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DOD R845 - old spring reverb

5/3/1998 9:51 PM
Daniel R. Haney
DOD R845 - old spring reverb
It's an old rackmount reverb unit. At $20, I thought  
the case would be good to cannibalize, but didn't  
get that far, and repaired it instead. Chips are  
dated 1988, 9" 3 spring reverb tank, RC4558 opamps,  
all chips socketed.  
The DOD R845 reverb has controls for spring  
drive, 4 band equalization and reverb mix, and  
output level. A NE570 compander chip does crude  
noise gating, but it 'breathes', delays the attack  
on notes then makes them interesting  
sound with reverb mix at max with no dry signal. It's nothing a Quadraverb or Intellifex can't do better,  
but still fun, as it gives the guitar a plaintive  
Anybody heard of this one?  
5/5/1998 2:52 PM
Mark Hammer
There was an article in Polyphony, back in 1981 or so called "Why Spring Reverb Will Never Die" (I have the issue, and if I can ever get my damn scanner working again, I'll send you a copy).  
Admittedly, the article was written long before things like the Quadraverb and Intellifex had reached their current zenith (although written in response to the emerging fervour over digital delays), but some of the points remain valid even now.  
The central thesis was that spring reverbs are dynamically sensitive devices (not unlike our fave, the Fuzz Face), and that they acquire different operating parameters every time you use a different input signal. Some may see this a a lack of consistency or quality control. The article's author preferred to see this as a well-spring of counterintuitive and creative possibilities. Personally, I think you found a good deal, rather than a white elephant.  
Is the EQ post-reverb or pre-reverb? Pre-reverb EQ makes for LOTS of interesting possibilities. Over a decade ago I picked up an old solid state Gibson amp that had an annoying reverb sound - too loud, too obvious - I looked at the circuit and found a low-end roll-off cap in the signal path on the way to the reverb tank. I swapped the cap for one half the value (raising the low end roll-off by an octave) and the reverb quality improved dramatically. Taking out the bass brought back the "air".  
The inclusion of a 570 compander also has interesting possibilities. Check a spec sheet for the 570 (or any 570-based project schematic) and you'll see that the attack and decay time constants are set by a single capacitor going to ground. Larger values add more time, smaller values speed things up. You may want to throw on a toggle switch on the front panel and switch between cap values for some interesting ambient sounds. If your current "swell" sound is interesting, imagine it swelling even more slowly. Run it in parallel with your main effects chain, and I suspect you will disappear into your basement, never to be heard from again.  
Surely there are things a Quadraverb can do that your spring unit can't, but I think you'll find the reverse is true also.
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