K67 capsule in a 2001 Royer mod mic

Hello,
i followed Dave's instruction to modify a 2001 microphone . It works great and is a vast improvement but it still not sounding as good as the G7 for example. Is a K67 a drop in replacement in this circuit or does it need further adjustment.
francois

If the Royer mod is for a flat capsule (like the K-12) then the K-67 will be too bright... I don't know the Royer mod, can you PM me info, or poast a schem, if that's not frowned upon...

Whatcapsule do you have in the G7, BTW?

Keith

the schematic from Dave's article is here
http://www.prosoundweb.com/recording/tapeop/tube_mic_25_3.shtml
the G7 has a capsule from a 414 and is built in a 460 housing.
francois

The K12 from the 414 is flatter than the K67. The K67 needs HF reduction. i don't see any in the Royer Schematic.

-Tell me, does the Royer mic sound thin, specially from 3 or 4 feet away?

If so, it might benefit from a K12 (414 capsule) instead of the over-prescent one that comes with the 2001. -the K67 will also be over-bright. -not QUITE as shrill as the MXL, but still too bright.

Keith

Did you use the jensen DB 12:1 transformer and output cap type selected in the writeup?

The honeybear microphone has an amp with no HF filter and a stock MXL v67 capsule. Sometimes that MXL capsule can work

The Royer mod is using the Jensen transformer and the parts from Mojave Audio it works well and i still like it but it does lack definition especially at a distance. how difficult would it be to insert a HF filter in the Royer circuit and use the K67 ?
francois

I think you need to stabilize the bias in the Royer circuit. This would be done by putting in a grid resistor to ground, >200M - <1000M. I find the lower end of the range to sound better. You also need to bypass the cathode resistor with a good cap like an Elna Cerafine electrolytic. The jensen transformer ratio in the original circuit is too high. You need about a 10:1 ratio. The circuit is operating as a triode so the gain is going to be low. The Royer circuit has some other issues, too.

I agree that if you look at the Royer circuit it looks like it might have issues: however built as it is written up it does work and sometimes very well with a voice. I think sometimes issues "help" the sound.

I kind of like the no grid resistor but this has a lot to do with leakage via the pins.

I even like the fil supply because of the simple current limiting due to the two dropping resistors.

The more I play with LD vocal microphones the more I tend not to use as many HiFi parts. It is more about EQ and dynamic changes with level than clean for me. For clean I would try SDs

Thanks Guys, so if i understand i should leave this mic alone the way it is
and build something else for the K67. I was told that the U67 is quite complicated to build is there something a little easier that would work with this capsule?
francois

I did not post not to use the 67 capsule.

I would look around this forum there was a post in the last week or two for a tube microphone that might have a circuit fragment you could try with the Royer mod.

Have you looked thur the microphone metas?

Thanks Gus,
yes i read many times the great info that's here. i might have missed or misunderstood the posts that addressed the HF roll off part of the circuit.
francois

I reread my posts and I just want to be clear. I am not dismissing burdij posts the opposite I made a royer or two but mine ended up with cathode bypassed caps and other changes but the stock mod was fine I wanted something different that that. I did hear a Royer mod that ETK made and it worked well.


Have fun tring different parts.

i found a post on usenet from David Bock that gave some interesting infos

" To say an amplifier has a HF
rolloff without qualifying and comparing is like assuming it is a
black box with simply a certain function and no side effects, but we
know from real world experience that it's not a black box and the HF
rolloff is achieved through some means, and every means has it's owm
unique set of effects and side effects which should not be ignored for
a thourough discussion. Looking at a single parameter and making a
judgement ignores the reality of the mic system as a whole.
For example, yes you are correct that the U87 achieves HF rollof
though frequency selective negative feedback through the capsule to
the FET. But what does that really mean? Well for one thing you now
have the "sound" of negative feedback (as compared to an amplifier
with no negative feedback, which will sound different). You also have
changed the frequency spectra of the noise floor as well as the
overload charachteristics and harmonic content. There are other ways
to get HF rolloff, like the U67/M269's feedback through the capsule &
transformer- different again than just running through the capsule to
the gain elemant. And then there's anopther way, using a shunt
capacitor to ground on the output of the gain device, or using the
shunt capacitance of the output transformer. All have different
effects and side effects.
So to really compare Neumann FET mics to tube mics based on frequency
response alone isn't really a scienfic approach, there's far too many
unequalized variables. But the comparison can be done, if you have a
U87 and and a U67 any or all of the feedback elements can be removed
and flat amps could be produced, at which time the age old question of
tubes vs. transistors in MICROPHONES could finnaly be answered.
But, you do raise a point people might not often remember, is that
most of these amplifiers are effectively bandpass filters, and that's
probably a really good thing when you think abvout where alot of mics
get used nowdays, not in real purpose built large studios! A mic with
reall flat low end would too often be "rumbly". Neumann was trying
(around the U87 time0 to build something that sonded good on alot of
applications, and made various copmpromises (which all engineering is)
to successfully achieve that goal.
Does this help? "

i hope it's not a bad thing to bring this quote here outside of the long thread it came from
francois

I wonder how a Peluso 47 capsule would sound with this mic mod?