Spring Reverb

by gaussmarkov

Spring Reverb Layout

G. Forrest Cook designed this spring reverb and his online publication is on solorb.com. Chris/stobiepole wanted to do this one and his prototype appears above.

It sounds really clean and natural…almost too good to be a spring reverb. But when you whack the reverb springs – *POW* – you get dub explosions.

| Up to Circuits Topic |
Trackback URL for this post: right-click and copy

30 Responses to “Spring Reverb”

  1. wayne said:

    hi.. interesting project, i was wondering whether u could post more pictures of inside the enclouse.. thanks..

    Posted 06.10.2007 at 1:34 pm

  2. Chris said:

    What sort of pictures do you want? Close-ups of the PCB? Tell me and I’ll see what I can do.

    Posted 06.10.2007 at 8:26 pm

  3. wayne said:

    yeah..close ups of the pcb with the components and how its connected to the reverbtank, thanks

    Posted 07.10.2007 at 9:28 am

  4. Ahren said:

    Do you think this could be easily modified to work as a reverb for vocals?

    Posted 13.11.2007 at 10:16 am

  5. gaussmarkov said:

    Hi Ahren,

    I’m not sure what you are after. You can certainly get your vocal to run through this reverb unit with the right setup.

    Posted 14.11.2007 at 12:04 am

  6. Ahren said:

    I would like to have XLR in and out, so you could go between the mic and PA. I’m just not sure what would have to be done to have the proper impedances. I can post this question at Aron’s forum if you prefer. Awesome site by the way!

    Posted 14.11.2007 at 6:35 pm

  7. gaussmarkov said:

    Thanks Ahren. I would prefer to keep more general discussion on Aron’s forum. It’s such a great resource and it’s better the more that we all participate there.

    Posted 14.11.2007 at 9:06 pm

  8. Will said:

    Hey gaussmarkov. Is there any sound samples of this reverb out there? cuz’ this project is really interesting. Thanks an nice site!

    Posted 28.11.2007 at 5:18 pm

  9. gaussmarkov said:

    hi Will! stobiepole verified the layout and he has not made any clips yet. he’s getting setup for recording stuff and hopefully we’ll get something up someday. but don’t hold your breath. 😉

    Posted 28.11.2007 at 8:43 pm

  10. xenonsky said:

    can you use different reverb tanks? I have a collection of tanks with different sizes of springs and different numbers of springs and I would like to be able to switch between them for different styles? this is a great project, thanks.

    Posted 31.05.2008 at 8:18 am

  11. gaussmarkov said:

    absolutely you can use different tanks! the basic issue is getting input and output impedances that work with the existing component values. 😎

    Posted 31.05.2008 at 2:17 pm

  12. Solderman said:

    Hi Gausmarkow

    Thanks for a splendid site. I really enjoy and have learned much from your “pats” section.
    I just made the “Spring reverb project” and I am very pleased with the result. One of my goals with this project was to cram every ting in to a BIMBOX 4004 (Same as a Hammond 1590B except that it is 40mm deep). It was not that complicated. I used your layout and etched my own PCB. One thing I discovered tough was that I needed (at least one) hole for a PCB fixture. At the top end of the PCB I used double-coated adhesive tape to secure the PCB to the flat backside of the “In” and “drive” pots, but at the other end I needed a hole to fixate the PCB. The layout is tight and quite crowded (good design job I think). To accomplice this I drilled a 4,5 mm hole in the only area I found that was big enough. This was between R28, C1,C15, Rev_Bias Trim. As a result you will cut the trace going from “Input_2” to C1. This I solved by drilling a new hole close to C1 and solder the wire there instead. If you have the time I think it would be nice to have a pad there just in case someone like me shuld have the same idée. Of cause one can always cut the PCB with more space around the traces to fit holes in each corner but in my case I have only 3 mm in length and 2 mm in with to play with to get the PCB to fit within this box together with the rest of the stuff.

    I will send you pictures of my build as soon as my wife gets back from here holiday with our digital camera.


    Posted 30.06.2008 at 10:09 pm

  13. gaussmarkov said:


    wonderful! send your pics and i will make some changes to the board.


    Posted 01.07.2008 at 6:24 pm

  14. matt n said:

    This is just what I have been looking for. My problem with trying this is that I am totally novice with wiring. I have a difficult time just heating up solder for speakers let-alone any of this kind of stuff. I have always wanted to treat the reverb tank as a unit and not impressed with the HoliGrail. I have the reverb tank, is there a possibility of getting the guts? How much would charge?

    Posted 01.08.2008 at 12:57 pm

  15. vhbram said:

    I’ve just built it, with the 8AB2A1B tank and it sounds great, but a bit too subtle I think. Could that be caused by the the tank?

    The decay is good, but I want more reverb than dry signal.

    I don’t know how to set the both drive and input bias so I set them that I have the most reverb and no distortion.

    Is this reverb really that subtle?

    Here is a soundsample at full drive and reverb level:


    Posted 23.09.2008 at 3:57 am

  16. rocklander said:

    is there any further instruction on what to do with biasing etc? I’ve not done any work with a xformer.. is it likely to present difficulties?
    is a particular tank required (possibly differing impedances I guess?)
    thanks in advance for any questions answered

    Posted 04.04.2009 at 12:17 am

  17. marmora said:

    I’ve got an old OC Electronics tank that’s the equivalent of the Accutronics’ 8FB3A1B. Input impedance 1475 and output 2250 ohms. Is is possible to mod this circuit for use with this tank?

    Posted 29.09.2009 at 8:28 pm

  18. george said:

    Hi, Gaussmarkov
    I have built it and now I’m experimenting with the matching transformer. Just checked the 42TM018 and it’s 10K:10K. Isn’t better to use 1K:8R? Like 42TL013 or 42TM013? By the way do you have any idea which is the difference btw TL and TM series? Thanks for your great website!

    Posted 05.12.2009 at 10:59 am

  19. Rangelife said:

    I’ve just built one of these – Set the voltage at the collectors of the two 2N3906 transistors to 6V.

    vhbram & george:
    The transformer in the partlist doesn’t seem to be able to drive the springs har enough. Do what george suggests, use a matching transformer. I used a 42TU013 (as suggested to me by Solderman) and it sounds much much better!

    Posted 01.01.2010 at 1:44 pm

  20. Pawel said:

    Is it possible to do this reverb without CD4011? Is it only for clipping detection, does it clip the sound, what it does?

    Posted 08.07.2010 at 9:14 am

  21. george said:

    Yes you can build it without the 4011. I have built it once without it but my second version is with the clipping leds and it’s pretty cool. Also I used a 4EB3C1B pan without the matching transformer and I have a nice warm reverb.
    Now, I’m dealing with the boominess that this circuit have. Any advice from anyone. With a careful transistor bias it’s better but I need better results.
    Cheers, G

    Posted 19.09.2010 at 5:57 am

  22. Bernard said:

    That´s quite interesting, I am not alone with my built in an alamo reverb unit by OC electronics type 51 reverb tank.
    Unfortunately it is broken and very hardly to find. Do you know what other reverb, f.ex. an Accoutronics will fit on my OC electronics Type 51? My best wishes, Bernard

    Posted 22.05.2011 at 1:11 pm

  23. derDon said:


    I’m just about to build one. Made a few changes, to acommodate my parts bin, and added a three-way Low Cut-Switch by adding 2 different pulldown resistors on the output of the reverb recovery amp with a 3-way spdt. Then I got the 160 Hz when the switch is in the mid position , and two other cutoff points on either side. I’m gonny start with 380 Hz and 560 Hz first (that’s 4.7k and 2.7k, I think). Is there any reason why the input and recovery amps wouldn’t work as npn stages with a 2N3904?
    Also, I have a small power transformer
    lying around that I want to use on this. It measures 1.2 kOhms on the primary and 2 ohms on the secondary. Could this actually work?
    Great circuit, and great site!

    Solder on,


    Posted 04.06.2011 at 6:52 am

  24. Fab said:

    hi! did anyone have any white noise coming from the recovery stage? i cant use this effects at higher volume with an amplifier (for guitar or bass)… im sure that the noise come from the 2n3906 collector, the pin that goes to pot…i tested it with my audio probe, before the transistor i havent find noise!
    is this normal?
    once i picked up an FM station… 🙁

    Posted 13.06.2011 at 8:37 am

  25. Springer said:


    I have a Fender Stage 185 Instrument Amp – fitted with a short Accutronics 8EB2C1B Reverb Tank. Question is would it be safe or will I damage the amp/reverb unit, if I switched in a longer reverb tank, namely an Accutronics 4DB2C1D which I have recently come in to the possession of.

    Thanks for assistance

    Posted 18.07.2011 at 1:12 pm

  26. Jukka said:

    Can you send me Spring Reverb Eagle PCB-files?

    Posted 12.11.2011 at 10:24 am

  27. Jim said:

    Having teething troubles with this build. I’ve posted on DIYStompboxes but nobody’s bitten. I’m just a bit confused about how to wire the tank to the rest of it?

    Posted 20.06.2012 at 3:08 pm

  28. Alex said:

    I seem to be having the same issue as Jim. I am not sure where to hood up the tank to the PCB. Can someone point me in the right direction?

    Posted 18.11.2012 at 7:56 pm

  29. EAT ME said:

    Hi, do you have an Eagle file with PCB, please? I would really like to make it and this would help me a lot and safe me lot of time. Thanks!

    Posted 12.03.2013 at 12:13 pm

  30. EAT ME said:

    Oh, sorry. I have found it! 🙂

    Posted 12.03.2013 at 12:36 pm