Small Clone Delay Time Pot Mod - is it real?

[GGBB]

I've come across a supposed delay time mod for the small clone that to my small brain doesn't compute as actually changing the delay time based on the schematic. But what do I know? Anyway, it's mentioned by a couple of people on the Tonepad build report site: http://www.tonepad.com/buildReports.asp?projectID=8. They seem to like it. I can't find any technical verification that it does what it claims - to me it seems like it's probably affecting depth not delay time. It replaces the 39k resistor between the CD4047 and the LFO with a pot and smaller resistor. An actual delay pot I think would vary the resistance between the CD4047's pins 2 and 3. So to you smart guys - what does this actually do? Is it really delay time? Or depth? Or something else? Snippet below, Tonepad's schematic here: http://www.tonepad.com/getFileInfo.asp?id=97.

[strungout]

Yes it's real!

I recently built one with that mod. When using a chorus, it basically sounds like two guitars are playing together, right? From what I hear, the delay mod delays the wet signal more or less, but very slightly (towards what could eventually reach 'slap-back' echo territory). I think I read that you could get it close to that, with the right setup but I didn't try it.

How it does that exactly... I couldn't tell you, really.

Where's Mark Hammer when you need him... 'wonder... if I stick a hammer to a searchlight and point it to the skies...? Think it was him who pointed out the mod idea. I could be wrong tho.

[GGBB]

I recently built one with that mod. When using a chorus, it basically sounds like two guitars are playing together, right? From what I hear, the delay mod delays the wet signal more or less, but very slightly (towards what could eventually reach 'slap-back' echo territory). I think I read that you could get it close to that, with the right setup but I didn't try it.

Are you using the original 150p cap value? What resistor and pot values are you using? Did you by any chance put it on a scope and get an actual measurement of the delay time range available?

[strungout]

[quote author=GGBB link=topic=122562.msg1156676#msg1156676 date=1560740955
Are you using the original 150p cap value? What resistor and pot values are you using? Did you by any chance put it on a scope and get an actual measurement of the delay time range available?
[/quote]

I'm using a 4k7 res in series with a 100k pot. I kept the stock 150pF cap. I don't have a scope, so I can't say what the range is. But it is very small and does interact with depth. I'll add that you can more easily hear it if you lift the dry signal (I put in a switch for that).

[GGBB]

Thanks. I assume that large resistance equals longer delay - correct? Do you find that the delay control is affected by the depth control and vice-versa (assuming you have either the depth switch or pot)?

[Fender3D]

It affects the voltage biasing D3.
The more the voltage the wider the modulation...

I guess you can substitute the green "wire" from pin 3 to the C19\D3 junction, in your schematic to obtain a variable delay instead....

[GGBB]

It affects the voltage biasing D3.
The more the voltage the wider the modulation...

I guess you can substitute the green "wire" from pin 3 to the C19\D3 junction, in your schematic to obtain a variable delay instead....

Are you saying that actual delay time is NOT being modified at all? Not that I am doubting you, but is this a circuit analysis on your part, or have you built and measured this?

My expectation was that this is a modulation change, not delay, so I would tend to agree. But I don't have any evidence personally, nor enough electronics theory to simply analyze.

strungout says hears delay time changes - especially when not mixed with dry.

strungout - could what you are hearing possibly be modulation depth changes, not delay time?

For my own understanding - what is the practical difference in this circuit (chorus) between changing the clock frequency / delay time, and changing the modulation depth? I know what "depth" sounds like in a chorus, but I don't know how that is different from delay time if it is. I assume they are related, because the LFO is only connected to the 4047 timer. Is depth achieved through nothing other than delay time?

I suppose what I could really use is a "Technology of Chorus Effect" document. RG? Anyone? 

[Fender3D]

With this mod delay time will change, of course, but it will change because of the wider modulation.
It might look like a delay control only when depth is set at minum or at very low settings
I would expect that the delay time control sets one point from where the depth control acts. I mean: you set a delay then modulate it (or not) how much you desire, with the depth control.

When you change delay, you'd usually prefer a lower modulation depth because of the higher detuning occurring with high delay time and wide modulation depth, btw it might be a funny option if you wanna know what your audience ate for dinner 

[GGBB]

With this mod delay time will change, of course, but it will change because of the wider modulation.

So how is this delay time change different than changing depth - which is also "wider modulation"?

[strungout]

With this mod delay time will change, of course, but it will change because of the wider modulation.
It might look like a delay control only when depth is set at minum or at very low settings
I would expect that the delay time control sets one point from where the depth control acts. I mean: you set a delay then modulate it (or not) how much you desire, with the depth control.

When you change delay, you'd usually prefer a lower modulation depth because of the higher detuning occurring with high delay time and wide modulation depth, btw it might be a funny option if you wanna know what your audience ate for dinner 

Yeah, Federico's explained it more precisely.

My understanding: the depth sets how far up and down the pitch goes and the delay stretches the wave, as in, it takes more time to reach up and then back down, while still going up and down to the same max pitch either way. But really, I have a pretty 'basic' understanding of what modulation effects do and how they do it. More complex than an overdrive pedal

[GGBB]

My understanding: the depth sets how far up and down the pitch goes and the delay stretches the wave, as in, it takes more time to reach up and then back down, while still going up and down to the same max pitch either way.

The way you describe it, delay sounds the same as rate/speed. I don't have a deep understanding either - I'm just trying to figure put how delay is different than depth - or now rate - and which one this mod actually changes.

[strungout]

Re-did a search and found this: https://www.diystompboxes.com/smfforum/index.php?topic=1092.msg156939;topicseen#msg156939...

(...)The new 100k pot lets you change the "center" of the delayed signal.  The lfo will modulate the delay about that center.  Did you try sweeping the 100k pot?  On mine, fully ccw the effect is almost imperceivable.  It then transitions through chorus and into slap back range fully clockwise, albeit with clock wine at the maximum delay.  Here, the clock whine is reduced by setting the depth to zero.
(...)

...and this: https://www.diystompboxes.com/smfforum/index.php?topic=18498.msg108756;topicseen#msg108756

In a previous post, I commented that I figured out how to make the clock fequency to the MN3007 chip variable by replacing the 39k resistor between the LFO and clock with a 1k fixed and 100k linear pot.  (I have to believe that this has been done a million times before, but I have not seen this in any of the mods that I have personally reviewed.)

My first goal was to speed up the clock/shorten the delay time into flanger range.  See my previous post for questions and comments in regard thereto.

I next tried to coax slap back delay out of my Small Clone using this new mod.  By replacing the 150 pf cap to the clock driver with a larger value (I think I used 420pf) and by twiddling with my new clock adjustment potentiometer, I could get the Small Clone to provide cool slap back delay effects ... BUT

The filter after the delay section does not suitably filter the clock out of the audio signal at such low clock frequencies.

I have to admit that I really do not understand exactly how the Low pass filter after the delay chip works.  Can anyone recommend a mod to lower the cutoff freq?

Also, I would imagine that an op-amp based active filter would be better for trying slap back with an MN3007.  Can anyone point me to a good reference to learn how to design a good high order filter?

Thanks for your help.

...and this: https://www.diystompboxes.com/smfforum/index.php?topic=18481.msg108590#msg108590



So... the 100k pot moves the clock frequency without having to change the 150pF cap... More tweakable than switching caps, which is limited to cap value steps (ie, 150pF, 180pF, 220pF, etc.). The pot lets you have 'in-between' values. That's what I gathered.

[GGBB]

Thanks for the links - I did read those before, but I still wasn't clear about the difference between delay time and depth or rate. I'm wondering if depth and delay are actually the same thing in a chorus circuit (at least the Small Clone).

[Fender3D]

The 3 controls interact each other since your dealing with the same LFO's output voltage...
look at this:



the sine wave is what you get at LFO out,
you can rise or lower its mid point (blue dashed line) with DELAY control;
you set how much is modulated up and down FROM its mid point with DEPTH control;
you set how many times you modulate it with RATE control.

Obviously DEPTH sets minimum and maximum delay time, then it needs a period to do its job, and you might confuse their interactions, but, semantically, controls can be described as I said..

[strungout]

Federico: Thanks for that diagram! Made it a lot clearer in my mind.

[bartimaeus]

I'm not sure of the particulars for the Small Clone, but I know some chorus pedals have a "clock" knob instead of a "depth" knob (like the Dr Scientist Cosmichorus). So maybe the "variable delay" mod on the Small Clone is actually more of a "variable clock" mod?