Dark Rift Delay - Distortion/Fuzz in Wet Signal

[absolvism]

Hello!

I just finished building a Dark Rift, and everything seems to be working... except the repeated/wet/delay signal has a distortion/fuzz in it..

So the first pluck always sounds normal, but then all the succeeding delay signal has a very pronounced fuzzy/scratchy undertone to the whole thing. I've tried different amps and cables and it appears that it's definitely in the pedal itself. If I set the mix to 100% dry, there is no fuzz, it's just in the wet.

Besides pulling the whole thing apart and starting over, does anyone have any ideas or directions to troubleshoot that they might be able to help point me in? I can record example audio if that would help.

Thanks so much in advance,
Ellis

 

[Nostradoomus]

Did you try swapping the LM833? I think I used a TL062 in mine as it sounded a bit cleaner.

 

[BurntFingers]

I still think the green led is worth investigating. It doesn't sound like that's been tried.

 

[absolvism]

I still think the green led is worth investigating. It doesn't sound like that's been tried.

Hey @BurntFingers I just did it, and wow- the distortion is DEFINITELY notably gone or at least reduced to a point where the pedal is certainly usable for the first time and within some normal range of expectation. I can see the led clipping and the output isn't crunching with every single note. It might not be the most ideal or final solution, but I can actually play on this thing now. I've only played around to test for a min before doing a more legit wiring, but it actually finally sounds pretty good!

I'm going to still investigate swapping the LM833 for a TL062 or TL072 (I only have a 072 on hand) and probing around a bit but wow, just from playing for a sec with it with the LED hack in place, this pedal feels like it's on the road to redemption.

EDIT: The fizzing is still there, especially on higher mix value, but it's reduced by about 80% and if it doesn't get better from here, it's still at least playable

 

[BurntFingers]

Awesome. That's a win.

 

[moonlightpedalbuilds]

Dark rift

 

[wrentema]

Install a 5mm green led between pin 7 and ground. Long leg to pin 7, short to gnd (pin 3 on the 2399).

This distortion in the repeats is well known across many diy forums. Modern thinking also suggests using 1 5v regulator per chip as oppose to both coming off the same 5v line.

You can test the led thing with a crocodile clip. Make a small hook at the end of the long leg, hook it around pin 7, the clip the other leg to ground. No soldering, no mess, but it worked for me on a different pedal using a similar topology.

I had the exact same problem and this indeed helped a lot. (Although I didn’t hear a difference with red and yellow leds.)
Can you explain why this works? Just curious.

 

[BurntFingers]

I had the exact same problem and this indeed helped a lot. (Although I didn’t hear a difference with red and yellow leds.)
Can you explain why this works? Just curious.

In basic terms, the first repeat is boosted causing the chip to distort. The green led clips this signal and stops it distorting by providing a ceiling of sorts.

 

[bschobs]

I would add though that this Dark Rift is noisier than most. I've built two PT2399 delay circuits since this one and the noise isn't really an issue with them (and yeah I tried swapping out different PT2399's from different sources)

 

[Danbieranowski]

In basic terms, the first repeat is boosted causing the chip to distort. The green led clips this signal and stops it distorting by providing a ceiling of sorts.

Brilliant.

 

[Chuck D. Bones]

One reason the Space Spiral (Dark Rift) is noisy is because EQD screwed-up the filtering going into and out of the PT2399. They did a better job on the Sea Machine.

 

[BurntFingers]

One reason the Space Spiral (Dark Rift) is noisy is because EQD screwed-up the filtering going into and out of the PT2399. They did a better job on the Sea Machine.

I bet they can't wait for the boneyard version.

 

[Chuck D. Bones]

Ha ha ha ha ha. I published a build report on my modded Sea Horse, but did not disclose the details of all the mods. I'm happy to do so if there is interest. The Sea Horse and Dark Rift are basically the same pedal, the main difference is the DR can produce longer delays. One of the mods I performed on the SH was to increase the range of the TIME control. Other mods were fixing the LFO tick, changing the LFO speed range and retuning the anti-aliasing filters. The filters can be fixed in the DR, but it takes more effort to undo the screw-ups on that board.

 

[Hoenig]

Just checking to see how this was going? I built a vero deep blue delay and ran into this problem. I socketed all the caps at the IC and spent a week trying different sizes until I found the least shitty sounding combo. Still breaks up but is usable in some settings. Never knew about the green led though!

 

[seers]

I listened to the sound clip a few more times. Around 11 seconds in, I hear the dry signal clean, the first repeat is clean, and the repeats after that are distorted. This points to the path thru the REPEATS control. Pretty sure I know the cause of the distortion. I have a question into The Man himself. If I'm right, this is easily fixed and there's nothing wrong with your PT2399.

As a check on my theory, turn REPEATS all the way down and see if you get any distortion.

I am having this exact issue, and when i turn my repeats down the signal cleans up beautifully. Could you shed some light on your theory? it may solve my problem, many thanks

 

[Chuck D. Bones]

Try turning D2 around.

 

[seers]

Try turning D2 around.

ive got a pcb where theyre both going the same way, i reversed d2 already

 

[Dan0h]

Install a 5mm green led between pin 7 and ground. Long leg to pin 7, short to gnd (pin 3 on the 2399).

This distortion in the repeats is well known across many diy forums. Modern thinking also suggests using 1 5v regulator per chip as oppose to both coming off the same 5v line.

You can test the led thing with a crocodile clip. Make a small hook at the end of the long leg, hook it around pin 7, the clip the other leg to ground. No soldering, no mess, but it worked for me on a different pedal using a similar topology.

I will be trying this mod this weekend. I have two other PT chip delays and this is the only one that has excess noise in the repeats. At first I thought it was an artifact of the Lo-fi ness, but if the led mod cleans it up I’ll be stoked.

 

[manfesto]

I will be trying this mod this weekend. I have two other PT chip delays and this is the only one that has excess noise in the repeats. At first I thought it was an artifact of the Lo-fi ness, but if the led mod cleans it up I’ll be stoked.

It does the trick (at the slight expense of maximum mix volume; it’s not bad but it’s noticeable), and if you’re lazy like me you can actually just solder the LED straight to the PT2399 and not have to disassemble the whole thing lol

 

[Bobbyd67]

Nice ! That this got resolved I am in the process of building 2 of these if I get that issue at least I'll know what to do

 

[Dan0h]

I could not wait till the weekend… and can confirm it does the job of removing the hiss/distortion on the repeats by >90%. It seems to have cut a tiny bit of high end out, almost unnoticeable and can no longer push it into deep self oscillation without very gnarly distortion occurring but I can get right up to the edge of oscillation and it’s pretty pristine. Kudos to who ever figured this out. Makes no sense to me but it works so there it is.