Hi everyone!
Is there an easy way to lower the output impedance of this circuit, so that it can be connected directly to a line input of a soundcard or hifi amp?
Big Muff Pi Versions and Schematics
Is there an easy way to lower the output impedance of this circuit, so that it can be connected directly to a line input of a soundcard or hifi amp?
Big Muff Pi Versions and Schematics
It's already fairly low, and would connect with no problem to a HiFi amp - only slight 'problem' is the highish value of the pot on the output - but turn that fully up, and use the pot on the amp instead.
But even using the pot would be fine anyway.
But even using the pot would be fine anyway.
1. Redesign the final stage; replace BJT common emitter amplifier stage with 12V-capable rail-to-rail opamp*, configured for the same gain (4.55X)
2. Move volume control; instead of after the final stage, place it before the final stage.
*TLV2370, TLV2372, MC33202
2. Move volume control; instead of after the final stage, place it before the final stage.
*TLV2370, TLV2372, MC33202
Thank you both!
I am using "halo big muff" circuit board, and i am a bit limited on Space, so it will be difficult to alter the design by much. Would it be beneficial to just omit the volume control pot and replace it with two resistors? I dont really need a volume control at all in this box.
I am using "halo big muff" circuit board, and i am a bit limited on Space, so it will be difficult to alter the design by much. Would it be beneficial to just omit the volume control pot and replace it with two resistors? I dont really need a volume control at all in this box.
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Yes, just remove the volume control entirely, and take the output from the end of the capacitor C2.
One more thing, would it be possible to use 7.4V or 11.1V instead of 9V on this circuit?
It would be awesome to power it with a lipo.
It would be awesome to power it with a lipo.
It should make very little difference, and don't forget a 9V battery doesn't stay at 9V for very long anyway.
With due respect, this is a musical instrument effects pedal, specifically a *distortion* one, and none of the above suggestions applies in this very particular case.
They would be fine in standard preamps, of course, but here there is heavy clipping involved, in cascaded stages, even the last "linear" stage (Q1) is driven "just" to clipping itself, so for starters the suggestion in post #3 :
while in the original schematic last stage is always being heavily driven, (1400 mV PP at least) and its output is being attenuated, an absolutely different situation.
Another suggestion, also in post #3 does not apply:
A modern and complex (has tons of transistors inside ) rail to rail Op Amp is very different, will behave different, will have very different output impedance (much lower), if clipping will do it in a different way, and besides will be extremely linear, not what a simple single transistor bipolar stage will do.
As of post#2:
Again, it's a pedal , it has a bypass switch to choose between straight guitar and distorted one.
Since volume would normally be different, the distortion-section-only output volume control is precisely meant to either balance both levels, or allow a somewhat higher one for the distorted one, for, say, a solo.
Disabling (or setting it to max, it's the same) the output volume and relying on a later one which affects both signals is not advisable, because it detracts from the preamp functionality.
As of post #4:
Perhaps you think so now, but when actually playing maybe you'll change your mind.
Besides, beyond the usefulness or not of having that distortion volume control, there's the very real result that signal at the output (if going direct, no pot or attenuator used) will always be producing an around 2*12/2.7*0.7=6.2Vpp square wave and feeding it (should I say slamming?) into the poor next preamp input.
It will most certainly make it overdrive (unless it's fully passive) and change the distortion "taste" or "flavour"
Any of the suggestions above will change sound and turn a Big Muff into something else.
I've referred to the first schematic, but in general applies to all versions.
Here the proper solution is to add, at the real pedal output, (so it applies to both direct and distorted signal), a unity gain buffer, which may very well be an Op Amp, rail to rail if you like, and preferrably 1M input, bypassed with 220pF , so as to simulate the input of a classic Tube amp connected with a good guitar cable, what the Big Muff expects to "see" .
That unity gain buffer will drive any reasonable preamp or sound card input.
As of the power supply, in this case the 9V one is critical, because the last transistor is *just* reaching clipping, with a higher one it never will, with a lower one it will all the time.
If anything , use 11.1V LiPo battery and trim voltage down to, say, 9V or slightly less.
Below 8V you'll hear the sound change.
They would be fine in standard preamps, of course, but here there is heavy clipping involved, in cascaded stages, even the last "linear" stage (Q1) is driven "just" to clipping itself, so for starters the suggestion in post #3 :
does not apply, because to begin with it would avoid reaching clipping in the last stage unless set to "10" ....
while in the original schematic last stage is always being heavily driven, (1400 mV PP at least) and its output is being attenuated, an absolutely different situation.
Another suggestion, also in post #3 does not apply:
A modern and complex (has tons of transistors inside ) rail to rail Op Amp is very different, will behave different, will have very different output impedance (much lower), if clipping will do it in a different way, and besides will be extremely linear, not what a simple single transistor bipolar stage will do.
As of post#2:
agree
Sorry but no.
Again, it's a pedal , it has a bypass switch to choose between straight guitar and distorted one.
Since volume would normally be different, the distortion-section-only output volume control is precisely meant to either balance both levels, or allow a somewhat higher one for the distorted one, for, say, a solo.
Disabling (or setting it to max, it's the same) the output volume and relying on a later one which affects both signals is not advisable, because it detracts from the preamp functionality.
As of post #4:
are you sure?
Perhaps you think so now, but when actually playing maybe you'll change your mind.
See above.
Besides, beyond the usefulness or not of having that distortion volume control, there's the very real result that signal at the output (if going direct, no pot or attenuator used) will always be producing an around 2*12/2.7*0.7=6.2Vpp square wave and feeding it (should I say slamming?) into the poor next preamp input.
It will most certainly make it overdrive (unless it's fully passive) and change the distortion "taste" or "flavour"
Any of the suggestions above will change sound and turn a Big Muff into something else.
I've referred to the first schematic, but in general applies to all versions.
Here the proper solution is to add, at the real pedal output, (so it applies to both direct and distorted signal), a unity gain buffer, which may very well be an Op Amp, rail to rail if you like, and preferrably 1M input, bypassed with 220pF , so as to simulate the input of a classic Tube amp connected with a good guitar cable, what the Big Muff expects to "see" .
That unity gain buffer will drive any reasonable preamp or sound card input.
As of the power supply, in this case the 9V one is critical, because the last transistor is *just* reaching clipping, with a higher one it never will, with a lower one it will all the time.
If anything , use 11.1V LiPo battery and trim voltage down to, say, 9V or slightly less.
Below 8V you'll hear the sound change.
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