D’lay Tone Control Mod

[Anonymous]

I have a couple “standard” D’lay boards I have built and also a couple extra sitting around so I wanted to build one up with some more experimental mods.

The first is that I would like to add a tone control to the repeats.  The fact that I am not very good at reading the schematics should probably be a hint to myself that this an ill advised path but nonetheless…

Would removing R2, C5 and C6 and replace R2 with a pot and cap going to ground work?

Because of my lack of knowledge in electronics I don’t fully understand what is going on with R2 and C5, C6 on either side of it going to ground.  I have tried to compare to other PT2399 schematics and it seems that a lot have just a single cap going to ground there and no R2…but I could be reading them wrong.

Anyway…any hints on how to implement a tone control here would be much appreciated.

The other “mod” that I plan to do is adding modulation.  I think that should be straightforward by just inserting modulation points at pin 1 and 3 on the time pot.  Although I recently read something about a resistor and cap in between pins 6 and 8 on the chip resulting in a “chorus-y” modulation effect so I might give that a try too.

Thanks in advance for any info on the tone control!

 

[Cybercow]

Brooks – TBH, I’d not mess around with any of the values around the PT2399. They establish the parameters of the delay – not the tone. Instead, I would add a “Tone TwEQ” circuit after the D’Lay circuit.

[Anonymous]

Since I have an extra board or two I am going to proceed against my better judgement (and solid recommendation)…knowing that I should be able to just plug the correct components in should thing not work out.  I get what you are saying about establishing the parameters of the chip…I have read (not fully comprehended) the write up on the chip at Electroclash and the Princeton application sheet (fairly sparse) as well as reviewed a lot of different schematics that have a “tone control”.  I think I at least have the basics to do some experimenting…will socket all those connections around the screen shot above.

I really like the basic D’Lays that I have built but have these extra boards and have that itch.  So far I have built them with the endless repeats (WF) mod and have put a switch with two different resistors coming off pin 6 / time pot for short time / long time selection.  Prior to that I used 2 pots in series to have a course / fine time adjustment.

I have a tone-TWEQ board built up waiting to be used as well as one in a stand alone enclosure.  But, what I am trying to do here is only effect the tone of the repeats…not the dry signal.  If I understand the schematic, what is happening is that the dry signal comes into the opamp and it is split and goes to the delay chip which is mixed back in with the dry signal at the end.  So, any changes around the signal going to / from the chip should only affect the repeats.  I guess I could accomplish the same thing using a paramix with the delay and a tone TWEQ behind it in the loop…

The reason I highlighted that section of the schematic is that it looks like 2 LPF in series and that is the area where most of the schematics with tone control seem to implement it.  But, like you said, these values may have nothing to do with actual tone / LPF’s but could be manipulating a parameter in the chip that affects tone or something else (i.e. usual tone control / filter values go out the window).

Anyway, I will pull the components and try to give it a go and report back.  Will also report back on implementing the modulation points…basically just changing the resistance to pin 6 by connecting across the time pot.  I ran across an interesting one I want to try that has the power coming in on a momentary switch to light the LED in an LED / LDR setup with a capacitor and a pot to control the dwell time…so in theory, based on the cap value and the resistance of the dwell pot how long it takes the LED to light up to full brightness and how long it takes to discharge thus impacting the resistance on the LDR.  The other is a simple LFO driving the LED in an LED / LDR setup.

 

[Cybercow]

Brooks – In my estimation, those LP filters are to keep the noise down from the delayed signal passing thru the PT2399. So still, I’d not mess with those at all.

However, PinkJimiPhoton wrote up a great tails mod for the D’Lay. I’d check out that post and do some testing/experimenting for injecting a Tone TwEQ at C24, between where the PT2399 Level pot meets up. OR . . . .  where the Repeats feedback signal passes thru the trimpot TR1.

Happy building!

[Billy]

Here’s some PT2399 data notes that should help explaining what sets unity gain, noise filtering etc

https://drive.google.com/file/d/1ra2Dg6j8X_qfJAmEfbz86knfPvUYilHR/view?usp=drivesdk

As CC says I’d probably try adding tone circuitry on the clean signal where it meets delayed signal after C24 prior to pin 6 IC1B

[Anonymous]

Thanks for the input!  It seems like I had seen those data notes in the past at some point but I didn’t come across them during this round of internet scouring…thanks for including.  I had read over that tails mod and thought about trying to retro it into one of the “standard” D’lays I have built.  I also dropped the idea of trying out the “chorus-y” mod I had read about when I saw a comment from PinkJimiPhoton saying no matter what he tried he could not get it to work…so I figured I would have no chance!

Further digging on any other delays out there with tone control of the delayed signal lead me to one that I had already built on vero a long time ago…which unfortunately went into the “builds that didn’t work” box.  It was the Triton delay and had a trimmer for tone control…but based on your input I think this might have been to filter out the noise on the repeats so maybe not even a true tone control.  But, it also has another “mod” that looks interesting…2 pots for time control on a footswitch that feed into another pot and capacitor going to ground and into pin 6.  Supposed to slowly change between the 2 delay time settings like turning the knob manually…the “dwell” pot controlling how slowly it changes.

The main goal is just to see what kind of weird / crazy noise i can get out of the pedal.  So, I may just socket the heck out of it…what is the worst that could happen?

Again, thanks for the feedback.

[Billy]

A couple you should look at that have tone pots / trimmers are the grind customs de profundis delay and Jon Pattons hamlet delay

[Anonymous]

hey bro,

the place to add a tone tweq would be in the WET SIGNAL PATH… but adding all them knobs is kinda overkill, imho….

the easiest place would be to add it right before c24, the 220n cap.  you could literally place a very simple low pass filter <like a guitar tone control> to the circuit there easily. say, a 10k-50k linear pot, at the node where r14 and c24 meet would work…. connect pin 2 of the pot to around a 22n cap to a convenient ground point, and pin 3 to the node of r14 and c24. that will give you a basic tone/treble cut/lowpass on the delayed signal alone, so you can darken up repeats without affecting the dry tone like you would grafting a tone tweq into the circuit at the end would do.

you could also mess around with the LPF on the chip itself somewhat, but that would be harder and take a bit of experimentation. change r6 and r7 to a 25k linear pot, ditch c8 <27n to ground> and change c7 to 22n. that way, the delay signal would be considerably brighter, but have more noise to it… BUT you could then turn the pot to find the “sweet spot” that sounds best to you, and it would become a functional tone control, too. that said, this is merely hypothetical without trying it, which i have not, but that’s the basic idea of how to accomplish your goal.

yeah, i tried deadastro’s “chorus mod” and i found it to be a waste of time. a lot of people hear a short delay and think it’s chorusing, like the one chip chorus that’s still somehow popular.

the deal with making a chorus with a 2399 is really coming down to starving the power supply to the jellybean. it needs 5v to run correctly, just SLIGHTLY browning that voltage out will make it so the 2399 will “wobble”… the actual guitar signal’s attack will be enough to throw the bias off enough to make the delays drift a bit. its quite a trippy effect, but not real useful, as the delays MAY bend up/down in pitch completely randomly, and never repeatedly. if ya wanna mess with that, i’d add a smallish pot, say 1k-5k or so to vb, the output of the regulator… then you can starve the chip of some voltage, and make it freak out…

but again, its not really a super useable sound imho.

the “chorus mod” did nothing on any of the circuits i tried it on, so i suspect rob’s hearing the signal being modulated in his head more than in his ears 😉

but some folks claim it works. beats me. didn’t do squat for my builds.
anyways, hope this helps a little

peace

pink jimi

[Anonymous]

Thanks for the info and suggestions! I will socket the areas you suggest and see what I can work out.  Unfortunately, to this point the only progress I have made is to pull the boards out of my box of PCB’s.  I decided to tackle organizing and cleaning my workspace before building anything else and that has taken considerably longer than expected…hopefully I will be back to building this weekend.

Not terribly concerned about getting useful sounds as much as some weird noise!  Hell, I can’t really play so I don’t get useful sounds out of the guitar under normal circumstances.

I will report back when I get to experimenting…having added the sag mod to the tone control and time modulation on the “to try” list.

[Author]

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