G7 microphone finally finished!!! (now with a short clip!)

[Jonkan]

My capsule couldnt take 80v, or the membrane got sucked into the backplate.
Thats why modified the dividers.

But i really dont think that would make a big difference?

I think you may have overread my statement about the mic being bass shy. It is bass light, but not at all to the point of it being strange or unusable.
In fact to me the bass as it is right now sounds extremely balanced and tight, which could translate to it being percieved as bass shy i guess.

But i havent tested it. How could you test something like that? Send a sweeping testtone or pink noise through speakers, record it with the mic and check for linearity? I could perhaps compare my mic to my cheap behringer measurement mic, which should be pretty flat. My acoustics at home however, most certainly isnt very flat.

Id have to use it more before i can be totally sure whats up if going by ear.

/J

 

[Benny]

I did not modify the polarization voltage. I just built everything as in Jakobs schematics. I'm using Daves M7 capsule too, with Lundahl output. But my microphone sounds a bit too thin, I think. Perhaps I should check all voltages and then try it with a different voltage divider to get the 80V down to 60V. How does a capsule sound if the membrane got sucked to the backplate?

 

[Jonkan]

It doesnt sound at all.

Perhaps a "fzzt" from the actual capsule when it gets sucked into the backplate, but thats about it.
/J

 

[burdij]

I have found that when the bass is lacking there may be a leakage path for the polarization voltage to ground.

One common condition that causes this is a mount made with a neoprene type rubber spacer that will have a very high but noticeable amount of resistance. The coloring agent in most rubbers is carbon black. If you are using this type of mount and one end is attached to the frame of the microphone, you will need to provide a spacer that is made of a good insulating material such as Delrin (acetal copolymer) or Teflon (polytetrafluoroethylene).

Also carefully clean all rosin and oils with flux cleaner followed by low water isopropyl alcohol.

 

[Gus]

There is more to it than transformer ratio.
just a hint not an answer

 

[bluezplaya]

Just curious, if folks are using the EF86 tube with the G7, which brand of tube do you prefer?

 

[Jonkan]

Ok, i actually have one of those rubber mounts for my capsule.

But underneath it i have a plate of wood that the mount is fastened to. That should effectively isolate the capsule from groundpaths, right? Or do i still need to get a teflon washer? Where might one get hold of such things?

I havent used any fluxcleaner on the pcbs, but i have cleaned it about four or five times with isopropanol, an old toothbrush and alot of scrubbing. Is that enough?

Gus: I will get back to you on that in a couple of years, when i hopefully understand more than i do today. That hint doesnt even get me started in the right direction. Is there some sort of bible on microphones i can read to grasp all of this...?
Thanks anyway!

Though I suppsose the transformer impedance could also affect the circuit somehow, and also how the transformer is loaded at the output would translate to the impedance the mic circuit sees. Was that what you were hinting at? (just guessing here).

/J

 

[gyraf]

I havent used any fluxcleaner on the pcbs, but i have cleaned it about four or five times with isopropanol, an old toothbrush and alot of scrubbing. Is that enough?

Yes, usually it is.

 

[Gus]

Another hint what can core size and alloy change at the same ratio?

A EF86 that has low noise.

 

[Jonkan]

I guess it could affect the capacitance of the transformer between the wire and core of the transformer.

And when the core saturates?

Thats what i have gathered so far anyway. But im not sure if thats what youre hinting at, or if i understood it correctly.

I got to read some nice articles on transformers anyway, so all is not lost.
/J

 

[steppenwolf]

My g7 has a nice extended bass response. I use it as a room mic during rehearsal and the kick sounds awesome on the recordings, full and punchy!
I use a Peluso CK-12 capsule with Lundahl output.

Did you swap the tube?
Mr. Gyraf himself told me to try a PF86 instead of the stock EF86.
Same tube, different filament voltage...
I got 3 NOS valvo PF86 for nothing on ebay and they are a lot quieter and nicer sounding than the crappy Tung-Sol EF806S I payed nearly 40€ for.

 

[imo]

I was going to mess with polarization voltages, but i wanted to build the circuit "as is" as a starting place; To have something to reference the changes. I was actually quite pleased with the sound, with the biggest impact seemingly being the screen design, allowing more room and more bass, while lacking a little bit of the high mid detail that the Lawson seemed to have. The circuit itself sounded very healthy to my ears. I actually tweaked the resistor a bit in the power supply to get more B+, as i was running a bit low initially
Ian

 

[burdij]

Wood is a fair insulator if its dry but when its damp or wet it is not. Teflon is used as the seal in some plumbing fixtures like valves. Delrin is commonly used in yo-yos, parts for paintball guns, sliders for motorcycles, castor bearing, and guitar picks. You could also use Lucite or Perspex type plastics (acrylics). That works for Neumann.

 

[bluezplaya]

I got 3 NOS valvo PF86 for nothing on ebay and they are a lot quieter and nicer sounding than the crappy Tung-Sol EF806S I payed nearly 40€ for.

I'm glad you mentioned that. I was looking into buying the Tung-Sol EF86. I have Tung Sol's in my guitar amp and they sound great, but now I will be looking for PF86.

 

[Jonkan]

I see.
Can leakage around the tube holder affect the sound too? I used an old tube holder that i found, and its not ceramic, but some kind of plastic. Would it be a good idea to consider changing it for a ceramic, or teflon one also?

I havent found any source here in sweden for teflon washers. I found some teflon shrink tube, would it be ok to just cut a circle out of that to mount underneath the rubbermount?

/J

 

[Jonkan]

Anyway, heres a clip of my friend singing and playing guitar about 30cm from the mic in cardioid mode. The mic is about halfway between the mouth and the top of the guitar.

All of this recorded in my living room, so youll have to excuse the bad acoustics.

The first half is through my BLA modded motu travelers preamps, the other half is through my Diy 1272 type preamp.

If not anything else these clips prove that i have managed to make a microphone that actually works :green:
http://www.figuresfromhere.com/music/g7skojtest.mp3

/J

 

[Benny]

Nice to hear a sample clip. Now I can definitely say that something is wrong with my G7. Compared to this mine has absolutely no bass frequencies. Like having a low cut filter at about 1kHz or so... :?
I'll have to check that the next days.

 

[bluezplaya]

The first half is through my BLA modded motu travelers preamps, the other half is through my Diy 1272 type preamp.

Sounds great! Would you attribute the sound mostly to the mic, or the converters?

 

[Jonkan]

Most of the sound is probably coming from my friends talent. That said, i find that single tracks of different ad conversion sound pretty much similar (of course there is some difference, but not that much), whereas if i change mic i can hear alot of difference. I also hear a bit of difference by changing micpre, probably due to the two more transformers in the signalpath with the 1272.

When you stack alot of tracks with an ad converter i can more easily hear the quality (or not) of the converter being used.

So the mic and placement of said mic definately is the most important to me after the performer.

Makes any sense?
/J

 

[bluezplaya]

It makes all the sense in the world and I appreciate your reply on that. Some people believe mics are the number one factor in a great track, some think converters, and some think pre's. I say use the best of all three! But when your friends vocal started "jumping" off of my computer speakers and hangin in the air between the speakers and my ears, it made me think he was in the room with me. My first impression was "wow, that's a great converter". But if you say it is the mic, then I am REALLY excited about building a G7 :green: :green: :green:

Can you tell me again which capsule and tube you used?