D-EF47 Tribute To Oliver Archut U47 Build Thread.

[hugo]

Hi,

I need your help, because i am lost...
I made this beautiful D-EF47 project, and i have this issue :
- On Omni mode (switch of PSU on left side), the mic works perfectly..
- On Cardioid, i had a big noise who stopped and now i have this low crackle, only on this mode..
DO you have any idea which process i can use to solve this ?
Thanks

Hugo

 

[Matt Nolan]

Check everything systematically. Probe voltages, try removing and re-installing the capsule wiring with the two sides wired the other way around (so the front becomes the back and vice versa). Try temporarily substituting the capsule halves with 50 to 100pF capacitors. Report back!

 

[hugo]

Check everything systematically. Probe voltages, try removing and re-installing the capsule wiring with the two sides wired the other way around (so the front becomes the back and vice versa). Try temporarily substituting the capsule halves with 50 to 100pF capacitors. Report back!

Thanks I will change the side of capsule, i'll tell you if it is ok.

 

[hugo]

I have just one more question...I removed some paint on the PSU, to make contact between the top and the bottom, i also removed paint behind the PSU/Mic 7pins connector. I did not make it for output xlr, but there is a good contact through the screws.. Is there a reason for my mic is "clicking" and the noise changes when i touch the metal top of psu ?...
Hugo

 

[ln76d]

Defiantely you have some problem with grounding.
Did you make test with fully assembled microphone?
Or at least with the headbasket mounted?

 

[hugo]

Defiantely you have some problem with grounding.
Did you make test with fully assembled microphone?
Or at least with the headbasket mounted?

Hi, thanks for your help... I made my test just after calibrating the PSU... Yes for sure there is a grounding problem..but where may i have to check if there is a missing contact somewhere ?
Thanks a lot.

 

[ln76d]

All the circuit ground points i would check with the beeper, all the metal connections and points where it meets.
Headbasket grounding is really important.

 

[hugo]

All the circuit ground points i would check with the beeper, all the metal connections and points where it meets.
Headbasket grounding is really important.

Great thank you

 

[wilberweb]

Hi, I'm new to this forum. I'm building Dan's D-EF47 mic and power supply coming down to the XLR 7 pin and 3 pin hook ups. does any one have good pictures of the b+ h+ and XLR hook ups, here is what I have so far. just waiting for the wire.

thank you

 

[TLRT]

Hi, I'm new to this forum. I'm building Dan's D-EF47 mic and power supply coming down to the XLR 7 pin and 3 pin hook ups. does any one have good pictures of the b+ h+ and XLR hook ups, here is what I have so far. just waiting for the wire.

thank you

Here are my pics:

 

[useme2305]

quick question regarding the PSU.

i'm in a 230V country. i have the toroidal from Triad which gives me 260V on the secondaries.
when i reverse it and use the secondaries as the primaries and vice versa i can get 210V.
which voltage would be better for this PSU?  260V or 210V?

also, is it ok to use this particular toroidal transformer in reverse to get the desired voltage?

i know i could just skip the toroidal in this case but i wanna make this build future proof in case it needs to be ran by 115V.

 

[Matt Nolan]

i know i could just skip the toroidal in this case

No! A transformer for isolation from the mains is a big plus in the safety books. Don't skip it even if the voltage you need is close to 230.

 

[Spencerleehorton]

Hi,
I have 6 transformers which have been designed specifically for this mic and valve, it's a B5887, if anyone's interested in getting one please msg me, they sound fantastic in this circuit.

Regards

Spence.

 

[TLRT]

We have here a company who can create any kind of custom toroids, I asked them to make one for me with 2 secondaries( 230VAC/0.11A and  20VAC/0.5A), so I can save some space, you can see the pics above...

quick question regarding the PSU.

i'm in a 230V country. i have the toroidal from Triad which gives me 260V on the secondaries.
when i reverse it and use the secondaries as the primaries and vice versa i can get 210V.
which voltage would be better for this PSU?  260V or 210V?

also, is it ok to use this particular toroidal transformer in reverse to get the desired voltage?

i know i could just skip the toroidal in this case but i wanna make this build future proof in case it needs to be ran by 115V.

 

[Ericbazaar]

Hi Spence,

i'm interested in your transformer. will compare to the haufe one in my next build. the haufe has to much low end in these circuit, but it sounds fantastic with two 6028 tubes.

best
andreas

 

[Spencerleehorton]

great stuff, i have messaged you.

regards

Spence.

 

[hugo]

Hi All,
I am starting a new D-EF47, and i have one remaining CEK89 capsule on hands from last projects.
Can i use that capsule (described as a 32mm K67 capsule) for this project or will i have some issues ?.. Is there a big improvement by using a RK47 microphone-parts  capsule ?
Thank you

 

[ln76d]

I wouldn't say about improvement, rather two different responses.
CEK89 looks like typical 32mm k67 used in most of chinese microphones.
These type of capsules works good with high polarisation (sounds better in rode NT1a than original edge terminated capsule), so you could think to rise voltage  a little. Anyway you will get very bright response with it.
Most wariants of K47 (if someone didn't screw copy of original design...) have bump in hi-midrange and top end is little bit falling.
With any type of k67 you can always tame high frequencies adding capacitor from plate to ground - 100pF-1nF range or build additional deemphasis network like in my project:
http://groupdiy.com/index.php?topic=63682.0
Even if you tame high freq response still there wouldn't be bump in hi-mid area.

 

[Spencerleehorton]

Hi all,
I have 3 of these B5887 transformers left for testing if anyone's interested, would really like some comparisons done against other types etc and some feedback, I've got 9 out there at the moment.

 

[Colorblind]

Hey all,

This my first tube mic build, and I can't wrap my head around the wiring from the 7-pin connector on the PSU, to the cable, to the mic.

On the PSU 7-pin connector, I've got the ground tab and pin 7 connected, and wires running from pins 1-7 to the corresponding number on the PSU PCB's 8-position terminal block connector. 

On the cable connectors, I'm confused about pin 3.  Do I just connect the cable shield to pin 3 at each end, or do I need to tie it in with pin 7 at each end, and/or the grounding tab on the PSU end of the cable connector?  The build guide shows pin 3 on the microphone connector left disconnected, which I think is adding to my confusion. 

Any help for this newbie would be great.

Thanks,

C