Correctly load your MM - How to change resistor loading with your phono preamp, easy!

[paul300b]

:)http://daveyw.edsstuff.org/vinyl/loading/

Loading plugs you make yourself! Great! easy! :)

[Owen Young]

Not a bad scheme, avoids soldering work & alterations to preamp.

For best fidelity however, best to install loading sockets on the preamp & use resistor plugs similar to above. Then, the usual 47k ohm preamp load R can be removed & loading Rs of the exact load value can be used... instead of having to do the calculations...
1/R total = 1/R1 + 1/R2

eg. My phono preamp...
7780

PS. Resistive loading is more applicable to MC carts.

[paul300b]

Cheers Owen. Yes, I use a one rca to two rca socket joiner thing, and solder a resistor to one rca, the other has the tonearm wiring. I used 32ohms (total) on a at 440ml to calm the top end down a bit.
I've an old SME tonearm with a resistor and capacitor soldered to the rca in the tonearm leads. An old 1970's trick perhaps?

[gortnipper]

My VS JLTi uses RCA jacks/plugs to change the loading. Plugs with a resistor soldered in to bridge the +/- change the loading. No plugs installed keep default 47k. A really handy set-up IMHO and cheap to build it out well with Switchcraft plugs (good enough for Shindo =).

7791

[paul300b]

Nice Gortnipper! There are review of mid-market phonostages in the Jan issue of Hi-fi news. A few use clip on resistors under the preamp (bottom) to change loading, which I thought was a good idea. Easy to get to, fast to change and it stops unwanted fiddlers.

[Owen Young]

The Artemis Labs PH-1 phono preamp has this easy scheme with a rear panel ZIF socket, into which you can simply clamp your loading Rs...
7792

[hopeman]

Different amp got different formula?

Here's the formula for my current phone-stage.


Quote,

To calculate the value of the resistor to connect to the load plug,
you need to know the input (or load) resistance that your
cartridge requires for optimum sound quality. You should find this
in the instructions for your cartridge. You can calculate the load
resistance by using the following formula:

Rload = RPPA20 x RTERM
_______________
RPPA20 - RTERM

RLOAD is the load resistor in Ω that you need to put in the plug.
RTERM is the load resistance in Ω that the cartridge needs.
RPPA20 is the factory-fitted input resistance of the PPA20 which
is 47 kΩ when set to mm and 470 Ω when set to mc.

Quote.

However for my current cart, with my previous amp, I switch R from
100, 250, 1K, almost no difference...

[Owen Young]

Almost all phonostages that provide loading sockets, require similar calculations, eg Artemis Labs:
7811

However, wouldn't it be good if you can install a load resistor without doing these calcs? ie. Wouldn't be best to chose a 100 ohm resistor when you want a 100 ohm load? Also, the signal is only going through one resistor, instead of 2 in parallel. For this to happen, ideally the preamp designer needs to make the standard 47-50k load R accessible for swapping out (without the use of a soldering iron would make it easier from all).

[Owen Young]

However for my current cart, with my previous amp, I switch R from
100, 250, 1K, almost no difference...Hi hopeman,
A MC cartr with 12 ohm coil imped (Benz Micro Wood SL) would normally perform well with loadings of ~90-120 ohms upward. As you reduce the load R too much the LF dynamics will begin to be affected. Also the top end may become softer/less bright, when loading down. You can chose just the right balance (of power/dynamics & tonal balance) for you.

Note, as you load down, output level may reduce a bit....don't confuse this with the above characteristics.