String damper question

[Kipper4]

Has anyone built the string damper?
On Mr Hammers page here
http://hammer.ampage.org/files/StringDamper.PDF

I guess that i can drop in a lm13700. I don't have the 13600.
Anyone see any potential problems or mods for the circuit?

[Mark Hammer]

It'll work.  Just keep in mind that it is a triggered effect, rather than a mere envelope follower.  So expect it to take a kittle bit of practice to tailor your playing to what the circuit expects.  Don't treat it as necessarily a problem wih the build.

[Kipper4]

Cheers Mark
Any mods to make it more player friendly?

[Kipper4]

I built this today but the buggers not playing ball.
Biggest problem is my ICL7660s inverter is not giving me -9v at pin5 im getting 0v
and whats more is im getting 4.5v at pin 3 instead of 0v

ideas please its been a long day and i cant cope.


pins 1 and 8 going to dc jack +9v
10 uf cap between 2 and 4
10 uf cap from pin 5 to 3

[armdnrdy]

Since the String Damper drawing doesn't include the added 7660 circuit....you might want to post a link to the inverter circuit that you used.

I built this today but the buggers not playing ball.
Biggest problem is my ICL7660s inverter is not giving me -9v at pin5 im getting 0v
and whats more is im getting 4.5v at pin 3 instead of 0v

ideas please its been a long day and i cant cope.


pins 1 and 8 going to dc jack +9v
10 uf cap between 2 and 4
10 uf cap from pin 5 to 3

[Kipper4]

Here you go Larry

https://www.google.co.uk/search?q=voltage+inverter+7660&ie=UTF-8&oe=UTF-8&hl=en-gb&client=safari#imgrc=PX0lkI6evOMrkM%3A

I fear I made a schoolboy error and hooked up the -9v to DC Jack ground where as I should have hooked up pin3 to it.
The chip was getting hot too.
If that s the case then my layout is complete rubbish.

[samhay]

The circuit doesn't need a negative supply. It's drawn a little different than you might be used to, but you can connect all the V- to ground and the ground symbol to half supply (provided by the 2 4k7 resistors).

Edit. Actually, you will have to move the pull-down resistor (R15) so that it is connected to your ground or else they will pull the -9V towards ground via R15.

[Kipper4]

 Guess essentially that's what I did Sam.

Icl7660s
Pin 1 and 8 +9 volts to DC Jack +9v
Pin 5 to my DC Jack ground
And using pin3 as my Vref (described as ground on the EMM schematic)

[samhay]

Pin 3 has to go to DC/audio jack ground. Pin 5 floats about 9V lower than this and is only connected to those points (excluding R15) marked as V-.

[Kipper4]

Yep Gottya Sam (excluding R15)
I'll give it another look tomorrow hopefully I won't be so weary.
You know what it's like when a team members on holiday and there's no holiday cover.
Gaaaahhhh

I just saw Jimi photon built it a while back and modded his.

http://www.diystompboxes.com/smfforum/index.php?topic=98970.0

[Kipper4]

I fried the charge pump. replaced it.
Still no luck. Excluded R15 and attached it to ground.
Made a few unmade connections missing from my layout. More schoolboy errors..........

I'll post up some voltages later and see if anyone can spot anything wrong.
Cheers guys

[pinkjimiphoton]

Yep Gottya Sam (excluding R15)
I'll give it another look tomorrow hopefully I won't be so weary.
You know what it's like when a team members on holiday and there's no holiday cover.
Gaaaahhhh

I just saw Jimi photon built it a while back and modded his.

http://www.diystompboxes.com/smfforum/index.php?topic=98970.0

hi kipper,
mine is on my "to fix" lists. you have to get a copy of the original layout from i think it was francisco pena and compare that project to the actual damper schematic. there's at least one or two mistakes on the fp board layout in the upper right corner of the board as it looks on the computer screen. i researched the bejesus out of this trying to figure out what was up, i used the other chip too which shouldn't matter, but kinda does.
my mods were simply using different size caps on a switch to change the range of the attack times. i had used solid core wire back when i built it and suspect that's the problem, but i opened it up to mess with something and could never get it to accurately trigger again. it kinda works intermittently. BUT that may ALSO be due to the fact that my dumbass true bypassed it. it's supposed to have a momentary switch to turn it off and on if memory serves. you step on the switch then play a note, and it swells in. let go of the switch and it resets for the next swell in. if you true bypass it, it's ALWAYS ON, i suspect it needs to discharge somehow or something when ya release the momentary switch.

i'm glad you just posted this bro, i think i just figured out what i did wrong on it. if i can find it in the pile of failed shiiiiite i'll see if adding a momentary like it should have makes a difference like i suspect it will.

the layout on the net from francisco is a little different from the string damper, but essentially the same circuit with the power supply suggested earlier in the thread by sam and armd

[lars-musik]

Well, ain't that strange. I am whining about wanting a "better" Slow Gear for so long - tortured myself with desperate EHX Attack/Decay builds, while all that time I already got the pdfs (from Mark's site as well as Franscisco's layout) on my computer. I thought I read somewhere that this circuit is a manually triggered one, but obviously I am mistaken. Guessing from Jimmy's video this could be what I was looking for all the time. Time to do a 1590a layout for it. A shame that Christmas is coming up and time is limited.
Kipper, keep us posted if this one works out for you!

EDIT: I somehow missed Jimmy's latest post. So it really needs switching during playing (did you do that in the video?) and therefore somehow disqualifies for me.

[Kipper4]

I decided to go the charge pump route Jim.
And what's more I don't have LM13600 I'm using LM13700. I applied Keens second law.
Some you win some you debug......

[pinkjimiphoton]

lars, i didn't "get it" at the time i made the video, what i wrote earlier today was as a result of having read the article on mark's site. if memory serves, it is indeed supposed to be a momentary switch. i did true bypass mine which is probably why i had so many problems with getting it to trigger, altho again, using solid core wire could have messed me up too.

[Mark Hammer]

The circuit description in the E&MM article explains how the circuit is triggered by the signal itself.  No external switching is required, momentary or otherwise.

[pinkjimiphoton]

true, but as shown in the schematic, it's a momentary switch, innit? it say to hold the switch down when you want the effect, and when you release it it's bypassed if memory serves.. let me find it and look...

switch 1 a just lights the led, right? switch 1 b connects the b+. as in the video, i DID have it working, but it was a bear to have any real control. in the text it says "now is the time to decide if you want on - off or momentary operation. yadyada"..... in that case you trigger it just before the note you want to swell in, but you have to wire the switch differently. i had true bypassed mine. but like i said, it's broken.
when trying to figure out what happened, i found some refs to some of the layouts having mistakes on them, and i found the board i was sent had been burned off one of those so i had to modify it somehow. i'd have to look, it's been a couple years now.

so yes, it should indeed trigger with tb or momentary switching. i gotta find it and have a play with it. winter time, time to build the fuzzboxes...

i think most of my confusion came from page 2 of the article on mark's site, maybe i'm just misunderstanding it?

[Mark Hammer]

As near as I can tell, SW1a/b is the designer's "bypass" switch that does not step around the circuit, as many of us are used to, but merely disables the effect by over-riding the internal envelope generator.  This is why the article shows A open when B is closed.

I might note that the PAiA Gator (which only has a rise time but no decay control) engages/disables the effect the same way.

[pinkjimiphoton]

yeah, it's always on, but the switch bypasses it. read that second page tho and it talks about using a momentary, which does make a lot of sense. you have to wait to trigger this thing sometimes, i think it has something to do with the cap charging and discharging. i think dod made a slow gear kinda deal that worked like that... maybe morley? my brain is getting kinda long in the tooth these days

[pinkjimiphoton]

found this, which may or may not be helpful/relevant



also, from before when it worked:

replace c9 with a dpdt with 2.2u and 4.7u for attack time increase

swap out r13 from 4.7k to 47k and r15 from 10k to 100k for unity gain mod.