Mesa Boogie - Throttle Box  [schematic]

All about modern commercial stompbox circuits from Electro Harmonix over MXR, Boss and Ibanez into the nineties.
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Dirk_Hendrik
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Post by Dirk_Hendrik »

FloPoeKo wrote:The coil in the pictures pretty much looks like the ones they put in the amp-eq-sections,
Any thoughts?

Are you sure? ;-)
http://www.coilws.com/index.php?main_pa ... th=208_291
Sorry. Plain out of planes.

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Ricotjuh
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Post by Ricotjuh »

temol wrote:
FloPoeKo wrote:On the Inductor:

Are we 100% sure it is 250mH and not 220mH?
here is a plot from ltspice simulation. With 250mH you have 678 Hz, with 220mH - 720 Hz and with 200mH - 760 Hz.
Lsweep.jpg
T.
Would the difference of 42Hz give an audible difference?

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temol
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Post by temol »

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.

T.

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FloPoeKo
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Post by FloPoeKo »

Dirk_Hendrik wrote:
FloPoeKo wrote:The coil in the pictures pretty much looks like the ones they put in the amp-eq-sections,
Any thoughts?

Are you sure? ;-)
http://www.coilws.com/index.php?main_pa ... th=208_291
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FloPoeKo
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Post by FloPoeKo »

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.

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PLUT0music
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Post by PLUT0music »

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.

Any thoughts on that?
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both circuits and graphs to compare
both circuits and graphs to compare

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for.try.soft
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Post by for.try.soft »

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.

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Post by Ricotjuh »

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?

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Post by Dr.Detroit »

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.

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Post by Ricotjuh »

Ok, thanks for your reply

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jhergonz
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Post by jhergonz »

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.

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Lani
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Post by Lani »

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.

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Post by riffy »

Ive built the circuit. IT shreds!

and I see 2 problems cloning this.

#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.


cheers

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