signal.

Can anyone shed some light how I can troubleshoot it? BV-12 problem? Or is it related to capsule failure??

Much much appreciate for any input!

 

[innercityman]

Not Sure if this thread is actively maintained but here's the problem I am having right now:

The U67 build was made way back in 2015. Capture installed is from Eric's HK67. Tube is E80F. It sounded so sweet and especially great for male voice recording.

But it just failed last month. No signal output at all. I thought it is the problem of PSU. So, I bought the PSU parts from studio939. Voltages with dummy load are good - B+ 210V and heater -6.3V.

However, connecting to U67 mic again, B+ rose to 230V (it can go higher before I unplug the power) and there's still no audio signal output at all. I even tried swapping tube from E80F into EF86. It's still the same. B+ rose to 230V and no audio signal.

Can anyone shed some light how I can troubleshoot it? BV-12 problem? Or is it related to capsule failure??

Much much appreciate for any input!

I would first check capsule. If no signal is coming out, there's a chance that the capsule is dead.

 

[MagnetoSound]

Have you tried measuring voltages at the mic?

Excessive B+ voltage suggests the tube might not be heating, or the B+ voltage may not be reaching the tube.

There could be a fault in either the mic or the cable.

 

[kinglok]

I would first check capsule. If no signal is coming out, there's a chance that the capsule is dead.

Thank you so much for reply. How can I check whether the capsule is broken? Any measurement?

 

[kinglok]

Have you tried measuring voltages at the mic?

Excessive B+ voltage suggests the tube might not be heating, or the B+ voltage may not be reaching the tube.

There could be a fault in either the mic or the cable.

I have checked inside the mic. B+ is still excessively high. Cable connection is fine. Any input is welcome!

 

[rock soderstrom]

How high is the heater voltage? How high is the cathode and anode voltage direct at tube? A too low or no load seems to cause the unregulated B+ to rise. The tube is not conducting (enough).

 

[innercityman]

Thank you so much for reply. How can I check whether the capsule is broken? Any measurement?

Just buy a cheap Chinese capsule on aliexpress or ebay. you can get one for less than 20€. Replace your capsule with it and see if it works or not.

 

[MagnetoSound]

At this stage, there are better ways of testing than replacing the capsule.

First, make sure the tube is heating. Get your meter on the heater pins at the tube socket and check for heater voltage. Then, check for anode (plate) voltage. According to your initial readings, one or other of these voltages is likely missing at the tube socket so you need to trace back from there to the connector to find the break. Be sure to check the heater ground connection as well. Don’t forget the heater voltage is negative wrt ground.

Tell us what you find.

 

[Murdock]

Like the others aid, also check your heater voltages. And check your 0V connections. When that one is missing the mic also doesn't work. Maybe the 0v cable from connector to pcb is open or a bad solder joint.