U47 Build using EF80

[0dbfs]

"not-microphonic-at-all" is usually pretty apparent.

I think knocking the tube with a pencil eraser type test and hearing "ringing" is a symptom with the goal being to minimize that behavior AMAP. I could be absolutely mistaken about the symptom and test though.

Cheers,
jb

 

[OPR]

Do you have any clips of the microphonic EF80? I'm still yet to hear a microphonic tube microphone.

I'll post up a clip soon... It's only apparent when you tap on the mic body but could possibly be an issue in Hi SPL Applications. I also have some more Telefunken EF800's coming and also a 5693 Steel tube! Which is apparently the electrically and sonically the Same as the EF12(but Cheep as chips!) which is a popular choice for 47 Builds. I also have two of Max from Ioaudio's BV08 coming..Cant wait!!

 

[micaddict]

also a 5693 Steel tube!

Yup. Underrated tube. Sounds great in the BeesNeez Arabella for instance. Relatively quiet, too.

 

[OPR]

Cant Wait to try it!  I will report back! 8)

 

[Spencerleehorton]

interesting about that 5693 Steel tube, post up the results when you get a chance.
I'll put up some audio files of my ones once i get a stereo pair sorted, single one on the drums sounds so good!!
recording just got simpler, thank you U47

regards

Spence.

 

[OPR]

How did you go with using the Diode for  Biasing?

 

[Spencerleehorton]

HI OPR,

Havent tried the diode fixed bias yet but will do once i get these other 3 U47's up and running.
will let you know.

regards

Spence.

 

[o3misha]

With diode you have to use bypass cap. Or you will have too much non leaner distortions and lower than expected gain because of negative feedback.

 

[OPR]

Yes the bypass cap would be a good Idea maybe a 47pf polystyrene  or something like that. or even  clean up the heater supply with a choke and tap the bias from that supply like the AMI Build assuming they used a choke!??. I did notice a differences in sound with diode biasing compared to conventional methods when I was working on C12 builds but maybe the bypass cap minimize would these differences and maybe not...

 

[Patrick from Davis]

"not-microphonic-at-all" is usually pretty apparent.

I think knocking the tube with a pencil eraser type test and hearing "ringing" is a symptom with the goal being to minimize that behavior AMAP. I could be absolutely mistaken about the symptom and test though.

Cheers,
jb

A slight detour here, but hopefully informative.

Microphonic tubes are like microphonic guitar pickups.  Sound causes them to vibrate and set up a feedback loop.  With the pickups, it is the ferromagnetic metal (steel) that vibrates, and the coils pick it up and make a signal out of it.  With a tube it is the internals and/or the body vibrating and setting up a feedback loop.  Here is a short video on a guitar amp with a microphonic preamp tube.  It is different than what most all of my guitar buddies first imagined. 

https://www.youtube.com/watch?v=QM2qWZYbInI#t=50

However, the tube in the guitar amp is in the same environment that a microphone tube is in.  More or less.  A class A, cathode biased, triode in a relatively sound intensive environment.
Patrick

 

[Spencerleehorton]

Front

 

[Spencerleehorton]

side

 

[Spencerleehorton]

all mics

 

[Spencerleehorton]

insides front

 

[Spencerleehorton]

insides back

 

[Spencerleehorton]

Hi all,

Just need to know what would happen if the PSU I've made for this U47 was given 48v from a mixing desk whether it would have any effect or change the sound of the mic?
If there is any effect what could I do to protect it.
This problem would occur when using this mic into a desk which has phantom power over all channels, so you can't turn it off/on individually.

Regards

Spence.

 

[OPR]

Looking Good Spence!!
Here are some pics of the U-47 style mic I just finished over the weekend which uses an ef800 tube , 9 polar patterns, Thiersch Blue Line PVC Capule , and Max IOaudio BV08.

 

[OPR]

Hi_Z Boards

 

[OPR]

More pics

 

[OPR]

more!!