Optimal Loading for Shelter 501 mk2

Hello all you Shelterphiles! A friend of mine is building me a preamp, and will set up the phono stage for my cartridge. I'm using the Shelter 501mk2 and a OL Silver Taper with its stock cable. Can anyone tell me how I should configure the loading on the phono stage?

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


When going direct into a phono stage, the recommended loading is 100 ohms. This would be a good starting point, but you may find that there could be some benefit by trying a little higher or lower. Many factors can influence this "optimal loading", not the least of which might be personal preference.
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.

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

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.

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.

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:

--------------- / 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.
Whoops, math error.

3800 in parallel with 47k is 3716 / 100 = 37 ohms or thereabouts. See http://www.1728.com/resistrs.htm for a little resistor calculation application.

I was hoping the 47k resistor on the phono stage could help explain the differences between your optimum setup and others who prefer 100-300 ohms with a 10:1 step up.

But the 47k load doesn't contribute much at all to the final loading resistance at all. If your TX103 resistor is before the step up (I don't know the circuit topology) the load is even less, 1 / (1/38 + 1/470) /100 = 35 ohms or so.

I guess I'll just have to do some experimentation myself.

And if anyone sees a problem with my math, please let me know. I want to understand how this works.
Williamdc, kudos to you for building your own K&K. I wimped out and had Kevin custom build one for me. Fine piece, indeed.
David, You want guesses? I got guesses.

02-18-04: Dougdeacon
"Within" seems to me like typical translated Japanese, for who the hell knows what. ;)

I live in Japan for 6yrs now and this translation is right-on! Very amusing.:)

I will try and wrestle an answer out of one of the local dealers next time I am in the Tokyo audio-hood.
Yes, my MM phono stage has the normal 47Kohm load. The resistor posts on the BentAudio stepups are wired across the secondary. The load is reflected back through the transformer, which in my case is wired for 20db of gain. We are currently using 4,078 ohm resistors, which the cartridge sees as a load of about 37.5. I think this is consistent with your revised calculations, but my partner is the math/science expert. I just do the talking! ;)

4yanx wrote,
"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 front "presentation" of the vocals."

That sounds exactly like increased dynamics at HFs and reduced ones at LFs. The vocalists mid-hi freq's come forward and the LF soundstage info is recessed. I'd expect to hear the same thing on that kind of record. I think we're hearing the same thing.

Spinitch, apparently the interpretation of the word "within" differs between Japanese and English. No surprise. If you can get a clarification from a local source we'd love to know!
Looking at several of my recent posts, I can confirm that "within" does not mean SPELL CHECK! :-(
If your female vocalists are accompanied by a purse or toe, you've got problems even a new Basis Reference wouldn't solve.
Actually, to quote J. Geils, first I look at the purse. Of course, a full purse would be essential in considering your doubtful remedy. :-) Toes, however, are secondary.

And, absent the purse or not, I'd at least be able to look at my table without hurling. And I don't mean me ancestor's sport.
For what it's worth, I use a Shelter 501 Mk2 into a Plinius M14 phono stage which has adjustable loading "on the fly" with a knob on the front. You can select, 47K, 1K, 470, 100, 47 or 22. To my ear 47K is the best with the sound becoming consistently more compressed as I decrease from there. Shelter also recommends 47K ohms for a high gain phonostage.
Jyprez, can you kindly provide the information or link to where Shleter recommends 47K for the Shleter 501? Thanks
It's on the data sheet they provided with the cartridge.
It says,
Recommended load impedance:
step-up trans within 20 ohms
head amplifier within 100 ohm
high gain EQ-amplifier within 47k ohm

I am using a high gain amplifier whereas Doug uses the Bent transformers
I see, thanks. Must be an updated sheet, as mine does not include that third ("EQ") line.
I finally got around to playing around with a lower loading, per our discussions above.

To recap:

I have a Teres 255 with a Shelter 501 Mk II into a K&K phono stage that includes a 20db (1:10) Lundahl step-up. I have been running happily with 100 ohms loading (using 10k Caddock resistors per the K&K loading kit).

Doug's using 38 ohms with his Bent transormers got some of us wondering if a lower loading would be better. I split the difference and went to 75 ohms (7.5k Caddocks).

That experiment didn't work out well, as I lost the bass. So 100 ohms seems like the right balance between bass and highs: I am sticking with it.

Lowering the load seen by the cartridge *reduced* bass? That doesn't make sense to me at all. Should be the other way around.

Do you live in Australia? ;-)

Not Australia: but I do live in Northern California, which some think ='s the opposite of the rest of the U.S.

But I do see your point about the loading. I'll get back to ya and the thread after more testing...

(as an aside -- did you ever try the Buggtussel cleaner on a moldy record?)
FWIW, when I had my MkII I found that 100 Ohm was the best setting with mine, too.
FWIW, when I had my MkII I found that 100 Ohm was the best setting with mine, too. I also have the K&K phono stage.
I've tried the Buggtussel on several moldy-looking records. It helps, though I've yet to see it completely remove the spots on (in?) the vinyl. Definitely better than not using it, though it won't return a moldy record to shiny black either. Maybe a B+.
I am pretty much with Dougdeacon on this as I have my Shelter 901 loaded at 36 ohms going into my Bent Audio step-up and Trumpet phono and it sounds best to me.
When I first experimented with cartridge loads last year I was convinced that 22-25 ohms was best in my setup (901 >> BentAudio Mu >> c-j MM phono). I was wrong.

It turns out I was compensating for other setup errors. My arm was too high. That emphasizes HF's of course, so I was unknowingly loading the cartridge down to compensate.

Since January or February we've been setting VTA (SRA to be precise) for every record we play. There's only one ideal SRA for any given record, so it's essential to dial that in before trying to fine-tune your cartridge loading.

The following protocol seems sensible:

1. Start with a load value used by others with setups similar to yours;

2. Optimize SRA and VTF for several familiar records of complex music, the guidelines on Lloyd Walker's website are excellent;

3. Now fine tune your loading using the same records.

This seems like the logical order for making these mutually dependent adjustments. Comments?
Ok, I figured out the problem pointed out by Doug. I thought I could get away with just sticking the resistor leads into the K&K load board trace holes. Nope, this resulted in no load resistors being in the circuit -- thus the weak bass.

Soldering in the Caddocks brought back the bass, etc. I am breaking in the new resistors now and will report back presently...