Preamp Causing Distortion

Hello. I’m a brand new user and I’m using Audacity to record my old vinyl LP’s to CD. I have a turntable with a Preamp, but when I use it (on the ‘IN’ setting), the resulting sound comes out a little garbled (probably too much gain?) I found if I disable the preamp and then amplify the recording using the audio track controls menu (the menu to the left of the waveform display) it sounds MUCH better! I raise this gain while its recording about 15db. Is this correct and does this sound practical?

Also, when I raise the gain it doesn’t show any change in the waveform display. But it sure makes a difference! Should it show any change in the waveform display?

Thanks! - Marvin


In theory you should be much better using the pre-amp, provided that it has a phono input, as then the hardware will apply the RIAA equalisation (when vinyl record masters are cut the engineers apply RIAA equalisation to basically ensure that the stylus doesn’t travel too far on loud and bassy bits). If you apply RIAA on the way out then the sound will be noticably “thin”.

Now when you say garbled - do you men that it’s clipping when you record - do the waveforms touch the top/bottom of the track window and flatten off? I so then you do have too much gain.


Hi WC. The preamp is built into the turntable so its a cheap one. I haven’t found the sound being ‘thin’. So it seems better to NOT apply the RIAA?

RE: ‘garbled’. Its hard to describe. It sounds like you’re singing under water. :wink: But not as pronounced. I don’t think its clipping when I record using the gain. The waveforms remain very tiny because I’m not using the preamp. They don’t even change when I apply the gain. But the sound is much better after I apply the gain.

Isn’t applying gain almost the same as using the pre-amp? Both processes amplify the signal, correct?

Thanks for your reply! Marvin


no - applying the gain is not quite the same as using the pre-amp. There are two processes involved:

  1. re-applying the RIAA equalisation curve
  2. amplification of the signal
    so if all you are doing is applyoing the gain then you are doing 2) and not 1)

If it were me I would prefer to use the pre-amp and find a way of making that work . Can you tell us what the deck/preamp is and how it’s connected to your computer (i.e. is it a USB deck or are you connecting to line-in) - and what computer & O/S - then we might be able to offer more insight for you.


Hi WC. Thanks for replies. The turntable I’m using is a Radio Shack model ‘Lab-320’. Its about 9 years old. No separate pre-amp. Its built into the turntable. I’m connecting to my computer through line-in. The audio in the comuter is integrated into the mother board. No separate audio card. (pretty basic so far, right? :wink:. My computer is a Dell XPS 410 and I’m running Windows Vista 32 bit.

I understand your points above. Makes sense. However, you mentioned in your first reply that the RIAA is applied on the master recording. And if I apply RIAA on the way out the sound will be noticably ‘thin’.

So when I use the gain in the Audacity program (and the RIAA equalisation is already present in the record) aren’t I increasing both the RIAA and the volume? The resulting sound is pretty good.

Would you suggest a better quality pre-amp? If so, what type?

Thanks again! - Marvin

Actually no Marvin - when the engineers cut the master they do the opposite RIAA equalisation i.e. they effectively reduce the bassy/volumy bits - so on the way out when you play the record you need to apply the RIAA to put the bassy bits back. This is why if you plug a record deck (one without a built-in pre-amp) into a hif- amp, say the Tap or Aux socket - then you would notice the thin-ness of the sound. People often complain about it on this forum when they do that inadvertently. In your case it seems as though the RIAA is being applied by the pre-amp circuitry in the deck - as you say the sound is ok.

I can’t really comment on whether an alternate pre-amp woul be good - I don’t know if your deck cabn even supply a raw signal without passing it through it’s own internal pre-amp that you say that it has (I tried googling - but there’s not much info on it out there.). Try searching the forums for pre-amp - I seem to remember there have been a few threads on this subject.

The other thing that you might consider is to invest in an external soundcard - two that get mentioned favourably on the forum are Behringer UCA202 and the Edirol UA-1EX. The Behringer is cheaper, the Edirol has more functionality. I myself use the Edirol and am very pleased with that - it does have its own gain control to control the signal level to the PC.

But before you buy anything - have you tried adjusting the Audacity gain control - the Mic slider? Or when you say you use the gain in the Audacity program, are you using the Amplify effect to raise the signal level after you have made a recording?


Hi WC - Thanks again for your fantastic replies!

I have the mic slider all the way up. But what seems to make the difference in amplification is the slider in the audio control box that only shows to the left of the waveform display while you are recording. I have this slider set to a gain of 15db.

So I’m OK. The resulting sound is pretty good. And I’m not a big ‘audiophile’ anyway. I’m going to print out our entire thread and keep it for reference.

Thanks again! - Marvin