TH 21st Century ADSR

[slo]

Just has a week long fight with this circuit. First I beardboarded it and it worked great, then I built it with a pcb. It worked perfect with just a trigger, generating a nice A/D response, controls all working, ditto with just a gate signal, for a nice A/R response. But do you think the gate and trigger would play nice together, no way! I had no attack and very erratic behaviiour from the circuit. Finally replaced the 470pf cap (very old) on the trigger input with a .01uf (new) and now it works 100%. I think the problem was the old cap and the soldering process, I could see a poor trigger on the scope and a much better one with the new cap. Anyway I am very happy now and learned a lot. My only question would be, do I leave the .01uf cap in, or replace it with the correct value? How does Thomas come up with such a value anyway?

Thanks
George

---

100-0020_IMG (Small).JPG
Description:	TH 21st Century ADSR
Filesize:	44.36 KB
Viewed:	154 Time(s)
This image has been reduced to fit the page. Click on it to enlarge.

---

[Thomas Henry]

How did I pick the value? In a nutshell: rule of thumb. I didn't calculate anything here.

A keyboard trigger is on the order of 5mS. I wanted something much narrower than that to fire the 555. C1 and R5 set a much shorter time constant, guaranteeing the 555 fires pronto.

The circuit should work well with the values shown with just about any keyboard. I suppose it's possible your keyboard may generate a pulse width that made the larger value necessary. And as you say, it's also possible the original cap was cruddy.

If it were me, and given how cheap caps are, I'd try the original value, or maybe a 0.001. But the 0.01 sounds kind of big to me.

Anyway, a little trial and error will settle it for your keyboard.

Thomas Henry

[slo]

Thanks Thomas, I'm using a PAIA Mdi2cv8 and the trigger is dead on 5ms, I will correct for the right value. I never doubted the design once as I have built your designs in the past.

Thanks
George

[philpeery]

HI George,

Did you design your own PCB for the ADSR? Would you be willing to share it with us? I've been wanting to build this one, along with the 2164 VCA (doubled up for good measure!), but haven't had the time to create and debug a board.

The ifnished module looks cool!

Thanks!

Phil

[Thomas Henry]

Be sure to check with Tim Servo for permission to pass the artwork around. Magic Smoke has the full rights to the 21st Century stuff, and you never know when they might have something planned instead.

Thanks,

Thomas Henry

[slo]

The PCB for this ADSR was got right from this board here. The link was to Thomas's old Midwest site. I modified it a bit to bring it up to the 21st Century version. With permission from Tim Servo, I can post it.
Glad you like my module, I spent a LOT of time getting a consistant design going across my panels, 'cos I want to spend a lot of time with them!

George

[Tim Servo]

[slo]

Have sent you a pm concerning the pcb Tim.

George

[slo]

I have posted the pcb image in the Thomas Henry designs download section. Thanks Tim.

George

[Danno Gee Ray]

Would you be able to post the component side parts placement diagram?

[softfin]

[slo]

To my knowledge there was no component side for the pcb. If you look closely at the schematic and orient the power pins on each IC then you should be able to figure where every thing goes, thats what I do when the component side is missing.

[Danno Gee Ray]

Didn't you design this PCB layout?

[Danno Gee Ray]

I can understand your not wanting to spoil it for book purchases. Why not just say that. I believe Thomas has every right to protect his intelectual property, and am a firm believer that every DIYer would benefit from buying his books. I make it a point to buy every one of them I can find as soon as they come to print.

I guess I was just getting lazy, but a little bit of effort on my part is worth it for a Thomas design.

[Thomas Henry]

[slo]

I was looking for an ADSR design and hopefully pcb one day when I came across a link to an archived site, it was Thomas's old Midwest electronics site. The graphics did not show up on my screen at all and somehow I managed to recover this pcb image. I knew it was a Thomas Henry design and I started looking though my pile of reference books and found the circuit in a Thomas Henry article in an old Radio/Electronics, it matched the pcb perfectly, pure luck on my part. So I have the old RE schematic, the pcb image and that was enough to build a great circuit
I guess I should have explained how this pcb came about right from the start.
Just for the record, I never once claimed authorship of this pcb.

George

[Danno Gee Ray]

In all, My bad. I thought that you had re-designed an old one to fit the new book. Either way, With Ray and Scott's permission, we have an opportunity to build another of Mr. Henry's wonderful design's.

I too have visited the archived remnants of his old site and when I did I felt saddened that it was no longer active. It was with great joy I then later saw Mr. Henry return to the community here on EM. It's a terrible thing, what one person's bad faith can do to a good thing. I also know the sting of it, and must say I don't blame Mr. Henry his reaction at all. I'm just gratified to see him active here, and feel privileged to be able to obtain his writings / designs. I would not want to see anything get in the way of that continuing.

[slo]

Danno Gee Ray said:

[EdisonRex]

[sonicwarrior]