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Sansui QSD-1 Unit is up for Auction

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par4ken

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The simplicity of Sansui's circuit still amazes me. Connect the resistor between the two emitters and the signals mix in phase, but connect it between the two collectors and you get out of phase blending. I had to scratch my head a bit to see how that works. I still like Scott's original pre-synth design, it could blend all the way from mono to L-R/R-L. Possibly a more practical version would limit the blend ratio to .414 at each extreme setting. A centre detent pot would be nice to indicate no blend then no switching would be required.
 

chucky3042

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How I configured mine I don't think would be directly applicable to the next gen SM but it was a fun little DIY so if you care here it is:


Sansui did it in the simplest way possible. To state the obvious a signal at the base of a transistor can have a relative matching or opposite polarity at the output. With a single input transistor for each 2 ch input Sansui just put a capacitor in series with a resistor & did opposite polarity blending. I don't remember the value which changed anyway on different models, but in 3 units that I did bother to measure the amount of blend, all were slightly different. But in general it was less than 7dB , closer to -10dB blend. Probably because Sansui was accounting for a certain amount of random/out of phase content in the program source.

Pity your reference QSD-1 was broken. The synth mode really works magic.
Pardon my complete old age stupidity but looking at your circuit, it pre grabs the rear signals and cross mixes it with its opposing front? Correct?? And then shoves it out as the new "stereo" - Where does the rear signals come from....the SM output??????????

Me confused wookie sized idiot
 

Sonik Wiz

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Pardon my complete old age stupidity but looking at your circuit, it pre grabs the rear signals and cross mixes it with its opposing front? Correct?? And then shoves it out as the new "stereo" - Where does the rear signals come from....the SM output??????????

Me confused wookie sized idiot
Don't play dumb with me Mr Chucky cuz I can play that game too & I'll win every time. Just ask my wife.

I thought I gave a pretty good overview as well as detail in my previous Chase post but more conceptually here's how it works: The Chase RLC-1 has two stereo L/R outputs designated Front & Back with a fader type control for F/B balance. Now if you were to take the rear ch outputs & invert for opposite polarity compared to the fronts, mix them together and you could control the relative amount of out of phase blending in the combined 2 ch output that goes to the SM input. When the Chase balance is pushed all the way forward there is zero opposite phase blending. All the way to the rear you get close to a L-R & R-L. At mid-point I get that magical Sansui blend that gives that 270deg wrap around effect.

Edit: It took a while but now I think see what's confusing to you. In the orginal Chase there were stereo front/back out puts but after my mod there is only front. The rear signals are only used internaly on my little matrix board. The physical rear ch output jacks don't connect to anything. Only the phase blended output now goes to the front output jacks & into the input on the SM.
 
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furui_suterioo

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The Chase RLC-1 has two stereo L/R outputs designated Front & Back with a fader type control for F/B balance. Now if you were to take the rear ch outputs & invert for opposite polarity compared to the fronts, mix them together and you could control the relative amount of out of phase blending in the combined 2 ch output that goes to the SM input. When the Chase balance is pushed all the way forward there is zero opposite phase blending. All the way to the rear you get close to a L-R & R-L. At mid-point I get that magical Sansui blend that gives that 270deg wrap around effect.
With the SM board that is going in my car, this seems like fun idea since my original plan was to have the front outputs of the head unit go to the SM board and rear output to the sub amp in order to retain some functionality of the fader knob, but this idea would make a much more interesting use for the fader than just controlling the sub, which i could easily find another output for and has it's own volume control anyways. I've got some breadboards and big bag of mixed spare components somewhere, so probably be a long while before I get those parts sorted but I will keep this in mind!
 

chucky3042

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Don't play dumb with me Mr Chucky cuz I can play that game too & I'll win every time. Just ask my wife.

I thought I gave a pretty good overview as well as detail in my previous Chase post but more conceptually here's how it works: The Chase RLC-1 has two stereo L/R outputs designated Front & Back with a fader type control for F/B balance. Now if you were to take the rear ch outputs & invert for opposite polarity compared to the fronts, mix them together and you could control the relative amount of out of phase blending in the combined 2 ch output that goes to the SM input. When the Chase balance is pushed all the way forward there is zero opposite phase blending. All the way to the rear you get close to a L-R & R-L. At mid-point I get that magical Sansui blend that gives that 270deg wrap around effect.

Edit: It took a while but now I think see what's confusing to you. In the orginal Chase there were stereo front/back out puts but after my mod there is only front. The rear signals are only used internaly on my little matrix board. The physical rear ch output jacks don't connect to anything. Only the phase blended output now goes to the front output jacks & into the input on the SM.
 

Sonik Wiz

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OK sorry, here's a clip from my favorite musical "Little shop of Horrors"

While I can embrace & enjoy Hobbits, Robbie the Robot, Deadpool & other flights of fancy it just seems to me that musicals are just so absurd. I mean the Jets & the Sharks are gonna have a fight to the death rumble. But first they will sing & dance a little bit? C'mon.

I loved the original Roger Corman film (don't forget Wasp Woman!) but saw the newer Steve Martin one time & that was enough. Maybe now that I'm old & feeble (not dying does that to ya) I might be more tolerant of the movie. If I chance across it I definitely give it a 2nd watch.

Otherwise the only 2 musical movies I've ever really had a love for is Across the Universe & Strictly Ballroom. It's been so long ago for the latter I'm not sure it really qualify's as a musical but there is a lot of music in it. And I certainly think it is Luhrmann's best.

Anyways looking forward to whatever next gem BBQ digs up on The Net!
 

jsrstereo

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Don't play dumb with me Mr Chucky cuz I can play that game too & I'll win every time. Just ask my wife.


Edit: It took a while but now I think see what's confusing to you. In the orginal Chase there were stereo front/back out puts but after my mod there is only front. The rear signals are only used internaly on my little matrix board. The physical rear ch output jacks don't connect to anything. Only the phase blended output now goes to the front output jacks & into the input on the SM.

Hey Mr. Wiz: Here's a dumb question from a verified non-techie:

What if I set my Akai SS-1 to the 4ch Matrix mode, then run the front output into my SMv2 - can the Akai's front matrix control pot then be used to adjust phase-blending so as to accomplish what your Chase mod does to create synthesizer ability for the SM? Or not?

Thanks: John R
 

Sonik Wiz

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Hey Mr. Wiz: Here's a dumb question from a verified non-techie:

What if I set my Akai SS-1 to the 4ch Matrix mode, then run the front output into my SMv2 - can the Akai's front matrix control pot then be used to adjust phase-blending so as to accomplish what your Chase mod does to create synthesizer ability for the SM? Or not?

Thanks: John R
The Front matrix knob controls in phase blending for the front chs. The Rear matrix knob controls opposite phase blending that goes to the rear chs. So try feeding the rear ch outputs from the Akai into the SM. A good test would be to use a left only (or right only) source to the Akai & advance the rear matrix control until you hear left back only (right back only) from the SM. That is the sweet spot for 270 deg wrap around effect.

Give it a shot & let us know!

EDIT: Looking at the specs in the Akai's user manual I see the freq response for the rear chs 10Hz to 10kHz -6dB. So if you seem to hear some high end treble missing that would be the reason why.
 
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