Mad Professor Sweet honey "Focus" loop question

[Vivek]

Please help me to understand the utility and design principle behind the "focus" loop which is AFTER the clipping diodes

[Vivek]

https://www.diystompboxes.com/smfforum/index.php?topic=108761.msg992371#msg992371

There is an earlier thread, but it does not go into details

[Vivek]

From their web site:

"Mad Professor Sweet Honey Overdrive (SHOD) is a super touch sensitive medium gain overdrive pedal. Distortion level can be controlled by pick attack and pickup strenght. Harder picking for overdrive and softer for cleaner tone. With the unique Focus control you can adjust the feel and dynamics of the pedal as well as overal EQ. Turning Focus CCW you need to play harder to get distortion and the tone is softer, great for jazz and blue. Focus turned CW gives a slight treble boost and earlier distortion. This type of overdrive has previously only been found in the BJF Honey Bee but is now presented in Mad Professor version. The Mad Professor SHOD has a tighter sound and is more versatile as it was designed to work with all kinds of guitars and amplifiers."

[willienillie]

The way I see it (keep in mind I have no idea what I'm talking about), it's similar to a presence control in an amp, a tone control in a negative feedback loop.  It should change the gain for a certain range of frequencies.

[Vivek]

I see it the same way too. Tone control in feedback path.

But if there is large distortion creating new harmonics, we are feedbacking stuff that was not part of the original signal.

Last week I had entered the schematic into LTSPICE. I will analyse it further.

PS what is best way to post LTspice files ?

[willienillie]

I don't even know who this Lieutenant Spice fella is, though I've heard him mentioned around here quite a bit.

[antonis]

It should be interesting a comparison of the present non-inverting configuration circuit with an inverting configuration one..
(not only on reverse Focus pot action..)

[MikeA]

I built one of these for someone else and did some bench testing before I sent it out, I was also curious about that Focus control.  I set Volume and Drive fully clockwise, Focus counterclockwise, then brought the input level up to just below the clipping point (highest possible input amplitude with a clean output.)  Then when I brought Focus up, it squared off the output waveform (clipped it.)  This was true at 400 Hz and 1kHz.  At 3kHz, increasing Focus peaked up the waveform but didn't square it off.  With Drive fully counterclockwise, Focus had no effect on the waveform or the level (less than 1 dB change.)  Here's how I described the Focus knob to the user, mostly plagarized:  The FOCUS knob adjusts the feel and dynamics of the pedal as well as overall EQ, and interacts with the DRIVE knob.  Turn FOCUS counterclockwise for a softer tone and slightly less distortion.  Turn it clockwise for a slight treble boost and an earlier onset of distortion.   The default setting is 12:00 noon.

[Vivek]

Then when I brought Focus up, it squared off the output waveform (clipped it.)  This was true at 400 Hz and 1kHz.  At 3kHz, increasing Focus peaked up the waveform but didn't square it off.  With Drive fully counterclockwise, Focus had no effect on the waveform or the level (less than 1 dB change.)  Here's how I described the Focus knob to the user, mostly plagarized:  The FOCUS knob adjusts the feel and dynamics of the pedal as well as overall EQ, and interacts with the DRIVE knob.  Turn FOCUS counterclockwise for a softer tone and slightly less distortion.  Turn it clockwise for a slight treble boost and an earlier onset of distortion.   The default setting is 12:00 noon.

I input the schematic in LTspice

I will soon post output to substantiate your findings

PS : I can send the LTspice for anyone who is interested

[FiveseveN]

On the topic of attaching SPICE files: this forum doesn't provide options to host attachments. For text files like .asc you could use a service like pastebin.com or just paste the contents here like so

Code Select Expand

Version 4
SHEET 1 880 680
WIRE -208 160 -208 128
FLAG -208 240 0
SYMBOL voltage -208 144 R0
WINDOW 123 24 124 Left 2
WINDOW 39 0 0 Left 2
SYMATTR Value2 AC 1
SYMATTR InstName V1
SYMATTR Value ""
TEXT -240 320 Left 2 !.ac oct 20 20 20k


[Vivek]

Version 4
SHEET 1 2316 996
WIRE -288 -432 -288 -480
WIRE -288 -288 -288 -352
WIRE -288 -64 -288 -112
WIRE -1152 80 -1168 80
WIRE -544 80 -768 80
WIRE -416 80 -544 80
WIRE -288 80 -288 16
WIRE -288 80 -352 80
WIRE -192 80 -288 80
WIRE 112 80 -112 80
WIRE 256 96 176 96
WIRE 432 96 256 96
WIRE 496 96 480 96
WIRE 544 96 496 96
WIRE 768 96 624 96
WIRE 976 96 768 96
WIRE 1120 96 976 96
WIRE 1360 96 1200 96
WIRE 1664 96 1360 96
WIRE 2000 96 1728 96
WIRE -1168 112 -1168 80
WIRE -544 112 -544 80
WIRE 112 112 48 112
WIRE 768 160 768 96
WIRE 768 160 688 160
WIRE 848 160 768 160
WIRE 1360 160 1360 96
WIRE 1520 160 1360 160
WIRE -1168 224 -1168 192
WIRE -544 224 -544 192
WIRE 688 224 688 160
WIRE 848 224 848 160
WIRE 1360 224 1360 160
WIRE 1520 224 1520 160
WIRE 976 240 976 96
WIRE 48 272 48 112
WIRE 112 272 48 272
WIRE 256 272 256 96
WIRE 256 272 176 272
WIRE -464 336 -544 336
WIRE -320 336 -384 336
WIRE -240 336 -320 336
WIRE -80 336 -160 336
WIRE 48 336 48 272
WIRE 48 336 -80 336
WIRE 1520 336 1520 288
WIRE 688 352 688 288
WIRE 848 352 848 288
WIRE 1360 368 1360 288
WIRE -544 400 -544 336
WIRE -320 400 -320 336
WIRE 48 400 48 336
WIRE 112 400 48 400
WIRE 256 400 256 272
WIRE 256 400 176 400
WIRE 976 496 976 304
WIRE -544 528 -544 464
WIRE -320 528 -320 464
WIRE 48 528 48 400
WIRE 112 528 48 528
WIRE 256 528 256 400
WIRE 256 528 176 528
WIRE 48 592 48 528
WIRE 976 688 976 576
WIRE 48 736 48 672
WIRE 112 736 48 736
WIRE 256 736 256 528
WIRE 256 736 192 736
WIRE -80 928 -80 336
WIRE 800 928 -80 928
WIRE 976 928 976 768
WIRE 976 928 880 928
WIRE 1360 928 1360 448
WIRE 1360 928 976 928
FLAG -320 528 0
FLAG -544 528 0
FLAG -288 -112 VB
FLAG -544 224 0
FLAG 688 352 0
FLAG 848 352 0
FLAG 1520 336 0
FLAG 2000 96 Output1
IOPIN 2000 96 Out
FLAG -288 -288 0
FLAG -288 -480 VB
FLAG -1152 80 Input
IOPIN -1152 80 Out
FLAG -1168 224 0
FLAG 256 96 OutputOpamp
FLAG 768 96 Afterhardclip
FLAG -768 80 Input
IOPIN -768 80 In
SYMBOL Opamps\\opamp 144 160 M180
WINDOW 0 -4 95 Left 2
SYMATTR InstName U1
SYMBOL cap 176 256 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C2
SYMATTR Value 100p
SYMBOL LED 112 416 R270
WINDOW 0 32 32 VTop 2
WINDOW 3 0 32 VBottom 2
SYMATTR InstName D2
SYMATTR Value NSPW500BS
SYMATTR Description Diode
SYMATTR Type diode
SYMBOL LED 176 512 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName D3
SYMATTR Value NSPW500BS
SYMATTR Description Diode
SYMATTR Type diode
SYMBOL res 32 576 R0
SYMATTR InstName R4
SYMATTR Value 3K
SYMBOL res 208 720 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName Drive
SYMATTR Value {drive}
SYMBOL res -256 352 R270
WINDOW 0 32 56 VTop 2
WINDOW 3 0 56 VBottom 2
SYMATTR InstName R5
SYMATTR Value 1K
SYMBOL res -480 352 R270
WINDOW 0 32 56 VTop 2
WINDOW 3 0 56 VBottom 2
SYMATTR InstName R6
SYMATTR Value 5k6
SYMBOL cap -336 400 R0
SYMATTR InstName C3
SYMATTR Value 220nF
SYMBOL cap -560 400 R0
SYMATTR InstName C4
SYMATTR Value 22µF
SYMBOL res -96 64 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R2
SYMATTR Value 6k8
SYMBOL res -304 -80 R0
SYMATTR InstName R3
SYMATTR Value 360K
SYMBOL cap -352 64 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C1
SYMATTR Value 4n7
SYMBOL res -560 96 R0
SYMATTR InstName R1
SYMATTR Value 1Megs
SYMBOL cap 496 80 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C5
SYMATTR Value 1µ
SYMBOL res 640 80 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R7
SYMATTR Value 2k
SYMBOL diode 672 224 R0
SYMATTR InstName D4
SYMBOL diode 864 288 R180
WINDOW 0 24 64 Left 2
WINDOW 3 24 0 Left 2
SYMATTR InstName D5
SYMBOL cap 960 240 R0
SYMATTR InstName C7
SYMATTR Value 22n
SYMBOL res 960 480 R0
WINDOW 3 40 70 Left 2
SYMATTR InstName Focus
SYMATTR Value {focus}
SYMBOL res 960 672 R0
SYMATTR InstName R8
SYMATTR Value 15k
SYMBOL res 1104 112 R270
WINDOW 0 32 56 VTop 2
WINDOW 3 0 56 VBottom 2
SYMATTR InstName R9
SYMATTR Value 10K
SYMBOL cap 1504 224 R0
SYMATTR InstName C9
SYMATTR Value 22n
SYMBOL cap 1344 224 R0
SYMATTR InstName C8
SYMATTR Value 4n7
SYMBOL res 1344 352 R0
SYMATTR InstName R10
SYMATTR Value 150k
SYMBOL voltage -288 -448 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName VB
SYMATTR Value 4.5
SYMBOL voltage -1168 96 R0
WINDOW 123 24 132 Left 2
WINDOW 3 50 51 Left 2
WINDOW 39 0 0 Left 0
SYMATTR Value2 AC 300mv
SYMATTR Value SINE(0 {ampl} {freq})
SYMATTR InstName V2
SYMBOL res 784 944 R270
WINDOW 0 32 56 VTop 2
WINDOW 3 0 56 VBottom 2
SYMATTR InstName R999
SYMATTR Value 10
SYMBOL cap 1728 80 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C10
SYMATTR Value 22n
TEXT 72 176 Left 2 !.lib opamp.sub
TEXT 992 616 Left 2 !.param focus 50k
TEXT 1000 488 Left 2 ;Focus is 50K B taper
TEXT 0 840 Left 2 ;Drive is 500K
TEXT 8 880 Left 2 !.param drive 200k
TEXT 184 -96 Left 2 !.tran 0 50ms 0 50n
TEXT 176 -144 Left 2 !;ac oct 10 20 20000
TEXT 992 592 Left 2 !; .step param focus list 1  25k 50k
TEXT -1472 344 Left 2 !.param freq=1000
TEXT -1472 384 Left 2 !;.step param freq list 500 2000 4000
TEXT 536 680 Left 2 !.options numdgt=7
TEXT 536 720 Left 2 !.options plotwinsize=0
TEXT -1472 424 Left 2 !; .step param ampl list  3mv 10mv 15mv 20mv 40mv 80mv 160mv 300mv
TEXT -1472 312 Left 2 !.param ampl 0.18v
TEXT 16 -400 Left 2 ;MAD PROFESSOR SWEET HONEY OVERDRIVE\n \nhttps://pcbguitarmania.com/wp-content/uploads/2018/11/Mad-Honey-Building-Docs.pdf\nhttp://revolutiondeux.blogspot.com/2010/06/mad-professor-sweet-honey-overdrive.html

[roseblood11]

I added the "Voice" pot from the Zendrive.

[Vivek]

Please post schem of your mod

Thanks !!!