Cartridge Loading

I'm about to buy a phono preamp. Some well reviewed preamps (e.g., Vincent Pho 800, CA CP2) do not provide adjustments to the load on the cartridge, especially capacitance. I've read comments that suggest you really need to get a good match between cartridge and preamp for the best sound. The Pro-Ject Phono Box S and the micro-iPhono2 do.

How critical is this tuning in general? My cartridge is an Audio-Technica OC9

Thanks for any advice.

 

Capacitance is not going to be a big deal with that cart or any moving coil but gain and resistive loading will certainly tailor the sound, so options are great to have. I think many people swap out phono preamps trying to get the sound they want when they should have bought something with options so they could figure out what worked best.

 

I completely agree. I think most people buy phono preamps based on reviews of their "sound quality" and buy blindly when it comes to compatibility and what their system needs for the best sound. I'd go so far as to say that most folks don't even know the basics when it comes to setting up a good turntable system. I also think lots of the "love this phono pre, hate this phono pre" statements are based on accidental compatibility or incompatibility without the knowledge of the listener.

 

Yes, this issue is close to my heart. I have used expensive mc,s for years .
The phono stage/ pre was a Leak point one.
Previous to this a mitchell iso hr. There's were fine.
For various reasons i switched to using a passive preamp.
This resulted in a requirement for a phono stage. I bid for and won an IFI phono stage on EBay.
This had a good review in Hi FI
It's well equipped, with various EQ curves, RCA, EMI, Decca, Columbia.
Loading ie capitance, resistance ie 47k all catered for RIAA, IEC warp filter , in addition high/ low cartridges are catered for.
I now realise that problems in the past with various cartridges were due to incorrect set up, and that sadly i never heard then at there best.
MM cartridges in particular, respond well. To correct loading.
In fact they are now my preferred cartridge!
So yes,very worthwhile to look into the various options, i don,t envy you on this task. As there are so many!

 

That happens for sure. With moving-magnets, I've seen wild swings in frequency-response simply to due to big differences in the capacitance of the phono stage.

 

It is really something to try different cart loads and hear the differences. Not unusual to find a clear winner in a load that is not the one specified by the cart manufacturer either.

 

And we can easily look at mathematical ideal loadings and use that to inform our listening experience.

 

I use a AT MC cartridge (AT33PTG/II), and tweaked the resistance a little bit with Y adapters, but did not find the difference to be very much compared with doing the same with an AT440 MM cartrdige, where the resistive loading made much bigger impacts. I wouldn't worry as much for MC cartridges. I think it's probably just an experimentation route, buy/sell a variety of preamps on the used market, should be able to break even along the way, and see whether you hear much in the way of differences, and what you like.

 

Isn't that the truth? I would love to buy a bunch of used carts and compare them then keep the winner. I have no idea what the "house sound" is of most components. I've heard so few really.Buying used means I wouldn't lose my shirt every time I flip a cart.

 

The Audio Technica OC9/MLII cartridge has a strongly rising response in the top two octaves.

Using SPICE simulation, an LRC shunt load network was derived which neutralises the HF peak and produces an almost dead flat frequency response.

The LRC network is used with an active MC headamp. Each LRC network is wired in shunt with the respective input from the cartridge.

The measurement setup is as set out below:

TURNTABLE SETUP
Linn Sondek turntable (unmodified)
Fidelity Research FR-64S tonearm
Audio Technica OC9/MLII cartridge (1.5g tracking weight)

HEAD AMP
AD797 head amp - see AD797 Head Amp Current Version February 2017.asc (note that DC offset trimpots are not included in simulation)
100R plugin load resistors

PREAMPLIFIER
Custom 10 tube preamp (with optimised RIAA equalisation)

COMPUTER
Desktop computer - Pentium 2.4GHz
CardDeluxe soundcard

SOFTWARE
Windows XP Pro SP3
Cool Edit Pro 2.0 96kHz/16 bit WAV file recording
Cool Edit Pro 2.0/Filters/FFT Filter/Inverse pink noise

SIGNAL SOURCE
Audio System Test Record
Sound Canada; McGill University Records
Side 1, Track 6 - General Purpose Pink Noise Signal

Subjectively, the OC9/MLII has a neutral timbral balance with the LRC networks in place, and is completely free of the hot top end for which this cartidge is well known. Great sound for not much money!

 

Welcome to the forum. You need to go into your user profile and fill-in the equipment profile listed under "information". That will help us understand where you are coming from and to give you the best advice. Without that info, and a budget for the new product, it's hard to give really useful advice.

In short, you will be best served with a better quality phono stage as a LOMC cartridge depends upon the quality of the gain stage to deliver the best sound. You'll get noise and frequency peaks or dips with cheaper preamps. Also loading is important for resistance in a MC cartridge. Not as much capacitance effect, and most MC preamps don't have flexible enough capacitance options to deal with them anyway. You may get lucky and find that the OC9 sounds fine in your system when just set at the 100 ohms that the more affordable units offer, but many find that a lower resistance load is best.
-Bill

 

For MM loading see www.john-oates.jouwweb.nl
Cartridge inductance can vary from 300 to 750 mH, modern cartridges have lesser inductance, perhaps because stronger magnets made that possible.
Nowaday's standard loading still is 47 kOhm, lowering this can tame a cartridge a bit, see Q.