Chase RLC-1 Meets the Involve SM v2

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Sonik Wiz

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Firstly to the mods: I had no idea where is most appropriated to put this post. Please move if needed.

The Chase RLC-1 is an interesting piece of audio gear. Its usefulness existed between the time nobody had remote control on their stereo and when everybody had remote controlled gear. Hooked in to the tape loop on a stereo receiver it added four source inputs, bass/treble control, volume & balance functions all by remote control. There are no buttons or knobs on the front panel, only LED’s. From left to right is Power, then as a group of five there is Mute, VCR, CD, Tape, and Aux. The LED’s do more than just indicate program source they also are used to indicate adjustments made by remote. It has to be seen to be believed but here’s how they function best as I can describe: when it is first plugged in all balance, fader etc are reset to neutral which is indicated by the middle LED which is labeled CD. If you push & hold the left balance button the middle light blinks once to show you where the current setting is. Then it blinks rapidly a few times & then the next to left LED starts blinking and then the next left LED blinks until finally you can’t go any further and it rests on Mute. After a second it reverts back to showing whatever input source you have selected. Sounds crazy but after about 2 mins it seems natural & easy peasy. Increasing the volume causes LED’s to successively light to right. Adjusting the F/B level causes the LED’s to light to the right for forward & to the left for rear.

CHASE 2.jpg


Remote control functions are handled by the humble PIC16C56. All audio signal processing is in the analog domain & handled by the
Phillips TEA6320.

I think I bought mine about ‘ 95 for a little over a $100. Actually I bought four of them though I only used two. A the time I had a Sansui QSD-1, Fosgate Tate 101A, Integrex Ambisonic decoder, and a Sony 4 ch reel to reel. My plan was to use one unit for the front channels & one for the rears. It worked but it was hard getting them to stay in synch & I spent most of my listening time fiddling with the balance etc. There was also a boomines that I couldn’t tame or adjusting the bass level & it seemed variable, even with some treble enhancement too. Just a few months ago I found out that is caused by a built in loudness control activated, as usual, by the master volume level. With a little circuit mod that can be eliminated. I tucked them away & hadn’t thought about them until I placed my pre-order for the Involve Surround Master v2.

One of the unique things about this product is that it has two separate stereo outputs for front and back. To be more clear it is like in a car where you have stereo in front and stereo in back with a fader in between to control F/B balance. I reasoned that with something like a Mid/ Side with front being Mid & rear being Side I could control the amount of in phase blending or out of phase blending to control the phase relationship to the input to the SMv2. Then do a M-S decode to get the stereo chs back. That way with the fader balance all the way forward it would be basically a mono signal to the decoder, all the way back would be basically L-R. The useful part would be adjusting it for optimum soundfield in between.

After a quick prototype plug in board test I changed my goals. Mainly because of the funny blinky light indicators it would be hard to determine exactly where original stereo was being output. So I changed the circuit that when the forward balance is all the way forward it is 100% unaltered stereo as in the input. Pushing the back button on the remote increased the out of phase blend until you reach a magic point where the front opens up wider, sounds panned extreme to the side emanate from the rear speakers and over all depth is enhanced. In QS/Involve decoders that point is .414 or ~ 7dB out of phase blending. Now some music will have greater or lesser amounts of random or out of phase already & that’s why having an adjustable blend is even better than the way Sansui implemented it. It is also a big bonus to control L/R balance to the SM. Closely balanced input is essential & fine tuning brings a more fundamental benefit than always trying to do it at the output. When it sounds right, it is right.

The final circuit design is so simple & works perfectly with the Chase & SM v2. Back L/R goes to an inverting op amp that makes it opposite phase/polarity compared to Front L/R. Front L/R goes to an op amp mixer where the two back ch signals are cross mixed. The inverted left signal is mixed with the front right. The inverted right signal is mixed with the left front. The degree of mixing between them is controlled by the F/B buttons on the remote control.

CHASE-RLC1 copy.jpg

I used the LM4562 op amps that is used in the Involve SM v2. The schematic shows single op amps used but actually I just used two of the dual LM4562. All resistors 20K Ohms except for R3/R4 = 50K ohms. I made several other modifications the Chase & built my little matrix board into the Chase. The only drawback was that I couldn’t use the Chase internal power supply because it is single ended & I wanted a bi-polar power supply for my op amps so, among other reasons, I wouldn’t have to use output coupling caps. Lucky I already had a nice external adjustable power supply for this. Set to +- 12 V, it connects to the matrix board in the Chase via a 4 pin Amphenol plug/socket as was used in hooking up mic plug ins. It has good contact area, index ID, and screw down locking

BEFORE:
CHASE BEFORE.jpg


AFTER:
CHASE AFTER.jpg


I have made several other mods to the Chase board. If anyone is interested in doing a project like this I can detail those changes as it really is essential to making a complimentary accessory worthy of the exemplary fidelity of the SM. All together I cannot detect any hum, hiss, noise or distortion added. Using my Zektor switcher I can set the SM to stereo, the Chase full forward and toggle back & forth between the Chase & compare it to the stereo output on my Oppo . It’s easy to level match I truly cannot detect any difference. Mission accomplished.
 

quadsearcher

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I'm missing some understanding. "inverted left signal is mixed with the front right", is the second op amp shown with polarity reversed? It looks to me like front right is also inverted, going into the - input of the op amp, so why invert both LB and RF to mix them?

Edit: I think I get it, LB is inverted twice and RF only once. Does the output need one more inversion for absolute phase? Kidding - I have no idea.o_O
 
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Sonik Wiz

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I'm missing some understanding. "inverted left signal is mixed with the front right", is the second op amp shown with polarity reversed? It looks to me like front right is also inverted, going into the - input of the op amp, so why invert both LB and RF to mix them?

Edit: I think I get it, LB is inverted twice and RF only once. Does the output need one more inversion for absolute phase? Kidding - I have no idea.o_O

Thank you for the one and only reply. Always happy to confuse whenever I can.

Yeah pretty much you are right. If the balance was thrown all the way forward the only signal would be present at the front L/R inputs. It is inverted compared to the original output from the Chase circuit board but the phase/polarity would be matching between the two chs so all is good. Unless you really want to dig up that 80's obsession with absolute phase. Then of course slap on another inverter stage at the output. And anyways who knows what the output polarity is from the basic Chase circuit is in regards to in to out?

The rear ch inputs are inverted relative to the front inputs and summed at resisters R3/R9 for the left and summed at R4/R10 to create the variable opposite phase blending between the chs that goes to the Surround Master.

The process of of playing stereo through a surround decoder is well known to have variable results from yawn to incredible. Being able to control phase & level balance to the decoder is a way to tweak that stereo to closer match what decoder needs to produce that incredible sound. It is totaly different than adjusting F/B or L/R output levels after decoding. Of all the quad & surround sound stuff that played before my ears I have never been happier than with the Chase RLC-1 & SM v2 combo for stereo to surround.
 

furui_suterioo

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Hello Sonik, do you have a diagram for a pre synth circuit that would work in a car system? I'd like to wire up a pot on the dash to control pre synth on the Involve(which is in the glove).
I have built a couple of DIY circuits before from diagrams but I'm not at the level of designing them myself(maybe one day).
Thanks.
 

Sonik Wiz

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Hello Sonik, do you have a diagram for a pre synth circuit that would work in a car system? I'd like to wire up a pot on the dash to control pre synth on the Involve(which is in the glove).
I have built a couple of DIY circuits before from diagrams but I'm not at the level of designing them myself(maybe one day).
Thanks.
Having an Involve in the car with pre-synth would be a class act!

I have pulled the RLC-1 out of my system long ago & working at a snails pace on better front end for my SMv2. The phase balance circuit I plan to use is here:


It shows 3 versions I intend to use the one shown in Fig 2. Now, you specifically asked for a circuit that would work in a car & the problem with using IC's is that like bipolar +- voltages where a car is single ended + volt only. There's ways to get around this but it's either simple/not very good or complex/better, that is to create a negative voltage referenced to ground.

In most Sansui decoders they used a single ended supply with conventional common transistors (except for custom made IC's designed to work from single ended). The phase blending in Sansui's was extremely simple being just 1 transistor in each input ch with a single blend resistor positioned correctly for the phase blending. This might be a better way to go if all you want is opposite phase blending for wrap around sound in your car. I am not good at working with transistors; figuring resistors for bias voltages, gain, etc. So I'm gonna give a shout out to @par4ken who might have some better advice. Stay tuned...
 
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furui_suterioo

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The phase blending in Sansui's was extremely simple being just 1 transistor in each input ch with a single blend resistor positioned correctly for the phase blending. This might be a better way to go if all you want is opposite phase blending for wrap around sound in your car.
Thanks for the info.
A simple circuit like this is probably what I'm looking for.
The Involve is great but sometimes just need a little more sound directed to the back speakers, and just fun to mess around with the sound.
 

Sonik Wiz

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Thanks for the info.
A simple circuit like this is probably what I'm looking for.
The Involve is great but sometimes just need a little more sound directed to the back speakers, and just fun to mess around with the sound.
Yup. Most folks are happy with simply raising the rear levels in that case. But it does not fundamentally change the decoding: it just alters what has already been decoded. Doing the right amount of opposite phase blending actually changes the decoding & balances the front/back at the same time.

Elsewhere I've mentioned how to do this on the PC in audio editors. You have more control over certain things (EQ, noise clean up) but of course you can't adjust it real time. Gotta go back & do it different again on the PC. Still if you like to experiment that would be a good way to see what it adds with out having to mess with hardware yet.
 

par4ken

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Having an Involve in the car with pre-synth would be a class act!

I have pulled the RLC-1 out of my system long ago & working at a snails pace on better front end for my SMv2. The phase balance circuit I plan to use is here:


It shows 3 versions I intend to use the one shown in Fig 2. Now, you specifically asked for a circuit that would work in a car & the problem with using IC's is that like bipolar +- voltages where a car is single ended + volt only. There's ways to get around this but it's either simple/not very good or complex/better, that is to create a negative voltage referenced to ground.

In most Sansui decoders they used a single ended supply with conventional common transistors (except for custom made IC's designed to work from single ended). The phase blending in Sansui's was extremely simple being just 1 transistor in each input ch with a single blend resistor positioned correctly for the phase blending. This might be a better way to go if all you want is opposite phase blending for wrap around sound in your car. I am not good at working with transistors; figuring resistors for bias voltages, gain, etc. So I'm gonna give a shout out to @par4ken who might have some better advice. Stay tuned...
The "Virtual Ground" is easy to implement to run op-amps from a single supply.
1*4vopTIn7s5F4E1Rtv5SsRQ.jpeg

Figure 2 This schematic is creating a virtual ground (Vcc/2) so that the output signal swings about Vcc/2 (Image from Reference 1)

Vcc Is your positive supply, the op-amps output which is half Vcc becomes your ground. The original circuit ground becomes -Vcc for the other op-amps. Coupling capacitors will be necessary for your audio circuit.

Original article can be found here.


Alternatively you can find converters that run on a single supply but output a bipolar voltage for the op-amps. Here is one that I like available on eBay.
 

ar surround

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Thank you for the one and only reply.
That's because I didn't see this thread until this afternoon...3+ years since it was posted. (It seems to happen often...stuff gets posted while one is viewing other posts and the next time one gets on the site, those posts don't show up as "new." Grrrrrrrrrrrr.)

Anyway, as you and I have discussed Wiz, 'phase blending' also helps with Dolby Surround upmixing. So when do I place my order with Wiz Audio for this neat device? :)
 

MidiMagic

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I built this to handle anything like what you built/wanted to build.


Two of them can be a complete RM/QS decoder - one for fronts, the other for backs.

And you can use regular 600-ohm to 600 ohm transformers to build it, instead of the product I used.
 
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