Do I need a MC cartridge now? Or an attenuator?


Hello folks,

I am turning to this network of smart folks for help in an area i don't know too much about.

I have a MoFi  Electronics StudioDeck+ turntable, and a MoFi Electronics UltraTracker MM Phono Cartridge. Previously, this MM cartridge output went to my McIntosh MA252 integrated amplifier using its phono input. The range of volume was fine and I could play it at a low volume - it sounded terrific.

I now have set up a mostly Laiv Harmony system  and the signal goes to the Laiv L-Ext for phonographs, and on through to the Laiv HP2A preamplifier and then to the Laiv GaNM Monoblocks. 

The sound volume control on the HP2A ranges down to minus 59 dB and then it shows an infinity sign and there is no sound output. However, the sound coming out at -59 dB is still rather loud. There is no volume control on the monoblocks; the HP2A does that entirely. In discussions with Laiv Harmony help (which is really responsive and helpful) has provided me with a couple of options. 

He wrote: "The MoFi UltraTracker is a high-output MM cartridge (~3.5 mV), while the LExt Phono is a dedicated MC phono stage with a fixed 70 dB of gain — optimized for low-output MC cartridges (around 0.3 mV).

"Using them together results in excessive gain — similar to feeding a line-level signal into a mic preamp — which causes the signal to be overly loud, distorted, or clipped. This is likely the issue you're experiencing.

"One option is to replace the current MM cartridge with a compatible low-output MC cartridge. You can also reach out to MoFi for recommendations on suitable MC alternatives that pair well with your setup."

A second alternative we discussed was to place a signal attenuator between the HP2A and the monoblocks - I have ordered Rothwell balanced in-line attenuators (minus 10dB) for about £71. I figured that can't hurt and is affordable enough to try.

Replacing my ultratracker with a moving coil from them is an about $1,000-$1,500 experiment.

My questions:

1) Are Rothwell attenuators OK to place in the line? Possible effect on the sound?

2) I am pretty pleased with my TT - I think it is very underestimated for its quality, out performing its price point in general. But would an UltraGold MC Phono cartridge for $1500 be wasted on that turntable? I am just not well enough versed in the differencs between their top TT and the one I have, to know if this makes sense.

Tim

timothy468

While I am not familiar with the Rothwell attenuators, Rothwell is a good company and since you already have them on order you certainly should give them a try.  They can't hurt anything and you should give them a listen and make up your own mind.  If the sound is OK to you then your problem is resolved.  If not then a low output MC cartridge is your best alternative and of course there are a lot of options there.  Ortofon just introduced a new low priced line that are getting good reviews that are worth considering.  Audio Technica also offer MC that are excellent that are well under the price you have been quoted.  

I think one of the issues you are going to encounter is proper cart loading, using the MC input on a MM cart is not going to give the proper loading the cart wants to see. 47kohm is normal for MM but MC rarely exceeds 1kohm. If the Rothwell allows for this then you’re fine, but if not you are not going to get an optimized sound from the MM cart into a MC stage.

You may be better to buy an inexpensive phono stage (MM) for now until you can upgrade to an MC cart. 

Even something like a Denon 301 MC is an option untill you can affored beter. 

This sounds to me like the old (Henny Youngman) joke about the tailor who made one leg of your pants too long.  So when you complain, he tells you to "limp", in order to make the pants appear to fit.

If you are only a very casual listener who is not that interested in ultimate sound quality, then sure, the Rothwell ought to work.  But it is a kludge that will compromise your sound quality no matter how good it is.  Also, I have to wonder about cartridge loading. If you are using an MM into an MC input, it not only affords far too much phono gain but also you may be loading the cartridge excessively. (High "load" here means that the input impedance of your phono stage is too low in impedance which here is another word for resistance.). There is no way to get around that, and that will really compromise the sound quality from any MM cartridge.  The standard load for an MM cartridge is 47,000 ohms (47K ohms).  Typical load for an MC cartridge is 100 to 1000 ohms.  There is no easy way to fix that with your phono stage. Furthermore, because your MM cartridge has a much higher signal voltage output than any low output MC cartridge, your cartridge is undoubtedly also overloading the phono input, which causes further distortion.  It's a mismatch any way you look at it. So you need either an MM phono stage or a new LOMC cartridge.  The Rothwell will only solve the gain problem.

I think trying to make that combination of cartridge and phono preamp work well together is going to be an exercise in kludgery that will result in you not getting the best out of either component. You’re likely to get better sound by replacing either with a properly matched component, even if it’s a budget model.

The Laiv Harmony HP2A, using their L-Ext (phono input) allows me to change the input impedance via their "selectable input impedance" at 22Ω / 47Ω / 100Ω / 470Ω / 1kΩ / 47kΩ. I am currently set up at 47kΩ (which matches the TT MM output) but the gain cannot be changed.

I have reached out to MoFi for help in determining if their MC cartridge will work with their Studiodeck+ turntable - I suspect it will. I think I then select the 100Ω input impedance, as the MoFi site tells me that their two replacement cartridges specs are "Recommended Load: ≥ 100 Ohm"

My phono experience with this TT/MM stylus into the McIntosh MA252 (into either of my speakers) has sounded superb. I cannot discern too much distortion in the new setup (though I suspect there is) - just too high a dB volume. It does not have a MC phono input however - I suppose I could go with their MA12000 which has one of each phono inputs. devil

I think I could put some other form of phono pre between the TT and the L-Ext but that seems like kludgery to me as well.

I will likely get the better MoFi MC stylus. I have slacked off in overspending lately anyway, and I can't have my wife getting used to that! 

 

Tim

I agree with the above comments.  However, the Laiv L-Ext Phono does have a 47k setting.

Bill

Similar to a Phono Box E Phono Preamp I got a while back on Amazon, but cheaper. I used that to eliminate hum and improve my signal to noise ratio from an old turntable to my reciever. Gave it when I sold the TT to a friend.

Attenuators can't fix your problem. Its just that simple. You need to understand the difference between gain and volume. You have a gain issue, and that means you have to fix the problem with gain. The high output of your phono cart is overdriving the input on your phono preamp. If you use volume/attenuators, the distortion will still be there no matter how much you lower the volume.

Anything involving gain is on the input of a component, and anything involving volume/attenuation is always on the output of a component. They are 2 separate things. You can only damage the signal with excess gain. Volume/attenuation can't alter or damage the signal in any way (aside from whatever slight coloration that may happen when the signal passes through the it). Its like having a record with a lot of scratches. If you lower the volume, the scratches are still there. You need to get a different phono pre or a different cartridge. Its your only option. 

As always, sound quality is subjective. That said, a LOMC cart should make a significant difference in sound quality. And its the type of difference I think you'll be very happy with. I can't make any guarantees, but I think there's a far greater chance you will like a new cart, than not like it.