Can a turntable cartridge overload/clip a phono stage input?

I'm not entirely sure how to word this but, I use my E-MU 1616M sound card with built-in phono stage to take recordings from my turntable (I have a couple and will soon be getting rid of one, let's say I'm using my Thorens TD 104 MKII with Ortofon M20FL Super) and I find that with a few discs, perhaps ones that are cut hot, I'd say the waveforms look clipped. I don't believe I have any way of altering the input sensitivity, but as it is a MM phono stage I'd assume it would be compatible without overloading with the majority of MM cartridges.


This is a screenshot of a recording I made earlier, turntable directly into MM input. Surely that level of clipping isn't right?

 

So that is the result you get with a signal going direct from your turntable to the sound card? Nothing else in the signal chain? No, that doesn't look right. But I've never used a sound card with a built in phono stage, so I don't know what to suggest. Somebody around here will.

 

Turntable going directly to the MM input, nothing in between. It is a particularly hot cut 12" single but still, it's clipping the input and I don't believe there's any way to change the sensitivity. Is this more an issue with the EMU 1616M phono stage?

 

No specific knowledge, but usually with these kinds of audio interfaces there is a way to toggle input sensitivity between 4 dBu and -10 dBV, but you shouldn't come anywhere close to overloading either one of these with a 5 mV signal coming directly off a cartridge. But I've never seen one of these interfaces that has a built in MM stage -- presumably that involves some kind of software RIAA equalization and some kind fixed gain? Can the RIAA equalization be applied in software after recording the signal? I would suggest taking the phono signal into a phono pre input and doing RIAA equalization afterwards, but the impedance loading on the cartridge will be all wrong. Best solution might be to get an outboard phono pre and bring the output of that into the line level inputs on the DAW.

 

The phono input is set to -10dBv, I'm assuming that is correct (if you see the photo below it is the Dock In 2L/2R input). It's definitely a hardware phono stage. I'm really quite baffled as to how an MM cartridge is overloading it.





Here's the specs regarding the phono stage if it helps:

Turntable Input (w/ground lug and hardware RIAA preamp)

Phono Input (stereo)
Type: RIAA equalized phono input
Maximum level:

Professional: 60mV RMS
Consumer: 15mV RMS
Input Impedance: 47Kohm
Frequency Response (20Hz - 20kHz): +0.1/-0.3dB
Dynamic Range (A-weighted): 96dB
Signal-to-Noise Ratio (15mV RMS unbal input, A-weighted): 96dB
THD+N (1kHz, 15mV RMS input): -90dB (.003%)
Stereo Crosstalk (1kHz at -1dBFS): < -80dB

 

Is the gain fixed of the phono inputs, or can you turn the gain down, or have you already tried bringing the gain all the way down on the preamp/interface? Also, you say the waveforms look clipped, but do they sound clipped? I mean, I see the picture of the waveform up against the edge of the display there, but sometimes with these DAWs and software, it's more a matter of the display and scale.

 

The gain is fixed as such, but I just made a test recording of the same hot disc with the +4 (Professional) setting enabled and I end up with a quieter recording that seems to preserve the peaks rather than overloading. Has to be normalised afterwards but does seem to be better!

 

Have you tried using this device with a different piece of recording software? It looks like your software only gives you a couple choices in terms of the gain settings on input and output to the computer. Other software should allow you to adjust that manually. Try something else like VinylStudio, Audacity, etc..

 

Ahh, I use Adobe Audition, the screenshot is the E-MU software that controls all the hardware elements. It would seem if I'm recording something cut hot I need to hit the professional level input gain, whereas other discs should be fine with the standard consumer level settings.

 

Perfect, with that setting you'll be able to handle much higher voltage peaks without running out of headroom. Not sure what your cart output is, I just assumed 5 mV, which shouldn't have been a problem with either input sensitivity, but glad you found that switching sensitivity worked.

 

AS far as I can find for the specs of the Ortofon M20FL:
Type moving iron
Output Voltage 4 mV
Frequency Response 20Hz - 20kHz
Tracking Force 1.5g
Mass 5g
Channel Separation > 27db
Channel Balance < 1.5db
Load Impedance 47k ohms
Output Impedance 800 ohms
Stylus D-20FL Super
Stylus Tip fine line
Dynamic Compliance 20x10-6cm/Dyne

It still doesn't make sense that it's overloading the 15mv consumer level input with an output voltage of 4mV...!
Nevertheless, the best solution is to load up the gain profile that allows a higher overhead.

 

Well, that 4 mV is probably for a 1kHz sine wave groove at a particular groove velocity. You were playing a 12" single right, 45 rpm? So not only were you talking about frequencies other than 1kHz but the groove velocity is probably way higher than the the spec measurement was made at, and then you said it was a record cut at a hot level too, yes? (I'm not clear on the relationship between linear velocity and the tracking velocity of the groove modulations, maybe there's an engineer on here who can illuminate, maybe it's unrelated to rotation speed). So maybe the combo is enough to put out something approaching what the 15 mV input threshold in that spec?

 

I am not familiar with the Creative phono amp. I wonder tho if you have a gain control on your program? It makes no sense to me the level would be non-adjustable, of course, records are cut at different levels, and styles of music vastly at different levels.

I do not think your phono amp is clipping. You are overdriven somewhere post phono amp (downstream)

 

The Creative sound card, being switchable between professional +4dBu and consumer -10dBv levels, likely has either an analog "booster", or just adds digital gain, applying a 4x voltage boost when consumer line level is selected.

The phono input on the sound card is likely gain matched for the DACs without the consumer boost turned on. The line input level setting should have no effect on a phono levels, but it does, incorrectly boosting phono also, a bad design or oversight.

Mixer controls in Windows should also control the analog input levels. In Windows 7, for example, Control Panel -> Sound -> Recording (tab). Select the interface and choose properties, then Levels (tab). The phono input is piggy-backed on input 2 of the E-mu, volume controls for that input port in "playback" may affect the recorded levels. If there is only a single level there for the whole card, you may be able to refine the levels instead with the Creative-supplied mixer control panel.

 

I assume that's the patchmix software you're using with the 1616? If so, you can insert a trim control on the phono in channel strip. That's the way I do it.

 

What dictates output at a given freq is amplitude, so RPM doesn´t matter. But as we can have a larger amplitude at outer grooves than on inner grooves, we can also have a larger amplitude with 45 contra 33.3. 45 will track higher amplitudes.