Optimal Loading for Shelter 501 mk2

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.

Williamdc, kudos to you for building your own K&K. I wimped out and had Kevin custom build one for me. Fine piece, indeed.

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.

David, You want guesses? I got guesses.

02-18-04: Dougdeacon
First
"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.

Williamdc,
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! ;)

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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.

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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!