GT convertible mics

[pucho812]

got a pair cheap at the local banjo center only 99.00(US) each on sale. Looks good for moding. I definately will do some b4 and after audio. Especially with and without ball end for live and without for studio as per GeeTEE. The mic itself is a fet and is transformerless
going to mod them... suggestions?

I will be posting a picture tomorrow and try hashing out a schemo Off the bat I am thinking of swaping the ceramic 1000pF cap on the back of the PCB. thinking a panasonic cap as a replacement or maybe a styroflex of same value.

 

[Gus]

I have a gt44 and two gt33s I don't like the capsules and grill. The electronics seem to be OK.

 

[Scodiddly]

Hmmm... there's been a used GT55 in the display case at a local store for months now - $200.

 

[pucho812]

damm I posted this in the wrong forum. this should be LAB.
How do I go about moving it? I have never done that b4. :?:

Gus, you don't like the capsule. Do you feel that is their weak point?

As for the electronics yes they are o.k. but I am thinking I could do some improvements.

You woldn't happen to have a schemo would you?

 

[Rossi]

BTW: the GT55 is basically the same mic as the M-Audio Luna. Same circuit etc. The only differences being cosmetics and the HF-disk on the GT mic. I actually prefer the sound without the disk. Sounds more natural IMHO.

 

[Emperor-TK]

Gus and I have been talking about what to do with our GT AM40/44 mics. A while back he posted that I should pop off the inner grille. I didn't get a chance to do that until a couple of days ago and it does make a big difference. The grill is lined with a couple of thick layers of cloth. It seems to serve two functions: it reduces high end and causes resonance, to where the mic sounds like it is inside a small box or a can. It was this boxy sound that I disliked the most with this mic. The downside of popping this grille off is that the mic tends to sound a little more brittle and grainy.

I also noted that an Oktava 012 capsule can be jammed into the GT and make both hot and ground connections. Not a permanent mounting solution, but it works for checking it out. My reaction: an Oktava 012 capsule in the GT sounds a lot like an Oktava. My guess is that the circuits in both mics are not very colored. I still haven't done a direct comparison to the oktava head on an oktava vs on a GT.

-Chris

 

[nacho459]

What is up with M-Audio and GT? There was an old line of GT mics that M-Audio distributed. I have a friend who's brother has worked for M-Audio since they were called Midi Man, and he sold me a Groove Tubes 1b-FET mic for $84. I never really understood the whole thing cause I figure the mic was probably just a rebrand with a cool GT casing, and GT and M-Audio are quite different companies. If M-Audio was doing distro for GT why just a few mics?

Weird :?:

 

[Rossi]

I was told that M-Audio was the worldwide distributor for GT for a while (after the Alesis interlude) and that's how M-Audio got into contact with asian microphone manufacurers. And they still use those contacts now to produce their own mics.

 

[mhelin]

[quote author="Rossi"]BTW: the GT55 is basically the same mic as the M-Audio Luna. Same circuit etc. The only differences being cosmetics and the HF-disk on the GT mic. I actually prefer the sound without the disk. Sounds more natural IMHO.[/quote]

What is a HF disk?

 

[BackHand]

[quote author="Rossi"]BTW: the GT55 is basically the same mic as the M-Audio Luna. Same circuit etc. The only differences being cosmetics and the HF-disk on the GT mic. I actually prefer the sound without the disk. Sounds more natural IMHO.[/quote]

same capsule?

 

[Rossi]

The HF-Disk is explained in the GT product literature. It is a small brass disk that's mounted at the center terminal (i.e. the screw in the middle of the diaphragm). The brass disk reflects soundwaves at high frequencies back on the diaphragm. The sound has a bit more shimmer, but imho the treble sounds a little unnatural due to the associated phase inaccuracies. Sounds a bit like when you use an exciter.

Otherwise the capsules were pretty similar. The GT capsule looked a little darker, if I remember correctly.

 

[mhelin]

Ok, thanks for the explanation. I asked this because my NT-1 (old model, not the current NT-1a) also seems to have this kind of HF-disk. I can confirm the sonical effects, and I'm also going to try the NT-1 without the disk.

 

[pucho812]

havn't had a chance to post pics yet. but I mentioned changing the 1000PF cap in the back to a styroflex of the same value. On my mics one has an extra cap wired to that 1000 pF cap. at first I was thinking was wired in series to make up a value to 1000pF like the one without it but no dice it's a 1000PF cap. me thinks I should just take that out.

 

[Gus]

Can you take a picture. My 33s and 44 don't have ceramics in the signal path. I saw film and what looks like silver micas in my 33s.

Does the microphone have a pad switch? if so it could be a cap that is part of the pad circuit.

The post make it sound like it is a different circuit or build than the 33s.

Zebra had pictures of the capsule with the grill on and off linked in the meta.

 

[pucho812]

1'st thing I am doing when I get home is starting my photo bucket freebie and posting pics. got the 460 info/pics for you as well. and no no pad switch. However mine did come stack as hypercardioid so that could be it except for the fact that out of this pair one has the extra one doesn.t :?

 

[pucho812]

here are pics of the inside...

Front of PCB

back side PCB
this has the extra 30pF cap circled smaller then I saw in at home. it's in brown and the 1000pF orange. I am thinking would be a good first change to this mix

 

[Gus]

Looks like the schoeps circuit. Kind of looks like a superlux build.

What does the capsule look like?

 

[pucho812]

so this is different then yours?

 

[Gus]

The gt33 is different. Zebra had some pictures in the GT33 GT44 thread but they seem to be missing.

 

[pucho812]

I was thinking yours was different. I am wondering if this is just a banjo center only mic much like the new cheap AKG mic comming out. it's called the convertable and came standard in Hypercardioid. Has no pads or rolloffs. It does have a ball end like an SM-58 which one can use for live and then it comes off for studio and looks like a gt-33.

Anyway got some better pics of the circuit and a pic of the capsule.

(cleaner pic of the circuit)

(cleaner pic of the back of the PCB)
the 30 pF cap was found ono one out of 2. The other cap is 1000Pf. which I am thinking I could replace.

pic of the capsule. I couldn't get the grill off but this is a nice side shot. measnuered 22-24 MM diameter