Peak Level Distortion at Low Input Levels

[BeachMark]

Repeated results recording music from a turntable has produced notable distortion in Audacity. The distortion is in the form of "sizzling" that occurs only during loud / peak portions of the music (Bizet's "Carmen"). The turntable's output is connected to an amplifier. Output to my PC's mic input is via one pair of the amp's tape outputs. Before recording, I assured the vinyl's music was clean by first listening to it via the amp's headphone jack. I also attached headphones to the tape's output, and though not as much gain, there was no notable distortion. I've tried recording the music using various Audacity input levels and all it does is alter recording volume without affecting the distortion I'm experiencing. What am I overlooking?

[kozikowski]

<<<What am I overlooking?>>>

The Line-Out of a sound device is roughly 1000 times hotter than what a Mic-In connection is expecting. Also typically, Mic-In service has a fixed, high gain amplifier before the volume control. You get the best noise performance that way.

So you're beating the crap out of the microphone amplifier and then trying to turn it down later--after it's too late.

You need to connect to the Line-In of your computer [pause]. This is where you tell me you're on a laptop and don't have a Line-In.

Koz

[BeachMark]

What you've stated makes sense — and yes, I'm using the mic input on a laptop using Vista. When plugging a jack into the mic input Vista responds first by prompting you to select how the input is to be handled — line-input is what I selected. Still, if the output I'm using is much too high for what is necessary, what should I be using as my source output?

[kozikowski]

<<<Vista responds first by prompting you to select how the input is to be handled — line-input is what I selected.>>>

If you dive for your laptop instruction book or on-line instructions, does it ever say in straight, uncomplicated English that the audio input will switch between Line and Mic? It's electrically possible to do that, there are sound mixing desks that work like that, but it's not likely. It's more likely that Windows thinks you have two different inputs, one that will handle much higher sound levels than the other, but since your laptop only has one connector, Windows doesn't actually do anything.

Koz

[kozikowski]

<<<output I'm using is much too high for what is necessary>>>

The only two graceful solutions I know of are to use your large deskside PC whose much larger sound card tends to have all the audio variations available including Line-In, and make good friends with someone who owns a Mac. PC and Mac machines diverged a while back. PC Laptops are directly compatible with a headset typically needed for internet phone calls and conferencing. They plug right in and go. All Macs in the last bunch of years have a very high quality Line-In connection, but have no provision for analog microphones at all.

There are good deal less graceful solutions. I designed an audio attenuator and built it into a little metal box. It's job is to lose enough signal so the Hot Line-In signals appear to be much lower Mic-In levels to the computer, and there used to be a Radio Shack audio cable that had a volume control built into it. I'll see if I can find that part number. Are you handy with a soldering iron and electric drill? The Radio Shack cable should work in theory....

I noticed you didn't say the magic words: "I have a USB turntable." Do you? they have a terrible failure rate, but many people actually do get them to work.

This brings up another point. Does your turntable have electronics inside it, or do those cables go directly to the tone arm and cartridge? Actually, that's not likely because you said you were able to hear music with your headphones. That wouldn't happen in an unamplified turntable.

Koz

[kozikowski]

http://www.radioshack.com/product/index ... age=search

Koz

[BeachMark]

If what you say is true regarding Vista's dubious handling of input, other than microphone, then this weakness should be addressed back to Microsoft, and Dell where my notebook originated. My turntable is a conventional one that requires amplification from an external source — no USB. Fortunately though, I already possess an in-line volume control with which I can experiment. Thank you again for your assistance and insight. When accomplished, I will post the results from using an inline volume control.

[kozikowski]

Just to bring this all the way around, which amplifier are you using--given that it has to process the phono cartridge signals and remove the RIAA distortion.

There was a spirited discussion here a while back about the quality of various stand-alone phono preamplifiers.

<<<this weakness should be addressed back to Microsoft, and Dell where my notebook originated.>>>

You can do that and let us know how you get on. I'm slowly decommissioning all my PCs as having outlived their usefulness.

Koz

[waxcylinder]

<<<this weakness should be addressed back to Microsoft, and Dell where my notebook originated.>>>

You can do that and let us know how you get on. I'm slowly decommissioning all my PCs as having outlived their usefulness.

Koz

Unfortunately I've noticed that Bill & Michael don't write back very quickly - if at all .........

WC

[BeachMark]

Success! Using the $8 in-line volume control to attenuate the output signal strength worked as you suggested. Just by having the in-line volume control in the circuit was enough to remove the unwanted distortion, since it could be left at a setting of full volume. You asked about the amplifier I'm using — it's an old Pioneer SX-980 (90w/ch). Despite having intermittently fouled front panel switches, the amp still manages to crank out good signal strength. ------------ Thank you very much for your great assistance in allowing me to continue digitizing my music collection.