Fairchild 670 Vertical Lateral Switching Circuit

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tardishead

Well-known member
Joined
Aug 11, 2004
Messages
623
Ouch - I have been staring at the schematic for ages - my head hurts.
I was wondering if it was at all possible to implement the Ver Lat switching circuit if the Control Amp Input Transformer is only one winding with a centre tap not 2 separate windings - all other input output transformers being identical to the original schematic.
I think not but does someone more clever than me have a genius solution??



 
are you gonna cut some vinyl?  cool beans,

that switch is a nightmare and a PITA,  ???

been looking at it for years, still don't get it,

looks like they turn the phase around on a left channel  signal and add it inverted into the right channel, or some weridass thing like that, leave it to the dead guys to mess us all up,  ;D

all of that stuff is also in the RDH4 if i recall correctly,

it looks like you are stuck getting a dual pri input if you want to run the switch, still working on it,

now there is that input pad, maybe the resistors would isolate the input center tap from the signal output transformer, there would probably be a change in the sound possibly, since you are changing the circuit a bit,

hmm, the input resistors are only 150 ohms, so not much isolation there, so scratch that idea,

check this lo tec animation

http://www.vinylrecorder.com/stereo.html

 
when you get stuck on a tuff diagram you can break out some colored pencils and trace out the MS switch portion of the 670 circuit only,

use a different color for each transformer winding,

then it might be possible to understand it,

if you want more fun, try to calculate the cathode current thru the 6386 triodes,

it is a 3 way simultanoeus equation,

way harder than computing cathode on a twin reverb gain stage where 1.5 k ohms = 2 volts if z ma goes thru, get me?

i worked it out, let me know if you want to see it,


626 Roland drum machine is the bomb
 
tardishead said:
Ouch - I have been staring at the schematic for ages - my head hurts.
I was wondering if it was at all possible to implement the Ver Lat switching circuit if the Control Amp Input Transformer is only one winding with a centre tap not 2 separate windings - all other input output transformers being identical to the original schematic.
I think not but does someone more clever than me have a genius solution??
Clearly it's not feasible because, in order to have the de-matrixing done, you need the signals from the input amp to be floating.
I'm afraid the only alternative is replacinf the xfmr or use an external matrix.
 

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