DIY Spring Reverb Rack?
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- alignin' 24-trk
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DIY Spring Reverb Rack?
So, my next little project will be building a stereo spring reverb rack unit, and it doesn't seem that there are any affordable units, currently in production. I don't know if any folks would be interested, but, if I get a working version going, I'll share the info. My goal is to get the unit together for $300-$400, tanks, rack case, and all. Also, just wondering if folks would be interested in a kit.
turn up the pedal steel.
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- audio school
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I would be interested in a standalone version. But I assume one could change the case.
I don't rack a lot of stuff myself.
Once I was on a recording project and asked the engineer if he had an old school spring reverb box to send the guitar through. The next day, he showed up with a hand built custom spring box that sounded great!
Ever since I have wanted to build my own.
I don't rack a lot of stuff myself.
Once I was on a recording project and asked the engineer if he had an old school spring reverb box to send the guitar through. The next day, he showed up with a hand built custom spring box that sounded great!
Ever since I have wanted to build my own.
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I'm interested, not necessarily in a kit, but just sharing some information about how it was built, circuit design, etc. I've been wanting to build one for a while, although I might just do mono (for the time being at least). I've been reading the Rod Elliot page about the driver and recovery circuits, doesn't seem too tough to put together but I'm curious to hear people's experiences with different circuits.
I'm thinking about doing the thing where each channel has two tanks wired out of phase, which i think cancels some hum and some of the sproing-y sound.
I'm also wondering whether I should put the whole thing in a regular rack case, or have part of it in a box elsewhere so that it doesn't pick up hum from other gear in the rack.
I'm thinking about doing the thing where each channel has two tanks wired out of phase, which i think cancels some hum and some of the sproing-y sound.
I'm also wondering whether I should put the whole thing in a regular rack case, or have part of it in a box elsewhere so that it doesn't pick up hum from other gear in the rack.
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- alignin' 24-trk
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cool
Sounds like some other folks are kicking this idea around, as well! If I get one together(and working), I'll share what I find out.
turn up the pedal steel.
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- tinnitus
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I built custom spring reverbs in the early 1980's. I used Accutronics new 3 spring tanks. I had them custom made with reversed polarity magnets on one of the return coils. That way they were wired in series creating a hum cancelling pickup.
The driver circuit was an opamp with a couple of hefty TIP power transistors in the discrete output drive section. The reverb tank driver coils were also wired one tank out of phase. That cancelled the sproing effect on transients by reducing the level of the fundamental signals. 3 springs added depth 2 spring tanks don't have.
A low noise opamp was used as the reverb recovery preamp. I made a one knob compressor/expander circuit that had no effect 1/2 way. Turned left it kicked in the 1/2 expander shortening the reverb time. Turn it right and the 2/1 compressor kicked in lengthening the reverb time. It did about 1/2 second to 3 seconds reverb time with the medium time reverb tanks.
I use Lexicon and Bricasti now days.
The driver circuit was an opamp with a couple of hefty TIP power transistors in the discrete output drive section. The reverb tank driver coils were also wired one tank out of phase. That cancelled the sproing effect on transients by reducing the level of the fundamental signals. 3 springs added depth 2 spring tanks don't have.
A low noise opamp was used as the reverb recovery preamp. I made a one knob compressor/expander circuit that had no effect 1/2 way. Turned left it kicked in the 1/2 expander shortening the reverb time. Turn it right and the 2/1 compressor kicked in lengthening the reverb time. It did about 1/2 second to 3 seconds reverb time with the medium time reverb tanks.
I use Lexicon and Bricasti now days.
Jim Williams
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I don't know PAIA. They probably used the short springs, Accutronics make a 3 spring version, not so good.
I've also used a current drive design, that seems to smooth out the impedance drive. You place the driver spring coils into the feedback loop of the system instead of driving the outputs through the coils to ground.
There are many variations to this theme, all include one variable that I can't overcome, the non-linear and scattered response of the springs themselves.
Another reason I use Bricasti and Lexicon these days. 35 years ago I had more smarts than money. Now I have more money than smarts.
I've also used a current drive design, that seems to smooth out the impedance drive. You place the driver spring coils into the feedback loop of the system instead of driving the outputs through the coils to ground.
There are many variations to this theme, all include one variable that I can't overcome, the non-linear and scattered response of the springs themselves.
Another reason I use Bricasti and Lexicon these days. 35 years ago I had more smarts than money. Now I have more money than smarts.
Jim Williams
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That is a typical current feedback drive design, probably best with a high current opamp like a LM6172. Those will dump over 100 ma allowing a lower impedance drive coil to be used. They come from 8 to 600 ohms from the factory. 600 ohm versions were popular when designers used the 5532 opamp as a driver as those will run a 600 ohm load, but not below that. The LM6172 will drive 150 ohm loads easily. Use a pair of current driving discrete power transistors and that 8 ohm coil can be used.
The recovery amp design is poor, an inverting opamp design with a 4.7k input resistor and a huge 2.2 meg feedback resistor. Better to use a non-inverting design with a low noise opamp. Something like an Analog Devices AD8599 would be good. Load the input at 50k ohms and set gain through the gain shunt resistor from pin 2 to ground. An el cap will filter out subharmonic noise. The driver amp design is a good example of how the recovery amp should look.
The recovery amp design is poor, an inverting opamp design with a 4.7k input resistor and a huge 2.2 meg feedback resistor. Better to use a non-inverting design with a low noise opamp. Something like an Analog Devices AD8599 would be good. Load the input at 50k ohms and set gain through the gain shunt resistor from pin 2 to ground. An el cap will filter out subharmonic noise. The driver amp design is a good example of how the recovery amp should look.
Jim Williams
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Very cool, I was thinking about using an adsr envelope generator + vca.Jim Williams wrote: A low noise opamp was used as the reverb recovery preamp. I made a one knob compressor/expander circuit that had no effect 1/2 way. Turned left it kicked in the 1/2 expander shortening the reverb time. Turn it right and the 2/1 compressor kicked in lengthening the reverb time. It did about 1/2 second to 3 seconds reverb time with the medium time reverb tanks.
But your approach sounds better. Did you use a 4301? I could imagine the rms+rectifier signal going to the wiper of a pot panning between +cv and -cv for expand/compress, or how did you do it?
Nice weekend all!
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This was 1982 folks. The only part I found back then that worked as a compander chip was the NE570.
I also used that part in 1988 when I designed a PWM subcode audio noise reduction scheme for Hasbro video games. I got about a 90 db s/n from using the 'black bars' between video frames to bury the subcode in.
I also used that part in 1988 when I designed a PWM subcode audio noise reduction scheme for Hasbro video games. I got about a 90 db s/n from using the 'black bars' between video frames to bury the subcode in.
Jim Williams
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I was 9 then.Jim Williams wrote:This was 1982 folks. The only part I found back then that worked as a compander chip was the NE570.
Thanks for the answer though.
I don?t even get what you are talking about, but sounds like I would love the idea!I also used that part in 1988 when I designed a PWM subcode audio noise reduction scheme for Hasbro video games. I got about a 90 db s/n from using the 'black bars' between video frames to bury the subcode in.
What are the likely max specs on reverb tanks? I see there's a bunch of springs with an 8 ohm input impedance, which you'd think would work great on the output of a tiny tube amp, but I'm imagining even a single watt might be more than the input section can handle.
Can't see any dissipation / handling specs for the Accutronics
Can't see any dissipation / handling specs for the Accutronics
The previous statement is from a guy who records his own, and other projects for fun. No money is made.
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