Harmonic Converger -- Warm up Amp Modelers and Kill Fizz

[antisolo]

A friend asked me to build one of these for him but the problem is I have no idea what kind of inductor to get. Never used them except for wahs. Choke? Power inductor? RF inductor?

[Jazznoise]

For 250 dollars you'd be well on your way to getting a soundcard with a mic-pre. You don't need a cab sim when you can record your cab!

[ayayay!]

I built mine using a plain old Dunlop wah inductor.  It's irreplaceable for me when I play gigs with no amp.  I just go pedalboard-> HC workalike -> DI out w/ cab sim (Behringer GI100, don't knock it 'til you try it.)

[sault]

I spent a lot of time looking and thinking about a Harmonic Converger.

After a lot of research, I believe I remember finding someone in a Line 6 forum who duplicated the frequency response by summing the output of a LP filter (around 5khz) with a small amount of the *original signal*. I do not believe any diodes were ever mentioned or believed to have been used.

Simply using a LP filter removes too much highs, blending some of that original signal back in keeps your dynamics, kinda like the Tubescreamer does.

I vaguely remember realizing that you could take a Big Muff tone stack, add a pot at the right place, and boom, there you go. An active version would also be pretty straightforward, too.

I'll have to go back and think a bit, and see if I can remember how exactly I figured that out...


Sault

EDIT:

Of course... using a transformer would make things a ton easier, wouldn't it? Never thought about that... never used transformers, never studied 'em, it was always AC coupling...

[ayayay!]

My guitarist used a POD for most of his stuff, and we had to use this on each track:  http://www.harmonycentral.com/docs/DOC-1652
Myself on the other hand, using what I described above, did not.  It was nice.  Both require a little work, so really it's up to you.  I will say, however, that he recently got the newest Line6 flooboard efx, and it has seemed to address this.  

Hey Sault, I was trying to get on your Gyrator page Tuesday night and was getting a 404.  Is it back up yet?  Thanks.  

[sault]

Hey Sault, I was trying to get on your Gyrator page Tuesday night and was getting a 404.  Is it back up yet?  Thanks. 

It is. Shouldn't have ever been down, actually. Can't say that makes me happy about the hosting company... but yeah, thanks for saying something. Looks like I managed to hose the CSS last time I made a tweak, and somehow managed to not notice. Oi...

[sault]

Okay, so here's my hat in the ring.... a tweaked Big Muff Pi tone stack, with a doubled up LP and the values tweaked so that the LP is higher than the HP (the opposite of how the tone stack is stock).

(basic BMP LT Spice file from here http://gaussmarkov.net/wordpress/tools/software/ltspice/ltspice-ac-analysis-with-the-bmp-tone-stack/ )

I played around with the values a little bit, but in the end only focused on cap values. I doubled up the LP section because the roll-off was too gentle without it, these values put the -3 db points in the 4-6khz range. The HP section cap was chosen to put its -3db point below 100hz, but its roll-off is very gentle anyways, there shouldn't be any appreciable loss.

Whatcha think?