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In Reply to: Phono preamp with MC loadings below 100 Ohms? posted by tketcham on September 8, 2006 at 09:05:04:
the use of a SUT or active "pre-pre" device.You can, if you want, adjust ANY input to have a lower impedance than tht which is allowed in the original design.
The question is are you happy with the preamp you have?
Don't make a mountain out of a mole hill.
Also what cartridge do you have or wish to use later? It doesn't matter just curious.
Follow Ups:
Garth, no, I don't (obviously) understand the difference between the sut and pre-pre, hence the comment in my original post. That, and I didn't think it made sense to pay as much or more for a device to "retro-fit" one of my current preamps when I could just get another preamp that has the capability already built in. Less gear, simpler.No problem with the molehill, Garth. I like what I listen to now. My interest is in trying out different cartridges to see what they sound like. I'm currently looking at:
Denon DL-301 II - 33 Ohms loading
Audio-Technica AT33PTG Prestige - 20 Ohms or moreBut neither of my current phono preamps have load settings that low so I was considering selling one of them and replacing it with a preamp that does. Key word is CONSIDERING. I may just get one of the cartridges and try it at 100 Ohms loading; it may sound fine. But I won't know how it might sound at a lower setting. Hence, my INTEREST in a preamp that does.
There just might be another source of confusion here. For example for your Denon DL-301 II the output impedance at 33 ohms is actually pretty close to the figure for the Denon DL103 (40 ohms). Now this "output impedance" is more likely than not the "coil" impedance (perhaps measured at 1kHz), not recommended "load" resistance.For example I've found that using a load resistance of less than 100 ohm with a DL103 gives wolly/sloppy bass, and in any event many user seem to find the 103 works best at 100ohm loading; things are different with a step-up transformer so let's not even go there.
Thus for the DL-301 II if at 100 ohms the sound is full, has good bass definition, and *isn't* screechy in the high end ... if that's the case ... then I'd suspect loading at less than 100ohm might not be a good idea.
--
Now for the AT33PTG Prestige the specs do provide a recommended "loading" of "20 Ohms or more" (just as you've indicated). But is that enought, is a recommendation for the primary coil impedance of a Setup Transformer, or the loading resistance for an active phono stage?; that difference I'll leave to someone more qualified to explain but I've noticed that the two are rarely the same.
So you see it's a hornet's nest of similar sounding specifications that mean very different things ... the sloppiness and lack of adherence to standard terms sure doesn't help!
For the AT33PTG Prestige again I'd apply the judgement (above) to the sound at 100 ohm loading and only after decide if going less than 100 ohm seemed even worth trying.
as it does point out the somewhat limited need for a phono preamp with impedance loadings below 100 Ohms. But I was thinking that it would be a nice feature to be able to actually try loadings that were below 100 Ohms to see for myself.
Remembers Garth's 100ohm resistor (in parallel with the phono stage's 100ohm) to get 50ohm? And you have two phono stages, correct?Well just get the "Y" adapters and (using a second interconnect) hook up *both* phono stages, set each to 100ohm and ... voila! ... the cartridge now *sees* 50ohm! If either of the cartridges sound better like this then going the next step ... resistors, soldering, etc. ... would make sense. If not then you're out the price of the Y adaptors only!
(I actually did this once and experienced the effects of reduced effective loading resistance. It had me stumped until I realized that I was of course putting the two loading resistances in parallel.)
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