[kenreau]

Thanks for all the great ideas and suggestions!  I'm just looking to stick my toe in the water to give this a try with minimal work as it is only temporary.  I'm definitely staying away from my cartridge leads.

Thanks to all,
Kenreau

[baldrick]

Hey! Soldering on resistors at your cartridge headshell sounds pretty bizarre and an excellent way to get into trouble! If you're going to use resistors just plug your TT leads into F-adapters (much neater than the T-adapters you usually see), and then make up plugs of different values you can plug into the 2nd leg of the adapter.

Analognut, you are right, it could get an inexperienced person into big trouble.  I have never thought anything of it.  If I can't modify the preamp I've always put the loading resistors on the headshell leads.  Done properly it provides a neat, compact solution that does not add any inductance to the circuit.

The F-adapter solution will work, but costs a lot more and adds un-necessary capacitance to the circuit.  However, soldering the resistors into the existing phono RCA plugs is a nice alternative to putting them on the cartridge headshell leads.

[Ericus Rex]

I use plug in resistors.

Where do you get these?  Are they just RCA plugs with resistors in-series?

[neobop]

Where do you get these?  Are they just RCA plugs with resistors in-series?

Hi,
My phono pre has little sockets that you plug resistors into for load and gain. I believe there is a Walker and PS Audio models that has the same provisions for loading. If you want to make plugs for a Parallel load, solder a resistor between the center and the ground on each plug. I think it might be a little better to do it inside your pre, but sometimes it not easy to get to.

These are the resistors I recommend. You'll only need 2 of each value you want.
http://www.mouser.com/Search/Refine.aspx?Keyword=RC55

It might be easier to call - 800 346-6873. Ask for IRC RC55 series. They are 1/4 watt .1% metal film. Catalog page 651. I have some Vishay 102 and these might be even better.

[doctorcilantro]

Cartridge loading changes with VTA. Interesting, but I'd have to say that I too disagree. I can't live without VTA on the fly. It varies from record to record. To me it's much more than relative bass output or sparkle up top. The harmonics change and you can hear when it's dialed in. I don't change it for every record though.

Getting the preferred load for a cartridge is kind of similar, but VTA changes will still be necessary. If you use the M97 as an example, it sounds laid back, mellow at 47K. At 62K the high end is around the same as 1K and below, and the lower treble dip isn't as pronounced. That is, as long as the total capacitance is low. That's in general, not specific to a record.

What if the cart has 27ohm internal resistance (factoring in internal and tonearm wire - this is a direct wire cart to pre setup) and you are running into 47K, or 35K for that matter.

Wouldn't the cable resistance form a voltage divider network with both the cart resistance and the pre load resistance, and the 35k dominates everything else, so there's negligible loss. But if the pre were loading at 100 ohms instead, that 27 ohms would cost you dearly.

My buddy tried to explain this to me; how does capacitance factor into the aforementioned picture?

[neobop]

AFAIK, the only carts with an impedance of < 27 ohms are LO. HO carts will have more internal resistance and inductance. The short answer is no, it won't cost you dearly, provided you have enough gain in the first place. Also, LO carts have virtually no inductance, so they're pretty much immune to capacitance loads. However, they will not benifit from long cable runs.

Traditional thinking about output impedance vs input impedance is, the impedance of input, should be at least 10x that of output. Like if an amp has an impedance too low for a given preamp, the combo will sound bad. No rules or cart loading guides really hold up. Electrical models can only give you a ballpark, and even then might be worthless. The mechanical factors, especially with HO carts, simply overwhelm the electrical models.

A cart puts out voltage and current. The tonearm wire's resistance and capacitance becomes part of the load it "sees". Yes, the preamp resistance should be greater than the carts internal resistance, and that's about all you can say. 

[neobop]

I think the role of capacitance in HO cart loading was misunderstood, yrs ago. Amp manufacturers thought it was used to tame the high end of the response. Adding C will roll off the extreme high end, but it often makes a cart sound brighter. What it does is lower the HF resonant peak. When that peak is lowered into the audible band, it becomes bright at that frequency. Above that frequency response rolls off quickly. Sometimes values of C are recommended by cart manufacturers to tune response.

Consider a speaker crossover. A coil (inductor) is series with the signal will become a low pass filter, or roll off the high end. A capacitor in series will be a high pass filter, but in parallel (like a preamp load) will be low pass. So the inductance of the cart itself, a characteristic of the signal, "sees" capacitance in parallel. In a spk x-over, a coil in series, followed by a cap to ground (parallel) is a 12dB low pass.