Gus

solidtube ideas
« on: June 24, 2004, 08:19:57 PM »
I owned a solidtube for a short time bad comes to mind.  I did like the capsule mount and the transformer did not look bad.

If I was to rebuild it  I would use the Royer CF circuit like the CB microphone, PDF is at jensen.com.  I would use a ef86 cathode follower and the capsule with a >=2.2uf to the transformer.  Now the fil supply would need to be dropped to about 6VDC and the B+ maybe to 100V.

I would take out the foam inside the grill.   I would get rid of the led that makes the tube glow.  I would point to point it. There has to be alot of solidtubes not being used for anything.


dale116dot7

solidtube ideas
« Reply #1 on: June 24, 2004, 10:14:39 PM »
I'd take a different approach, I think. First, I'd attack the grille and foam insert. Then I'd probably keep the circuitry on the PC board but start with small changes. First, go to a 6072 tube, replace the transformer with a 'real' output transformer, and ditch the CF stage - drive the transformer from the first tube, like a real C12 does. Then, maybe replace the capsule with maybe a new C414 capsule, or maybe once I get my DIY capsule built, with one of those, with the external polarization circuitry.

I think that's what I'd do...

Scenaria

solidtube ideas
« Reply #2 on: June 24, 2004, 10:19:10 PM »
uhhh

this mic is an electret no?

just sell it :) its worth more selling it for $400 or $500 than modifying :)

CJ

solidtube ideas
« Reply #3 on: June 24, 2004, 10:49:45 PM »
Sorry for the OT:
Gus , here is the plot on that mic xfmr you sent.
Looks pretty good, actually.
Pri: 152 ohms and 12 henries
Sec: 46 ohms and 4460 millihhenries.
self res. at 300 khz
I can send it back or hack it. Let me know.
cj




If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

zebra50

solidtube ideas
« Reply #4 on: June 25, 2004, 07:08:06 AM »
That looks like the xfo's in MXL mics.

I had some good results with the Royer 'Country Boy' mic circuit using a shure electret element. I think the simplicity of the circuit is a real plus.

CJ (or anyone) - I was measuring some Oktava mic transfomers last night and could not get inductance readings for the primary windings - it was off scale. My multimeter only goes up to 40H, but I had expected that to be enough. Is >40H a sensible value, or did I fnck up somehow? I've only just bought the meter and this is my first attempt at measuring inductances.
I got about 1H-2H for  the secondaries.

Stewart
Ribbon microphone services
http://www.xaudia.com
Microphone blog

Gus

solidtube ideas
« Reply #5 on: June 25, 2004, 09:59:36 AM »
Hack it

It does not sound good IMO.  As we know sometimes what is measured does not help explain sound.

  The china transformers seem to blur the sound.  Maybe the winding is OK and just needs a core upgrade?

yes it is a V67 transformer

Marik

solidtube ideas
« Reply #6 on: June 25, 2004, 01:30:18 PM »
If you gonna hack it, send it to me (unless you have particular scientific interest)--I wanted to try the coil with nickel or cobalt lams. BTW, what sound difference between two would you expect?
Samar Audio & Microphone Design

www.samaraudiodesign.com

The Art of Ribbon Microphones

zebra50

solidtube ideas
« Reply #7 on: June 25, 2004, 02:55:32 PM »
Marik,
I have two of these. I'm happy to send you one, although it'll take a few days to cross the pond. Email me with an adress if you're interested.
Stewart
Ribbon microphone services
http://www.xaudia.com
Microphone blog

solidtube ideas
« Reply #8 on: June 25, 2004, 03:09:57 PM »
Oh,,,send me the other one then..

I actually have one for sale now.  :oops:

Gustav

zebra50

solidtube ideas
« Reply #9 on: June 25, 2004, 03:37:08 PM »
Hold on!

What are we talking about?

I'm talking about giving away an MXL transformer.

Did you think I meant a solidtube mic?

 :shock:

Confused
Ribbon microphone services
http://www.xaudia.com
Microphone blog


Marik

solidtube ideas
« Reply #10 on: June 25, 2004, 04:42:34 PM »
Thanks Stewart,

I will send you email later tonight.
Samar Audio & Microphone Design

www.samaraudiodesign.com

The Art of Ribbon Microphones

CJ

solidtube ideas
« Reply #11 on: June 25, 2004, 05:06:08 PM »
Zebra, I have the same problem with the Sencore inductance bridge.
It only goes to about 10 henries, then I have to switch over to ther General Radio bridge, which will go to 1100 henries!
cj
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

solidtube ideas
« Reply #12 on: June 25, 2004, 05:09:15 PM »
:grin: Just thought you were gonne send it for experimenting...and was kiddint about sending it to me.
I do have one for sale though.


Gustav

CJ

solidtube ideas
« Reply #13 on: June 25, 2004, 05:18:31 PM »
I just found some DuKane lams and they match up with the chinese transformer perfectly.
I think I will measure incremental inductance before and after the lam transplant.
if it looks different, I will send it to Gus for a test drive.
cj
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

zebra50

solidtube ideas
« Reply #14 on: June 25, 2004, 06:19:59 PM »
Thanks CJ. I got sensible values for the mkl2500 transformer tonight, so I think my technique  is OK. I guess the others are just bigger than the meter's range.

Gustav,
I thought you were kidding but this thread's gone way OT & if you had wanted the other tranny I could probably spare it.

 :guinness:  :sam:  :guinness:
Ribbon microphone services
http://www.xaudia.com
Microphone blog

CJ

solidtube ideas
« Reply #15 on: June 25, 2004, 11:33:55 PM »
OK, I did a re lam job on Gus' mic xfmr with some DuKane lams, thanks to Bill Y for the transformers!
The inductance almost doubled, here is the inductance vs frequency, as well as the orig. lam on the left, and the new ones on the right.
I think I will send this back to Gus for a test drive, as I think it will be a little more livevly now.
cj :guinness:

If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

Gus

solidtube ideas
« Reply #16 on: June 26, 2004, 10:09:19 AM »
Thanks Chris.  Can you tell anything about how it is wound by looking at the coil?  Please unwind it I have a few more.

FWIW the Nady 1050 uses the same size core lams.

I was thinking in a DIY way when I sent you the transformer.  Maybe people can rewind and recore the transformer when modding a china microphone.

How soon before a "redesigned" transformer is in an AD for a china built microphone(s)!!!!!!!!!!!!!!!!!!!????????????????

I had built a CF microphone circuit for the v67 thinking of DRUM use that stock transformer sounded BAD.  Chris no need to send it I will look for some lams.

CJ

solidtube ideas
« Reply #17 on: June 28, 2004, 04:26:20 PM »
I can see the winding structure thru the bobbin.
It is pri-sec-pri, which is good.
Those lams are cool 1950's iron, si I want you to try it, as I haveno way of testing it in a mic.
cj
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html


 

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