Low Rider questions

[AntKnee]

(1) Low Rider
(2) 2 Octave down quiet, 1 octave down jumps up when letting string ring out
(3) Have tried no troubleshooting yet
(4) Mods/Changes: C10 substitute 1n, C12 substitute 10n, Q2 and Q3 substitute 2N5457, all per the project notes.

Thats pretty much is, just wondering if 2 octave down is supposed to be quiter than the rest and if 1 octave down jumping is normal. Otherwise, sounds great and works on first try. I have not boxed it yet, used my test rig for the first time!

[AntKnee]

Oh, just realized I have not adjusted the trimpot at all yet. So, also please tell me what to do with it, or how to get the best adjustment.
Thank you!

[AntKnee]

Sorry to keep replying to my own thread, but...
I did get the trimpot adjusted, seems to have helped with the jumping a bit too. Still wondering about the quiet 2 octave down, though. Any other advice also appreciated!

[Thomas_H]

All octave down and clean have the same output level.  Octave up is a little thinner.
Trimmer is for octave up only

Fuessing whats wrong will not help withthis complicted circuit.
You may want to use an audio probe to check how our signals travel.

[AntKnee]

I'm not even sure there is a problem. I have read another thread and someone asked about it, but the reply indicated that the lower octave just sounds more quiet because of its low frequency.
Just thought I would ask to see if anyone had any say on the matter.
About the probing... I wouldnt know where to start with it anyway. I'm very new to this, this is my third project, and I am honestly kind of surprised the thing works on the first shot.

[midwayfair]

The second octave down will sound quieter. Part of it is how our ears work -- a very low-octave signal of the same amplitude will sound much quieter than one in a higher octave.

The "jumping" is what happens as your signal dips below the threshold of the rectifier that creates the octave (all the octaves are created with essentially envelope signals). Basically, it's a form of gating. You can replace the diodes in the octave generation sections with something with lower forward voltage -- schottky diodes are good -- and you may get slightly better tracking ... sometimes. You can also boost the input signal, but that may result in some distortion. I've tried boosting the front end of the whole effect (the first op amp feedback loop), but that introduced distortion, too.

All that said ... there are two ways to make the second octave down louder if you are willing to rework some things.

1) There is a limiting resistor at the output of the second octave down, just before the potentiometer that serves as its volume control. You can lower that resistor and increase the maximum final amplitude of the second octave down without affecting much else. The overall effect is small, but it might help some.

2) You can boost the output of the entire effect. Just increase the 10K resistor in the feedback loop of the last op amp before the output. I think I went with 22K on the last one I built, but you can go about as high as 33K before you start overdriving it. The price is that the other octaves become a little bit fussy to dial in, so you'd actually want to use log taper pots for the whole thing.

Go through the schematic carefully. It's a beast of an effect, but the audio paths are actually fairly linear. It's easiest to work backwards from any given control to follow the effect.

[AntKnee]

1) There is a limiting resistor at the output of the second octave down, just before the potentiometer that serves as its volume control. You can lower that resistor and increase the maximum final amplitude of the second octave down without affecting much else. The overall effect is small, but it might help some.

2) You can boost the output of the entire effect. Just increase the 10K resistor in the feedback loop of the last op amp before the output. I think I went with 22K on the last one I built, but you can go about as high as 33K before you start overdriving it. The price is that the other octaves become a little bit fussy to dial in, so you'd actually want to use log taper pots for the whole thing.

Thank You!
1) Is it R46? That one is a 120k. How much should it be lowered? Ive got some 68k spares.
2) Is it R52? I will try 22k
(Just want to be sure, I'm still new to schematics.)

[AntKnee]

bump for schematical assistance! (see post above)
Attached for reference.

[madbean]

Lowering R46 to 68k should make a significant difference. I would socket that resistor while you are at it so you can try other values.

If it is still not enough, increasing R29 from 27k to 47k or 68k will give you more output.

[AntKnee]

Lowering R46 to 68k should make a significant difference. I would socket that resistor while you are at it so you can try other values.

If it is still not enough, increasing R29 from 27k to 47k or 68k will give you more output.

Thanks, Brian!
Could I just increase R29 and not mess with R46? Its under the pot and will be harder to remove.