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Phono Input Adaptor

I no longer use my turntable and would like to use the phono input for another device with higher output. The phono input on my amplifier (Luxman L-230) is connected to a pre-amplifier that also applies some equalization that boosts bass and reduces treble. So, I will need to attenuate the incoming signal and correct the frequency spectrum.

Does anyone have any experience doing this? How did you do it, and are you happy with the result?

Thanks



karodimitrov's picture

Re: Phono Input Adaptor

1-Open the Amp.2- Remove from the phono-board two caps-3,3 Mf(C-104a and C104b).3-Remove from phono-board two resistors-R108a and R108b.Connect with jumper (or coaxial cable)holes in the board left after removal of capacitors(their negative sides-left sides of scheme) to points left after R 108a and R 108b (to socket A1 of the scheme).4-Fully remove C301a,C301bC302a,C302b,R301a,R301b,R302a,R302b(see schematic).5-In place of those 4 caps put jumpers(+>-/+>-/+>-/+>-).6-Enjoy
Hope understand my bad English!

karodimitrov's picture

Re: Phono Input Adaptor

P.S.Forgot...By selection of resistors R100a and R100b,R701a and R701b may adjust the power of the input signal.Also disable power to the integrated circuit (socket A11 or by removing R154a,R154b)do not need it now.
Success!

Re: Phono Input Adaptor

Thanks karodimitrov.

Rather than disabling and bypassing the built-in preamp, I was interested in the use of an external adaptor that would attenuate the incoming signal strength, modify the frequency characteristics of the signal, then connect it to the existing phono preamplifier.

These are commercially available, but I don't know how well they work.

George

karodimitrov's picture

Re: Phono Input Adaptor

By divider resistors with the input you can reduce the signal, but remains RIAA correction.You need to do a reverse of RIAA filter.Additional elements, additional noises.There is a signal of about 250 millivolts, passes through the filter and then fell to about 3.Possible- passive external filter...
Don't know...Phono input is very sensitive.
You decide, nothing is impossible.

Krasimir