Phono preamp with adjustable impedance and capacitance?

Yes, agreed. Really, all folk need to do to is get within manufacturer spec or thereabouts and forget about it. Listen to music.

If you want exacting FR from your front end, cartridges are the wrong place to go looking. They all have bumps and wiggles, correct amplification notwithstanding.

 

Well, a MC cartridge, with its very low inductance, isn't going to have the same challenges with respect to frequency response changes in the audible range due to capacitance loading that a MM is going to have. That's another solution too.

 

I have the EAR 324. I performed dozens of needle drops measuring the frequency response of many different moving magnet cartridges for the purpose of making adjustments to capacitance and resistance to achieve a flat frequency response. Although it was possible to do that, after countless hours of experimentation I came to the conclusion that it’s best to just load the cartridge within the spec of the manufacturer. If you don’t like the sound of your cart loaded within spec, don’t try to change its sound with alternate loading; just get a different cartridge that you like, as-is. Because even though you can “fix” a non-linear frequency response with alternate loading, it does other negative things to the sound that aren’t measurable, but clearly audible.
Most, if not all moving magnets currently available want to see capacitance between 100-200pF, which is relatively low. This is critically important. If you add the capacitance of your tonearm interconnect and the input of the phono stage and it’s higher than the spec of your cart, it will only do bad things for the treble response of your cart. It will be harsh, bright, and rolled off in the upper treble at the same time. As long as you have a 1 meter (or shorter) RCA cable with a low capacitance spec (for example Blue Jeans Cable LC-1) and a phono stage who’s input capacitance is 100pF or less, you’re good. Every moving magnet cartridge I know of sold today is designed to see 47,000 ohms and every modern phono stage is gonna have that.
As far as moving coil… the resistance loading is going to be right about 10x the cartridge’s coil impedance (i.e. if the cartridge coil impedance is listed at 10 ohms, you would set your phono stage to 100 ohms). But again, just set it at what the cartridge manufacturer says. If they say anything above 100 ohms, still set it at 100 ohms. Some people really like to get into setting the phono stage to values above the cartridge manufacturers recommended minimum. That’s fine if you’re into tweaking but will likely drive most people nuts and is not necessary. Really. Just don’t set it below the value they recommend. Capacitance loading for moving coils is not a meaningful adjustment in normal circumstances.
So… as long as you have a capacitance value of 100pF or below for the input on your phono stage (when using moving magnets) and it has a resistance value 10x the coil impedance of your moving coil, that’s all you need to avoid an electrical mismatch between the phono stage and cartridge.
All this being said, my favorite phono stage that’s a reasonable amount of money, will be a great match for virtually every moving magnet and moving coil currently being made, is the MoFi Electronics StudioPhono. The advantage it has over most others is that it has two features I feel are essential for a phono pre - a mono switch and a subsonic filter. You want a mono switch for mono records to cut out all of the vertical-induced groove noise, an audible effect that is not subtle. And the subsonic filter will dramatically reduce the constant high-amplitude sub-sonic resonance that every single tonearm/cartridge produces. It also filters out high amplitude resonance induced by record warps. This will allow your amp and woofers to run more efficiently. And it was designed by the same guy who designed the EAR 324 - Tim De Paravicini.
MoFi Electronics - StudioPhono MM/MC Phono Preamplifier

 

Yes, but FR bumps and wiggles remain. It's a relative flatness. Simpler and more direct route for OP is simply to correctly load his 2M blue with any number of relatively affordable viable phono preamp options prescient of capacitance and its effects. Done.

 

Agreed. Most manufacturers of standalone phono stages figured this out and adjusted their designs accordingly. However, there are still many built-in phono stages and a few oddball standalone units that deviate from this.

I had one of these for awhile and liked it overall but it had a glaring weakness. It does not like higher output cartridges and will distort on hot peaks while using them. I actually ended up corresponding with MOFI's design/engineering department over this. They plan on adding a 34dB gain setting possibly in the future but it hasn't been added yet. I'd probably stick with carts that have 4mV or less output with this phono stage to be on the same side. I wouldn't use it with 2M, Goldring 1000 or 2000 series, certain high output DJ carts, etc. I never tried the SP with MC carts so I have no idea how it performs on that score.

 

Be careful where you post this sort of stuff, they'll burn you at the stake for telling them what they should already know.

 

Thanks for the advice but I couldn’t help myself. “I tells it like it is.”

I truly hope that everyone stays safe and healthy and that we all enjoy listening to music, especially in these times.

Cheers,
John

 

If your brain was fried before, I suspect now it's completely melted and you're curled up in the fetal position in a corner LOL...

 

Changing the capacitance produces a clear and easily measurable difference in the Frequency response of MM phono cartridges. Changing cables of pretty much any sort (other than phono cables) very rarely produces a measurable impact on the sound, even when your ears still seem to hear a difference between them.

Whether this effect is more or less significant to your ears is a subjective call. But in terms of measurements, this is pretty clear cut.