Optimal Loading for Shelter 501 mk2

Shelter's specs call for a load of 100 ohms when running directly into a preamp. I'd start there.

http://www.eifl.co.jp/index/export/501.html

Enjoy!

Oy. Now you went and got me started, Doug. :-)

The site that Doug refers to says the "load" should be "within 100 ohm for a head amp" and "within 20 ohm for a step-up" (for both 501MkII AND 901)

There are few things with this information that have never been explained to my satisfaction (not to mention conflicting load figures on at least two other sites).

First, does "within" mean not above? Not below? Or, is it merely a poorly translated way of saying "about"?

Second, what is exactly meant by step-up? I have a phono stage that has a step-up wired directly in an MC section, internal to the unit. Is that considered a step-up? It isn't in the normal sense of, say, running a step-up trannie through the MM section of a preamp.

Third, I do not know if "within 20 ohm for a step-up" is actually referring to load or whether it refers to the upper limit of the "static" impedance of the transformer, not the load impedance.

I will say this. I load my 501MkII at 100 ohm and it sounds great. That said, I have found certain LP's that sound much more dynamic loading at 300 ohm (which I can do with a flip of the switch). I cannot go below 100 ohm (unless I want to do some soldering) so I do not know if I am missing out on something better. My guess is that if you load at 100 ohm you will be thrilled in most all circumstances. Whether small changes will result in big improvements probably depends upon your ear and your equipment.

David, You want guesses? I got guesses.

First
"Within" seems to me like typical translated Japanese, for who the hell knows what. ;)

Second
Whether the transformer is physically inside or outside a preamp is obviously irrelevant. If it's between the cartridge and the first gain stage then the cartridge is driving a current-sensitive transformer rather than a voltage-sensitive gain stage. I gather the basic idea is to optimize the output of the cartridge for whatever it's driving. That does not necessarily mean you should use the same load as outboard tranny users of course. That would only be true if the turns ratio of our trannies was the same and the load presented by the following gain stage was the same. The fact that your tranny is internally wired might also be a factor, since the wire is likely to have different impedance than an external cable.

Third
Since most outboard 20dB tranny users seem to prefer a load around 40 ohms with either the 501 or 901, I'm guessing the EIFL "specification" of 20 ohms isn't simply referring to the load seen by the cartridge. I don't know of anyone who likes that low a load. The operative word in the above was, "guessing".

Interesting that some of your records sound more "dynamic" with a much higher load. By changing loads we can affect changes in the dynamics of different frequencies, but never in overall dynamics. If I raise the load on my 901 from our normal 38 ohms to 42 my HFs start to get too dynamic and the LFs begin to lose weight. Dropping the load to 35 or below has the opposite effect. I'll admit I've never tried 300.

"My guess is that if you load at 100 ohm you will be thrilled in most all circumstances. Whether small changes will result in big improvements probably depends upon your ear and your equipment." Since Peter_s is not running through any kind of tranny, I agree!

Yes, my use of the word "dynamics" was misplaced. I will say though that my experience in load changing has been somewhat different.

On certain LP's that have little bass info and not much in the way of complex mixing, say a female vocalist with an accompanying pirce or tow, things can sound a bit less "thin" using the 300 ohm setting. A slightly reduced soundstage but better upfront "presentation" of the vocals.

Conversely, on certain LP's with a ton-o-bass and/or many different pieces in the mix, things are best at 100 ohm.

That said, this occurs on certain LP's only and may be due more the recording than the load setting. About 90% of the time I just leave it at 100 ohm.

Doug,

So you have said you use 38 ohms (after accounting for step-up math) on your Bent TX103s.

Correct me if I am wrong, but don't you also have a 47k resistor load on your phono stage?

I don't know the step-up amount you are using, but lets say it is 20db (10:1). So your Bent resistor is 3800 ohms and your phono stage resistance is 47000 ohms. Total step-up load would be:

1
--------------- / 100 = 350 ohms
1 1
-- + --
3800 47000

So do you actually have a load of 350 ohms on your Shelter?

I am not trying to dis you, I am just trying to figure things out. And no doubt it is my calculation which is probably wrong. Your Teres/Shelter comments have been very helpful to me.

I am building a K&K phono stage for my Shelter 501 cart now so this is of more than academic interest to me.