G7 finished!! But bad bass-response in omni-position

[gyraf]

Yes, these differences could come from different ways of calculating VA of the transformers. Some do this on basis of voltage drop, others on core temperature rise. I'll look into it, when I get a chance.

 

[Greg]

Salossi:

Did you ever get your voltage problems sorted out. I used the 5K as I stated above with Avel transformers. I also made sure to overspec the VA a little. And fortunately, my voltages are almost dead on.

163.7V after the 10K
80.8 after the 470K voltage divider

I did a quick testing on my voice and I like my initial testing, but I definitely will do some more testing very soon. This is the first mic I've ever built. Fun stuff! :thumb:

 

[Salossi]

Hi Greg,

Unfortunately I didn´t find the time to solve my problem with the g7-voltages. I tried to change the resistor, but this doesn´t change very much. I think I have to change the trannies and then, perhaps, regulate the voltages in my psu.

But, my g7 sounds surprisingly good, even with the low voltage. And it got a very hot output, much more than my diy-mic with transformerless output.

I hope, I will find some time soon to complete this mic!!! Besides the low voltages I have to build a new capsule-holder (mine is too soft and the capsule moves very much if the mic is tilted... sometimes the capsule even touches the inside of the grille with it´s rim) and I have to build a shock mount. This is very important, because the mic is very heavy. So it is not easy to fix it with a standard-mic-mount... ouuuu, my english must be very bad...... sorry, hope you understand, what I want to say....

What about your mic, Greg? Any Pics??? Let me know, I´d like to see more diy´ed g7 stuff!

Greets, Sascha

 

[Greg]

I've got a few little cosmetic things to do, and I'm going to put the PSU in a different box. Once I get that done, I will post some pics and maybe some sound clips if possible.

One more thing... I measured the secondaries on my power transformers, and they both measure higher than the specified 9V and 220V. This is probably the main reason my voltages are ok.

PS: Your English is fine.

 

[Klaus Mogensen]

I have played around with different transformer, resistor combinations today and get to the same conclusion as Gus; that the 5 VA rating is too small for the first transformer.

I tried

A )
1. trans: 220v: 9V, 5 VA
2. trans: 12 V : 220 V
Resistor: 5 kOhm
Unloaded: 184 V, loaded 128 V

It drops to the same low value (around 130 V) as when I used a 15 V: 220 V second transformer, so it is limited by the current as Gus writes.

B)
1. trans: 220V : 9 V, 10 VA
2. trans: 12V : 220 V
Resistor: 10 kOhm
Unloaded: 202 V, loaded > 160 V (I turned it off, not to burn the components)

C) same transformers as B)
resistor: 33 kOhm
Unloaded: 180 V, load: 144 V

D) same transformer as B) and C)
resistor: 27 kOhm
Unloaded: 189 V, load 155 V

So now I'm satisfied with D)
I also prefer not to go to low on the resistor value, not to compromise the filtering.

Best, Klaus

 

[Dr_J]

Hi,

this threat was a good starting point for my build / experimental, but... it was a long run of trail and error...

So, I want to bring in my experience.

I used 2 BLOCK Print Powertransformers, e.g.
http://www.conrad.de/ce/de/product/710518/?insert=62&insertNoDeeplink&productname=EI-48168-Printtransformator-VC-10-VA-Primaer-230-V-Sekundaer-9-V-111-A-10-VA-VC-1019-Block

Here my experimental series...

1)

1. trans: 230v: 9V, 5VA
2. trans: 15V : 230V, 5VA
Resistor: 10 kOhm
Unloaded: 128V


2)

1. trans: 230v: 9V, 10VA
2. trans: 15V : 230V, 5VA
Resistor: 10 kOhm
Unloaded: 128V


3)

1. trans: 230v: 9V, 10VA
2. trans: 12V : 230V, 3.2VA
Resistor: 10 kOhm
Unloaded: 164V
Loaded:   132V


4)

1. trans: 230v: 9V, 5VA
2. trans: 12V : 230V, 3.2VA
Resistor: 10 kOhm
Unloaded: 166V
Loaded:  125V


5)

1. trans: 230v: 9V, 10VA
2. trans: 15V : 230V, 5VA
Resistor: 10 kOhm
Unloaded: 198V
Loaded:   164V (Heater 10V)
Loaded:  173V (Heater 6.3V)



I tried to make some correlation, but with really not much success :-[  ... in the end it was just trail and error iteration...


ROCK-ON!