I'm having a little trouble understanding how the High Peak and Low Peak settings work in the OCD. From what I can see in the schematic, when the LP setting has the output of the opamp go through the 22k and 33k resistors in parallel,this means it goes through a 13.2k resistor, much lower than the 33k resistor it goes through in the HP setting. How does going through a smaller resistance produce a lower peak and a warmer tone with a decreased distortion than going through a higher resistance as in the HP.
this is the schematic I used:
https://tornadoalleyfx.files.wordpress.com/2015/07/ocd_schem.gif
Hi, have a look at this: http://www.muzique.com/schem/filter.htm (http://www.muzique.com/schem/filter.htm)
So, a higher corner frequency means that I will have a low peak distortion?
It looks like this to me. As I read it it's a simple low pass filter with a shallow "knee", so it cuts off more or less of the high frequencies AFTER all the overdrive. But frankly: I'm an absolute n00b - I hope some of the genius gentlemen here will chime in to bail me out :)
I think this could very well just be a treble control, but I'm not sure about it either. Thank you very much!
It's a shelving low pass filter, there's an example of it here http://www.linkwitzlab.com/filters.htm (http://www.linkwitzlab.com/filters.htm) with the maths if you're interested. The corner frequency is at the low end for guitar, so I think it's designed to give a the impression of a bass boost. I don't know why the switch is called HP/LP it's a low pass filter in either position, the switch just changes the corner frequency and the minimum amount of cut.
Quote from: kraigen on May 01, 2017, 01:09:56 AM
I'm having a little trouble understanding how the High Peak and Low Peak settings work in the OCD. From what I can see in the schematic, when the LP setting has the output of the opamp go through the 22k and 33k resistors in parallel,this means it goes through a 13.2k resistor, much lower than the 33k resistor it goes through in the HP setting. How does going through a smaller resistance produce a lower peak and a warmer tone with a decreased distortion than going through a higher resistance as in the HP.
this is the schematic I used:
https://tornadoalleyfx.files.wordpress.com/2015/07/ocd_schem.gif
It's the other way around - HP uses the parallel combination, LP uses 33k. Less resistance raises the corner frequency of the low-pass RC filter, thereby allowing more high frequency content at the output. In this case a little over an octave. Therefore a "high" peak.
Quote from: slacker on May 01, 2017, 06:46:08 AM
It's a shelving low pass filter, there's an example of it here http://www.linkwitzlab.com/filters.htm (http://www.linkwitzlab.com/filters.htm) with the maths if you're interested. The corner frequency is at the low end for guitar, so I think it's designed to give a the impression of a bass boost. I don't know why the switch is called HP/LP it's a low pass filter in either position, the switch just changes the corner frequency and the minimum amount of cut.
Assuming that schematics I have seen for it are accurate, the toggle simply changes the overall range where the treble-cut is applied. So, not really a switch between highpass and lowpass, in the sense of filter topology. Just a higher or lower range.
Wouldn't be the first time a manufacturer labelled/legended a control as something
other than what those with more electronic knowledge knew it to be. It happens.
Quote from: GGBB on May 01, 2017, 12:09:22 PM
Quote from: kraigen on May 01, 2017, 01:09:56 AM
I'm having a little trouble understanding how the High Peak and Low Peak settings work in the OCD. From what I can see in the schematic, when the LP setting has the output of the opamp go through the 22k and 33k resistors in parallel,this means it goes through a 13.2k resistor, much lower than the 33k resistor it goes through in the HP setting. How does going through a smaller resistance produce a lower peak and a warmer tone with a decreased distortion than going through a higher resistance as in the HP.
this is the schematic I used:
https://tornadoalleyfx.files.wordpress.com/2015/07/ocd_schem.gif
It's the other way around - HP uses the parallel combination, LP uses 33k. Less resistance raises the corner frequency of the low-pass RC filter, thereby allowing more high frequency content at the output. In this case a little over an octave. Therefore a "high" peak.
Really? The schematic led me to believe that when the switch is open, you are in HP mode using the 33k resistor.
Quote from: kraigen on May 01, 2017, 01:13:34 PM
Really? The schematic led me to believe that when the switch is open, you are in HP mode using the 33k resistor.
That's not how I read it. The open position is labeled "LP" and the closed position is labeled "HP."
That switch is just a marketing scam because the average consumer wants more switches and knobs.
Here we have a tone knob "range limiting" switch to fool the buyer into thinking it is a "range expanding" switch.
Do away with it in your own pedal and simply turn the tone knob for the desired sound :P
I see it as a low-pass at a low frequency or a low-pass at a higher frequency.
Which-is-which is unimportant.
Quote from: Ben Lyman on May 01, 2017, 03:13:40 PM
That switch is just a marketing scam because the average consumer wants more switches and knobs.
Here we have a tone knob "range limiting" switch to fool the buyer into thinking it is a "range expanding" switch.
Do away with it in your own pedal and simply turn the tone knob for the desired sound :P
Nah. Paul/PRR nailed it, I think.
Sometimes it is more convenient for the user to have a toggle that switches ranges, than it is to have a pot that provides the full scope of adjustments. The Tone pot is a fairly modest value - 10k in Version 3 - which doesn't provide a wide range of adjustment (still some treble bleed even at max brightness), but does allow nice dialability
within each range.
Think of it this way: Imagine you had a Rate pot on a phaser, whose speed range went from 12hz to .12hz. So, faster than most phaser LFOs, to slower than many LFOs. Cool. Only trouble is, you now have a 100:1 range of adjustment in one puny little knob. Are you ever going to be able to replicate a speed setting precisely? Probably not. Far better to have a Rate control with a toggle that switches between fast and slow ranges. Not a gimmick. A
convenience.So the OCD uses two ranges of treble cut adjustment with a Tone pot that has a limited span of adjustment within each range, but easy repeatability of setting.
Sometimes, I'll grant you, manufacturers
do throw on controls to make things snazzier. Sometimes, it's just a freebie or easter egg that the designer recognizes could be had for the price of a SPST toggle. Sometimes they do it out of consumer pressure, though. When my buddy Tim started producing the Retro-Sonic compressor (a Ross clone) some years back, we discussed having a gain-recovery option and I worked out values for him for a 3-way toggle to give slow, medium, and fast recovery. He manufactured the compressor with the 3-way toggle for a while (as EHX still does with the Soul Preacher), and then I saw he started making it with a pot instead. When I asked why the switch he said it was simply customer pressure. Even though I'll bet few set the gain recovery to anything
other than 7:00 or 5:00, they felt like they were hemmed in and missing out, via 3 fixed presets, so they kept asking for a continuously variable control, and Tim yielded.
I don't own an OCD, but I do have a Joyo clone of one that someone gave me. The toggle/pot combination is effective at doing what it attempts to do.
hmm... you have a point there. I still stand by my own personal motto:
"More switches and knobs equals less music" ;D
> The Tone pot ... ... doesn't provide a wide range of adjustment
The pot sets the shelf-depth.
This has little to do with the cutoff frequency.
If you love knobs, replace the 22k/33k with say 100k pot and 10k fixed, so you can dial 110k-10k and shift frequency about 10:1. Ah, but then the "tone" (depth) pot's action changes from a lot to hardly-any. And fine control of frequency is not so very important on a soft-corner filter like this. A 2-way switch is a reasonable design, does make "a change", lets you shape your racket to fit into the overall band sound (mellower or brighter), costs little.
Thank you so much for taking the time to answer, this is very interesting.