What is this Radio Shack EQ Everybody's Talking About?

ubertar · Post by **ubertar** » Tue Oct 04, 2011 4:26 pm

There was a guy a while back... I forget his name... who used to do tube conversions of these. He'd replace the transistors with EL84s, IIRC. He had to add a little more circuitry to make them fully compatible, but it was minimal. Really incredible sounding.

germaniac · Post by **germaniac** » Wed Oct 05, 2011 11:31 am

Okay, so far in this whole thread, no one has proved the existence of the purported "blackfaced 7-band EQ." May I ask the consent of everyone here to officially conclude it's a fiction, an urban legend? Otherwise, may I ask someone to show all of us pictures/evidence of the item please?

Regards,
Joe

shedshrine · Post by **shedshrine** » Wed Oct 05, 2011 12:26 pm

sleeper color eq's

RefD wrote:
dorfenheimer wrote:THe short lived silver-faced mercenary endorsed reissue edition that Fletcher raved about at the time.

too bad it's 10 bands instead of the proper 7!

not to mention the frequency centres are in the wrong places and the Q is too sharp.

taken as its own thing, tho, it was pretty damned rad...but definitely not faithful to the original.

Rob Coates · Post by **Rob Coates** » Wed Oct 05, 2011 3:37 pm

I've also discovered that old SAE and ADC Soundshaper EQs were inductor based. Anyone know if that's in fact true? If so, were any of these discrete, class A?

germaniac · Post by **germaniac** » Wed Oct 05, 2011 3:47 pm

Rob Coates wrote:I've also discovered that old SAE and ADC Soundshaper EQs were inductor based. Anyone know if that's in fact true? If so, were any of these discrete, class A?

I have a TEAC/ADC Soundshaper One that has the exact same innards as the Realistic 31-1987. So yes, discrete class A, all the same design, probably all made in the same factory in Taiwan or whatever.

Rob Coates · Post by **Rob Coates** » Sun Oct 09, 2011 7:44 am

Have been doing some mixing with the RS 1987. I have to keep asking myself: How can this silly looking little box sound so good? Seems to beat any of my other EQs for broad strokes of vintage color.

floid · Post by **floid** » Fri Oct 14, 2011 7:30 am

germaniac · Post by **germaniac** » Fri Oct 14, 2011 9:59 am

Hey Floid, excellent work! Interesting, I don't recognize that PCB, so I'm thinking that's one of the very earliest RS EQs. Maybe the one where a single slider for each frequency controls both channels? (RS 31-1986 maybe?) As you said, those inductors are a bit small (smaller than those in the 31-1987). But all the same, you still have the two sets of four xstrs that make up the discrete op amp. . . .

So your unit has controls for LEVEL, Q, and a rotary switch for FREQUENCY? (BTW, I recognize those PM-1000 knobs.) I've read that when you change frequency by changing the cap but not the inductor, it supposedly skews the slope of that band off-center (that is, makes the slope non-symmetrical). I've never tried it, but do you notice anything? At any rate, I've been meaning to do something similar with one of my RS EQs. Once again, nice work, and thanks for posting the pix!

Joe

inverseroom · Post by **inverseroom** » Sun Oct 16, 2011 4:50 pm

Oh wow. It's alive.

joelpatterson · Post by **joelpatterson** » Sun Oct 16, 2011 10:05 pm

Nah... it's all a dream...

floid · Post by **floid** » Mon Oct 17, 2011 8:50 am

the original chassis is long gone so i can't confirm model # or anything like that, but it was roughly seven inches wide, four tall, four or five deep. The faceplate was black plastic with "silvered" highlights, with a natural finish aluminum plate over the sliders. There were five dual gang sliders, as you said - the main reason i went ahead and racked the poor sucker was to have independent channel control. Also, if you squint just right, you can make out the traces on the back of the PCB that look to be hand drawn, something i've never seen before or since.

as far as changing cap value and not inductor value: i'm an admitted hack, but from what i understand, an LC resonance's lower leg is determined by value of C, while the upper leg is determined by value of L. So altering only one value effects a change in Q, since you're moving the legs further apart or closer together. Adding a resistance to the network (LCR), however, allows one to set Q as well - with the side effect of changing impedance, thus affecting depth of available cut/boost. I'd welcome any experts out there who care to set me straight or explain deeper.

but, essentially, the flavor does change by frequency. some bands in the low midrange have a tendency to overwhelm the circuit at extreme settings, and down on the bass end i increased cap value so much (notice the no-name yellow films, the biggest i could find for a reasonable price) that the q becomes so wide as to practically act as a shelf. It definitely ain't much good at carving up a bass drum! but for rooms, guitars, all the typical victims of audio destruction...

Rob Coates · Post by **Rob Coates** » Fri Oct 21, 2011 6:11 am

Very nice! Wish I had the skills to do something like that with mine. What would it take and how difficult would it be for a complete novice like me that burns his fingers every time he gets out the soldering iron to just replace the faceplate and sliders with 5 rotary pots (leaving everything else as is)?

pandemic · Post by **pandemic** » Sun Feb 19, 2012 8:42 am

I recently got one of the eq's from ebay for some experimenting. It is (I believe) the same as the one Floid described above although the inductors are different colors and some of the caps are different sizes. I plugged it in to make sure that it worked and then proceeded to dismantle it and add 1/4" I/0 and start replacing the dual gang slide pots with linear taper rotory ones. I could find only one at the Rat Shack (250K) so I tried it. I plan to rack it at some point but for now it is just sitting loose next to my recorder.

I wanted to see how it sounded so I recorded some vocals with it. It could def. use some way to switch frequencies for each band but it sounded pretty good stock. I was surprised at how quiet my cheap recording chain sounded (not dead quiet, but I have less than 100$ invested).

SM58-Shure M268 (modified direct outs)-Realistic EQ-Line in D32XD

The Shure mixer channel is set to about 7-8 where it does not seem to overload and I do have to make up some gain at the D32's input. The Realistic EQ is sitting loose on the table and I imagine shielding it in a case would reduce some noise (honestly, there is not much to reduce). I imagine balancing the signal chain would help as well.

The Realistic part number is 40-2010 and when I get it in a case I will post some photo's. I am logging the entire build for a blog entry and will post it on Tapeop as well. I plan to buy a 32-1987 to see whats inside as well...

So far this looks like a usable, cheap and quiet EQ and with some tweaking may indeed be the Mythical RSEQ......

or maybe we are all just dreaming........

joninc · Post by **joninc** » Tue Feb 21, 2012 12:32 am

i read this whole thread. wow. what a major waste of time.

that said, i did just buy a rs 31-1987 off ebay. a lot of fun for $40?

time will tell....

pandemic · Post by **pandemic** » Tue Feb 21, 2012 3:05 pm

Hey Joninc

Would you mind snapping a pic of the guts of that thing when you get it. I am curious as to the size of the inductors...Thanks

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What is this Radio Shack EQ Everybody's Talking About?

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