7 ms·

Analog Spring Reverb: How it works

71 points by PascLeRasc 7y ago

tobr 7y ago
Wouldn’t it be more useful to describe a spring reverb as ”electro-acoustic” or ”electro-mechanical”, rather than “analog”? I think “analog” is best reserved as contrast with “digital”.
- TheOtherHobbes 7y ago
  Yes, it would. There are some good digital emulations of spring reverbs, but they don't make an apocalyptic SPPPPRRROOOOOOOOOOOIIIIINNNNGGGGGGGG!!!!! sound when you slap their sides.
  - rzzzt 7y ago
    I guess it'd be easy to emulate as well, by including some accelerometers...
    - JoachimS 7y ago
      Cool idea!
  - squeaky-clean 7y ago
    Actually ;P , Dave Smith already does this with the spring reverb on all the DSI flagship synths. There's an accelerometer on the side of the synth you can slap/punch and it responds with that SPROROIIOIING. Here's a video of him showing it on the prophet-6, the OB-6 can do it too. https://www.youtube.com/watch?v=fmhdYJDnfsU&feature=youtu.be&t=557 https://www.youtube.com/watch?v=fmhdYJDnfsU&feature=youtu.be...
- mrob 7y ago
  Is there such a thing as a fully analog reverb that's not electro-acoustic? Bucket-brigade devices are sometimes called "analog", and they were occasionally used for reverb (more commonly for the simpler delay effects they were better suited to), but they're discrete in the time domain so arguably they're partly digital. Maybe you could do reverb with a tape delay with really tiny heads, but I don't know of any such product.
  - squarefoot 7y ago
    "Maybe you could do reverb with a tape delay with really tiny heads, but I don't know of any such product." Lots of heads and carefully tuned feedback (possibly also across different heads adding phase changes) could help in that direction. It would sound interesting, though the resulting contraption would also be big, clunky and expensive.
    - jacobush 7y ago
      ... or really fast tape with normal heads.
    - woofyman 7y ago
      Echoplex tape reverb https://en.m.wikipedia.org/wiki/Echoplex https://en.m.wikipedia.org/wiki/Echoplex
  - NikkiA 7y ago
    Here you go: https://reverb-res.cloudinary.com/image/upload/s--Or_7-p6K--/a_exif,c_limit,f_auto,fl_progressive,g_south,h_620,q_auto:eco,w_620/v1476733441/b3bbbjzasrdsd7ktoimp.jpg https://reverb-res.cloudinary.com/image/upload/s--Or_7-p6K--... Elk Echo Machine v3 (EM-3) from 1970
    - deleted 7y ago
      [deleted]
    - mrob 7y ago
      Echo isn't the same as reverb. Reverb is a simulation of acoustic spaces small enough that you don't hear distinct echoes. You need multiple short delays to simulate the time taken for sound to travel between surfaces of the room, and feedback between them to simulate the reflections. AFAIK all tape delays are too slow to produce reverb sounds.
      - cardiffspaceman 7y ago
        Recording studios have had access to tunnels to create echos. https://www.acontinuouslean.com/2013/12/02/secret-capitol-studios-sound/ https://www.acontinuouslean.com/2013/12/02/secret-capitol-st...
- frabert 7y ago
  Interestingly, analog reverbs and some other kinds of time-delay effects (echo, flanger, chorus) were made using so-called bucket-brigade devices which are indeed analog in the amplitude domain, but not in the time domain, where they are very much digital...
  - pjc5e 7y ago
    I think it would be more correct to say they are discrete in the time domain rather than digital. This is just semantic nitpicking though since digital usually implies discrete time. I never heard about continuous time digital electronics, it might be interesting to think about though it feels like an oxymoron.
    - dspig 7y ago
      Would it be continuous time if not clocked, e.g. switches or 555 timer feeding into logic gates, and levels just switch when they switch. Of course no logic transitions are actually instant...
      - squeaky-clean 7y ago
        The clock is what defines the sampling rate of the delay, so a 555 is just a simpler version of what they already use. The true audio is always moving continuously. When the BBD receives a clock signal, it samples the incoming audio, and to reconstruct that audio as accurately as possible you have to play it back at that same rate it was sampled in. Very similar to how digital (PCM) audio works, except using charged capacitors instead of bits in a digital memory. If you don't clock it at all, you'll just be sending out the constant voltage equal to whatever your first capacitor has charged, which results in no audible sound. You can adjust your clock speed and have it play back at speeds slower or faster than the incoming rate, with the pitch changing too, just like slowing a record or tape machine. The output isn't really discrete though, only the internals, and even then like you say, even logic transitions aren't actually instant (but at a rate so much faster than audio we ignore it). The BBDs use filters on both the input and output that remove the very high-end of the audio range (a lowpass filter). These filters will be made to match or be lower than the current clock rate [0]. One before going into the BBD removes any frequencies too high to be stored accurately (an anti-aliasing filter), and then one after the BBD removes any high frequencies which were created by the near-instant shapes of the capacitors discharging (a reconstruction filter). These means your output audio is "continuous", but also has zero frequency content above your filter cutoff (okay there's a teeny amount of information, nothing in reality is perfect). To create the delay effect you take a long line of them (usually 512-4096) and the length of your delay is equal to the number of "buckets" times your clock rate. If you had a near infinite amount of buckets and ran them so fast there was no loss in fidelity from the sampling rate, you'd basically have a tape delay. The fun thing about BBDs though is that they don't always pass on their charge to the next bucket perfectly. So longer delay lines mean introducing more errors accumulating as your audio passes through the delay line. A near-infinite BBD would turn into audio mush. Though you can still get a very high number of buckets and a very high clock rate for near digital fidelity, but at that point it's getting more expensive than just using a digital effect, and you're ditching the unique charm of a nice effect. Here are some more detailed explanations of a bbd [1] [2] The posts by Richard Crowley in [2] are particularly cool to the HN audience I'd hope. > Curiously enough, BBD were a pre-cursor to EEPROM, DRAM, and FLASH RAM. Microscopic capacitors are used to store the data. In the case of DRAM, the capacitors aren't terribly good, and they must be "reminded" (refreshed) on a regular basis (many times per second). Very similar to BBD. [0] okay technically 1/2 the clock rate because of nyquist-shannon, I just mean it will be linked to the sampling rate. [2] https://www.electrosmash.com/mn3007-bucket-brigade-devices https://www.electrosmash.com/mn3007-bucket-brigade-devices [3] https://www.gearslutz.com/board/geekslutz-forum/897599-how-does-bbd-store-audio.html https://www.gearslutz.com/board/geekslutz-forum/897599-how-d...
- mb_72 7y ago
  Any time 'analog' is used with reference to boutique guitar FX it's because they want to try and convince you to pay more money than other equivalents. Same goes for 'hand-made' etc etc. In a crowded market where 90% of the companies are making more or less the same pedals with the same circuits you need to try and stand out in some way.
- Gravityloss 7y ago
  It is a useful differentiation. There are a lot of digital effects out there. They digitize the input signal, do some calculations and again convert to analog for the output. A lot of reverb units are like that. Some amplifiers have digital reverb builtin.
  - ben7799 7y ago
    Also good to call out the better digital reverb units do this: 1) Split analog signal 2) Pass through one side to output (probably with a signal boost) 3) Take the other side & digitize 4) Apply effect to digital signal 5) Convert output digital signal to analgo 6) Mix into the output of step 2 I find this to be a very audible difference.
  - tobr 7y ago
    But what changes in a digital spring reverb is not that you switch some analog circuitry for digital. Either you simply attach a DAC to the input and an ADC to the output, but that doesn’t really mean that you get rid of analog circuitry. Or more likely, you’re replacing mechanical parts for a software model that achieves a similar sound. What’s interesting in that is not that you go from analog to digital, but from real mechanical equipment to a software simulation.
- squeaky-clean 7y ago
  Digital emulations of a spring reverb are definitely a thing too. https://www.sweetwater.com/store/detail/FRV1--boss-frv-1-63-fender-reverb-pedal https://www.sweetwater.com/store/detail/FRV1--boss-frv-1-63-... https://www.sweetwater.com/store/detail/HolyGrailN--electro-harmonix-holy-grail-nano-reverb-pedal https://www.sweetwater.com/store/detail/HolyGrailN--electro-... https://www.sweetwater.com/store/detail/SpringReverb--softube-spring-reverb-plug-in https://www.sweetwater.com/store/detail/SpringReverb--softub...
- leoc 7y ago
  It's both: the two categories are basically orthogonal. A record player is another electro-mechanical analogue audio device. Although, granted, an electro-mechanical digital effect would certainly be quite impractical. ;D At least if you demand actual audio recording and reproduction rather than a piano-roll system.
exabrial 7y ago
Boutique guitar stompboxes are an interesting market: there's a lot of cork sniffing sane nose thumbing generally, even though two designs may be electrically exact. That being said I really do like their design. The spring reverb in my guitar amp sounds great but does not have tone control and get overly bright with a single coil guitar.
- asmithmd1 7y ago
  Check out the build quality of Bartel Amps. Mark Bartel has been hand making every part of the amps he designed for over 20 years. He is an EE who makes product decisions based on science - not marketing https://www.instagram.com/p/BxpP0IugJqZ/?igshid=1gns8qkaz6ou5 https://www.instagram.com/p/BxpP0IugJqZ/?igshid=1gns8qkaz6ou...
  - JoachimS 7y ago
    That is a work of art. The cable post and how everything is layed out and tightened down looks fantastic. I haven't opened my Orange Tremlord. I expect it to look nice, but not nice like this. The Orange Tremlord has a very nice reverb with a real reverb tank. And is imho a very nice amp: https://www.youtube.com/watch?v=C3mc5oZC_vM https://www.youtube.com/watch?v=C3mc5oZC_vM
    - asmithmd1 7y ago
      I agree the amps are art. Compare the Bartel amp to this https://www.designboom.com/art/leonardo-ulian-technological-mandala-06-29-2017/ https://www.designboom.com/art/leonardo-ulian-technological-... - cool, but they don’t work
  - 52-6F-62 7y ago
    Oh that's just great. So an MSRP of ~ $6375 CAD. They're beautifully done—guess it goes on the bucket list. Here I thought the wiring job on my AC30 was the nicest I'd seen in a long time (http://www.voxshowroom.com/uk/amp/ac30hw2_2010.html http://www.voxshowroom.com/uk/amp/ac30hw2_2010.html - also w/ tremolo and spring reverb tank)
squarefoot 7y ago
And for really big deep FX, use a slinky! https://www.youtube.com/watch?v=oXItDwgf6hM https://www.youtube.com/watch?v=oXItDwgf6hM Not exactly portable, but definitely worth the build.
- disantlor 7y ago
  in a similar vein: https://www.youtube.com/watch?v=CZWAntOnrx4 https://www.youtube.com/watch?v=CZWAntOnrx4

71 points by PascLeRasc 7y ago

tobr 7y ago

Wouldn’t it be more useful to describe a spring reverb as ”electro-acoustic” or ”electro-mechanical”, rather than “analog”? I think “analog” is best reserved as contrast with “digital”.

TheOtherHobbes 7y ago
Yes, it would. There are some good digital emulations of spring reverbs, but they don't make an apocalyptic SPPPPRRROOOOOOOOOOOIIIIINNNNGGGGGGGG!!!!! sound when you slap their sides.
- rzzzt 7y ago
  I guess it'd be easy to emulate as well, by including some accelerometers...
  - JoachimS 7y ago
    Cool idea!
- squeaky-clean 7y ago
  Actually ;P , Dave Smith already does this with the spring reverb on all the DSI flagship synths. There's an accelerometer on the side of the synth you can slap/punch and it responds with that SPROROIIOIING. Here's a video of him showing it on the prophet-6, the OB-6 can do it too. https://www.youtube.com/watch?v=fmhdYJDnfsU&feature=youtu.be&t=557 https://www.youtube.com/watch?v=fmhdYJDnfsU&feature=youtu.be...
mrob 7y ago
Is there such a thing as a fully analog reverb that's not electro-acoustic? Bucket-brigade devices are sometimes called "analog", and they were occasionally used for reverb (more commonly for the simpler delay effects they were better suited to), but they're discrete in the time domain so arguably they're partly digital. Maybe you could do reverb with a tape delay with really tiny heads, but I don't know of any such product.
- squarefoot 7y ago
  "Maybe you could do reverb with a tape delay with really tiny heads, but I don't know of any such product." Lots of heads and carefully tuned feedback (possibly also across different heads adding phase changes) could help in that direction. It would sound interesting, though the resulting contraption would also be big, clunky and expensive.
  - jacobush 7y ago
    ... or really fast tape with normal heads.
  - woofyman 7y ago
    Echoplex tape reverb https://en.m.wikipedia.org/wiki/Echoplex https://en.m.wikipedia.org/wiki/Echoplex
- NikkiA 7y ago
  Here you go: https://reverb-res.cloudinary.com/image/upload/s--Or_7-p6K--/a_exif,c_limit,f_auto,fl_progressive,g_south,h_620,q_auto:eco,w_620/v1476733441/b3bbbjzasrdsd7ktoimp.jpg https://reverb-res.cloudinary.com/image/upload/s--Or_7-p6K--... Elk Echo Machine v3 (EM-3) from 1970
  - deleted 7y ago
    [deleted]
  - mrob 7y ago
    Echo isn't the same as reverb. Reverb is a simulation of acoustic spaces small enough that you don't hear distinct echoes. You need multiple short delays to simulate the time taken for sound to travel between surfaces of the room, and feedback between them to simulate the reflections. AFAIK all tape delays are too slow to produce reverb sounds.
    - cardiffspaceman 7y ago
      Recording studios have had access to tunnels to create echos. https://www.acontinuouslean.com/2013/12/02/secret-capitol-studios-sound/ https://www.acontinuouslean.com/2013/12/02/secret-capitol-st...
frabert 7y ago
Interestingly, analog reverbs and some other kinds of time-delay effects (echo, flanger, chorus) were made using so-called bucket-brigade devices which are indeed analog in the amplitude domain, but not in the time domain, where they are very much digital...
- pjc5e 7y ago
  I think it would be more correct to say they are discrete in the time domain rather than digital. This is just semantic nitpicking though since digital usually implies discrete time. I never heard about continuous time digital electronics, it might be interesting to think about though it feels like an oxymoron.
  - dspig 7y ago
    Would it be continuous time if not clocked, e.g. switches or 555 timer feeding into logic gates, and levels just switch when they switch. Of course no logic transitions are actually instant...
    - squeaky-clean 7y ago
      The clock is what defines the sampling rate of the delay, so a 555 is just a simpler version of what they already use. The true audio is always moving continuously. When the BBD receives a clock signal, it samples the incoming audio, and to reconstruct that audio as accurately as possible you have to play it back at that same rate it was sampled in. Very similar to how digital (PCM) audio works, except using charged capacitors instead of bits in a digital memory. If you don't clock it at all, you'll just be sending out the constant voltage equal to whatever your first capacitor has charged, which results in no audible sound. You can adjust your clock speed and have it play back at speeds slower or faster than the incoming rate, with the pitch changing too, just like slowing a record or tape machine. The output isn't really discrete though, only the internals, and even then like you say, even logic transitions aren't actually instant (but at a rate so much faster than audio we ignore it). The BBDs use filters on both the input and output that remove the very high-end of the audio range (a lowpass filter). These filters will be made to match or be lower than the current clock rate [0]. One before going into the BBD removes any frequencies too high to be stored accurately (an anti-aliasing filter), and then one after the BBD removes any high frequencies which were created by the near-instant shapes of the capacitors discharging (a reconstruction filter). These means your output audio is "continuous", but also has zero frequency content above your filter cutoff (okay there's a teeny amount of information, nothing in reality is perfect). To create the delay effect you take a long line of them (usually 512-4096) and the length of your delay is equal to the number of "buckets" times your clock rate. If you had a near infinite amount of buckets and ran them so fast there was no loss in fidelity from the sampling rate, you'd basically have a tape delay. The fun thing about BBDs though is that they don't always pass on their charge to the next bucket perfectly. So longer delay lines mean introducing more errors accumulating as your audio passes through the delay line. A near-infinite BBD would turn into audio mush. Though you can still get a very high number of buckets and a very high clock rate for near digital fidelity, but at that point it's getting more expensive than just using a digital effect, and you're ditching the unique charm of a nice effect. Here are some more detailed explanations of a bbd [1] [2] The posts by Richard Crowley in [2] are particularly cool to the HN audience I'd hope. > Curiously enough, BBD were a pre-cursor to EEPROM, DRAM, and FLASH RAM. Microscopic capacitors are used to store the data. In the case of DRAM, the capacitors aren't terribly good, and they must be "reminded" (refreshed) on a regular basis (many times per second). Very similar to BBD. [0] okay technically 1/2 the clock rate because of nyquist-shannon, I just mean it will be linked to the sampling rate. [2] https://www.electrosmash.com/mn3007-bucket-brigade-devices https://www.electrosmash.com/mn3007-bucket-brigade-devices [3] https://www.gearslutz.com/board/geekslutz-forum/897599-how-does-bbd-store-audio.html https://www.gearslutz.com/board/geekslutz-forum/897599-how-d...
mb_72 7y ago
Any time 'analog' is used with reference to boutique guitar FX it's because they want to try and convince you to pay more money than other equivalents. Same goes for 'hand-made' etc etc. In a crowded market where 90% of the companies are making more or less the same pedals with the same circuits you need to try and stand out in some way.
Gravityloss 7y ago
It is a useful differentiation. There are a lot of digital effects out there. They digitize the input signal, do some calculations and again convert to analog for the output. A lot of reverb units are like that. Some amplifiers have digital reverb builtin.
- ben7799 7y ago
  Also good to call out the better digital reverb units do this: 1) Split analog signal 2) Pass through one side to output (probably with a signal boost) 3) Take the other side & digitize 4) Apply effect to digital signal 5) Convert output digital signal to analgo 6) Mix into the output of step 2 I find this to be a very audible difference.
- tobr 7y ago
  But what changes in a digital spring reverb is not that you switch some analog circuitry for digital. Either you simply attach a DAC to the input and an ADC to the output, but that doesn’t really mean that you get rid of analog circuitry. Or more likely, you’re replacing mechanical parts for a software model that achieves a similar sound. What’s interesting in that is not that you go from analog to digital, but from real mechanical equipment to a software simulation.
squeaky-clean 7y ago
Digital emulations of a spring reverb are definitely a thing too. https://www.sweetwater.com/store/detail/FRV1--boss-frv-1-63-fender-reverb-pedal https://www.sweetwater.com/store/detail/FRV1--boss-frv-1-63-... https://www.sweetwater.com/store/detail/HolyGrailN--electro-harmonix-holy-grail-nano-reverb-pedal https://www.sweetwater.com/store/detail/HolyGrailN--electro-... https://www.sweetwater.com/store/detail/SpringReverb--softube-spring-reverb-plug-in https://www.sweetwater.com/store/detail/SpringReverb--softub...
leoc 7y ago
It's both: the two categories are basically orthogonal. A record player is another electro-mechanical analogue audio device. Although, granted, an electro-mechanical digital effect would certainly be quite impractical. ;D At least if you demand actual audio recording and reproduction rather than a piano-roll system.

exabrial 7y ago

Boutique guitar stompboxes are an interesting market: there's a lot of cork sniffing sane nose thumbing generally, even though two designs may be electrically exact. That being said I really do like their design. The spring reverb in my guitar amp sounds great but does not have tone control and get overly bright with a single coil guitar.

asmithmd1 7y ago
Check out the build quality of Bartel Amps. Mark Bartel has been hand making every part of the amps he designed for over 20 years. He is an EE who makes product decisions based on science - not marketing https://www.instagram.com/p/BxpP0IugJqZ/?igshid=1gns8qkaz6ou5 https://www.instagram.com/p/BxpP0IugJqZ/?igshid=1gns8qkaz6ou...
- JoachimS 7y ago
  That is a work of art. The cable post and how everything is layed out and tightened down looks fantastic. I haven't opened my Orange Tremlord. I expect it to look nice, but not nice like this. The Orange Tremlord has a very nice reverb with a real reverb tank. And is imho a very nice amp: https://www.youtube.com/watch?v=C3mc5oZC_vM https://www.youtube.com/watch?v=C3mc5oZC_vM
  - asmithmd1 7y ago
    I agree the amps are art. Compare the Bartel amp to this https://www.designboom.com/art/leonardo-ulian-technological-mandala-06-29-2017/ https://www.designboom.com/art/leonardo-ulian-technological-... - cool, but they don’t work
- 52-6F-62 7y ago
  Oh that's just great. So an MSRP of ~ $6375 CAD. They're beautifully done—guess it goes on the bucket list. Here I thought the wiring job on my AC30 was the nicest I'd seen in a long time (http://www.voxshowroom.com/uk/amp/ac30hw2_2010.html http://www.voxshowroom.com/uk/amp/ac30hw2_2010.html - also w/ tremolo and spring reverb tank)

squarefoot 7y ago

And for really big deep FX, use a slinky! https://www.youtube.com/watch?v=oXItDwgf6hM https://www.youtube.com/watch?v=oXItDwgf6hM Not exactly portable, but definitely worth the build.

disantlor 7y ago
in a similar vein: https://www.youtube.com/watch?v=CZWAntOnrx4 https://www.youtube.com/watch?v=CZWAntOnrx4