Tascam RS-20B Story...

[sweetbeats]

It actually is little more than an anecdote or vignette (not the monster-length threads like the 58, M-520 or M-___ threads), but I thought I'd put this up anyway.

I've had my RS-20B dual-spring 'verb box for a couple years now. Recapped it a couple nights ago. I had originally been thinking about upgrading opamps...they're all 4558's which of course were decent stuff back in the day but now would be dwarfed spec-wise by "modern" offerings. Thankfully Dr. ZEE talked, or rather suggested me out of the idea. So I left the stock opamps in there and just swapped out all the electrolytic caps.

Ever see the inside of one? I have pictures. You don't care about seeing the inside of one? Oh well. Too bad.

The RS-20B is a neat spring reverb unit. There are actually two springs for each of the two channels, so 4 springs in all. There are control surface switches to route and mix the input signal as either stereo or dual mono as well as cross-mix it (R to L and L to R...different sound). Each channel has a 200Hz HPF, input and output level trims and a built in peak limiter. It also sports I/O jacks on 1/4" and RCA connectors and the output is switcheable between -10dBV or +4dBu

Here it is racked (above the patchbay):

Here it is all exposed and whatnot prior to the recap...the upper and lower PCB's are identical except that the upper one includes the PSU:

Here's a closer shot of the springs:

I had to be careful with the recap and take notes because you can't get a service manual for this thing. I tried. Jimmy at Tascam hunted...they have a file but their original copy is gone.

 

[jedblue]

They sure have a sound all of their own those stand alone spring reverbs. I have an old Boss RX-100 which is similar in concept. I was using it just last night looking for the perfect short analog delay / reverb on the vocal track of an all analog album I've just recorded for a friend. With the spring on one aux send handling reverb, the Nagra IV full track on another aux send for tape delay (one repeat only running at 7 1/2 ips), source vocal panned to centre, reverb return left at 9 o'clock and echo return right at 3 o'clock, I got exactly what I was looking for...

Elvis lives and is being mixed in my attic at this moment .

Geoff

 

[sweetbeats]

Geoff! I used to have a Boss RX-100! I actually sold it to help fund the pruchase of the RS-20B. I tell ya...that RX-100 has a surprisingly lush sound. I always really liked how it sounded.

 

[jedblue]

Hah Cory, good story, the analog world of homerecording.com seems to be a tightly knit matrix connected by one or two degrees of equipment seperation....

 

[A Reel Person]

That's totally awesome! Thank you!

I have the "std" RS-20, so I guess it's the springs with circuit cards and nothing else,... no knobs or switches. Never seen inside it, though.

 

[sweetbeats]

Dave,

Yeah, I've often wondered how different the two are inside.

Neat thing about the standard RS-20 is that its bound to be cleaner in and out signal-wise. The 'B' version is neat-o but every bell and whistle adds noise and distortion. It is solidly built as is all the Tascam rack gear from this era so I'd say the standard non-'B' version is as desirable a find as the 'B' version.

Geoff, Yeah. Its good to be able to find a place where others actually know about the wierd stuff sitting in your basement.

I still have the Roland DC-30 which is an analog echo/chorus box. It has the same knobs as the RX-100 so it was made around the same time. I'm going to recap it at some point but it also is a neat sounding box. Great low fidelity analog echo that'll feedback to distortion or decay smoothly with all the artifacts you'd want. Not a Space Echo, but good for vintage slapback or dub.

 

[RRuskin]

I've had my RS-20B dual-spring 'verb box for a couple years now. Recapped it a couple nights ago. I had originally been thinking about upgrading opamps...they're all 4558's which of course were decent stuff back in the day but now would be dwarfed spec-wise by "modern" offerings. Thankfully Dr. ZEE talked, or rather suggested me out of the idea. So I left the stock opamps in there and just swapped out all the electrolytic caps

.

Good move on not upgrading the 4558's. In this particular instance, to my mind, having a slower chip is an advantage. It helps keep the "twang" of a short spring out a bit better.

 

[sweetbeats]

Riiiiighhhht...yes. That makes sense. Dr. ZEE didn't cite that specifically, but his argument would include that point.

One of the most important things I've picked up in the past several months with regard to opamp upgrades is that a particular opamp works in concert with an entire circuit path...there are other things effected by a different chip. One may function the same way logically, but I don't think it is safe to always assume that its going to be a gauranteed improvement or never be a disaster. The RS-20B being what it is (a noisy audio slurry-maker) doesn't seem to lend itself to some fast opamp with low noise and distortion specs. How are you going to even hear that change through the spring artifacts?? I'm laughing at myself now for even considering it! So Dr. ZEE got my thoughts churning and you just put an extra nail in it.

 

[sweetbeats]

Now that you're all drooling and want an RS-20B, I came across this on eBay today:

http://cgi.ebay.com/TASCAM-DUAL-REVERB-REVERBERATION-RS-20B-RS-20B-SYSTEM_W0QQitemZ250447585520QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item3a4fd6e0f0&_trksid=p3286.c0.m14&_trkparms=65%3A10%7C66%3A2%7C39%3A1%7C240%3A1318%7C301%3A0%7C293%3A2%7C294%3A50

Its the first time I've seen one in over a year. No affiliation and I can't vouch for the condition, but it caught my eye just because I have one and I think its super neat-o.

Too bad about the rust......but it might be inconsequential to the condition of the interior so...

 

[Dr ZEE]

Sweet!
First of all , thanks for posting inside photos.
That is a nice unit.

... How are you going to even hear that change through the spring artifacts?? ....

Yeah

I would describe Springs as one of a kind non-hi-fi electro-mechanical devices that live by their own "laws of nature"
From my miserable experience of experimenting with springs' circuits and observing their behavior I've come to some set of unscientific conclusions about them...well, sort of
All sprigs are diffrent and "unique" and non of them are "universal" in respect to "optimum" circuit design, performance and applications.
Springs have their limited "sweet zones", "ok zones" and their unavoidable "ugly zones". And to get the desired result you really need to experiment with the circuit working out the specific spring reverb unit. And at the end, the best result you can count on is finding an acceptable compromise.

Springs are rough devices. So I'd say, in this situation, worring about "upgrading" op-amps would be somewhat similar to worring about what kind of polishing compound to apply before sandblasting heh heh Bad analogy, but you get the point

I have a short video with the segment where you can see how the sine-sweep looks after "spring-treatment", if you care to look it's here, click there video-link (...Breadboard Experiments / Circuits Tests Lab Demonstration...), the first part of the video shows the soft-clipping/overdrive/shift thing.

 

[luscmu]

Where can I find rackmount ears for RS-20B?

Hello,

Can't even find the right keywords to google in on them. Also have the multi headphone amp MH-40, same size but no brackets. Cheers in advance for a point in the right direction.

P.S Definite neat-o reverb ha, digging it.