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YuSynth ADSR... Decay doesn't begin till gate is released?
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Author YuSynth ADSR... Decay doesn't begin till gate is released?
JRock
Hi. I've built the YuSynth ADSR EG. I'm pretty sure it's right on. Has anyone else built this? The decay doesn't start till the gate is released?
It's not really a problem, I just want to know if I did something wrong hmmm.....
Thanks thumbs up
questionable
Haven't built one of those (yet). You might have better luck with a response and troubleshooting over at the electro-music.com Yusynth forum. I would think, however, that the decay should start when the attack ends, and the release should start after the gate ends.
kindredlost
I had a few ideas to send you this morning but abandoned the reply. It rambled too much.

The same problem is discussed by another builder on the electro-music forum. So far no response there but a view of the soldered board and a good explanation of the same problem is described.

Some things to ask... Did you build the improved version? Was your board etched a while back? There has been some fixes listed, but none are exactly related to your problem.

Some rough ideas for things to check include...

Make certain your decay pot wiring is good. A bad connection could cause a very rapid or no decay stage. It might imitate a lost decay function.

Check the direction of D2 - D4.

Most likely NOT the problem but... Check the pad at C4 and the trace between Q2 and pin 3 of the 7555. Make certain you have continuity there. The same can be said for C3 between pins 4 and 11 of the TL074. The graphic has these pads very close to the traces but could be not quite touching in a poor transfer to the PCB.

If you have another TL074 chip, then replace it (I hope it is in a socket). The newer version of the Yusynth EG uses a portion of the Quad OpAmp to clean up the sustain to decay interference. If something is flakey there then it could be a problem.

R12 should be 4.7k and not 5k as is on the component layout diagram. Probably not important and should work anyway.

If you have the older version then make certain pin 6 is picking up a good signal. This is what detects the end of the attack stage. If you are using the newer EG then I think all that is tied into the Schmitt Trigger function, but I could be wrong.

Anyway there are a few things to check. Good luck.

-David
questionable
Once you get it sorted, please report back. I've got three etched boards on the workbench and my mouser order is arriving on friday...
JRock
Ha ha ha! lol

That was me applause

That was the in - between board that I built. I've built another "new design" one that I finished yesterday.

Yves was so gracious as to answer my posts himself I didn't want to post again on EM for fear he would think I was ungrateful or complaining about the module, which neither is true....

The Decay definitely works. If I send a trigger pulse or a short gate it runs through the ADSR phases like I would expect.

yeah. On the first one I used a 5.1K and a 1.5M instead of 4.7K and 1.2M

This new one I used the prescribed values with the same results.

Don't get me wrong. It works great. It's just not the way I expected. I can't be the only one to have built one of these?

hmmm.....

Thanks for your responses
prinsen
spinning

Hmm, I'm confused now...
So, on the new one the decay stage "definitely works" but not the way you were expecting it to? If so; how did you expect it to work? And how does it actually work?
JRock
Ok. I expect it to begin after the Attack phase regardless of whether I am still holding a key or not. I would expect the release to begin when I let go of the key. The decay doesn't begin till I release the note though. As long as the release is long enough I can hear the decay cycle as the release plays out. That's how I know the decay phase works.


Something funny that I noticed is that it works the way I expect an EG to behave (Decay beginning after Attack) when I first turn it on if I haven't used it for a bit. Then shortly thereafter it switches to the decay not beginning till I release the gate.

I'm pretty sure I assembled it correctly. I would love to hear from someone else that has built one so I have something to compare to.
prinsen
Check if one (or more) of the semis is getting hot. The fact that the ADSR fails after it's been powered on for some time suggests so. And if so, you need to double check for shorts and bad wiring, once again, and to swap the overheating component(s).

More questions...
Did you etch your own board?
Does sustain work?
JRock
I did etch my own boards. They came out nice and clean though.

That's the thing... It's what really puzzles me. I have the same situation on 2 modules. I can understand a short or a wire foul up on one of them, but 2 of them? I try to be pretty careful.. especially the second time around doing something!

Like I always say "If it's worth doing right It's worth doing twice!"

I don't think there are any overheating components but I'll doublecheck.

It's tough to tell about the sustain. It has some effect. I'll fire it up in a little bit and check that again too.
kindredlost
Some sound clips might help us.

A clip with...
A=0
D=50%
S=0
R=0
...would be a good way to start.

Maybe a stereo clip with the adsr to an osc pitch in the right channel and the gate to a vca with another osc in the left channel.
sduck
What kind of TL074 did you use? You might want to check the connections around this, as it looks like it will determine how the decay works.
JRock
Alright. Let me finish drawing out this schematic I'm working on and I'll get some sounds up. thumbs up It'll be within the hour.
JRock
Alright. I think it's something to do with the .01uF Capacitor attached to pin 5 (Control Voltage) of the 7555 to ground. At first it works cause the cap is discharging, or hasn't filled up all the way (just my guess hmmm..... )

I switched it with a .022 but it still stops decaying. I think it's this cause when I touch pin 5 it works like it should (maybe because of my capacitance?)

Should I try a bigger cap or a smaller cap? Or am I on the wrong track entirely? Is it my resistance allowing the cap to discharge?
JRock
Seems to work if I stick a resistor to ground along with the Cap! It's motherfucking bacon yo
sduck
My guess now would be that you've got a cold solder on that ic. Not necessarily pin 5, but close by probably. I don't think touching the cap affects it in the way you think - my guess would be that you're just applying enough pressure for a decent electrical contact to be made, so the circuit works.
JRock
That's what I thought at first. I have it in a socket. But I pushed it and pulled it and scooched it around to get it to seat properly in the socket and the pressure and the movement didn't work. It only worked when I actually touched pin 5. Orrr touched both of the leads from the cap. But it didn't work if I just shorted pin 5 to ground. I reworked the joints for the socket and for the cap and I still got the same thing. I changed the value of the cap and it was still the same.

It was something about my resistance to ground was the only thing I could figger...

I clipped a resistor to the leads from the cap and Voila! It worked! I tried a few different values and soldered it on and it works great hmmm.....

I'm not sure why. Maybe has something to do with a long power lead and the cap discharging... That's just a guess hihi It's the only thing I can think of It's peanut butter jelly time!

On with the BWWOOUUHHNNN and The BEEERRRRNNNNNTTTTTT!!!
sduck
Well, it works! Doesn't matter how, as long as it does. Congratulations!
raveboyy
so can I use the ´new version´ PCB picture from yusynth page for making a board as it is? no need to modificate anything? Does the PCB fit into eurorack as it is?

Cheers
satindas
I just built a couple of these (v2's) and I'm experiencing exactly the same problem... with both of them; Sustain seems to be stuck at 100% and the Decay and Release seem to operate in tandem.
Yves layout with the headers all around the board didn't really work for me so I laid it out in KiCad and had 10 of them made up by itead. I've checked the KiCad layout against Yves schematic so many times now I could probably draw it from memory, I've checked the board for shorts, replaced the 7555 and the TL074 and I can't find a thing wrong with it (according to the schematic), I added the 470K across C5 and still no change. WTF!
alain6870
You should check your pcb once more as I built 4 of them working all like a charm. Did you check the diode polarity? If you don't find the mistake try to share à picture of both side of your pcb this can help. meh
raveboyy
satindas wrote:
I just built a couple of these (v2's) and I'm experiencing exactly the same problem... with both of them; Sustain seems to be stuck at 100% and the Decay and Release seem to operate in tandem.
Yves layout with the headers all around the board didn't really work for me so I laid it out in KiCad and had 10 of them made up by itead. I've checked the KiCad layout against Yves schematic so many times now I could probably draw it from memory, I've checked the board for shorts, replaced the 7555 and the TL074 and I can't find a thing wrong with it (according to the schematic), I added the 470K across C5 and still no change. WTF!


I've built 2 of them using Yves's layout and they are both working great. But I remember I had some confusion with parts placement template vs BOM.... Try to check Yves's layout against the schematic if everything matches...there might be some slight difference. BTW, I'm not saying there is, i just thought it might be worth a try hmmm.....
alcide
Are the sleeves of your gate in & eg out jacks properly grounded ? I've had all kinds of erratic behaviours with diy'ed modules i had just finished building and wanted to try too hastily... the most obvious things sometimes ...
satindas
Thanks for the replies thumbs up

I've built 3 of these (home etched) from Yves layout before without any problems. Like I say, I've been over it and over it with a magnifier and my DVM constantly referring to both the original schematic and the KiCad .sch

I'm not much of an expert with 555's but I'm beginning to suspect that the timing cap is not charging to 2/3 vcc, or whatever the threshold voltage is, which may be due to a slight layout problem; I have a 15v line running beneath the decoupling cap attached to pin 5 of the 7555 and I'm wondering if this is affecting the threshold level.... It's late and my head is fried so more probing around that area tomorrow.

alcide wrote:
Are the sleeves of your gate in & eg out jacks properly grounded ? I've had all kinds of erratic behaviours with diy'ed modules i had just finished building and wanted to try too hastily... the most obvious things sometimes ...
... all jacks (earthenvar) have their ground lugs linked and share a common connection but definitely another thing to check thumbs up
satindas
Ok I got this fixed SlayerBadger! but not without completely freaking out over some of the readings I was getting and the ridiculously simple solution.
With a gate applied to the input I eventually got to reading 14.87v at pin 3 of U2. Fine up to there, more than enough to initiate the decay phase. However at the output (pin 1) of U2a I was reading just 7.37v , so there was the problem.
The decay will not initiate without at least 10v at pin 6 of U1 so I started looking for shorts but nothing. I tried a number of TL074's and they all gave the same readings.
Here's the bit that I really don't understand and I'd be grateful if anyone can explain; At pin 9 (inverting input of U2c) I was reading 0v and yet I still had -7.37V at the output (pin 8)! How does an op amp invert a 0v input to the exact opposite of the output one of its compliments ?
So... I stuck a LM324 in there and hey presto the whole thing sprung to life and now works perfectly!

3 whole evenings of fucking around and all I needed to do was use a different Op Amp. And I doubt I'll ever understand why, although I do intend to check every one of those TL074's . Probably just got a bad batch or something. Dead Banana
alain6870
I use TL074 in m'y design without any problem. Did you take à picture of your pcb, this can help to solve your problem ? Can you share it? Anyway I believe that you maybe have an input impédance problem in one of your Opamp, check for short around this part of thé circuit.
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