MC high output vs MM
Following my recent experiments with getting the best from a high output MC cart, a pre owned Hanna EH, I thought I’d share my thoughts for anyone interested.
I put a pre owned LP12 in my study connected to a nac 62, powered by a hicap, and feeding a nap 140 in to Focal 302 speakers. I had a few carts kicking around from previous use on my P3 so tried the venerable vms20e with cap 210, at vm95e, and a Grado Gold moving iron. The AT gave me the best sound but still not up to the level I expect from an LP12. I was intending to get another Hana MC low output but a pre owned low hours EH (high output for mm phono stage) came up. Worth a try? I thought so having previously enjoyed the sound of a DL110 high output mc cart. I also allowed that if I didn’t get on with the EH I could move it on to my P3 that I still occasionally use with a Nait 2.
So fitted, aligned, weighted and tracked and first play through the nac62 with 322 cards. I was both impressed and disappointed. Impressed with the level of detail but disappointed with the lack of openness or space between frequencies. The sound was compressed, better than the MM carts I have, but not the openness and separation that I enjoy from MC carts generally. I have a number of 5 series phono cards, S,K,E and N, and an 82 sitting unused. Remembering having read that the E card had a different gain as well as loading suited to ‘mid’ output MC’s I decided to try the EH cart with these. First though I needed to check if there was any danger to the cart, the cards, or the pre by doing so. The internet is a great learning tool. I understand enough about basic electrics and physics to grasp basic principles. I have no understanding of electronics. The following is what I think is relevant to changing the loading on a cart. Forgive if obvious and simple to those already experienced in all of this.
The first thing that loading is applied in parallel not series, ie the load across the cart decreases as the applied load increases. A selected 47k ohm load applies less load to the cart than a 100 ohm one.
The major difference between the design of mc and mm carts means that the mc coil mounted on the cantilever utilises finer and fewer windings compared to the more robust arrangement of the coils mounted close to the cantilever in a MM design, thereby affecting electrical output.
The mechanical damping of the stylus and cantilever is vastly different between a relatively heavy magnet or iron lump mounted on the cantilever (mm) vs the lighter coil mount on the mc design.
Physics/ electrical theory tells us that changing the electrical characteristics around the assembly will change the electro mechanical damping that affects the stylus and cantilever. This in theory can affect the tracking and information retrieval possible from the vinyl groove.
Due to the fixed capacitance on MM carts and phono input stages, varying the load would have little effect even if it were available. On the other hand due to massively lower output of an mc design, varying the load should have a noticeable effect on electro mechanical damping and output, as well as useable range of gain, or volume control.
A theoretical loading of x10 is often conventionally quoted as being necessary for loading an mc cart, particularly to avoid high frequency peaks, plenty of graphs showing this on the ‘net, and also theorised as necessary to avoid tracking problems due to either excessive or insufficient electro mechanical damping. Less load increases damping = stiffer cantilever and difficulty in tracking fine detail changes. Ie. A cart designed to be loaded at 47k ohms will potentially lose effectiveness in both areas if loaded at 47 ohms, and the reverse applies. Carrying all this in my head I then looked at discussion around these areas before first taking the low risk of running the EH on the 82 with an E phono card. Happily the sound opened up and gave me what I might have expected from a mc cart as opposed to an mm.
I then came across a pre owned variable load phono stage, the PH-10 and decided this would allow me to re instate the 62 and use this phono stage. Having connected it I then decided to run sq tests on the cart at different loads and gain adjustments via the phono stage.
I have spent six days playing with settings and comparing the sound against two references. The first is against my main room kit of P8/SL/PH-10/552DR/300DR/D9.2. Obviously too many variables for a direct comparison but it was useful to compare openness and space between frequencies, distortion or not etc. The more useful comparison though was using the same nac 62 set up and comparing the Aries/Vega input against the Lp12/EH/PH-10 input. It is useful to bear in mind that the streamer output is up to 4mv rather than the normal cd output of 2mv.
Comparison was made with Coltrane, Miles, Chet, Joni, Cohen, Eels, and finally a very loud original vinyl Tommy.
An almost match of sq came from a remarkably low load setting of 100 ohms ( against the nominal 47k ohms spec of the EH) and -3db gain. Going above 100 ohms to 220 ohms gave an unusable range of gain at low levels and was more of a step than going from 1000 ohms to 47k ohms. At 100 ohms setting, sq and gain (volume setting) more or less equivalent to the streaming input, there was no distortion or high frequency effects noticed by me even at very loud volumes. No compromise was needed using a high output mc designed for input to a 47k phono stage. Why not?
A good starting point may be here if Richard allows the reference
If not look up Jim Hagerman, Hagtech, and Jim Austin Stereophile.
The outcome is that I am now running a high output mc on a variable input mc phono setting rather than the spec’d mm standard input. I shall see how and if the sound changes over time due to any unwanted influences on either tracking sensitivity or electromechanical damping.
