[linux-audio-user] [OT] recording fom turntable (ripping LPs)

Aaron Heller heller at AI.SRI.COM
Tue May 4 14:41:24 EDT 2004

There are further considerations beyond RIAA equalization and gain. 

Moving magnet phonograph cartridges are designed to work into a specific load, typically 47k ohms and 250 pF (e.g., see "Recommended Load" for a Shure V15 on http://www.shure.com/v15vxmr.html), which is significantly different than the load presented by a microphone preamp.   The wrong load will change the frequency and transient response of the cartridge.

Phono preamps are designed to present the correct load to a phono cartridge.  Good ones have switchable loads to accommodate different cartridges and to compensate for the capacitance in the connecting cable.  In high-end gear, it is common practice is to modify the input circuitry of the preamp to specifically match the cartridge and cable in use.

There are also moving coil phono cartridges, which have different requirements.  

By contrast, professional microphones typically have source impedance of about 150 to 200 ohms and are designed to be loaded with a pure resistance in the range of 1 to 5 k ohms.  (here are the specs for a Neumann U87 http://www.neumann.com/infopool/mics/en/u87ai_t_data.htm).

If you are serious, my recommendation would be to use a dedicated phono preamp.  There are some very good ones for around $150 like the Parasound PPH-100, which handles both MM and MC cartridges.

Aaron Heller <heller at ai.sri.com>
Menlo Park, CA USA

Jan Depner wrote:

> I just had a similar problem.  I was getting hum from my receiver/amp so
> I connected the turntable outputs directly to a mic preamp (to get
> enough gain to record).  The problem is that records are/were recorded
> using what is known as the RIAA EQ.  You can find the technical reasons
> on the web.  Basically it boosts the treble and cuts the bass.  All
> phono preamps are supposed to reverse this curve so if you're not using
> a phono preamp you get a very tinny sound.  What I did was to put the
> reproducing RIAA EQ curve into JAMin (setting compression ratios to 1),
> run the inputs through JAMin, and then record using Ardour.  I could
> have put the EQ into Ardour but it's nice to hear it before you record
> it.  The RIAA EQ .jam file is now in the jamin/examples directory when
> you get JAMin from CVS.  Just put it into ~/.jamin and load it when you
> start JAMin.
> Jan
> On Tue, 2004-05-04 at 04:26, Erik Steffl wrote:
>>   so i finally got the recording on sb live! platinum working and I'd 
>>like to rip my old LP collection. So I bought the only turntable with 
>>pre-amp I have found, connected it and the sound was terrible (I think 
>>it was mostly too weak, wasn't even at 50% at max), it's also a cheap 
>>denon. I connected it to the RCA inputs on the liveDrive (front panel). 
>>BTW the liveDrive RCA work ok with line6 guitar pod and iPod.
>>   so my off-topic question is - how to connect the turntable? which 
>>turntable to get? since I mostly plan to use it to rip the LPs and I'm 
>>not going to use it afterward I'd prefer cheaper solutions (not the 
>>denon though:-)
>>   I also have receiver with phono input (so no pre-amp in turntable 
>>needed) but I have no way to get the signal out of receiver, it only has 
>>speaker outputs.
>>   so I guess I need sort-of-decent turntable with pre-amp or turntable 
>>plus external pre-amp? any recommendations?
>>   (and yes, I am using linux box with gramofile, so this is at least 
>>close to the topic:-)
>>   TIA
>>	erik

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