Resistor to Power Amp input

Hi Guys,
Need some guidance here, I jsut come out with the idea of properly running my CD player as a player and pre amp to my NAD c370 Power amp input. (Bypass the NAD c370 own pre amp)

But the Marantz CD63KI output is 2V RMS @ 200ohm.. Dont know is it powerful or not, but at CDP lowest volume, the power amp is starting to get rather loud already.

I am thinking of adding a resistor each for left and right input (of course, externally). What are the suitable resistor that I should use? Metal film, Wire wound, foil?

I am not technical incline, so please advise. Dont worry, I wont blame you if smoke coming out from my system, I have been warned.

The Marantz CD-63 KI employs digital attenuation as a form of volume control. The drawback associated with digital attenuation is that for every 6dB drop in output (half the volume), you lose 1 bit (out of the possible 16 bits) of resolution.

Hi Admin,
Thanks for the profound information... Hope to meet you up one day to explain to me how exactly it happen. As of now, does it mean, it is better for me to use the second half of the volume control range to enjoy the maximum resolution?

Which mean I need a greater resistor to make that happen. Anyway, it is just a experiment for me, I need to know what I can achieve by bypassing the pre-amp. Thanks a lot.

Friend,
Try this link for more info: http://www.wadia.com/technology/technicalpapers/Digital_Volume_Control_2.pdf

It's an effective description and Wadia are particularly noted for their digital expertise.

Thank you Sir for the information.

Ha, that mean I will ensure my digital volume is on the second half or more to make the best of it. Hope I find myself a resistor that doesnt blown when driven up to that volume. Or some nasty damage to my power amp. I've been warned

Full blast the digital attenuation and use passive resistors network to reduce the gain of the overall system. Why do they employ digital attenuation compare to vca approach??? i doubt you will damage the amplifier if you dont cause the amp to hum loud....

hmmm.. dont quite get the meaning hoy. does it mean the resistor will cause hum instead? cant wait to try it out this weekend. Will inform about the outcome.

I promise to update u guys on the outcome, here is goes.

It take 9k to 1M ohm to make the max volume sound from cdp with reasonable loudness. No hum detected. Just music..

But then again, it doesnt sound as dynamic or details as it goes through the amp active pre-amp section.
So, finally matching is more important than theory of purity.

Reducing the volume at the input of amp require attenuator network of 2 resistors per input, one in series and one to ground to maintain the load impedance. Its not just a matter of one suitable resistor in series and the job done. A volume control in between 2 components is theoritically this method, just that the resistance in series is variable.

Thanks for the knowledge cmboy.

But the pre output from my amp to my power is connected to source without the feedback ground. So I do the same for my little experiment. 1 resistor per side.

hmm... wonder I should try out again ur points and see the differences take place.

Alamak forgot to check on this post!

Well it is not advisable to connect a series resistor of value of 1M. Definitely you will not get a solid sound. You should connect like a passive volume. Say a 10K alps pot will do the job..If you wanna fix it permanent, unsolder the pot and measure the resistance of the pot..

get a passive preamp

sorry, dont really understand what is pot. You mean the passive volume control?

Anyway, dont worry, I am content using the amp own preamp. Thanks for the inputs guys!

so adrian, whats the result? mind to share with others
funny but i did the same thing,
diff is i have a passive vol/fader in between source & amp

source : philips Q50
power amps : two x rb970bx (bridged 170wrms x 2)

i gave up my sansui c1000 pre
& im ok with this setup
no humming, distortion etc









pure sound?? am not sure
but 1 thing for sure amys vocals on fenomena just improves drastically
i can really hears the echo, not like before using pre

Hi azri, Thanks for the idea. Frankly speaking, the sound is a bit less lively with the resistor on, maybe i didnt do it correctly. But matching is important, that's why the amp original pre out is the best match for me, music just a tag livelier.

U may say that original pre add color to the sound. But it is the final result of the music presentation that count.

Now I go back to my old tweaks of changing the pre out to power in jumper... haha, that stop me from upgrading for awhile.