Danelectro Spring King

[Uma Floresta]

I just picked one up. I've never seen gutshots anywhere, so I thought I'd provide some for the curious:

[cheeb]

I am amazed. Never in my wildest dreams did I expect that thing to have actual springs in there. I always just assumed it was a modeler.

[Uma Floresta]

I am amazed. Never in my wildest dreams did I expect that thing to have actual springs in there. I always just assumed it was a modeler.

Yeah, the springs aren't just for show. It seems to be a hybrid of a short, slapback delay with some feedback and spring reverb. I think the slapback makes up for the fact that the springs are fairly short. The volume control acts as a mix between the delay and the spring reverb - or actually, controls the amount of signal being sent through the springs. It actually sounds pretty believable. Pretty clever, I think.

Some clips from around the web:

http://www.inrerocknroll.com/tunes/Rbilly.mp3

http://www.megaupload.com/?d=77QQCOSF

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

http://www.youtube.com/watch?v=iBJpR_ASl1A

[mojotron]

Interesting - any close ups of the circuit board?

[Uma Floresta]

A little closer

[jayp5150]

I was told once that this was a digital verb and the springs were there for the kick pad feature... never looked into it any further. Uma's description of the function is way more appealing to me.

I actually forgot about these, I might have to hunt for one come birthday time lol.

[Uma Floresta]

Some closer shots of the PCB:

As you can see, this uses a PT2399S delay chip:





According to the datasheet, the 3.6k resistor at pin six should be setting the fixed delay time, yes?

The feedback on this delay chip is set fairly high - I'd like to be able to control this value.  Any thoughts as where a fixed feedback control might likely be found so I can make it into an external control? I've looked at several delay schematics, and it seems that often the feedback control is located somewhere in the circuit that will connect back to pins 14 and 16. Should I be looking for a single resistor that connects the two at some point?

As far as I can tell, Volume controls the strength of signal fed through the springs, Tone is tone of course, and Reverb controls the mix of dry to reverberated signal.

Datasheet info:

[Uma Floresta]

There are also four other chips, including two TL0723s. I assume they have to do with driving the signal into the springs, and then a recovery stage after the springs:

[Mick Bailey]

Incredible! I turned one down and bought something else because I thought it would be just another digital pedal in a bloated enclosure. What a revelation.

I'm now driven towards making a reverb/delay using a short springline and a Rebote delay in the same box. Excellent.

Dude, where's my spring? Where's my spring, dude?

[Uma Floresta]

Incredible! I turned one down and bought something else because I thought it would be just another digital pedal in a bloated enclosure. What a revelation.

I'm now driven towards making a reverb/delay using a short springline and a Rebote delay in the same box. Excellent.

Dude, where's my spring? Where's my spring, dude?

Yes, it's pretty cleverly designed, I'd say.

[earthtonesaudio]

The feedback on this delay chip is set fairly high - I'd like to be able to control this value.  Any thoughts as where a fixed feedback control might likely be found so I can make it into an external control? I've looked at several delay schematics, and it seems that often the feedback control is located somewhere in the circuit that will connect back to pins 14 and 16. Should I be looking for a single resistor that connects the two at some point?

You're on the right track.  With my Fab Echo, I just poked around inside, shorting things out until I found a suitable place to put a jumper... I wanted more feedback, but you could do the same thing for less feedback by finding the appropriate resistor using the jumper method.  Just jumper the likely resistors and note when the feedback goes up to 100%, that's probably the feedback resistor.  You can then replace it with a pot.

Another resource for you, it's likely this pedal uses the same sort of delay circuit:
http://www.diystompboxes.com/smfforum/index.php?topic=64519.0

Look for a schematic of the Fab Echo, because the "Repeats" control is probably in the exact same spot as the fixed feedback resistor in the Spring King.  Have fun with the surface mount stuff.

[Uma Floresta]

The feedback on this delay chip is set fairly high - I'd like to be able to control this value.  Any thoughts as where a fixed feedback control might likely be found so I can make it into an external control? I've looked at several delay schematics, and it seems that often the feedback control is located somewhere in the circuit that will connect back to pins 14 and 16. Should I be looking for a single resistor that connects the two at some point?

You're on the right track.  With my Fab Echo, I just poked around inside, shorting things out until I found a suitable place to put a jumper... I wanted more feedback, but you could do the same thing for less feedback by finding the appropriate resistor using the jumper method.  Just jumper the likely resistors and note when the feedback goes up to 100%, that's probably the feedback resistor.  You can then replace it with a pot.

Another resource for you, it's likely this pedal uses the same sort of delay circuit:
http://www.diystompboxes.com/smfforum/index.php?topic=64519.0

Look for a schematic of the Fab Echo, because the "Repeats" control is probably in the exact same spot as the fixed feedback resistor in the Spring King.  Have fun with the surface mount stuff.

Good idea! Thanks for the tips!

[George Giblet]

Thanks Uma.   Didn't expect digital + a spring.

What I think they have done is use a small spring to get the character of the spring then wrapped a longer delay around it to make it bigger (more or less).

[paperhouse]

if you're gonna add a feedback control why not add a delay time control too 

[gez]

Anyone ever put springs in the feedback loop of a short delay?

[Uma Floresta]

The feedback on this delay chip is set fairly high - I'd like to be able to control this value.  Any thoughts as where a fixed feedback control might likely be found so I can make it into an external control? I've looked at several delay schematics, and it seems that often the feedback control is located somewhere in the circuit that will connect back to pins 14 and 16. Should I be looking for a single resistor that connects the two at some point?

You're on the right track.  With my Fab Echo, I just poked around inside, shorting things out until I found a suitable place to put a jumper... I wanted more feedback, but you could do the same thing for less feedback by finding the appropriate resistor using the jumper method.  Just jumper the likely resistors and note when the feedback goes up to 100%, that's probably the feedback resistor.  You can then replace it with a pot.

Another resource for you, it's likely this pedal uses the same sort of delay circuit:
http://www.diystompboxes.com/smfforum/index.php?topic=64519.0

Look for a schematic of the Fab Echo, because the "Repeats" control is probably in the exact same spot as the fixed feedback resistor in the Spring King.  Have fun with the surface mount stuff.

Your method worked like a charm. I just poked around in there with a U-shaped wire shorting out various resistors until I found the right one. I completed the mod this morning. Now I can use it 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 surf drippy 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.

[Uma Floresta]

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.

[earthtonesaudio]

Good job with the mods, and thanks for the pics.  Sounds like you have a pretty versatile pedal now!

[Mick Bailey]

You get a fair bit for your money with this when you add up the cost of the components, springline, enclosure and hardware for a DIY build. I know that's not what it's about - just making the point of what good value this pedal is comparatively. Given the depreciation of Danelectro stuff they'd be a bargain used buy.

[petemoore]

  I'm impressed with the design.
  Has cool features including kick plate, is compact and sounds good...
  But I find it's making sense that the short portion after when is handled with springs...by that I mean the complex algorythms and thickness of springs...well you've got to have springs or a fairly whopping amount of re-echoeing by some other means to get that.
  Then to get the longer delays [similar but not really like a longer spring], the echo. That means all the complex and short lived algorythms get simply repeated [as opposed to one real long super complex batch of reverb re-echoes or whatever...
  I guess the point ITTMake here is long springs can get muddy and ill-defined, short springs can't get the longer dwells...take the sorta still defined complex short spring and simply echo that [instead of adding algorythms to sum to a point too complex..muddy].
  One question...is there any delay between the source and the reverb springs?..that might be neat and get a cleaner tone at attack...a slight moment of clean before springtone.
  BTW my reverb [accutronics-long 2 spring] was working, longspring tank is kind of doesn't belong unless in a cabinet, and 1 big cabinet for a tanks seems to much, really belongs in an amp...still thinking it could go on the floor because it's not much wider than my current pedalboard...that's wide...hard to hide that long tank and associated wiring/circuit.