FLUNKEE INVERSION? LPF Suggestion?

[Feral Feline]

I've looked online and found that the FX25 inverts, but that's bandpass...


When the Flunkee's in LowPass mode is it still inverting the signal?
Looking at the schematic, the signal-path enters each op-amp on the non-inverting pin, so I can only guess it inverts on the 13700's darlington buffers. I tried to do my homework before posting here, even scoured the 13700 datasheet, but feel I've missed something.

Also...
I'd like to add a clean blend to mine.
If you've any suggestions on a good corner frequency for an LPF on the clean signal (for bass guitar usage), feel free to hit me up with wherever you think it Hertz best.


Mm Goi Sai,
FF

[Zerro]

Buffers don't invert anything, nor the 13700s. But why you care for this?

F0 for knee of LPF is defined by C7 and C8. You may change both values, but both must have the same value. For bass try 22nF for example.

For clear sound blend you can see this example from You You pedal. It makes almost the same thing but by pedal pot. Look at the MIX output. That's my tip.

[Feral Feline]

Buffers don't invert anything, nor the 13700s. But why you care for this?

F0 for knee of LPF is defined by C7 and C8. You may change both values, but both must have the same value. For bass try 22nF for example.

For clear sound blend you can see this example from You You pedal. It makes almost the same thing but by pedal pot. Look at the MIX output. That's my tip.

Thanks Zerro.

Whether the 13700 inverts phase or not matters to me because I don't want to have phase-cancellation with the planned clean blend. Some people say the 13700 inverts phase, some people say it doesn't. My understanding of the 13700's datasheet is rudimentary at best, hence this thread.

I have already increased C7 & C8 caps; what I'm asking for is a recommended LPF corner-frequency just for the clean blend, one that would complement bass guitar.

Thanks for your reply and many thanks for the You You schematic, I've not seen that one before!

Cheers,
FF

[Zerro]

Hi, F.F. From schematic you see, that signal is going to non-inverting input. That seems, that output cannot be in reverted phase. That would be in case of second, inverting input - that's why vendor assigned it this way. So, don't worry, what is going out, is what is going in. BTW, in inner schema of vendor is clear, that outputs 5 and 12 are not additionally inverted by anything - it is clear output. So, all is depending, what input you will use.

Buffers doesn't invert anything - what you put in, is what you get out - it's buffer.

Another thing is phase shift, which occurs when any freq. filtering is done upon some signal, as Wah pedals, SVF filters like that You-You I sent to you, or finally that Flunkee, which is only other way of SVF, like that You-You. But this phase shift is normal. Every this shift is basic thing, that when mixed with origin, will cause Hi or Bass effect. So here is question, if you need to mix origin and filter output once again. For to set amount of effect? This does pot for SENSE. Of course, output from fx will be allways slightly different from original, even if Fx amount is set minimal.

But as you want - clear or fx output. That mix schema I sent will help. Only you will need to add one opamp. For clear output. (If you want to set here some LPF, then 7kHz is mostly top of freq range for normal electric guitar.) So, find some prospects of bass amps with EQ, and see, what freq is utmost at their EQ settings. I will attach that LP opamp later.

[Zerro]

Here is opamp for clear chanell. Connect it after 1. opamp, point together with pin 1, C6 and C2. First set Gain with trimmer R, and according it's resistance, count capacity C for desired LP freq knee. C=1/(2 Pi R f)

For R=1k0 (gain cca 2), and LPF=6,4 kHz it will be capacity cca 25 nF. For 3,2 kHz it will be cca 50 nF.

For R=2k2 (gain cca 3), and LPF=6,4 kHz it will be capacity cca 11 nF. For 3,2 kHz it will be cca 22 nF.

Set it by yourself. Hi :@)

[Feral Feline]

Thanks again Zerro, that's a lot of great food for thought for me.

Here's the range I've been looking at for the clean-blend's LPF:

resistor cap & Hertz followed by the Hz of the nearest note
2k2 + 47n = 1540Hz       1567.9   G6
2k2 + 56n   = 1292.5Hz      1244.5   Eb6 / 1318.5 E6
2k2 + 68n   = 1064.4Hz      1046.5   C6   
2k2 + 82n   = 882.7Hz         880    A5
2k2 + 100n= 723.8Hz        739.9   F#5/Gb5

2k + 47n    = 1694Hz!      1661.2   G#6/Ab6
2k + 56n   = 1421.7Hz      1396.9   F6/1479.9 F#6/Gb6
2k + 68n   = 1170.9Hz      1174.6   D6   
2k + 82n   = 970.9Hz         987.7   B5
2k + 100n   = 796.2Hz        783.9   G5

I've been calculating the above using Orman's online calc:
http://www.muzique.com/schem/filter.htm

The first one above (2k2 + 47n) is in Fuzzdog's Bass Looper, so I played around with  values in the same ballpark.


Unfortunately, I won't have space for an op-amp blender, I'm going with a basic JFET transistor split'n'blend. The Flunkee is already a tight fit in a 1590A.

[Zerro]

Hi, that calc is really handy. What you get here you can use for that circuit I described. Only resistors will be maybe another, according your needed gain. Or, tune R and C preciselly according desired freq, and change that second resistor around inverting input of opamp, to get desired gain.
That mix circuit I attached before has one pot too. Only tandem. But you can use it instead that j-fet blend. I don't have your conception of blending in your stompbox now. Something like send-return?

[Feral Feline]

Nothing too fancy...

Signal in > split

Ch A = dry/clean, maybe throw the LFP on it as well, space permitting.

Ch B = Flunkee

Ch A & B blended back together > signal out.

What I'm having a tough time deciding now is where to cut off the frequency of the Clean-blend LPF. Will it sound weird if I put it way down low at 400Hz? ie will it sound like two different parts? Will a cutoff at 1600Hz sound more natural since it's closer to full range?

I know I should breadboard it, but a lot of my stuff is packed away for moving. I'll get back to trying stuff on breadboard after the move. Meanwhile, I'm still trying to build a few more pedals before EVERYTHING gets shipped overseas. 

[Zerro]

Typical Bass EQ has ranges, as you see at attached picture - top is at 10kHz - so, feel free to set it wherever you please.