--- In "stoatwizard" <> wrote:
>
> --- In "tk7859" <g0sbw@> wrote:
>
> > Some of you might note the album "Jecklin Disc" in the above photos
> > URL. This shows photos of a work in progress but not yet reported on.
> > It is, however, somewhat topical. Preliminary results are very
> > promising (apart from one major faux pas). I will report on this
> > project shortly including comparison of the DIY project with my NT4.
>
> I am intrigued as to why there are three mic capsules in what appears
> to be a line array on the Jecklin disc. Is this a crafty way to reduce
> the self-noise of the elecret inserts in a similar way to
> paralleling transistors for low-impedance input stages?
Hello Stoatwizard and the Group
Yes, the use of three paralled capsule vertical line array was an
attempt to decrease self noise of the extremely cheap capsules and,
hopefully, at the same time increase sesitivity.
I had read that this might be acheived in this way. As I still had 9
capsules available from the 20 I originally purchased I decided to
give it a try for the Jecklin disc and the parabolic under construction.
It was a mistake. The parallelled triplets have a much lower
sensitivity than a single capsule. I therefore reverted to single
capsules for these two DIY projects.
The relevant figures are:
The noninal DC resistance of the cheap capsules is 1.0k. with some
variation between samples. I chose the six most similar and arranged
them in triplets so that the combined DC resistance of each triplet
was the same at 0.33k. When coupled to the 3.5mm stereo jackplug the
DC resistance of each of the right and left circuits was the same at 0.34k
The replacement single capsules are well matched at 1.29k and they are
much more sensitive than the triplets.
If I add a 1k resistor in series in each of the triplets circuits the
DC resistance would appear the same as that of the single capsule. I
wonder if the sensitivity would increase accordingly?
Any thoughts before I experiment?
The "Jecklin" album at
m("btinternet.com/my_photos","//uk.pg.photos.yahoo.com/ph/g0sbw");">http:
has a further three photos showing the offending triplets as removed,
the head with single capsules plus strainer/tights wind protection and
the dead cat cover.
Cheers
Tom Robinson
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