Help with circuit diagram.

Mark 1234

AK Subscriber
Subscriber
Also posted in Turntables.

Hello I am trying to figure out exactly what the phone level dial on an exclusive C3 amp is actually doing. From the schematic it is before the phono amp board. There are also 25k, 50k and 100k load buttons. Both these buttons and dial are for the phono 2 input only. Schematic link.
https://www.hifiengine.com/manual_library/pioneer/exclusive-c3.shtml

Is it acting as a variable load resistor like you could put at the output of a step up transformer or is it actually playing a part in amplifying the input signal.

Thank you.
 
Not a TT/phono guy so ok to disregard. Thought it was an impedance matching thing to go with your cartridge.
If you look at your cart specifications/datasheet it will ge a resistance, typically 47kohms and a capacitance (pf?)
Select 25k/50k/100k to match your cart. Some amps have phono adjustment for both ohms and capacitance.
Normally provided for one phono with the other either "hard-coded" or for MC option..
 
Wound't the schematic have a capacitor to ground not a variable (resistor) pot to ground at the input of the phono stage if that was the case?
 
By way of example, section of Yamaha CA-1000 below, couldn't
find your schematic.

The switch on the right goes to the phono stage. Note that the
100k position has no resistor connected, this is because the phono
stage has an "input resistance" of 100k, by that I mean it looks
like a 100k resistor. Also note that the 50k position actually
has a 100k resistor, so there is the phono input resistance of
100k in parallel (to GND) with a 100k resistor gives 50k effective
(I think)

Probably find something similiar on your amp/schematic

upload_2019-3-23_21-43-58.png
 
Thank you. The VR2 level knob near the left center is what i was trying to find out what it was controlling. Is it playing any part in amplifying the input signal from the phono?
C3 board.jpg Level knob.jpg
 
MBZ had the correct answer in POST #2. It's a 3 position variable Phono Cartridge IMPEDANCE MATCHING setup. Nothing more, nothing less. Pull the spec sheet for the Phono cartridge you intend to use, and set the knob to the closest match. No muss no Fuss. The correct section of the schematic is higher up than you show. See Switch Assy #1 AWS-058 below.


ScreenHunter 106.jpg
 
Thank you. I posted the wider view right after the smaller but it did not take. Sreger posted an answer to my question in another section about the dial just being a level adjustment to match other inputs. The dial has no numbers so this makes sense.
 
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