Arcana Love

[NickDanger]

Hey friends. Noticed there’s not a lot of love or discussion about the Arcana/Secret Freq around here. I really think it’s an underrated (and maybe poorly marketed) pedal. I was tinkering around with it after socketing the diodes, and removed one clipping diode at a time, to some great results. With no clipping diodes, it sounds fantastic. Maybe even better than with.
Next, I removed the transistor, expecting the pedal to stop passing the signal. But since this transistor is in a weird place in the circuit.. it kept on keeping on. And still sounded great. Maybe affected the mids/freq control somehow.

now I’m not super savvy with schematics and the history of distortion circuits, so I was wondering if any of you freqs (ha) could help me understand what the transistor is doing in this circuit? And with that and the diodes removed, does this resemble any other circuits out there closely?

really having fun experimenting and finding these happy accidents. Happy building, stay safe!

 

[Robert]

The transistor is part of the gyrator circuit.

The Freq control is basically a one-band narrow EQ centered at ~825Hz. It's what makes the Freq so secret.

 

[NickDanger]

The transistor is part of the gyrator circuit.

The Freq control is basically a one-band narrow EQ centered at ~825Hz. It's what makes the Freq so secret.

pretty interesting! Thanks for this. By removing the transistor, what exactly happens in the gyrator circuit, then? I just want to make sure nothing is about to blow up ?

 

[Chuck D. Bones]

It stops gyrating. ?

Pulling the transistor disables the 825Hz hump. You'll get a slight treble boost if you turn FREQ all the way up. No harm to the rest of the circuit.

 

[NickDanger]

It stops gyrating. ?

Pulling the transistor disables the 825Hz hump. You'll get a slight treble boost if you turn FREQ all the way up. No harm to the rest of the circuit.

Thank you! I actually used my ears (that’s all I have that works) last night and did some experimenting and pretty much found the same thing. Still kept the diodes out, but found that I quite liked that mid hump! I think I was lying to myself without the transistor, and the freq knob “seemed” to be giving me more mids, when it fact it was that treble/gain increase I was hearing.

What a neat little circuit. I also swapped in a TL072 instead of the 82 and quite dug it. Not much difference there from what I understand.

really goes from weezer blue album to brian may territory. I highly recommend building one if anyone’s needing a new dirtbox!