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.

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.

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.

Doug,

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?)

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...