First off, let me say that this will not be a "clone". Let's say M50 - style at this point. "Cloning" this mic is just too expensive, at least for me.
[quote author="Gus"]Were are you going to get a BV11 or a real M50 capsule?[/quote]
I just got off the phone with Peluso. They make a SDC omni capsule, about 18mm in diameter, $90 each. Any other reasonable suggestions?
As far as transformer and other electronics, the BV11 is $350, too much $$ for me, but maybe not others. But, we are still tied to a very expensive AC701 anyway. This is why I think we should opt for the G7 basis for the design. That, and I do not have the skills to redesign the electronics as far as matching tube to transformer, etc.
G7 is cathode biased and 50b is fixed bias.
How does this affect the sound? I would think we'd get less color/saturation based on what I've read, but I am not an expert here. We would get more gain -- all else being equal -- with a fixed bias design, right? OTOH, cathode bias uses negative feedback which could smooth things over and lower distortion, correct? I am learning here....
Can someone explain to me the relationship between capsule size and noise? I've never really understood this. A larger capsule generally will have a higher capacitance, is this reflected in noise figures?
When I originally mentioned lower noise, I was thinking a clone could have a lower noise floor due to because of better tolerances on components we have today. I fully realize that a tube mic will not be a "quiet" mic, comparatively speaking. The goal here, for me, is to get some of the character from the M50.
I would reread Mariks posts that might be even better because of the different size spheres.
The spheres I have to work on existing SDC stick mics, like the 603. But I want to try this with a tube mic. The Royer mod on the 603's would be an option if this doesn't pan out.
You will not be building a M50 but something kind of like a M50
Details count.
Correct on both counts. I am hoping to get "enough" character to be "close enough". We know we won't make a 100% piece without a lot of $$$ and skill.
There is a part that needs adjustment for the overall gain control Neumann DESIGNED into the circuit. Do you understand how the M50 circuit works?
Not completely. Looking at the M50b schemo, between C1 and R2 there is a calibration input. How does this function? Is there a trimmer on the PSU?
Understood.
If I was building a M50 clone I would design my own supply not use the G7.
I think we're at the point of not really cloning the mic. Unless someone chimes in with some skills. For me, it's easiest to work back the G7 by changing the capsule (the Peluso is 37pF BTW), drop the polarization switch on the PSU, etc.
What do you think?