Even if the difference is audible, does it matter?
I think that the problem is the availability of coils with such a high inductance, not the difference of a few Hz.
OK, I think I will give it a shot and make an inductor. From what it looks, I can make it as small as 12x12mm for the footprint and 10mm in height. The pitch would likely be 7,5mm and 5mm with three pins, one can be snipped of depending on the lead pitch will be used. It will be a pot-core, not toroid though.
I´m open for any kind of suggestions.
I see a lot of talk about the big 250mH inductor. Anybody ever had the idea, instead of using this gyrator with an actual inductor, to use the leftover opamp and building another gyrator like in the EQ?
So far i didn't build it yet either, but I did put it into my simulation program to see, if it could work.
And I got pretty close, not ideal though.
According to this calculator (http://sim.okawa-denshi.jp/en/RLCbpkeisan.htm), when you move MidCut pot, you change Q of the bandpass filter from 0.1 to 10. So, it can't be done by using simple gyrator instead of coil bandpass filter.
For the tone potentiometer, a 20K potentiometer is required. However, I can only find a 20K W-taper that is also used with a Tubescreamer. Can I also use this for this? Or do I have to go to a 25K version?
Ricotjuh wrote:For the tone potentiometer, a 20K potentiometer is required. However, I can only find a 20K W-taper that is also used with a Tubescreamer. Can I also use this for this? Or do I have to go to a 25K version?
The tone control here works the same way the Tubescreamer tone does, so a 20k W-taper should be fine.
I simulate PLUTOmusic's gyrator version of mid scoop in LTSpice, and it works almost the same with the inductor version, but 75k should be connected to Half voltage(+B) and not on ground.
Do you think it's possible to use a telecom/dsl transformer. They can usually be connected in a number of ways to get different values of inductance. They type I have has four 100uH coils in it and you can hook them up in series or parallel to get different values. Just a thought.
#1 is the inductor. 250mH is hard to find online. sometimes can be mistaken for 250uH (ebay etc etc) . but armed with an LCR meter, you can just measure inductors easy. 24v relay coil / reed relays . ive selected an inductor with a metal core as small as possible. my coil DCR was around 300ohms. midcut control works as expected(signal output waveform monitored thru scope)
#2 problem is getting an W or S taper pot for the tone control. almost impossible to find. Ive used a linear 20k and it behaves like a frigin on-off switch. maybe ill just subs a tone control circuit w/c works on log or linear pot control.
I built this modified version of Mesa Boogie Throttle box.
The difference with the original is that, this is inductor less, and the EQ switch is external. Info can be found in this thread.
Maybe next time, I'll try changing the tone control into BMP style tone control circuit to control the Fatness. then put the TS style tone control after the EQ stage and call it Presence.
I also don't like how the gain control behaves, it makes the tone dark when dialled down. That's just a personal opinion.