Hamlet Delay by Jon Patton

[MAO]

02/25/2018 - I got ahold of the pedal that I made using the 2nd layout, and I'm sorry to report this one also has noise when using the tails wiring. I had wired it as true bypass, which is noise free (other than the usual PT2399 artifacts) and that fooled me into thinking the noise was resolved. The noise exists in both layouts when bypassing with tails. My apologies.  

09/04/2017 Update: New layout added, dated 09/04/2017. Verified (still has noise with tails bypass).

08/26/16 Update: I was unable to get rid of the noise mentioned below while using the charge pump. I removed the charge pump, rebiased the 2n5457 and the pedal is quiet. I'm concerned the layout itself may be the issue. Maybe the ICs are to close to each other? FWIW, The pedal still sounds really good running at 9Vs.    



Info here

Version 1.2 Build Doc

I converted the 25k tone trimmer an external pot, and reversed the connections so CW = brighter/noisier CCW = darker/less noise. 50k linear may be better for more highend rolloff (and more noise rolloff)

If using an LT1054, lift pin 1. And the zener can be increased to 12v.    

(note the ICL7660SCPA is mounted upside down)

[Mark SL]

How do we add a bypass led?

It is confirmed other than that.

Thanks

[MAO]

2 options:

1. Tails - non true bypass (verified)
Use DPDT stomp switch, FS1 to lug 1, FS2 to lug 2, LED(-) to lug 4, PCB Stomp Ground to lug 5 and input jack ground (lugs 3 and 6 not used)
Input jack tip to PCB in, Output jack tip to PCB out. LED+ to PCB LED+

2. No tails - true bypass (verified)
Use 3PDT stomp switch wired as usual.
Jumper FS1 and FS2
Add additional 4M7 resistor across input jack tip and ring.  

[MAO]

After boxing this one up, I was getting strange noises in the tails bypass mode.

Seemed like the PT2399 was not happy when breaking FS1 and FS2 connection and leaving FS1 hanging.

I could get rid of the noise by grounding FS1 while in bypass mode, but there was a pop echoing when the switch was opened or closed.

At some point I'll try the 1776 opto-tron switch to see if that allows the grounding of FS1 without the pop.

For now, I went with true bypass as described above. I also went with the 50K linear Tone pot. Helps get rid of some noise with the longer delay times.

[MAO]

I was unable to get the Tails bypass quiet, in fact, I later realized there was still some residual noise with the effect on. Even when battery powered. Thought I had it resolved a couple of times, but when using headphones I found there was still a faint noise in the background.

While audio probing with headphones, I discovered when I removed the charge pump the noise would disappear. (I tried swapping charge pumps, no change)

At this point, I'm not 100% sure if it was the layout causing the issue, maybe the charge pump is too close to the PT2399? Or if I had a bad component/solder joint somewhere I couldn't pin down.  

I suspect it may be the layout though as I ended up unplugging the charge pump, replaced the pump's 1n5817s with jumpers, re-biased the 2n5457 to 4.5v and the pedal is quiet. The tails bypass is quiet as well.

It actually still sounds great with just the 9v supply.

If someone else builds this layout and also has charge pump noise, let me know and I'll re-do the layout and better separate the ICs 
 
       

[MAO]

This new layout still had noise with tails bypass. Verified by me.

Changes to the original circuit:
I added some additional power supply filtering.
Tone control originally 25k trimmer, 50k allows dialing out a bit more noise. CCW = less treble/less noise
Delay pot originally 100k with a 150k resistor across lugs 1 & 3 giving a bit more available delay...along with some noise.
Volume control originally a 10k trimmer.

[Stymie13]

Hey, what are the two wires on the bottom left between the 100n cap and the transistor? Thanks for the layout!

[MAO]

Oops, looks like I didn't label those.

They are "extra" ground hookups, I use them for the input jack ground and the stomp switch ground.

Keeps the offboard wiring tidy

[Stymie13]

Got it, thanks again.

[Stymie13]

Finished this layout. Very cool delay, love the tone control. Unfortunately, I'm getting some motor boating/oscillation when the delay is bypassed. The frequency changes with the delay control and seems to be silenced if I turn the output volume down below unity. I should have some time to tinker with it tomorrow, any thoughts would be appreciated.

[MAO]

Sorry to hear that.

I had a similar issue with the 1st layout I had tried.

I ended up having to remove the charge pump to get rid of the noise.

Try removing it and see if the noise goes away. You may need to re-bias the 2n5457 for 4.5v

If you have the same results, I'll build another one and get back to you.

[MAO]

Another thing to try (without removing the charge pump) is to wrap a wire tightly around the 220nf, completely covering it from top to bottom (hopefully it's a box cap or greenie), and ground one end of that wire, essentially you are then shielding the exterior of the 220nf cap, just be sure you don't short anything else out.

I would just use your regular hookup wire, wrap the cap with it as best you can and ground one end with an alligator clip to the enclosure. It's just temporary, so it wont really matter how long you have to run that wire to ground it somewhere convenient. Again, just be careful you don't short anything else out.  

If the noise goes away, that cap is acting like an antenna when the stomp switch is open (which leaves the input of that cap floating)  

Looking at the layout again, I'm now worried it may be to close to the charge pump...

Jon had the 220nf and PT2399 a little bit farther away from the charge pump in his perf layout.

Now I'm going to have to build another...most likely the week of the 23rd.

 

[Stymie13]

Thanks MAO. I tried insulating the 220n cap just as suggested, no effect on the noise. I played with Q2 bias which also had no discernible effect. Pulling the charge pump definitely eliminates it. The few minutes I played it with/without the CP, I couldn't really tell the difference between 9V and 18V. I understand the headroom in theory but even with a hot signal (humbucker>G2 Muff>Hamlet) I couldn't tell much difference. The PT2399 noise is unbearable in a recording/studio environment but for live, loud, heavy rock it doesn't bother me. If you know it's there its noticeable when all other instruments drop out leaving just the delayed guitar signals but so is snare vibration, 60 Hz hum, etc.

[Stymie13]

I wonder if the 7660S is the culprit? I don't have an LT1054 to try but am curious if it makes a difference in this application.

[MAO]

Sorry to say, I tried that with the 1st layout without success.

And I agree, the delay still sounded great at 9v.

I really thought the noise issue was solved with layout #2.
I sent an email to the guy I made it for, waiting to hear back.

What puzzles me is why the noise when interupting the delay path? What is it about opening that connection causes the charge pump noise to become apparent? Not sure.

I remember if you ground that connection when open, no noise, but you do get a repeating click when you engage the delay.

I wonder if it would be better to open the signal path after the delay chip, rather than before it?

[Stymie13]

This is a really cool delay circuit if you don't use the tails option. I tried to use it with a UK Electronics tap temp kit also and it did NOT like it. After much debugging and tail chasing, I finally pulled the tap kit and it started working fine again. Not educated enough to know why but thought I'd share. Up the Irons!

[traktop]

I was about to go for it.
So you still find it too noisy for recordings?

[Stymie13]

I'm not much of an engineer but would think you could edit the noise out. I suppose I'm not the most critical of fidelity as I don't mind the artifacts of the PT2399 too much. In a mix I don't think it would bother me but front and center on a standalone track it would be noticeable. I really only notice it when playing at practice volume by myself. With any other instruments I don't hear it.

[MAO]

I wonder if this info from the ROG Thunderbird would resolve the noise.

"Use a stereo jack for the input and wire the “R” pad to the ring terminal.
The purpose of the 2N4403 transistor is to avoid the return current from the
charge pump IC through the same ground wire that carries the return of the input
signal. The charge pump ICs draw current peaks at the switching frequency
which will otherwise make its way through the signal path."

[Stymie13]

Yeah, not sure. I would love to use the circuit as designed. I even purchased a JMK circuit board and built it w/ the Taptation chip set which works great as long as you run the modulation pot turned completely off. However, the same noise is present with the charge pump in the circuit. Pulled it out and it sounds great even with tails.