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Old 4th March 2005, 09:20 PM   #1
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Default Phono preamp dissection.

Could someone elaborate a bit on this phono preamp?
It’s a vintage Sansui schematic.
I own the preamp and would like to understand what happens.
I see two diff pairs and two push pull (?) outputs in series, pin 7 and 8 are externally tied together or attenuated with a resistor/capacitor network to match the sensitivity of the cartridge.
What is the purpose of TR07? Not marked but that would be the transistor in the middle between the two parts of the amplifier.
Where do I find the RIAA corrector?

It would be nice to hear what you guys come up with.

/Hugo
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Old 4th March 2005, 09:21 PM   #2
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Attenuator circuit
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Old 4th March 2005, 09:34 PM   #3
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Regulator.
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Old 4th March 2005, 09:41 PM   #4
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Hmmm...front panel says: Sensitivity 1.5mV, 3mV, 6mV.

/Hugo
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Old 4th March 2005, 09:43 PM   #5
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No, I meant that TR07 is a regulator. The voltage divider on the base sets the emitter voltage.
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Old 5th March 2005, 10:24 AM   #6
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Haha, your one word post puzzled me.
Now, that regulator will be there for some reason but as it’s not in the signal path…
Does someone know why there are two amplifiers (more gain?) and where the corrector network would be?

/Hugo
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Old 5th March 2005, 05:55 PM   #7
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May gees is that the first stage which TR01 to TR06 is the MC AMP, and there for has it own Voltage regulator (TR07), helps to get a’ god S/N for MC input stage.

The RIAA stage is R19 to R21 which C07 and the other side off the range is generate by R26 and C08 in the fead back line, the second amp is the MM AMP.

The switch board is some mystery butt, another gees, these tree selection is to generate a load impedance for MM pickups and sensitivity on the MM/MC pickups, so that it will work as god it can with any brand.

Input for MC is when the switch position is set to (1) and MM is for (2) and (3).

//

Thomas
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