ABDUCTOR II DELAY.

[iefes]

Hey Rob, thanks for your feedback. I've got an internal trim-pot as a volume control, so the taper is linear. I think it is set quite high actually, almost cranked. There's a large volume increase on the last 10° of the turn.

Does this help to identify the issue somehow?

[deadastronaut]

hi, well it shouldn't be cranked. thats asking for hiss.

on mine its around 1'0clock-ish to be unity...



lets ask samhay: if you wanted to omit the volume pot completely  tinker with R9 feedback loop resistor.?

and take the lug 3 vol pot to out jack....not sure on value of R9 though. ?

[iefes]

Hi Rob, yes, that's probably a good idea to try. I'll remove the volume-pot and try different values for R9. Maybe something in the range of 22k to 47k. For unity it should be 22k right? Or does it matter that the input of the opamp is fed from 5 different sources, each with a series resistor of 22k ? Is each signal amplified the same amount due to all those 22k resistors?
However, lowering the gain of the output stage should at least bring down the hiss a little bit. Let's see 

[deadastronaut]

erm...not sure on the value, but might be worth tinkering with....

socket it maybe...

[samhay]

...you rang?

If you don't want the volume pot, you should probably aim to have the dry signal at unity gain, which is the case when R9 = 22k.
This does mean that that wet signal can be louder than the dry signal, bit this might be useful sometimes.

[iefes]

Okay, I tried different values for R9 and settled with 22k which resulted in unity volume, just as samhay suggested. I also left out the volume control. now it's better. There is definitely still some hiss even with the volume of each delay-chip turned all the way down and also without the delay-chips. I compared it using a true bypass looper. However, I'm not 100% happy but now I can use it and it's going back on my pedalboard :-)

But another question came up: Did anybody else experience that the modulation bleed through even with the depth at minimum? Normally like this there's no modulation, but sometimes suddenly a few repeats are highly modulated, just like I would increase the depth just for a moment. I might add a switch to completely kill the modulation. And I think I will decrease the maximum delay time. I feel that the repeats are too noisy at the long time settings and I mostly use the short times anyway.

However, I'm happy it's working better now and I can finally use it again. It's a great delay pedal, no doubt! Thanks Rob!

[deadastronaut]

is your depth pot faulty?.....they can get jumpy if they are dodgy....

had that on an effect once...swapped the pot, and sorted it.

[iefes]

I'll check it next time I open the enclosure. Thanks!

[Yupnitski]

Hi!
Just to add some info about a Abductor build I've been on for a while.
I bought two pcb's years ago and started populating the other once I got my hands on it. Knowing that an error in component value etc. could make this a painful project to troubleshoot so I populated the board with time. Once I got it done (this was a few years ago) there was no signal. No bypass or delayed. At the time my troubleshooting skills were not that well polished so all I could find was that the 2M delay pot was failing. That has nothing to do with the bypass not working and at the moment I had to put the project aside for a while. Time passed and just a week ago I found the board in my "to-do" box and started fixing it.
It didn't take long that I found out that for some reason, there guitar signal stops at Volume pot lug 2 (signal output). Hmm, let's check the pot. Pot was OK. What the... Ok, let's check continuity between Volume pot lug 2 and Output pad...yep, all fine. There's nothing much that could do this...unless...the Output path is grounded. It was indeed connected to ground, but where!? Checked all the wiring and the Volume pot, no apparent errors found. Ok, if there's a solder bridge or something on the board? Checking... No solder bridge, but the ground and Output layers are connected on the pcb itself! On both pcb's I bought, they are clearly crossing over each other. I'll put a pic if this later in the evening.
So if there's someone who has this kind of symptoms, check the Volume 2 pad with a DMM if it's connected to the ground layer

[deadastronaut]

Hi thats correct, there was an error on the vol pot part of the board....that was a long time ago...i did have a diagram on my site to fix that.....but removed it as it was so long ago i figured those building it would have by then...

Anyway, its long since been remedied, and glad you got it fixed. 

[Yupnitski]

Yeah, all fine now! 
I'll skip posting the photo then

[deadastronaut]

Come on, lets see your build too....   

Dont be shy 

[Yupnitski]

Haha!
Not being shy about the build, I was actually referring to the error on the PCB
But yeah, I'll post pics when I get it boxed - in couple of days or so

[deadastronaut]

 

Cool...

[Yupnitski]

Ok, now I got it boxed. Though I have to order more those 2399's since some of that are socketed now are a bit dodgy (goes without saying when it's about 2399's...). Also, when I got this boxed, I started getting a high pitched whine with the first 20% of Time pot (with the shortest delay that is). When I roll the Time up past the first 20% the whine goes away. This is with the effect bypassed AND effect ON. Actually, when the effect is ON, I have to roll the Time pot to nearly 50% to get the whine go away. I have to check if I have to re-route wires and/or shorten them. The wires aren't too long to start with, but maybe there's something that should be routed differently. Any ideas?
Anyways, the pics I promised

[deadastronaut]

looks great , very nice...

as for the whine even bypassed thats weird...as it just goes in and out though the opamp

when bypassed.......hmmmmm.... have you socketed the tails bypass fet?...just thinking aloud really...hmmmm

[Yupnitski]

Thanks man!
All the semiconductors were socketed in the beginning (like with every build I do), but when I got it working I removed the sockets and soldered everything, excluding the IC's. I bet it's the routing of the wires because it didn't act up until I boxed it. All the wires to the pots get squeezed between the PCB and the pots, so that's the most obvious change to the un-boxed situation. Oh, and yes, I've insulated all the pot casings with tape so there shouldn't be any risk for a short.
By the way, how much "artefacts" should there be - if any - in the delay signal with longer delays? I know that 2399's do add some when pushed to its maximum, but should this be any different? At the moment, I've been able to cut down the "artefacts" a bit with changing 2399's (some work better than others), but I haven't got rid of them completely.

[duck_arse]

check the output voltage on each of your regulators as you make it whine and then not whine - see if they are loading too much or summink.

[Yupnitski]

Yeah, I had a thought about the regulator (there's only one) and the current drain for the PT's. I recall one thread from years ago and there were discussions about how well one 78L05 supplies multiple PT's. Typically that kind of regulator has 100mA output limit and I tried to find some concrete statement about what the consumption for one PT is, but didn't find any. Some said 20mA max. and some said more.
There's the shadow of the PT's reputation in general hanging over this though.
I already loosened the nut on the mode switch and lifted the board a bit but that didn't change it one iota, so the regulator thingy will be next. Can't make it happen until next week, but I'll keep this thread updated when I get to shake the build a bit more

[Yupnitski]

Ok, back at this!
Well, it's not the 5457 or the regulator. Well, the 5457 appeared somewhat weird when I tested with a component tester, so I replaced it anyways. I also noticed that the frequency of the whine reacts to the Time pot, so the freq keeps going up until Time pot is 50% of its rotation. With the Mode switch in long delay, there's no whine.
I poked the pcb with my finger and I got the whine disappear when I hit the R18/R19/R20/C23 junction connected to the IC1's LPF2 section. I have quite a few "green beanie" caps on the board and I recall having one or two bad experiences with those in the past (some might be ebayed from China, so...). I think I'm going to drag the board back to work, remove the greenies and solder some proper caps in.
I'm just being careful with the pads and I have to remove them at work because that's the only place I have access to a solder suction station. So, it's gonna take a few more days to get back here with results - if any