Sansui RA-500 Story...


Reel deep thoughts...
This is a really quick a Sansui RA-500 "Reverberation Amplifier" (its a home hi-fi spring reverb unit from the 70s) from my Dad for free. He's passed off a bunch of stuff for me to help him sell on eBay but I saw this thing in there and thought "hmmmmm..."

I did a quick clean up and hooked it up to have a listen and actually it sounded pretty nice! Switches were glitchey and hence the consistency of the output, but what was coming out sounded nice.

Now the way this thing works is the output is a summation of the wet and dry signals...and the reverb tank takes a mono sum of the stereo input and feeds that to two springs in the tank, so its not a true stereo reverb...but because of the two separate springs the reverb has a nice spread to it, and there is a simple way using the connections on the back to get a 100% wet mono signal out of it. There is also a simple mod that can be done to convert it to 100% wet output only out both L and R outputs. But I'm leaving that alone for now.

This is what it looks like:



It has a wonderfully 70s "display" to show the status of the reverb level...its actually really ineffective of telling you anything at all but it looks fantastic!


And here's a short YouTube video showing how the display is ganged to the reverb "time" (actually level) control with good old fashioned string and pulleys...and you can see that when the reverb "time" is increased the display


And in normal sweetbeats fashion I couldn't leave the damn thing alone.

I cleaned it up fairly well (not as in-depth as maybe other projects), serviced the pots and switches, and upon looking at the smallish PCB inside and finding that I had the parts on-hand, I recapped it and replaced the power regulator transistor. The one that was in there was non-original, looked like it was about to fall off, and looked like a makeshift heatsink had been tacked on it...rrrrrreally janky. So I put a more robust part in place with a more proper heatsink though it probably isn't necessary. I put all good quality caps in place and increased the filter capacitance.

Here are some shots of the works:




The neat thing is its 100% discrete.

And how does it sound? Like I said it sounds nice. Both the wet and dry signals sound nice going through this thing. The reverb is conservative, though starts to get a *little* poinkey at maximum level on program peaks...but backed off a little at has a really nice ambiance especially for only pseudo-stereo. Here is a sound sample were I'm randomly changing the reverb level from all the way off to all the way on throughout the song as well as backing it off to that more conservative level at times before all the way off. The song is "Inside Outside" by UK band "Delirious?".

Sansui RA-500 Test

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These old home stereo reverbs from the 70's are pretty fun to play with. I had an old pioneer for a while, borrowed from my friend actually, it was very poinky, and was fun to use as an odd effect once in a while, probably wasn't working right honestly. This one sounds like it's a little more usable. That's awesome you couldn't leave it alone, and had to swap out some of the electronics. Looks great!
Nice looking unit there, Cory! :)

Shame they didn't make it to a more standard component size to stack up with other gear.

Seen those sold locally for as low as $50. But I'm sure guitar9, (flowerpot guy) would ask $600 for it! :D

Cheers! :)
Likely I'll use it as a sexond analog reverb send...either in mono (connected according to instructions for how to get mono 100% wet signal at the output), or do the simple mod to achieve the pseudo stereo reverb 100% at the output. If I do this I'll likely bypass the controls on the front to eliminate signal going through all the wiring and mechanical switch contacts...I'd make it easy to revert to stock. If I did this then it would be a straight-up simple spring reverb tank with discrete input buffer and output drive amps.
At first glance, I thought this was a new discussion, then I noticed- 2014, so I dont know if 'sweetbeats' is using it anymore, perhaps he can post an update on that.

I am the Admin of the 'Sansui Lounge' facebook group, where we discuss all things Sansui-related, mainly the 1970's era classic amps (AU-717, etc) or receivers (G series, 9090db etc..)

I actually have an RA-500 that I acquired for dirt cheap many years ago, though I never really had a chance to try it. Sansui made several of them after the RA-500, the later ones are all-black and can be rack mounted. They can be found online (Ebay), prices may be higher than they used to, though I really dont see the need to have to spend very much on one.

Sansui or other hi fi manufacturers intended them to basically just add extra reverb to whatever music someone was listening to, and enjoy the somewhat pyschedelic light display.

But based on sweetbeat's comments, I suppose there is no law that says it cant be tried with pro audio equipment as an effect for recording, just to see how it might sound.

In my case, I have a 1979 Roland Cube 40 amp and I notice its reverb seems weak- I tried to check the spring inside, though did not spot anything wrong that I could see, so I just left it at that and bought an external reverb pedal.

I also have a 1968 Fender Vibro Champ amp (all tube)- this model does not come with reverb at all (though it has a nice Vibrato control), so again- can simply use an external reverb pedal, but if sweetbeats thinks the vintage RA-500 is noteworthy, perhaps I should get mine out and see how it sounds- either with my guitar amps, or thru a mixer as a recording effect.
Well that was going to be my next statement, but I wanted to know what was going on that they were looking for a new one. The foam buffers can degrade and dampen the springs, or maybe a loose wire…like, it’s probably something that can be fixed.
What’s going on that you need a replacement spring assembly…?
Hi an thanks for your prompt reply, yes al the tank because, I have a slightly relaxed spring which gives an imbalance between Left and Right, do you have photo about the foam buffers inside your tank ?
I sold mine a decade ago. Can you post a pic of yours so we can see what you’re talking about?

If ultimately you need a replacement, I think @BeatleFred has the right idea, you’ll likely need to purchase another complete device.
I can’t tell from the pics what’s “slightly relaxed.” It’s not the tension of the spring that affects the sound, it’s the size and type of spring wire as well as the coil size and number of coils. How do you know this “slightly relaxed” spring is the cause of your imbalance? How did you measure the imbalance?
Ritchie, unless you enjoy trying to fix things, which is fine- nothing wrong with that..., but as I said, there is no place that sells individual Sansui parts, especially from 50 years ago. If you are in Europe- check Ebay Germany, RA-500's should not be too expensive, you can just get another one that already still works, or use the spring reverb from it, though I dont see what sense it makes to take an already-good one and remove a part to fix the one you have.

Or you can check Ebay here in the US- they are not large heavy items, so packing/shipping abroad should not be too complicated/expensive.

The other option is to check online places that sell replacement springs for guitar amps, though I dont know if those type of springs would fit and work inside the RA-500 in the same way. I have a spring reverb in my vintage 1979 Roland Cube 40 amp, and the reverb seems very weak, being I am just not very handy, and I did not spot anything I could see that was wrong, I simply just bought an inexpensive reverb pedal instead to use with the amp.

The Cube 40 happens to be a small size amp, so who knows... maybe it could fit inside an RA-500... or some other brand/model small amp.
Here is a website, maybe you can contact him and see if he might know about Sansui Reverb tanks:

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