Octagon - did I do something incorrectly?

[mlp]

Everything seems to work -but there's a very noticeable delay from my pick attack to the octave down signal starting (as an example). It's like everything has a "double tracker" length delay.

Is this expected behavior?
Thanks,
Michael

 

[mlp]

If it matters, this is the 2018 Octagon - pre-rotary switch.

 

[mlp]

Is the delay intentional or unavoidable? Thanks.

 

[zgrav]

What program setting on the Octagon are you asking about? The settings for the delay varies from program to program. You should be able to get an octave down effect from the chip without much of a noticeable delay, but that does not necessarily mean that the program on the setting you are using was designed to provide that option.

 

[mlp]

Specifically the "Dual Pitch Shifter" - where the potentiometer at min is an octave down, and at max is (supposed to be) an octave up. There is a very noticeable delay that I did not expect, and do not want.
Also, I said "supposed to be" because it is almost, but not quite, an octave up. Perhaps the pot doesn't go close enough to 100K due to tolerance on the part - I did not measure before putting it in.

 

[zgrav]

You could check the resistance on your potentiometer to see if you are getting 100K, since the range of that control could affect how much of a pitch shift you get from the program. I don't know if the issues you are having are in the programming for that effect or not. I would think a pitch shifter should do what you want it to do -- work without a noticeable delay and give you a full octave shift. I don't think there is anything in the circuit that would cause a delay in the effect -- that should all be controlled within the FV-1 chip. How much of a delay are you getting? Two noticeable plucks on a string when you hit the string once?

 

[mlp]

Yes, there is a clear delay. If you say “ta da” it’s just like that.

 

[mlp]

Also thanks for replying!

 

[zgrav]

Just an idea, but maybe see what the resistance is on the delay pot at minimum as well. if the other one is not giving you a full range, perhaps that is true on the delay pot as well. Also check your voltage to see if you are getting 3.3v on terminal 3 for all of the control pots. Maybe the expected control voltage is a little bit off and affecting the range you are getting on the controls. Look at the circuit diagram on your build doc and you can see that the 3 control pots vary the voltage being sent into the FV-1.

Also, for some fun reading.... here is a link to the FV-1 datasheet http://www.spinsemi.com/Products/datasheets/spn1001/FV-1.pdf

The diagrams there say that the control pots should be 50K, but I've built a few of these projects using 100K pots with no control issues.

 

[ryanisradd]

The delay is inherit to the FV-1 I'm pretty sure. Every pitch shifter I've heard/played using an FV-1 has as delay to it unfortunately. Still makes for some cool riffs though!

 

[Robert]

The control pots are voltage dividers so the actual value isn't extremely critical, I've seen 5K - 1M used. What is more important is that the wiper sweeps all the way to each extreme. If there is still a significant resistance between lugs 2 and 3 when the pot is turned all the way up then you won't get the full sweep of the parameter.

Pitch shifting in the FV-1 isn't perfect by any means. There is some latency and it almost always has that undersampled/glitchy quality. Running the clock at a higher frequency will improve the latency somewhat, but it'll affect other parameters simultaneously. (reduced maximum delay time, LFOs will run faster, filter cutoff frequencies will shift, etc)

 

[zgrav]

At least on the organ donor, the shifted pitch on the FV-1 has a very short delay with the chip, so you can hear the note behind when you feel the pick hits the string, but not enough to give you the "ta da" described above.