Riptide Real Spring Reverb

[Ripthorn]

Got the pot spacing fixed. Updated rev 1.1 on Github.

[Toy Sun]

Thanks for all the ongoing improvement and help, so appreciated.

Well... did my first SMT soldering on those transistors and the first board done, added the pots and fired it up.

Worked          The         First        Time

Always a good feeling! Then proceeded to jam out on the sound for about an hour, going through all the alligator clips and hum from unboxed. Sounds great and love the level of control. I'm on the long tank, as nobody had the medium. It's a bit long for me, so I'm going to look for a medium. Hmm, maybe put both tanks in a big box and have a tank toggle?!

Best,
J

[Toy Sun]

I wanted to come back to this thread to report on the finished project. It sounds wonderful and I couldn't be more pleased. A stompbox spring reverb has been one of my goals for a long time and thanks to Ripthorn, I've got it. Learned a lot from this one, including my first foray into SMT - so nice to only have 2 transistors to do and not an FV-1 or something.
Here are a few images - I would love to do a sound demo, but I'm not all dialed for recording right now.
I went for a 70's hi-fi vibe, but deviated into a circles theme. The top plate is walnut veneer, knobs are Buchla style. To get this kind of thing, I flip the Hammond box and that gives me the ability to add height for the lighting. I have a laser, which is how this all gets done 
The reverb tank is spring mounted, which seems to help with physical vibration issues. It has been ok so far.
Once again, big thanks to Ripthorn, you are the best!

John

[bluebunny]

Great build, John!  Wood panel, light-plate ... what's not to like?   

[Ripthorn]

Looks amazing! Glad you like the circuit!

[Toy Sun]

Jumping back to/revisiting this thread and this project. My unit has a high-pitched whine that I can't solve with my skill set. I've experimented with different PSUs, isolating various factors, etc.. But no luck. Have not gotten down to working on the component level to solve, would need help with that.

But I'm also thinking of building another one with a bigger spring. We've discussed how some component values in the circuit would have to change to get this to work. Can anyone recommend the changes? Here are some great resources, but TBH, the math and circuit design aspects are a bit beyond me.

Overview on spring reverb: https://www.tubesandmore.com/tech-articles/spring-reverb-tanks-explained-and-compared

The small tank that Riptide is designed for: https://www.tubesandmore.com/products/reverb-tank-accutronics-amc2ef3-long-decay-2-spring
Input Impedance: 600Ω
Output Impedance: 1500Ω

Closest tank that I find on that site, would consider just trying it:
https://www.tubesandmore.com/products/reverb-tank-mod-4eb3c1b-long-decay-2-spring
Input: 600 Ω
Output: 2,250 Ω

Riptide Overview:
https://scientificguitarist.wixsite.com/home/riptide-spring-reverb

Big thanks again to Ripthorn for creating this circuit (and supplying Gerbers - you rock!)

[PRR]

Spring reverb design is not an exact discipline.

Adjust R4 to get plenty of drive without audible clipping or flat dynamics.

[Ripthorn]

I've not had any oscillation issues and neither have the others that I know have made the design, but that doesn't mean that it can't happen. If you want, you could ship the thing to me and I can check it out, free of charge, just cover shipping.

[John Lyons]

My unit has a high-pitched whine.

Perhaps the charge pump IC?
Some types will whine.

[Rob Strand]

Perhaps the charge pump IC?
Some types will whine.

The most likely cause for sure.

To confirm it's the converter you would need to disable the converter and power the unit from +/-9V battery (or trusted bench supply).   When doing this, don't feed power back into the converter output.   You need to completely disconnect both the input and output sides of the converter from the rest of the circuit.

Bad PCB layout can cause the converter to inject noise into the audio signal path.

[Ripthorn]

My unit has a high-pitched whine.

Perhaps the charge pump IC?
Some types will whine.

Ha! I had forgotten that I used dual supply in this pedal, otherwise I would have suggested this  . I've done at least a dozen original designs since this one that I can't even remember all the specifics 

[Toy Sun]

I also came to the conclusion that it must be the charge pump. In fact, I think the charge pump is causing this problem in a couple of other pedals that I've built. The funny thing is that my kids hear it and I don't.
That's a super generous offer to analyze my pedal if I send it in, but I think I'm gonna work on it myself. First step will see if I just got a bad component - these did come from Tayda. I also think I could maybe swap in a Max 1044?

Still want to also try a larger reverb tank so if anybody has any ideas on what component values I need to change for that (see earlier in thread) I'd appreciate it.
Thanks.

[Rob Strand]

Still want to also try a larger reverb tank so if anybody has any ideas on what component values I need to change for that (see earlier in thread) I'd appreciate it.

If the tank input impedance is the same (or close) you can just plug in a different spring.  Doesn't matter about the physical size.   The tank input impedance is main the thing that needs to match the circuit.

[John Lyons]

This tank works well and sounds better than the blue tanks.
https://www.tubesandmore.com/products/reverb-tank-mod-mn-8bb2c1b-medium-decay-3-spring-mini

[PRR]

...my kids hear it and I don't....

And your womenfolk?

Loss of hi-freq hearing with age is standard in males. I dunno if it is related to military service, rock&roll, or testosterone.

[Toy Sun]

Well, my wife is 10 years younger than me, so there's that

Spring tank specifics - thanks for the tip John L. That tank has these values:
Input: 190 Ω
Output: 2,575 Ω

The blue plastic one that Ripthorn designed for is this:
Input Impedance: 600Ω
Output Impedance: 1500Ω

I guess for $18, why not try it?

Thanks,
J

[Rob Strand]

Well, my wife is 10 years younger than me, so there's that

Spring tank specifics - thanks for the tip John L. That tank has these values:
Input: 190 Ω
Output: 2,575 Ω

The blue plastic one that Ripthorn designed for is this:
Input Impedance: 600Ω
Output Impedance: 1500Ω

I guess for $18, why not try it?

Thanks,
J

If you want to keep things working the same with the different input impedance tank there's a couple of tweaks required.

The lower impedance tanks need more drive current to get the same tank output level.   You can see a good example here, which is likely to be taken from the Accutronics reverb datasheet,  table 1,

https://sound-au.com/articles/reverb.htm

A 600 ohm tank driven at 3.1mA rms will produce the same output as a 200 ohm tank driven at 5.8mA rms.   So the 200 ohm tank requires 5.8/3.1 = 1.87 times more drive current.

To increase the drive current on the riptide you need to decrease resistor R4 (150 ohm).  For the 200 ohm tank,

R4_new = R4 /1.87  = 150 / 1.87 = 80 ohm;  so use about 82 ohm.

A follow on effect of changing R4 is C4 (10uF) needs to be increased by the same factor to keep the same LF roll-off,

C4_new = 1.87 * C4 = 1.87 * 10uF  = 18.7uF; so use about 22uF.