G7 build question

[Potato Cakes]

Hello, friends,

I'm working on a G7 build that I've had sitting around and I read on Jakob's site that the 10u/35 capacitor and 2k2 trimmer were to be omitted as they were for feedback. However, photos of completed builds show these components in place. I also noticed that there were two 10u/35 caps in the schematic but only one was silk screened on the PCB. Could someone who has built one of these please shed some light on this?

I have all of the parts minus the capsule which I plan on ordering one of the Eric Heiserman HK12 later this summer. I anxious to see how this one compares to my other mics.

Thanks!

Paul

 

[ln76d]

According to schematic there's only one 10uF capacitor inside psu.
Feedback is 100uF and 2.2k pot - both you don't need.
Check again.

 

[Potato Cakes]

Here's the schematic off the website. It shows two 100uF/35 electrolytics in the mic. Also the in the build pictures it shows the 2k2 trimmer and the 100uF/35V. In my earlier post I meant 100uF in the mic schematic and not 10uF.

Thanks!

Paul

 

[Potato Cakes]

Here a pice of the build off of Jakob's website. However I just looked up a couple of other people's G7 builds to make sure that I wasn't crazy and they did not have the trimmer nor the 100uF cap. So I am crazy. And I'm going to stop second guessing myself and just proceed with the directions as they are written.

Thanks for responding. I sometimes need help realizing that I am being silly and that I shouldn't ask stupid questions.

Thanks!

Paul

 

[ln76d]

Paul - always is better to ask, even twice

Here's basic mod for G7 which improves sound quality a lot.
Better mod is completely change of capsule input arrangement.
You can look for my S16 and S216 threads here - S216 still didn't finished due to lack of time - but there's few usefull informations.
Ask Eric about HK12 and polarisation voltage - if 80V is too much - you will need to change 10k resistor in PSU - you could use 22k potentiometer to adjust proper value and i recommend to make it also as a listening test.

 

[Tim Campbell]

What change of capsule input arrangement?

 

[ln76d]

Best option which can be made is to use negative voltage for capsule poalrisation but it's little bit simplified, especially if someone want to use PCB. Another better option is to use typical AKG topology like C12 or C12VR.
Capacitor between front and back diaphragm (original 10nF for G7) permantently connected is the worst scenario.
Neumann used 1nF mostly and even this value is set too high. Please notice that in M49c not without a reason was switch inside microphone for "cardioid only" mode operation.
It can be reduced to few pF range for better sensitivity and frequency shaping but best option is to remove it completely.

 

[Potato Cakes]

Thanks for the info!

I may make it to spec first, do some recording, then swap out the parts for comparison. I believe Eric's HK12's can handle 80V. I will double check with him before I actually make the order.

Thanks!

Paul

 

[hitchhiker]

Leave off the cap and trimmer, IIRC Jacob used it for testing.