Mod question on sea machine build.

[Locrian99]

Hello,

So I built a clone of the sea machine m, pretty nifty little chorus/modulation weird noise maker thingy.   I've been really enjoying the noises I can get out of this thing, and has some pretty useful chorus sounds too.   I wanted to get the dimension pot (seems like you could also call this the repeats pot to get a little closer/just reach self oscillation.    It gets close but doesn't get there.   I think I just need to raise the value of r9 in the schematic.   I was thinking I'd try a 1.2k first as I presume I'm going to lose a little bit on the other side of the rotation in doing so.   I wasn't sure if I would need to be concerned with the value of C5 I'm making this change.   

Also I though a kill switch for the dry signal might be a fun thing to play with.   I saw some mention of this in Reddit and it sounded like this could be done by adding a dpdt for r14 Place r14 between two lugs and just a jumper between the other two.   Does this sound accurate?  For that matter if it is just a matter of changing the resistor for the first I guess I could just put the two resistor values on a dpdt for dimension pot (there's already 6 pots why not add a couple switches.).   


Anyways any thoughts suggestions here would be awesome. 

[Kevin Mitchell]

For an attempt to get self-oscillation I would first swap the 5K "DIM" pot for a 10K. Yes you could call it a repeat pot, or a feedback pot. With a higher value pot when it's fully clockwise you'll have more resistance to ground - allowing more signal to feedback.

You're almost on-the-mark with the R14 idea. Removing it completely cuts out the dry signal mix and can be actuated with a DPDT switch instead of hardwired as it is. You're not going to want a jumper because that'll insert the buffered input signal into the mix which is the opposite of what you're after.

[Locrian99]

Awesome I'll try the 10k.   I was somewhat reluctant to go that route Thinking it'd lose some precision in hindsight though that really probably makes the most sense.  Thanks for the info. 

[Locrian99]

So assuming I removed the correct 10k resistor it should work with nothing there right?

[bean]

So assuming I removed the correct 10k resistor it should work with nothing there right?

As mentioned above, if you lift R14 you will kill the dry and get more of a vibrato sound. To get some feedback oscillation, socket R10 and try lower values. Try half - maybe 4k7 - to see if it gets you there. You could even go all the way down to 1k on R10 if you want but that might be too much.

[Locrian99]

So assuming I removed the correct 10k resistor it should work with nothing there right?

As mentioned above, if you lift R14 you will kill the dry and get more of a vibrato sound. To get some feedback oscillation, socket R10 and try lower values. Try half - maybe 4k7 - to see if it gets you there. You could even go all the way down to 1k on R10 if you want but that might be too much.

Cool.   Thank you, I'm pretty green still not positive I thought the correct 10k was the one I pulled from the layout (doing a stripboard layout).   Works in the position to go through the 10k but no audio in the other.   Felt pretty confident I had the right one... layout is using a 74 instead of 2 72's but that really shouldn't change much following the schematic.  I put the switch for the circled one.   

[Locrian99]

Nevermind that is working.  Thanks I'll try the socketed ones. 

[duck_arse]

I'm messing at elec bongo into delay at the moment. I'd try reduce the value of R10 as said, but I'd fist be messing about with C9, which seems way large to me. I'd start 100nF, see if that changed anything useful.

[Locrian99]

I'm messing at elec bongo into delay at the moment. I'd try reduce the value of R10 as said, but I'd fist be messing about with C9, which seems way large to me. I'd start 100nF, see if that changed anything useful.

I hadn't even noticed that.   That is changed in the layout I used as a 3.3nf.  And was the topic of several conversations on a forum post when the original layout was posted. 

[duck_arse]

3n3 ?? that's quite a change. mostly I see 10k and 10nF in those filter spots. last night I was doing something with a Hammer type tone control on what would be R10 on your circuit [? 10k pot and 68nF on wiper to ground ?], and was surprised to get infinite repeats. well, infinite in as much as I could be bothered waiting.

[bean]

3n3 ?? that's quite a change. mostly I see 10k and 10nF in those filter spots. last night I was doing something with a Hammer type tone control on what would be R10 on your circuit [? 10k pot and 68nF on wiper to ground ?], and was surprised to get infinite repeats. well, infinite in as much as I could be bothered waiting.

Word is, those repeats are still going to this day.

[Locrian99]

3n3 ?? that's quite a change. mostly I see 10k and 10nF in those filter spots. last night I was doing something with a Hammer type tone control on what would be R10 on your circuit [? 10k pot and 68nF on wiper to ground ?], and was surprised to get infinite repeats. well, infinite in as much as I could be bothered waiting.

Interesting.   I haven't had a chance to mess with this part yet.  Did the dry signal kill and got sucked into playing around with that for far too long.   Hopefully I'll get a bit of time tonight to play with that.  Going to try beans suggestion first and drop r10 down tonight.  I need to start breadboarding these things first apparently as I'm getting to the point now where just building it and it working isn't quite satisfying anymore and I could certainly use the practice in schematic reading. 

[Locrian99]

Cool so I'm pretty happy with the pedal now.   Thank you all for the info.   Final question, I want to make the "vibe switch" aka dry signal cut foot switchable when an led.   I think I'd have to use a 3pdt to do this and wire it as like this

Pin 1 connected to pin 4 with r14
Pin 2 input from board where (r14 in)
Pin 3 empty
Pin 4 as above
Pin 5 out to board (r14 out)
Pin 6 empty
Pin 7 empty
Pin 8 led + with inline clr
Pin 9 +9V


Is there a better way to do this?

Thanks

[duck_arse]

a double pole double throw switch. common A to R14. N/C A to opamp pin 1. led to indicate "the dry switch is now open!" - [dash, not minus] supply via CLR to common B. led Anode to N/O B. led Kathode to ground.
done.

really and truly, learn how to draw the basic switch diagram correctly. learn multi-poles. learn switch/poles sense. once you can properly draw a switch, switching problems become much much easier to understand and solve.

[edit :] oops. forgot. you can reduce noise chances by connecting N/O A to ground, so that resistor sees sig or grnd.

[Locrian99]

a double pole double throw switch. common A to R14. N/C A to opamp pin 1. led to indicate "the dry switch is now open!" - [dash, not minus] supply via CLR to common B. led Anode to N/O B. led Kathode to ground.
done.

really and truly, learn how to draw the basic switch diagram correctly. learn multi-poles. learn switch/poles sense. once you can properly draw a switch, switching problems become much much easier to understand and solve.

[edit :] oops. forgot. you can reduce noise chances by connecting N/O A to ground, so that resistor sees sig or grnd.

Took me a minute to understand the wiring here.   I realized I was looking at the switch as tying the commons together rather than the common sending the signal to pin 1.   So I was trying to make the signal go from common 1 to common 2 via pin 1 of nc and pin 2 of nc with them tied together when I should be looking at it as common 1 connects to either the pole above it or the pole below.  It complicates things a bit when it's already on vero on a layout as opposed to on a breadboard as well.  Looking past having to have the resistor on the switch instead of inline or I might be able to figure out how to leave it in the strip somewhere.  Anyways Changed my way of looking at it Thanks.