ABDUCTOR II DELAY.

[samhay]

^what are you putting it with?

[iefes]

It's running straight into the amp with its own power supply. No guitar connected to the effects input, so the input is grounded.

[samhay]

What happens to the noise if you turn all the level pots CCW?

[iefes]

They all are completely ccw, still noise. I've also removed all the PT2399s without any improvement. Next step would be to try to disconnect the delay line completely from the mixing stage to see if it is still present then. What do you think?

[samhay]

Without any PT23999s, the delay line shouldn't be able to make any real noise.
I suspect you either have:
a very noisy power supply
an usually noisy TL072
a build error, which is giving much more gain than expected - how loud is the dry signal?

[iefes]

The power supply should be fine. I tried different ones that produce no noise at all on all my other effects including digital effects such as a Boss DD-20. I've used them for years and never had noise issues. I also tried 0.1uF caps across the rails of the TL072 without any improvement.
I've tried a OP275 instead of the TL072 without improvement.
Much more gain shouldn't be the case. In fact, I've used a 51k instead of the 56k in the feedback loop and I need to turn the output-volume trimpot to about 75% to get the bypass volume.

If I remember right, the noise was lower when I pulled the 78L05 regulator, that's why I tried a "stronger" LM317 in its place, but this also didn't improve anything.

I'm running out of ideas, the last thing that comes to my mind would be a problematic PCB layout that induces noise somehow, but then more people would complain about the noise.

Is there any other area in the circuit that could introduce the noise, even though it appears only at pin7 ?

However, thanks a lot already for taking your time!

[samhay]

It's a bit of a puzzle. I don't have one of these to prod, so working purely from theory, but it doesn't sound like an obvious build error.
I expect when Rob emerges from the dark side of the moon he will chip in with suggestions.

I had forgotten that this design has an LFO. What happens if you pull IC6?
Also, if Q1 (the FET) is socketed, does it make any difference if you pull this?

[iefes]

I tried pulling the LFO driver the other day. It did improve the hiss issue a little bit, but definitely not a lot. I'm not at home this weekend so I'll have to wait until Monday to check if pulling the FET will give any insights. Thanks!

[iefes]

Okay, without the FET the hiss remains the same. Tried it with the LFO IC again and it's the same -> no change in the amount of hiss. 

[stallik]

Finally got round to building an abductor 2 using a blue board from Rob without the labels.
I don't have a noise problem, I have a quiet problem. I have a short between signal and ground which I can't spot.
Tomorrow, as they say, is another day.....

[stallik]

Found the short. Red wire is output, black is ground. Shorted on the pcb
Now got sound but only delay 2 & 4 are working + LFO
Need some sleep before looking at where delay 1&3 have gone.... and the feedback



Sorted the missing delays and feedback - forgot to reconnect the earths after cutting the pcb tracks 





Plain box - it's only temporary
Nice one Rob - this is great fun!

[BetterOffShred]

So my build was done and boxedish.. but listening to the video and my unit, I feel like my unit has a lot more distortion in the repeats.  Like the added hiss on the repeats including the first one.  I know pt2399s get distorted as the repeats carry out, but it's immediate on mine even at relatively short delay times.  I was planning on changing the 1n caps at pins 13/14 and 15/16 to 2n2.. though I know that darkens it up, but I like that.   Any other ideas where to look for hissy repeats ?  It's almost there! 

[iefes]

Did you try different PT2399 ICs in the first position? Some chips produce more hiss and if you have a bad one as the first delay stage you'll amplify the hiss in every stage. Try swapping the chips around if you just have these.

Btw, still no improvement to my hiss-issues with the output buffer.

[stallik]

This may be a complete red herring regarding noise but here goes.

When I built mine, I only had a 1meg pot available for time. It was a standard miniature Alpha from Tayda. Although this limited the delay time available, the pedal was pretty quiet. I added a 1meg resistor in series to get longer times and while it removed the shorter times, it was still pretty quiet.

Just received a 2.5meg pot via eBay and shoved that in. The pedal is as noisy as hell at all delay time settings. In bypass it hisses quite a bit and I think this is being amplified through the delay. It doesn't make any scratching noises when turned but it feels very scratchy if that makes sense. The pot is a very nasty, low quality job so i shouldn't be surprised. Shoved the original back in and all is pretty quiet again.

[BetterOffShred]

Yeah I had originally wanted to put a B1M in.. I'll try it. Thanks for the idea.   

Also, I have tried. Numerous 2399s.  I ordered some SMD and adapter boards for them too .. I want this thing to be quiet.  It's so damn fun

[BetterOffShred]

B1M didn't affect my build.  Tried like 10 more 2399s from different batches, didn't help.  Put 4401s in instead if 3904s..  it actually seems better.. but not much.  It's unboxed still and I have a bunch of florescent lights and stuff.  I may box it up just to see.  It's pretty rough to pull it all out and stuff... but I'm just going to try. 

[iefes]

Interesting stuff about the delay time pot, thanks for that. I'm afraid it won't help with my issues but it's interesting to know.
Are there any other suggestions what could be causing the strong hiss on the output stage? I never had this kind of issue in my setup.

[BetterOffShred]

After building a different delay and having it sound hissy during repeats as well, and then boxing it and it not being noticeable I decided to just box up the Abductor because the hiss was only there if I listened real close .. 

Long story short it's pretty much quiet as a mouse now and I think my hiss artifacts are a byproduct of my test rig and the shoddy grounding and fluorescent lighting in my workshop. 

It took me a while and I learned a lot about delays and filtering, but this is definitely one of my favorite delays.  It's so much fun. Thanks Rob for making it available. 

Kind of went for the "Fire in the sky" theme.   That movie freaked me out when I was a kid   

[deadastronaut]

cool build....thats my fave film ever...

checkout an epsode of ''paranormal witness''  with the travis walton story..

even travis said is the closest portrayal of what happened....

i have the original 70's book of the story too..great read,


@iefes: your volume isnt way up is it?...should be around 1 0clock - ish...

[BetterOffShred]

Sick man, I'll check it out!   Love the delay.  Ran out of 100ns or I would be building my dreamtime right now!