(Warning:Keith is not a real expert, he's just the guy with the website and too much time on his hands, so don't take anything he says as gospel.)
> Steve wrote:
>I have been playing blues harp for about 28 years now.
>One item of interest, recently I decided to experiment
>with tube preamps and different mics.
>A Shure 520 D has been my mic of choice, but a friend gave
>me a JT30. I install volume pots on all my harp mics, and
>use a '63 Fender Tremolulx amp.
>In addition, I have a "Fisher" tube preamp. This is a
>dual tube, 6SG7 and 12AU7 preamp. I modified it
>to use only the 6SG7 and accept HI Z input. Currently,
>1 Meg Ohm.
>What it interesting is the output of the SHure 520D is
>higher than the JT30. The Shure can over drive
>the preamp giving a wonderful Chicago sound.
>The JT30 doesn't overdrive, is a bit less bass present,
>and offers a nice alternative....
>Have you any experience comparing these mics?????
>PS, the pot I use is a 1 meg ohm inside the mics....
>On the JT30, I added the .001 uF cap, with the 520D, no
I am finding that the JT-30 elements vary a lot. I have a real hot one, but I have a few others which are not as hot. What I find is that the elements mellow out with age.
My objection with the 520d (Green Bullet) is that the response is too good. I wind up amplifying all the the little breathy reedy sounds when I want to only get the rich horn like overtones. I don't play loud at the harp and rely on the amp to make me loud. As a result I get good rich tone, but have to turn the treble down to avoid the reedyness. If I want a Chicago sound, the jt30 is better for me, because it has that limited response. It also seems to cover up my lack of skill in playing a little. The 520 seems to emphasize my mistakes.
The 1M pot is what I use because it's hard to find 5M audio taper pots. The only difference between 5M and 1M is the 5M seems to feed back a little less, but that may be because there is a difference in the element. It's hard to tell. I am told that If they made 10M pots, that they would be even better.
I can't see any difference from adding the cap. I've added a cap to a couple of mics and I can't hear the difference. The cap is like chicken soup for a cold. It won't hurt and I might help.