iRiver H-1x0: Distortion from line out at 0dB?

[epithetless]

During a drive yesterday, I confirmed what I have occasionally suspected: When my H-120 is hooked up to my car stereo via a cassette adapter plugged into the line out jack, and the volume is set to the max 0dB in Rockbox, I sometimes hear the music distort slightly. Dropping the player volume by 3-6 dB seems to make the distortion go away. I'm certainly not blasting my music from the speakers, so I doubt they are to blame. The music I last experieced this with was the piano-based pop of Regina Spektor's Begin to Hope, nothing too harsh or overdriven in itself, and the distortion is not present in the recording during critical headphone listening from the unit. No EQ elements were applied in Rockbox. Is there a chance that Rockbox (or the H-120 Rockboxed) could be producing this distortion at max volume? Has anyone else had a similar experience?

Alternately, could my cassette adapter be the culprit? Does anyone have an explanation as to why it wouldn't be able to handle a signal at line-out level (which I would have assumed was optimal)?

[Skyly]

You said no EQ effects were applied so I might be wrong, but I found myself having similar concerns with my H340. I first noticed it like you did, plugged into a car system via a cassette adapter. I could have the music loud by increasing the car's volume, but increasing the iriver's only created distortion, so it wasn't the speakers. Later I often felt like my earphones were blown out, then I compared to a friend's earphones and the distortion was still there.

Do you get the problem with the iriver firmware? Other earphones?

Yesterday I turned off all the audio perks. Mainly the Bass setting, but that's probably the first thing you checked. But yeah, EQ, Bass, Treble, Replaygain, Crossfeed, whatever else there was. Then I began enabling and increasing them one by one again. Now I can again play songs incredibly loud with no distortion. Made me happy, because I was worried about the H340's quality, so I hope that's all it is for you.

[Llorean]

I've found cassette adapters *often* distort at 0dB. In fact, I usually leave my iRiver at -20 and it's much more suitable.

The distortion is caused by the adapter though, as the same unit at 0dB into a line in has no problems.

[epithetless]

I've found cassette adapters *often* distort at 0dB. In fact, I usually leave my iRiver at -20 and it's much more suitable.

The distortion is caused by the adapter though, as the same unit at 0dB into a line in has no problems.

Well, that's some fantastic news! I had suspected/hoped/prayed it was the adapter, so it's nice to get some confirmation on their intrinsic crapulousness. I was intending to patch my H120 through the aux-in of my computer system right when I got home today...with eyes cinched shut and fingers crossed...but now I'll take my time with it. and maybe breathe a little.

[Mmmm]

I think you'll find that if you play your music through the headphone socket instead , you'll get no distortion. I have some headphones that produce distortion from the line out but not the headphone socket. Other (much bigger) headphones don't produce distortion at all though.

So my conclusion is the output from the line out is different from the headphone socket and small speakers get overloaded when using the lineout. I'm afraid I don't know any technical detail but if I were you I'd just use the headphone socket in your car.

[Rincewind]

I had this issue with a cassette adapter, too. I had to put the volume at approximately -25 (with replaygain) to get normal sound.

the headphone jack has a different impedance, i think it is 32 ohm for phones and 14 ohm for line-out but I don't know the line-out value for shure.

[bascule]

I think you'll find that if you play your music through the headphone socket instead , you'll get no distortion.

That may depend on the particular cassette adapter. Most are probably designed to be plugged into a headphone socket for lowest common denominator reasons (how many cheap portable (CD/MP3) devices have line out?).

So my conclusion is the output from the line out is different from the headphone socket and small speakers get overloaded when using the lineout.

Correct, both the signal level and expected input impedance are different, so a cassette adapter designed for headphone socket use will distort if subjected to line-level signals. However, a better quality adapter designed for line-level will be fine.

Oh, and it's not the speakers that get overloaded, but the adapter itself, that then transfers a distorted signal to the tape head.

[epithetless]

Any recommendations for a better quality adapter designed for line-level...to optimize the merits of a Rockboxed player? (Just posting within the guidelines and keeping it Rockbox-related.)