Some closer shots of the PCB:

As you can see, this uses a PT2399S delay chip. This is a very common digital delay chip, used in everything from the BYOC delay, Freakshow Digilog, Danelectro Fab Delay, Rebote Delay, and others. The Spring King basically starts out with a fairly normal slap delay circuit, with a fixed delay time and feedback setting, and then feeds that delay signal through the springs and then out to a gain recovery stage. So, it's a hybrid delay and spring reverb. Pretty clever, I think. I believe that the slapback delay basically helps compensate for the small springs, making it sound as if they were bigger. It doesn't sound like a Fender tank, obviously, but works pretty well considering.

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According to the datasheet, the 3.6k resistor (marked "362") at pin six is responsible for the delay time, and is a fixed delay time value. Simply desoldering that resistor and wiring the pads up to an external potentiometer would give you control over the delay time. Shorter delay time might "tighten up" the overall reverb sound, while a longer delay time should make it sound even "looser." I'm guessing this would be have the effect of simulating shorter and longer springs.

The feedback on this delay circuit is set fairly high - it'd be nice to be able to control this as well. I haven't located the exact mod for this yet, but it shouldn't be too difficult. Hopefully I'll have figured it out by tomorrow. Once I try adding delay time and feedback controls, I'll let you all know how it turned out.

As far as I can tell, the existing controls work like this:

Volume controls the strength of delay signal fed through the springs
Tone is tone, not sure if it's pre-springs or post-springs, but doesn't seem to effect delay tone, only spring reverb tone
Reverb controls the mix of dry and reverberated signals

There is certainly enough room on this for two extra controls - it's huge!!

http://www.reverbnation.com/thedeadranchhands

http://www.youtube.com/watch?v=jZEW74mHjQk

No tubes, sorry! I suppose I could glue one to the PCB. Or better yet, drill a hole in the enclosure and have a tube sticking up through it, with an LED underneath to make it appear to glow.

I worked out where to add feedback control using the "short it out until it does something different" method. Also added a delay time control. Now it works as a delay pedal as well as a reverb. At longer delay times and/or higher feedback levels the delay gets gritty and low fi. Very nice! I'll have to work out where to add a control for delay volume level eventually. It's fairly quiet unless it starts to self-oscillate.

I also discovered that with the feedback and delay time at minimum (essentially no delay sound at all), the springs still sound good, and give off that dripping faucet sound. So now I can have just the spring reverb, with no delay, or just delay, or a mix of both. Very cool.

I used a 50k pot for the delay control and a 100k for feedback. If you happen to try this mod, be careful that your wires don't droop down, or they'll mute the springs. I used double-sided tape to secure them to the inside of the enclosure.

image

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http://www.reverbnation.com/thedeadranchhands

http://www.youtube.com/watch?v=jZEW74mHjQk

Cool project! Now you just need to post some soundsamples ;-).

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Awesome! I'm looking forward to seeing what else you find out about the spring king.

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NicholausLee
Awesome! I'm looking forward to seeing what else you find out about the spring king.

Well, I poked around to see if I could get a level control on the delay, but no such luck - looks like I'll have to actually study some schematics involving this chip gasp

I have found that a slightly shorter delay time than stock, with perhaps a slightly lower feedback level sounds just great. It sounds tighter and more "real." It's easy to make the SK sound trashy, but it can actually sound surprisingly good - you just have to find the sweet spots. It's not one of those pedals that sounds good at every setting. I'll update if I can figure out the level control mod.

http://www.reverbnation.com/thedeadranchhands

http://www.youtube.com/watch?v=jZEW74mHjQk

Here's a pic of it after the mod - I will eventually pick up some matching chickenhead knobs. I just used what I had. Probably a lower value feedback pot would also be in order.

image

http://www.reverbnation.com/thedeadranchhands

http://www.youtube.com/watch?v=jZEW74mHjQk

NicholausLee
Might be a stupid question, but what does the "Feedback" control actually effect in terms of tone?

How long of a delay do you get out of that chip? Just a quick "slap" type of delay, or a long second or two or more?

Also, is there any technical reason you couldn't replace the springs for a better spring box? Other than space restrictions. Would that effect the tone of the reverb?

Feedback just controls how many repeats the delay gives you. If you turn it up it will start to self-oscillate.

I've only just recently been reading up about this subject, but apparently each spring size has different current requirement, and needs to be driven by a specific current to get the most desirable sound.

See: http://members.tripod.com/~roymal/reverb.htm

Unfortunately, the math is way over my head.

There is another option for inexpensive spring reverb - the Stage Center Reverb. General Guitar Gadgets sells the circuit board, and Small Bear sells the reverb tank that goes with it (I think it's a bigger thank than the SK, but I'm not sure). I may try building that one someday.

http://www.reverbnation.com/thedeadranchhands

http://www.youtube.com/watch?v=jZEW74mHjQk

Clips are up in the downloads section. Excuse the poor playing!

Edit: I guess they have to approve it first. Here's a link to the MP3:

http://www.uncledig.com/clipgallery/Uma%20Floresta%20-%20Spring%20King-02.mp3

0 - 1:41 - Delay only, various settings

1:41 - 2:38 - Reverb only, max Level and Reverb, Tone at noon

2:38 - 5:18 both Reverb and delay mixed, various reverb settings, from moderate to maxed out

Songs used - "A Crack in the Ceiling" - Uma Floresta
"Egypt, Texas" - Shadowy Men on a Shadowy Planet
And some generic twangy stuff

http://www.reverbnation.com/thedeadranchhands

http://www.youtube.com/watch?v=jZEW74mHjQk

Last edited: May 06, 2008 07:26:02

wow, that sounds really good. the delay is fine. does all the tricks.

www.myspace.com/captaintwangandhisrhythmcat

wow that sounds freaking cool!!!!!! wish i would have known when i still had mine! oh well!

-Zanti

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