MK7 - tube mic project

[Jeremy.Starseed]

I received Greg's list yesterday. It's a gem.

 

[bradb]

could i get a pic of where and how the caps are mounted on the back of the pcb under the tube?


I've got my PSUs wired up and waiting for the edcor trannies and cases... getting close.

basically all I have yet to acquire are the tubes and the capsule.

 

[e.oelberg]

just look at the first page of this thread, it's not problematic

nicholas

 

[bradb]

saw that earlier...

 

[ioaudio]

sorry, busy times at the moment.

 

[bradb]

ah, perfect thats what I was looking for, thanks Max!

 

[ioaudio]

no prob.

 

[Jeremy.Starseed]

Hi.

Are the trafoes available for sale now? Almost? All gone? Please, not gone....

I will have to settle for one, however, not three as I had hoped.

Please, let me know...

Many thanks for all your work,

Jeremy

 

[ioaudio]

no single transformers, only sets as shown below, available soon.

 

[Jeremy.Starseed]

Kit form is even better, and that is what I meant...I just forgot to be specific.

 

[bradb]

Would it be safe to say that we shouldn't skimp on the output cap feeding the tranny?


has anyone put anything "good" in there, any good results?

 

[bradb]

Just got my 9pin tube sockets in the mail from tubes and more...

seem too big.....  are people using these?  If not, what's the better choice?  come on people, lets help each other out!

 

[pH]

I used a 9 pin socket and had to enlarge the pcb hole a little, but you should be able to make any of them work fine.

 

[Gus]

For the people having heater hum problems.  Maybe try lower voltage drop diodes in the heater supply bridge like a shockley diode.

 

[e.oelberg]

Would it be safe to say that we shouldn't skimp on the output cap feeding the tranny?


has anyone put anything "good" in there, any good results?

I played around with different values and types. WIMA 1,068 and 0.47 mundorf and LT 0.47 from those WIMA sounds best to my ears, no I put in a
russian MP Caps 0.47 this one sounds great
nicholas

 

[bradb]

I just wired up Max's PSU design using the Edcor trannies.

Here are my unloaded voltages:

"150V" = 173.6 Vdc
Pattern = 137, 69, ~0 Vdc
Heater = 14.77 to 14.25 Vdc (when i adjust the pot full range)
Heater AC measurement: 0.1 mVac (just thought I'd check that)

 

[ioaudio]

brad,

the voltages look ok unloaded. try the heater with a dummy load before connecting the tube.
did you use the choke?

-max

 

[bradb]

I did use the choke.

I calculated the heater load as 31.5 Ohms from data sheets... does that look right?

 

[ioaudio]

ef86 or pf86?

 

[bradb]

for the EF86