semi parametric tube eq

[nattyjo]

Hi all, my first post and hope someone can help.
I would like to build a full valve semi parametric eq with freq and gain adjustment. It would be for line levels as effect to sweep over audio spectrum.
I have googled it but with no luck.
Is it impossible to do with valves?

 

[ruffrecords]

You can do semi-parametric with switched frequencies rather than swept with pots completely passively and add a tube gain make up stage. Check out my universal EQ here:

http://groupdiy.com/index.php?topic=50484.msg639985#msg639985

Cheers

Ian

 

[nattyjo]

You can do semi-parametric with switched frequencies rather than swept with pots completely passively and add a tube gain make up stage. Check out my universal EQ here:

http://groupdiy.com/index.php?topic=50484.msg639985#msg639985

Cheers

Ian

Hi Ian thanks for reply.  I should have be more precise on what I would like.
I want it to be continously sweepable, not switched. I'm afraid that if switched you hear clicks and pops as you sweep.
So maybe is there a way to design a valve based gyrator circuit?

 

[ruffrecords]

I am sure I have seen a valve based gyrator somewhere.

Cheers

Ian

 

[gyraf]

maybe glass audio?

 

[ruffrecords]

The only trouble with using gyrators instead of real inductors is that gyrators do not have the energy storage properties of inductors so they will definitely not sound the same. Maybe you should use a gyrator with an inductor to simulate a variable capacitor and couple it with a regular inductor. Or there's the twin T or other phase shift networks you could use.

Cheers

Ian

 

[nattyjo]

Yes good idea Ian but unfortunately I'm not able to design this.
Can you maybe point me in the good direction with some schem?

 

[ruffrecords]

Yes good idea Ian but unfortunately I'm not able to design this.
Can you maybe point me in the good direction with some schem?

Ah, I had nor realised you were looking for a ready made design. I guess you can Google as well as I can and I cannot say I have seen a complete design for what you need in the searches I have done. If you come across one let me know and I'll happily give it the once over.

Cheers

ian