Phono Cart Impedance Question


I have a little bit of hiss through my 6 ohm, 0.28mV cart but only at a volume pushing the upper end of my listening volume...and it's only audible before I drop the needle, and even then not from the listening position.  I realize I therefore likely have a "non problem"!  

But I still have a generic question on to the sensitivity of producing hiss as it relates to cartridge impedance alone.  If one kept all other cart specs identical (including output of course) would you expect hiss to go up or down at the same volume and system gain if I used an 8 ohm or 12 ohm cart instead?  It seems like the hiss would likely go up just like moving to a higher impedance speaker under the same gain setup but perhaps I'm looking at this incorrectly? I realize moving to a slightly output cart could very well reduce the hiss.

Thoughts?   Sorry if this is a ridiculously obvious question and answer.

128x128three_easy_payments

Showing 4 responses by lewm

dan, possibly you got that result, because a 10-ohm load resistance would result in a very severe high frequency roll off in the audible range, using almost any cartridge except maybe a very LOMC with a 2-ohm or lower internal resistance.  You threw out the baby with the bathwater, as the saying goes.  "Hiss" is probably at about 2kHz or higher frequencies, usually.
Whatever you decide, keep in mind that all tubes change noise characteristics as they age, and the curve for increasing noise as tubes go from SLN to not so SLN is not predictable from tube to tube. So SLN tubes are a crap shoot wherein the game is rigged against you. No aspersions on RAM tubes are intended; it just is what it is.
Just to note that running the phono stage with no cartridge connected is very likely to produce volume control dependent levels of hiss. Most of our phono stages will behave that way.
By the terms "8 ohm" and "12 ohm", I presume you refer to the internal resistance of the cartridge itself.  Yes?  If so, what is the value of the load resistor in your phono stage.  If the value is anything above 100 ohms, the answer likely would be "no difference".  But it also depends upon what is causing the hiss.  There are a few different sources of noise that might be described as a hiss.  So your question is not very specific.