Distortion in needledrops

[funkyt]

Yo everyone wassup.

I am a club deejay from Singapore, and am trying to record my hiphop rnb vinyl into my computer in order to use my music on the Serato Scratch Live system during my club sets.

Previous experiments on recording from my Vestax PMC 007 mixer into my M-Audio M44 PCI card (or Creative X-Fi Elite Pro) have not produced good results -- the mids and highs were lacking. So I figured that perhaps the mixer's pre-amp wasn't particularly good.

So I borrowed my uncle's NAD Monitor Series Pre Amp Tuner 1700, which had not been used for many years, cleaned the connections which were starting to get mouldy, and set up for recording in this manner:

Turntable --> RCA into NAD pre amp phono --> RCA outputs to two 1/4" in M Audio break out box --> PC

I am using a new Shure M447 cartridge, with a clean needle.

I used Adobe audition 1.0 for recording at 44100Hz 32 bit. I set the NAD pre amp to output at 'low level' and adjusted the NAD volume control to 12 o'clock. This gave me peaks of around -3dB and -4dB on Adobe Audition.

I proceeded to record my music in this manner. However, I can sense some distortion in the music, it appears that it is cause by 'too much bass'. I have checked that the bass and treble EQ on my pre amp is all set to neutral (12 o'clock).

Here's a short clip of my recording:

http://www.mediafire.com/?91zwcwjxjki

I tried analysing the waveforms and noticed that there were many 'slanted straight lines' in the waveforms (not the horizontal flat lines caused by digital clipping.

Here's a snapshot of the 'slanted straight lines':

http://www.mediafire.com/?8dmnokzvhzj

And here's a zoomed snapshot:

http://www.mediafire.com/?fmhyy1ndldw

I notice this pattern occurs in all the recordings using this setup. Could the above be caused by analog clipping?

I would greatly appreciate any comments and suggestions to help fix this problem. :)

[pbthal]

Yo everyone wassup.

I am a club deejay from Singapore, and am trying to record my hiphop rnb vinyl into my computer in order to use my music on the Serato Scratch Live system during my club sets.

Previous experiments on recording from my Vestax PMC 007 mixer into my M-Audio M44 PCI card (or Creative X-Fi Elite Pro) have not produced good results -- the mids and highs were lacking. So I figured that perhaps the mixer's pre-amp wasn't particularly good.

So I borrowed my uncle's NAD Monitor Series Pre Amp Tuner 1700, which had not been used for many years, cleaned the connections which were starting to get mouldy, and set up for recording in this manner:

Turntable --> RCA into NAD pre amp phono --> RCA outputs to two 1/4" in M Audio break out box --> PC

I am using a new Shure M447 cartridge, with a clean needle.

I used Adobe audition 1.0 for recording at 44100Hz 32 bit. I set the NAD pre amp to output at 'low level' and adjusted the NAD volume control to 12 o'clock. This gave me peaks of around -3dB and -4dB on Adobe Audition.

I proceeded to record my music in this manner. However, I can sense some distortion in the music, it appears that it is cause by 'too much bass'. I have checked that the bass and treble EQ on my pre amp is all set to neutral (12 o'clock).

Here's a short clip of my recording:

http://www.mediafire.com/?91zwcwjxjki

I tried analysing the waveforms and noticed that there were many 'slanted straight lines' in the waveforms (not the horizontal flat lines caused by digital clipping.

Here's a snapshot of the 'slanted straight lines':

http://www.mediafire.com/?8dmnokzvhzj

And here's a zoomed snapshot:

http://www.mediafire.com/?fmhyy1ndldw

I notice this pattern occurs in all the recordings using this setup. Could the above be caused by analog clipping?

I would greatly appreciate any comments and suggestions to help fix this problem. :)

Does your preamp have a line level out? By using the volume control you are gonna get distortion

[funkyt]

By line level out, do you mean by an output that cannot be adjusted using a volume control?

There was one output that was labelled as 'normal' and another as 'high'. I used the one labelled as 'normal'. Both can be controlled by the volume control.

Btw, I am curious as to what the EPL function and outputs are for. What does EPL stand for?

[DaleH]

By line level out, do you mean by an output that cannot be adjusted using a volume control?



Try using the tape out or tape record jacks and select record phono on the tape loop. This will bypass all the junk in the preamp. Digital recording may soft limit peaks with a sloped cutoff on some cards. Try just 16/44.1 also as a test.

[pbthal]

By line level out, do you mean by an output that cannot be adjusted using a volume control?

There was one output that was labelled as 'normal' and another as 'high'. I used the one labelled as 'normal'. Both can be controlled by the volume control.

Btw, I am curious as to what the EPL function and outputs are for. What does EPL stand for?

You can use the EPL. it is Effects processing loop

[funkyt]

Ok, I'll try that when I get home today.

It is strange tho, that even when I listen to the music through the headphones plugged into the pre amp, the music already sounds distorted..

[DaleH]

Also make sure the MM/MC switch on the back of the NAD is on MM. If it's on MC you'll overload the phono input.

[funkyt]

Ok, I'll try that out!

Thanks for your suggestions! :)

[nelamvr6]

Also make sure the MM/MC switch on the back of the NAD is on MM. If it's on MC you'll overload the phono input.

That sounds to me like it might be the culprit if the sound is distorted while monitoring on headset out of the receiver.

[rsub8]

Here's a short clip of my recording:

http://www.mediafire.com/?91zwcwjxjki

I tried analysing the waveforms and noticed that there were many 'slanted straight lines' in the waveforms (not the horizontal flat lines caused by digital clipping.

Here's a snapshot of the 'slanted straight lines':

http://www.mediafire.com/?8dmnokzvhzj

And here's a zoomed snapshot:

http://www.mediafire.com/?fmhyy1ndldw

I notice this pattern occurs in all the recordings using this setup. Could the above be caused by analog clipping?

I would greatly appreciate any comments and suggestions to help fix this problem. :)
It's being clipped before getting to the A/D converter of the soundcard, and if I'd have to guess, I'd say the phono preamp is overloading.

The slanted lines are exactly how clipped waveform peaks appear after passing through a low pass (DC blocking or rumble) filter somewhere in the signal path (probably at the output of the phono preamp or at the input of your soundcard, or both).

[funkyt]

Hi guys,

Yes, the switch was set to MC. Switching it to MM seems to have solved the problem! Thank you all so much!

Everything sounds so clear now..

I still detect a few patterns of the sloping lines that I mentioned in certain cases.. Is that normal? I'm juz wondering if I missed anything out.. I'll try to post up some recordings and let you guys take a listen :)

Cheers!
Ti-Eu

[rsub8]

Hi guys,

Yes, the switch was set to MC. Switching it to MM seems to have solved the problem! Thank you all so much!

Everything sounds so clear now..

I still detect a few patterns of the sloping lines that I mentioned in certain cases.. Is that normal? I'm juz wondering if I missed anything out.. I'll try to post up some recordings and let you guys take a listen :)

Cheers!
Ti-Eu
So the turntable preamp was clipping. Glad you were able to fix the problem. If you're still getting the same sort of waveforms in your recordings, this could be a sign of clipping elsewhere in the signal chain.

[funkyt]

Although the sound quality is much better now, but I'm still concerned as there still appears to be some form of clipping when I listen to the music, and I still observe some similar waveform patterns in the new recordings.

Here's a link to two clips of my new recordings after correcting the MM switch.

http://www.mediafire.com/?dnndbzhvmmh
http://www.mediafire.com/?ezzynzem1tu

Would appreciate any comments on the quality of my needledrops, esp with regards to distortion. :)

Also, should I turn on the Infrasonic switch on my NAD pre amp?

[dinchart]

"Also, should I turn on the Infrasonic switch on my NAD pre amp?"

Can't hurt. It was designed to filter out TT rumble.

You may want to consider a different cartridge. Your Shure is a scratch cart with a very high output (9.5 mV) and a big fat stylus -- good for taking turntabalist abuse, not so good for hi fidelity. I think you would get better sound with a M92 or the equivalent Audio Technica (95E?). what TT are you using?

[funkyt]

I'm using a Technics DD SL1210-MK2 TT.

Yea, I am seriously contemplating buying a new cartridge for the purpose of doing some great sounding recordings, so that my Serato system will sound as good as possible. Although I have to convert my recordings to mp3 for my club sets, I feel that I still would like to have quality recordings, for higher quality playback, and for the purposes of remixing.

What do you recommend? The shure M447 cart I am using is now supposed to output high bass, and I hope that other cartridges would not have less bass compared to my Shure..

I am considering the following:

1) Audio Technica AT440MLa
2) Shure M97xE

Would they be suitable for Hiphop RnB singles/LPs?

[dinchart]

I'm using a Technics DD SL1210-MK2 TT.

...[w]hat do you recommend? The shure M447 cart I am using is now supposed to output high bass, and I hope that other cartridges would not have less bass compared to my Shure..

I am considering the following:

1) Audio Technica AT440MLa
2) Shure M97xE

Would they be suitable for Hiphop RnB singles/LPs?

Both the M97xE & 440MLa have much lower output voltages than the M44, but either will do a better job of accurately retrieving low frequencies for recording purposes than your M44. It comes down to which of those two is a better tracker (you have some heavily modulated grooves to deal with on hip hop records). I'm not really familiar with ATs (I've only owned one, a much cheaper model than the 440MLa), but I've run plenty of Shures over the years, and always found them to be the tracking kings.

BTW, if you didn't already know, your M44 needs a couple of weeks of solid use to break in.

[funkyt]

Thanks for the info dinchart. :)

I didn't expect my M44 to require so many weeks to break in.. I thought breaking in only affected the stability during scratching -- how does it adversely affect the sound performance?

[funkyt]

Correction, I meant, how does *not* breaking in well enough affect the performance?

[dinchart]

Correction, I meant, how does *not* breaking in well enough affect the performance?


Look at Chapter 1:

http://www.shure.com/ProAudio/Products/us_pro_djlibrary_bookshure

BTW, break in here has to do with skip resistance; I don't think it has anything to do with your distortion issue.

You know, another good needledrop cartridge might be Denon DL160, which is a lower compliance cart that either the Shure or the AT and should be a good match for your tonearm. I don't have one but there is a good review here:

http://forum.audiogon.com/cgi-bin/frr.pl?ranlg&1031089600&read&3&4&


Good luck. It's not my scene but I really enjoy some of the insane things turntabalists do.

[rsub8]

http://www.mediafire.com/?dnndbzhvmmh

Would appreciate any comments on the quality of my needledrops, esp with regards to distortion. :)

Also, should I turn on the Infrasonic switch on my NAD pre amp?
I took a look at the waveform of the above music snippet, and didn't take very long to find clipping. Plenty of it happening at around 15.619 into the track. I'd suspect that either your cartridge output is too high for your preamp, or the preamp gain is set too high.

The clipping isn't a result of low frequency ("infrasonic") overload, because the clipping happens on positive and negative waveform peaks within just a couple of milliseconds of each other. If a low frequency waveform (from rumble, etc.) were solely responsible for overload (having a period of tens of milliseconds), this wouldn't be the case.

That said, the infrasonic switch couldn't hurt. Just don't expect it to fix the clipping, at least in terms of what you're getting here, however.

[funkyt]

Thanks dinchart for your comments and links. :)

[funkyt]

rsub8,

I'm not familiar with the shape of clipping, as I only know horizontal straight lines from digital clipping. Since we're talking about analog clipping here, are your referring to the slanted straight lines? Is it true to say that in all forms of analog recordings, it is abnormal to see such lines?

As for the the possible reasons for clipping, i usually set my pre amp volume such that my digital recordings peak around -3dB. I could set it lower to see if the problem disappears, but I reckon I would lose out on some dynamic range from not using some bits in my recording.

As the M447 is stated by Shure to be a high output cart of up to 9.5 mV, it is quite possible for the pre amp input to be overloaded.. But it would be strange for Shure to release a cart that would overload a pre amp wouldn't it? Unless it is common for DJ mixers to contain pre amps that can take high phono input levels.

I am considering buying a new cart for the purposes of recording only, perhaps that will solve the problem..

[rsub8]

rsub8,

I'm not familiar with the shape of clipping, as I only know horizontal straight lines from digital clipping. Since we're talking about analog clipping here, are your referring to the slanted straight lines? Is it true to say that in all forms of analog recordings, it is abnormal to see such lines?

As for the the possible reasons for clipping, i usually set my pre amp volume such that my digital recordings peak around -3dB. I could set it lower to see if the problem disappears, but I reckon I would lose out on some dynamic range from not using some bits in my recording.

As the M447 is stated by Shure to be a high output cart of up to 9.5 mV, it is quite possible for the pre amp input to be overloaded.. But it would be strange for Shure to release a cart that would overload a pre amp wouldn't it? Unless it is common for DJ mixers to contain pre amps that can take high phono input levels.

I am considering buying a new cart for the purposes of recording only, perhaps that will solve the problem..
As I said earlier (and attempted to detail quite painstakingly in several posts a few months ago) ;), when a clipped waveform is high-pass filtered, this is exactly what it looks like. Same thing as when (if) you've ever seen some amplifier reviews, that show the reproduction of a (for example) 20 Hz square wave. It starts out as "horizontal lines." If there is any DC blocking or low pass filtering in the signal chain (very likely in a phono preamp, and very likely at the input of your sound card), you get slanted lines, not horizontal ones. (And in post #10, I said low-pass filtered. I meant high-pass, sorry.)

I added the waveform below from an earlier post of mine. This is from the DCC Creedence Clearwater Revival "Cosmo's Factory" except that I deliberately clipped it by applying a gain increase (upper waveform). Flat tops. The lower waveform is after passing through a 16 Hz high-pass filter, similar to a preamp rumble filter (as an example, but just because you haven't activated the preamp's rumble filter, doesn't mean that there isn't other high-pass filtering in the signal chain). Notice that the same clipped parts now are straight lines - but tilted.

I can't determine if your clipping is occuring in your soundcard (the analog circuitry of the card, that is - if the clipping were digital, you'd have horizontal lines), but it seems unlikely. It could be that your phono preamp has too much gain for a 9.5 mV cartridge. It might be just perfect for a 4 mV cart, but 9.5 would be like having more than an extra 6 dB of gain.

[funkyt]

I've tried doing a recording with the volume turned down in my pre amp, and recorded with peaks of -12dB, but the clipping still seems to occur.

I doubt the culprit is my sound card, and my guess is also my cartridge. Will try to borrow a different cart and doing some testing and keep you guys posted.

[funkyt]

Hi rsub8,

I managed to dig up an old Stanton AL 500 II cart just for the purpose of testing. It has an ouput of 4.5mV. However the clipping in the waveform still persists.

I also tried changing from my M Audio sound card to my Creative X-Fi Elite Pro sound card, and the clipping still occurs.

So I guess we can safely say that the problem is not due to

1) Too high an output at the cartridge
2) Clipping in the soundcard

Please correct me if I'm wrong. :)

I've attached 2 images below. The 1st shows a part of waveform recorded from my NAD preamp (with clipping). The 2nd shows the same part of the waveform recorded using my Vestax PMC 007 DJ mixer (which does not appear to show clipping).

I've read through your previous post and understand much better now how the analog clipping works in your example. However, the slanted straight lines in my recordings do not appear to be triggered by the clipping shown in your example, as they occur in sporadic moments along part of the upward or downward slopes, and also often along the whole slope.

I shall try to doing a recording using a line input source of NAD preamp using a CD to see if the culprit is the NAD phono pre amp..