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Vinyl Asylum: RE: John Elison, can you show me the pic of the rca y adaptor for cartridge loading? by Biff

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RE: John Elison, can you show me the pic of the rca y adaptor for cartridge loading?

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I had it handy, here's the whole thing:








I use Radio Shack parts (you will need 2 sets, a set for each channel): "Y" adapter # 274-501 ($6.99) and an RCA plug # 274-850 ($3.99). They are gold plated and seem to be well made and a good value for the money. I'm not a "cable"/IC guy, and for me its not worth spending big bucks on these parts (YMMV) since I've never seen a double blind test proving the extra expense is worth it.

The "Y" adapter has 2 female jacks and 1 male plug. The male plug goes into the preamp and one of the turntable plugs into one of the female jacks. With the RCA plug, you solder an appropriate resistor across its connections - this in effect puts that resistor in parallel with the preamps internal load when they are all plugged together. Once this is done, repeat for the other channel.

The change in internal loading of the preamp is governed by the equation of parallel resistors:

R(T) = R(1)*R(2)/[R(1)+R(2)]

where R(T) is the final loading value, R(1) is one resistance (say your internal loading of 47k ohm) and R(2) is the other resistance (say the resistor you soldered across the RCA plug). So for example, if the preamp is of a standard loading of 47k ohm, and you add a 100k ohm resistor via
the RCA plug, the actual loading the cartridge would see is 31.97k ohm or 32k ohm in the real world. As you can see, it's possible to lower the resistive loading but not increase it - to do the latter you will need to open the preamp up and increase its internal manufactured setting.

One last thing to be aware of is the total capacitance the cartridge sees - this can affect results with MM cartridges since most have high internal inductance (Grados excepted here). Try to keep external capacitance WAY down - this means tonearm wiring, ICs and the internal capacitance of the preamp's loading. The easiest thing of the 3 to do is to keep the ICs short - under a meter if possible; next would be to open up the preamp and remove any internal input capacitance loading that was supplied by the manufacturer - NOT for the faint at heart. Keeping the ICs short is your best bet here."



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Topic - John Elison, can you show me the pic of the rca y adaptor for cartridge loading? - tubesforever 13:42:51 08/2/09 ( 4)