Gyraf Pultec finished (Shopping list included!)

[JPrisus]

I checked out the Metas, still a little unclear as to the fequency points of the Gyraf schematic. Isn't there a formula for choosing cap values based on the inductor present in the circuit? The thing is, i'm very picky about what Hz I want, since i'll be using this every day in practical apps... i'd like to plan out which caps i'll need beforehand if possible.

Thanks!

 

[CJ]

formula for resonance:



?=1⁄ 2 ∏ ×√ LC
L in henries, C in farads

Your formula approach will not match your actual results, but it will get you in the ballpark.
Having an exact frequency is tough due to the Q of the circuit.
Pick your cap values by ear. It is faster than formulas and gives real world results.
cj

if you manipulate that, you get

C = 1/ 4 ∏²?²L

where frequency and inductance are known.

 

[JPrisus]

Gotcha CJ... i suppose i'll design the front panel for the values I actually want, then experiment with the caps to reach those exact values. I'm a novice at this, but that makes sense. Thanks!

 

[CJ]

No problem.
That method also alllows you to try different kinds of caps.
I found the square WIMA's to work best in equalizers.
Manley uses them also in the Massive.
cj

 

[JPrisus]

[quote author="cjenrick"]No problem.
That method also alllows you to try different kinds of caps.
I found the square WIMA's to work best in equalizers.
Manley uses them also in the Massive.
cj[/quote]

Thanks... i'll try the WIMA's, as I certainly trust the Massive's design.

 

[Brizco]

is it possible to use 380volt / 1,5Ampere bridge rectifiers instead of the 350volt?

thanxx

 

[gyraf]

Why not?

 

[Brizco]

two soldering points blew up!

and i dont know why, maybe the tube, or the bridge rectifiers...?

the two points are: A1 pin from the tube and negative pole from the 4700 / 25v cap.

now i change the rectifiers, the tube, and the cap
and the 380v rectifiers are nearest to the 350v


any other idea why two soldering points blew up? no voltage was connected!

 

[Brizco]

hello

on the two 220u 350v (i use 400v) is a constant voltage of 350volt!
is this Normal (its not powered on)? how can i unload them?

thank you alot!!!!

 

[rafafredd]

You have to discharge it. Use a resistor instead of a short from + to - terminals. BE CAREFULL.

Depending on the schem you could include a 220k resistor across the terminals for automatic bleeding when the unit is turned off.

 

[Brizco]

thank you for your help

im using the gyraf pultec schematic... ehem...
and my english isnt that good to understand what a terminal for automatic bleeding is

can you explain how whre i have to put the 220k res?

thank you very much!!

 

[BVB]

Hi Brizco,

You just have to solder them accros the + and - of your 220µF caps.That's all.

Greets

 

[Brizco]

i have to connect the positive and the negative pole of a 220u cap? right?

 

[BVB]

[quote author="Brizco"]i have to connect the positive and the negative pole of a 220u cap? right?[/quote]

more specific it should be:

I have to connect the resistor to the positive and the negative pole of a 220µ cap.

Then the cap will discharge slowly on it's own.

Greets

 

[Brizco]

thank you for your patiance!

i made it and it works! :thumb:

i can let these resistors connected everytime?

i will go testing the unit tonight in my studio! yippie!! :grin:

thank you very much!

 

[dukasound]

Hi
Does 10K pot for Low Boost Log or Lin?
Thanks
Duka

 

[Brizco]

i use a linear but cant say if it is working, because the unit is not tested yet...

 

[Bauman]

I was wondering, you guys are using shorting or non-shorting 2x6 switches on the pultec ???

 

[gyraf]

Shorting.

But non-shorting will work as well..

Jakob E.

 

[Bauman]

cheers Jakob! Gonna do a couple of yer pultecs but with Quad8 outs :green:

thnx!
Fabio