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Phono Preamp Help - 47K Ohms - 100 Ohms .. Huh?

I am relatively new to analog and therefore have little experience matching a cartridge with a phono preamp. I currently have a Shelter 901 which the user manual specs at "within 100 Ohms" as the recommended load impedance for the head amp. I've been shopping for a new phono pre and find that many top phono pre's are all rated at 47K Ohms and are not switchable.

This got me thinking that maybe 47K Ohms was the right setting for ALL phono stages and sounds the best... So since I currently use a Black Cube which IS switchable between 47K Ohms and 100 Ohms I decided to play around.

When in the 100 Ohm setting, I feel the sound is crystal clear - nearly perfect - yet the midrange seems recessed ever so slightly causing some recordings which I know should have heft and body to be somewhat recessed sounding and maybe thin. Also, at 100 Ohms, the sound is not quite as involving as I like. It's not exactly bright but quite close.... really close - in fact, as extended as I've ever heard a system be without being able to confirm it as being bright.

Switching das cube over to 47K Ohms gives a dynamite midrange. Very impressive vocals. Solo instruments seem incredibly lifelike - highs are ever-so-slightly rolled when compared to the 100 Ohm but during complex music, and even not-so-complex music the mids seem somehow congested as if the notes are bumping into one another slightly - perhaps muddy - more or less "confused". This sucks because everything else seems to be close to perfect.

Each setting has its virtues but I feel the 47K Ohm setting would be ideal without the midrange confusion.

Now for the questions...

If my Shelter 901 is designed for "within 100 Ohms" what the heck does that mean? Within? Does this mean I need to stay at 100 Ohms for the best match to the cartridge?

When switching to 47K as I said above, there are some advantages and clearly a few disadvantages. Are the downfalls more related to the phono preamp, the cartridge or even the impedance match? I mean, could the congestion be a result of the black cube itself vs. a direct result of the impedance settings?

What's more important - the preamp or the impedance setting?
bwhite
Post removed 
twl
3,251 posts
 
Bwhite, I personally think that you should try a slight raising of your VTA, and leave it at 100 ohms. Recessed mids are a trait of a too-low VTA. Raise it up, a little. If there is a percieved brightness, it's probably in the Cube. Running the cart "unloaded" at 47k is just compensating for other errors, that are causing the problem. I know that raising the VTA can cause some brightness, but in this case I think you need to. The Shelter could not be considered a "bright" cart, so if you are having "brightness" problems, it is somewhere else. You might try a little self-stick black felt, from the crafts section in Walmart, on the headshell. The Ittok could be "ringing" a little. That is a high-energy cart, and sends alot of energy back into the arm.
bwhite OP
807 posts
 
Hi Twl, Okay.. now.. the VTA is that the adjustment I can do with the hex bolt? or is that the knob on the arm? I think if I remember correctly its the hex bolt... So I'll try that.

My Ittok is the BLACK Ittok which is/was released right before the Ekos and is essentially an Ekos without the integrated arm rest. This Black Ittok is damped unlike the silver Ittok arms and it does not ring like 'em.

The brightness I referred to is not actually "bright". It is however, as close to being bright as I've ever heard without being bright.

I'll try to raise the VTA slightly and see what happens.
oldears
386 posts
 
47 Kohms is the typical "correct" load for MM cartridges.
You can optimize MM cartridges by changing the capicatance, but this is not relevant to your question.
There can be interactions as to the prefered settings between VTA and cartridge loadings. In general low output MC cartriges specify a low impedance loading. You may prefer the sound at a higher impedance which generally gives more air but is less focused in the bass. If your sound is bright at the lower impedance loading you should definitely try to adjust the VTA by lowering the rear of the arm until the sound is "focused". If you go to far the bass will become "wooly". Then go back and raise the impedance setting until you get the sound you like best.
This takes a lot of patience, but the results are rewarding.
bwhite OP
807 posts
 
Okay... I messed with the VTA. Quite frankly I don't know if it went up or down but the bass is better, the highs are nice and the mids are much more accurate. This is what I was trying to acheive.

Thanks all who helped!

This brings me to the phono stage question regarding various loadings. I guess from what I've read, its best to match the output of the cartridge however it is difficult to find a better phono pre (the kind without the toggle switches) that is at 100 Ohms. The Linn Linto is at 150, the LAMM is at 40, Jadis is at 47K, The Joule's are at 47K, the Lukaschek is at 22K.... I cannot find one at 100 Ohms What gives?
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