loading resistor question

I am considering changing the value of my turntable preamp loading resistor. It allows you to choose the value but I have to supply the resistor.

Are there audio grade resistors to use for this purpose? Are there any sound difference one can discern between different make resistors?
On the surface of itt it would appear so. That all one needs to do is geve a taughter resistance to to the incoming signal but this must be compensated for with appropriate input and secondary gain stages. (I think)
Jazzgene....I asked the manufacturer of my preamp - Ayre for a resistor ...they sent it to me free. Works great.
After some research, I don't think loading resistor on a phono preamp will be too picky on the make of the resistor.

I am going to try 500 ohms with my cartridge. 1/4 watt. I might just try a few different makes, Vishay and Takman or so and see if there is any discernable difference.

The preamp is a Sutherland PhD.
I use Vishay TX2575 for this purpose.
IMO these are the "cleanest" resistors I have "not heard."
Ditto Doak, love mine that I got from you.

Direct order form

Price is high for a resistor but yo only need two.

I would use plain old carbon resisters until you find the best value. Once that is achieved, I would think a wire wound may be the best, or one of the best.
I like 500 ohm the best so far. 1k ohm is a bit tippy bright. 200 ohm is a bit too dark.

The Sutherland PhD has a loading card which you fill with resistors of your choice. The cards have a limit on the size of the resistors. A standard axial 1/4 w resistor size would fit. Not shure Vishay TX2575's lead will fit the through hole on the card. These look like 1/2 watt resistors.
I'm with Doak too. Other good choices are tantalum types made by Shinkoh or Audio Note and Caddock TF020 or MK132. This is the most critical use of a resistor in your audio system, IMO, and the choice does make a difference.
It's a bit dangerous to use carbon here, even for trials, because they tend to have wide tolerances. So if you play first with carbon types, plan to measure them with an ohmmeter before inserting them, so you know for sure what you are hearing. And too, a carbon resistor will have colorations that will go away when you substitute a Vishay or a tant or a Caddock, e.g.
I would not use a wire wound unless it was a non-inductive type and you otherwise like it.
So if you play first with carbon types, plan to measure them with an ohmmeter before inserting them, so you know for sure what you are hearing. And too, a carbon resistor will have colorations that will go away when you substitute a Vishay or a tant or a Caddock, e.g.
I would not use a wire wound unless it was a non-inductive type and you otherwise like it.
Lewm (System | Threads | Answers | This Thread)

I suggested the carbon for trial because of the cost. A typical 5% wouldn't make that big a difference in the sound when your changing the values at lot more extreme than that. Vishay resistors are to fragile to keep swapping them out, and buying a handful of different values is way to costly IMO.
This link may be of interest to you. Scroll down to get to the photo and instructions, though I don't know if it will work with your phono stage.
Invest in a good resister as the noise that is created across it will be amplified along with the signal. The % value is less important than the construction/materials.
Thank you for all your responses. So it looks like the loading resistor in a phono preamp indeed does make a difference in the quality of the sound.

I'll investigate some more and get a decent pair of 500 ohm resistors. The Sutherland PhD load card allows you to load it with 4 different values and you can easily go from one value to another by rotating the card.
Just ordered Vishay tx2575 500ohms. Will update when I get them and hear them. Should be better than the RatShack metal films I have installed now. It better be at the price.
Yes, they are rather expensive as resistors go, but that's one place I've found investing $25 or so to pay big dividends.

My two cents about MC cartridge loading:

A moving coil cartridge is an electromagnetic generator and, thus, obeys the laws of electromagnetic induction. Electromagnetic induction is the production of voltage across a conductor situated in a changing magnetic field, or conversely a conductor moving through a stationary magnetic field.

Faraday found that the electromotive force (EMF) produced around a closed path is proportional to the rate of change of the magnetic flux through any surface bounded by that path. In practice, this means that an electrical current will be induced in any closed circuit when the magnetic flux through a surface bounded by the conductor changes. This applies whether the field itself changes in strength or the conductor is moved through it (as is the case in a moving coil cartridge).

In other words, the EMF generated by Faraday's law of induction due to relative movement of a coil and a magnetic field is the phenomenon underlying a moving coil cartridge. When a coil is moved relative to a permanent magnet, an electromotive force is created. If the terminals of the coil are not connected, the EMF appears as a voltage across the terminals. If the terminals of the coil are connected through an electrical load Rload, a current will flow; if Rload=0, the maximal current flows, limited by the internal resistance of the coil windings.

A conventional MC preamplifier is a voltage amplifier with a predetermined (mostly adjustable) input impedance. A cartridge connected to a conventional MC preamplifier sees the input impedance of the preamp as load Rload. The current flowing through Rload generates a voltage drop across Rload which, in turn, is the input voltage fed to the preamplifier and to be amplified.

Two facts need to be pointed out:

(1) As the load is in series with the internal resistance of the moving coil cartridge, a voltage divider is formed with the result that only a portion of the output voltage of the MC cartridge is available for further amplification. Generally, the higher the internal resistance of the cartridge and the lower the load, the less input voltage is available for the preamplifier.

(2) Since it is the voltage across the load resistor that is amplified by a conventional MC preamplifier, the electrical and physical characteristics of the load resistor have a significant influence on the sound. Nobody will deny that differences do exist between real life resistors; thus, it is crucial to use only the very highest quality of resistor as a load for the MC cartridge. But the consumer sometimes has no influence on the quality of the resistor that is used in a particular preamplifier as load resistor, and often, for reasons of economy, not the very best resistors are used. The result is that you listen, at least to some extent, to the sound of the resistor in addition to the signal produced by the cartridge.

There are as many opinions about correct cartridge loading as there are cartridge users around. When using a CMC-Pre, it is common practice to select a load in the region of a few tens of ohms up to 47k or 100k. Since the range recommended by cartridge manufacturers is so broad, the task of selecting the correct load is still not easy.
In view of the physical basics discussed above, it would make more sense to load the cartridge with a high value, i.e. 1kO or above to have an output voltage as high as possible. However, many consumers seem to believe that a considerably lower value is more favorable, particularly in a system having a tendency towards excessive brightness or upper frequency distortion.

The many discussions about correct loading boil down to the fact that the cartridge load resistor is used as “tone control” or “equalizer” to compensate for blemishes in the rest of the reproduction chain. A correctly designed, inherently neutral MC cartridge, properly integrated in a neutral reproduction chain, should not need a low value load.

Any comment?
Just got my Vishay TX2575 pair. Installed them and they blew away my skepticism. They really do sound much better than the stock Sutherland resistors. I can't believe it but my ears tell me different.

The music has much more delicacy and you hear more nuances and there is a sense of the music floating with instruments more separated. What can I say... I might have to order some more in different ohm values and make a custom load card with these resistors.

Thanks to Doak for the recommendation.
Doak- Just a copy/paste from this site: (http://mr-labs.com/theory.htm) Good info though.
Welcome Gene. :-)
Romaxim, in a nutshell:

The issue is that with LOMC, the inductance of the cartridge and the capacitance of the cable and input form a tank circuit resonant at ultrasonic or RF frequencies. The activity of the cartridge on the LP is enough to excite the tuned circuit that results.

If your preamp is stable with RFI then this is no worries. If the preamp is unstable (common with many SS phono preamps) the loading might be quite critical. Essentially the loading is reducing the 'Q' of the circuit, which in turn reduces the intensity of the RFI or ultrasonic noise that is generated. So a load is good practice in any event.
Ralph- His, "two cents" were taken from this preamp ad: (http://mr-labs.com/theory.htm) The company has a different take on, and method of handling, MC cart loading.
Rodman99999, thanks for pointing that out. If I read that ad properly, it still sounds like there can be an issue with RFI caused by the tank circuit I mentioned.

However if this preamp is immune to RFI, the loading of the cartridge will not be found to have much effect. In our preamps we find that the loading effects the background noise a little but has no effect on the tonality.
Ralph- Most of the loading I've done has put the resistor in parallel preamp's load resistance, and out of the actual signal path. That would account for not changing the tonality. We do know that resistors can be noisy critters though, and that wire wounds, and metal films, such as the Vishays(my faves) are the quietest(why Jazzgene would hear such improvement). I'm certain their cost is a major reason they aren't used in more phono stages for loading(a shame). Anyone interested in what Ralph is referring to(Tank Circuit), can check this out: (http://www.hagtech.com/loading.html)
And that is just the loading resistor. IMagine what the sound is like when you do the whole audio path in vishay resistors!!!!!

Same is true with half track tape electronics. Have been doing both for quite a few years. Just as an FYI, I prefer the VSR vishays. Same performance as the more expensive S104 versions, but toll. is only 0.1% vs. 0.01%.

If nothing else, be sure to replace all your pre amp shunt resistors or any R's that are loading an output stage.

Yes, the resistors themselves do make a difference!