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Flint Reverb Summary Paper – Three Classic Reverb Types

Flint Tremolo & ReverbThe magical combination of tremolo and reverb is the earliest example of a perfect guitar effects marriage. Our new Flint Tremolo & Reverb pedal delivers three classic tremolo circuits, along with three completely unique and complimentary reverb types.

You get the classic ’60s Spring Tank Reverb, the inventive ’70s Electronic Plate Reverb, and the nostalgic ’80s Hall Rack Reverb. Pete Celi, our Lead DSP Engineer and Sound Designer illustrates the research and sound design process that went into creating our reverbs in Flint.


Flint Reverb Summary Paper – Three Classic Reverb Types

The ’60s Combo Amp Spring Tank

The full-size 2-spring tank was commonly used in vintage amps, and it continues its popularity today for its classic tones. The 2-spring tank uses spring segments of differing delay times (a function of the mass and tension of the spring), which adds to the complexity of the sound and smooths out the time and frequency response of the reverb. Contributing greatly to the sound are the input (driving) and output (recovery) tube circuits. These circuits are designed to reduce low-end boominess and to minimize coupling of the low- frequency cabinet resonance into the tank. The high frequencies roll off naturally due to the limits of the spring’s ability to transmit the shorter wavelengths of the higher frequencies.



The signal from the driving circuit drives a coil which in turn produces a fluctuating magnetic field that moves a magnet attached to the spring. This results in a twisting wave that travels down the spring. The time it takes for the wave to travel down the spring is a function of frequency, with lower frequency waves traveling down the spring more quickly than higher frequencies. This accounts for the ‘drippy’ or ‘boingy’ sound that the reverb produces when given a percussive attack. At the other end of the spring, the signal is recovered by the inverse process which includes coils, magnets, and a recovery circuit. In addition to being recovered, the wave will continue to reflect back and forth along the spring, creating a wash of reverberation that evolves in time due to the frequency-dependent delay times of the spring. The length of time that the reverb lasts when given an impulsive input is known as the ‘decay time’, which is controlled by physical dampers that absorb energy from the spring.

At low mix levels, the 2-spring tank adds a depth and dimension to the sound. Generally speaking, the 2-spring combo-amp reverbs tend to sound a bit less splashy and trashy than their 3-spring stand-alone counterparts at the extremes, but add a full, integrated explosion of sound when cranked up.

The ’70s Electronic Reverb

During the 1970s, digital electronic systems advanced to the point where high-quality real-time electronic reverberation was possible. A single memory chip was capable of storing 1024 bits, and the possibilities seemed endless. The most famous early electronic reverb was a $20,000 plate-style reverb that used eighty(!) of these memory chips. The amazing hardware-based algorithm used multiple delay- lines configured in parallel, with each delay featuring multiple output taps and filtered feedback paths.



The lengths of the delay lines and individual taps were derived mathematically to produce the most natural reverberation. The reverb algorithm also employed modulation by mixing various taps under internal control to create changes in reflection phases to further reduce undesirable resonances and add depth. The result is a rich, smooth reverb with a quick build-up in density due to the summation of the many parallel output taps.

The ’80s Hall Studio Rack Reverb

By the late ’80s, continued advances in digital ICs and microprocessors lead to (relatively) low-cost digital reverbs that could run many different reverb algorithms and allowed for preset storage and deep parameter editing. Cost sensitivity and the limited available processing power of the day led to the necessary invention of efficient algorithms with minimized computational and memory requirements. To create a Hall-style reverb, a well-practiced technique was to create an early reflections section that fed into a late reverb generator.



A simple multi-tapped delay line was sufficient to create early reflections. The late reverberation was accomplished by a regenerating ‘series-loop’ of delays, all-pass filters, and low-pass filters. Inputs could be injected into the loop in more than one place, and the outputs might consist of the summation of several points from the loop. Delay-line modulation was employed to reduce artifacts and achieve a smoother, more pleasing decay. These hall reverbs have a signature sound of distinctive early reflections followed by the slowly-building density of the late reverberation. The modulation adds an increased sense of warmth and depth.

Enter the World of Flint

The three reverb types in Flint pay homage to these three classic reverb sounds. While not focusing on any specific recreation, these classics served as philosophical and sonic guides in the creation of our ’60s, ’70s and ’80s reverb types.

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33 Responses

    1. @Tyler – thanks for the note! Flint does not include a shimmer effect— if you’re looking for that your best bet would be blueSky. 🙂

  1. Tyler, not to be lame or anything but you really didn’t read the description, did you?

    The ‘shimmer’ effect is the opposite of 60’s, 70’s and 80’s reverb. It dates back to mid-2000’s U2, and would never be included in a ‘classic amp tremolo & reverb’ pedal.

    Not sure why I feel the need to correct you though…?

  2. @Mikey D – thanks for the feedback. There are a lot of directions that we could go in, but phaser wasn’t our direction this time. 🙂

  3. When will we be getting high res pictures and sound clips??
    Will you test it out with both a strat and a tele?? Cheers!

  4. Hi, is it possible to put this or the timeline in place of the reverb tank feed of a vintage deluxe reverb? There are many types of reverb sounds coming from the old Gibbs reverb tanks and then Gibbs went out of business and then Accutronics started making these reverb tanks butthey sounded cheap compared to the Gibbs. So just a hint players cannot find a really nice reverb tank replacement for all of the older amps.

  5. Love this. I like the vintage meets new features thing. Love the sound clips, and thorough explanation of what u were going after..

    1. Thanks @Lego! There are a lot of very interesting sounds you can create by pairing early tremolo circuits with later reverbs! 🙂

  6. I’m curious why more pedal makers aren’t getting privy to the idea of midi controls to change the patches and parameters ala Eventide and G-Lab (Cost?). I want all of my sounds at my feet changing dynamically depending on the song and I don’t want to be shoegazing or having to remember to change pedal settings between songs. Right now the only companies expressing interest in making my life easier are the two previously mentioned. Your pedals sound great but I want to utilize their potential to the fullest and with ease (midi). Unfortunately the old paradigm of using a pedal for one sound is getting old and too expensive. I’m only buying cheap and small pedals for the one sound they do best and when I spend big money I want them to change with midi. This also means I’m stuck using those two pedal makers whose pedals aren’t always the sound I want.

    Please make midi switched pedals!!!

    Nice recordings of the Flint but the proof is in the playing.

    1. @Justin – thanks for the feedback. The philosophy behind Flint is to capture the essence and vibe of the classic combination of tremolo and reverb, so a complete MIDI integration may have been at odds with that goal. There are looper/switcher setups that you could try for non-MIDI pedals. We do understand that some like to control their rig via MIDI, that’s one of the reasons behind the MIDI implementation in our TimeLine delay. There are always possibilities of other MIDI-enabled products from us in the future. 🙂

    1. Thanks J.J.! Our good friend Dan Cohen played that clip, it’s from a song he actually wrote about his grandma! 🙂

  7. Hey guys: you convinced me me buy a Lex rotary (I love it), a Timeline(I love it too) and now you’re coming with a vintage reverb and tremolo? My wife does not love you guys!!! She hate you all!!! If I die for some reason (wife’s reaction during my night sleep), you will be the responsible!!!!kakakakakakakakakakaka!

  8. @Luis – if you’re using just the Reverb, your dry path is analog. When the Tremolo is engaged, the entire signal is effected by the Tremolo, so there is no dry path in that case.

    When using the selectable Analog Buffered Bypass, you can have reverb trails that continue after bypassing the pedal. 🙂

  9. I can finally get rid of my RV-5. only problem is I run a stereo setup from my timeline, I cant plug my timeline into this because it does not have stereo inputs

    1. Hi Justin— Flint has a stereo input. To run in stereo, all you need to do is flip a jumper inside your pedal, and use a TRS splitter cable. So no problem running your TimeLine into Flint. Thanks! 🙂

  10. Ethan- since I consider you guys super in tune with product features, I’m sure you guys are way ahead of me, but- have you considered the stereo trs feature for your other 1 in/ 2 out pedals, and is that a possible mod for older pedals?
    Thank you, Sean
    PS- you guys are making me want to play more, which is what it’s all about!

  11. Just got one on the basis I the demos and feature set alone. What a great idea this pedal is! It’s concept pedals taken to a new high. I haven’t heard of strymon before somebody showed me the demo for the flint- it definitely ignited a lot of ideas so i got it.

    Once I’ve recovered I’m getting the el capistan!

    More power to you guys.

  12. BTW, I commented earlier on wanting an ultimate trem/vib pedal, rather than the combo platter that is Flint.

    And the reason for my desire is simple…I’m a studio cat. I own a fully state of the art facility in Burbank, CA ( And in the studio world, we have LOTS of reverb options. I mean, we have everything available to us. But guess what…we have NO trem options other than actual amps (pain to pull out during a mix session), pedals (haven’t found the magic one yet) and plug-ins (boring!). So, we studio cats don’t really need reverb products…but we do need TREM & VIB products!

    Thanks for listening…and if you Strymon guys ever want to pop over for a studio visit, we’d love to have you…I just bought a Timeline for a client and he’s loving it from top to bottom!

  13. A question about placing Flint in the signal chain, to you guys at Strymon, and to others at this forum who have experience with Flint:
    The order of effects in the signal chain is known to have great impact on the final sound. In a vintage guitar amp both tremolo and reverb would be places between the pre-amp stages and the output tubes. A pedal effect like Flint could of course be places in the effects loop of a modern amp, but also between the guitar and the amp input. A tremolo placed between the guitar and input stage of the amp will affect the drive characteristics of the amp in a different way than a tremolo is placed in an effects loop. Traditional wisdom of composing effect chains has been that reverb should be last in the signal chain, i.e. at the end of the effects loop.
    What experiences do you have with placing the Flint in the signal chain, i.e. before the input, in an effects loop, first in the chain, last in the chain, in relation to other effects, etc.?

  14. If I am running an election Calistan at the end of my chain, do you recommend running the Flint in front or after the el Calistan?
    I normally run reverb after delay and tremolo before.

    1. @Mike – Thanks for checking out the blog! 🙂 This would really depend on what your preference is for this since you use the effects in different spots in your signal chain. I use my reverb at the end of the signal chain and since it is unlikely that I use the tremolo and delay at the same time, I would place the Flint after the El Capistan.

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