[redshifter]

i have a marantz 2225 receiver which is the heart of my bedroom spearker rig. on the digital end, there is a sony cd changer connected via optical to a sony md deck. i'm using the md deck as the dac, as it sounds much better than the changer. with the md deck, i can change the line-out volume, + or - 20 db. the problem i'm having is, when the md is set to line level out (0 db--default setting on power on), the music distorts through the aux input on the marantz. i have to turn the md line out to -20 to get rid of this distortion. my old receiver did not have this problem.

i also have a tt hooked up to the marantz and it has no distortion problems at all with the tt.

any ideas what is causing this?

 

[mkmelt]

Try hooking the CD changer's analog output to the AUX input on the Marantz to see if the sound is distorted. If it sounds distorted too it may be that your Marantz receiver was not designed to accept a line level signal greater than 1 volt, while your CD changer and/or your MD player may be 2 volt or even more. If this is the case there are some in-line attenuators you can use to lower the level of the signal coming from the MD player before it reaches the Marantz. The reason you don't hear overload distortion on the phono input is that the maximum output of a conventional magnetic phono cartridge is typically 50 to 100 millivolts. This is well under the overload level for the phono preamplifier circuit.

 

[redshifter]

thanks mkmelt.

so it is by design and not a hardware failure? can i use any old attenuator or are there higher quality ones?

 

[mkmelt]

This is by design, not likely to be a hardware failure. Before CD players, the typical line level sources were AM/FM tuners and cassette and reel to reel tape decks. Output from these devices was typically specified as 1 volt RMS, this works out to be about 700 millivolts peak to peak, definitely less than 2 volts output by the fixed level output of many CD players.

The in-line attenuators I am familiar with are small double ended passive devices, basically two phono plugs with resistor wired between them. I doubt you could hear any noise attributable to them in the circuit, you won't notice anything at all except for the obviously lower signal level. These are sold by Radio Shack, Parts Express and probably others. I have seen values of -10db and -20db for the amount of attenuation. I would start with the -10db attenuators, and if that is still too much signal try doubling them up on one channel using some cables patched together. If that works, then replace the -10 with a pair of -20db attenuators. Of course, if you can solder you can make your own attenuators and experiment with the value of the resistors until you have the level you need, and then solder these in place. A bit of shrink-wrap tubing would cover the wire connections.