@lewm Matching the gain setting on the SUT or preamp with cartridge output rating. It sounds very different when changing the settings. Sometimes if too much gain is added the sound it harsh and unrefined. When not enough gain is added the music sounds flat and lacks energy. In essence, matching the gain to the output of the cart. What I've heard is that the MSL SUT is made specifically for their cartridges. Whether this results in optimal performance or not is what makes me consider buying one. Cheers
SUT With a Manley Steelhead RC?
I own a Manley Steelhead RC and am using as my main cartridge a My Sonic Lab Signature Platinum. MSL makes their own SUT that I have been thinking about purchasing, but I'm wondering if it's necessary with the Manley. I find the Steelhead to be the best sounding phono preamp I've ever owned, but I'm always wondering about ways to make it even better.
I sent a message to Bob at Bob's Devices, but his reply to me was ambiguous. He made it sound at first as if there would be little sonic benefit, and also seemed to say that his SUT would be superior to the one inside the Steelhead. I tried to ask more questions but he went radio silent after that, and if I try to call their phone number I can't seem to talk to anyone. This is not a complaint about their company, BTW. I've heard nothing but good things about his products.
Any useful advice is appreciated!
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@rsf507 Thanks for responding. What phono preamp was feeding into with the MSL SUT? |
Dear Snackey, Your response, "Matching the gain setting on the SUT or preamp with cartridge output rating.", is not quite the way to think about it. The cartridge has a certain signal output, expressed in mV in relation to stylus velocity. The standard stylus velocity is either 3.54cm/sec for older cartridges or 5cm/sec for modern cartridges. So that number in mV is the output at that velocity and is just a guideline for thinking about phono gain. Since the typical MM cartridge makes about 5mV at standard velocity, and since a SUT is connected to MM inputs, the paradigm is to choose a SUT with a step-up ratio equal to whatever it would take to raise the voltage output to about 5mV (give or take). So you need to know the turns ratio of the SUT. The limiting factor is the effect that the SUT has on the impedance seen by the cartridge. The input impedance of the phono stage is reduced by the square of the turns ratio. So for a SUT with a 1:10 turns ratio, placing it between the MM inputs and the cartridge output will reduce the impedance of the phono stage as seen by the cartridge by a factor of 100, etc. The convention is that the phono input impedance ought best to be about 10X higher than the internal R of the cartridge for best signal transfer (although there is no danger in using a lower ratio, but as you go below 10X, there is loss of cartridge output to ground and possible high frequency roll off due to capacitance). So, in choosing a SUT you want to have enough boost to result in a about a 5mV output at the MM phono inputs without violating that 10X rule of thumb. But with a high gain MC phono stage or with an outboard active voltage booster stage (see Hagerman Piccolo for example), you don't have to think about any of that. You just need enough total gain ahead of the amplifier to drive the amplifier. (Typically, that requires about 1V more or less.) There is no need to worry about "matching". To make this more confusing, most SUTs are labelled for the internal R of the cartridge that works best, e.g., a "3 ohm" SUT is intended for LOMCs with a very low internal resistance but it doesn't have to be exactly 3 ohms. A 40 ohm SUT is for those LOMCs with a rather high internal resistance (Denon typically), but it doesn't have to be exactly 40 ohms. You need to do some digging to discover the turns ratio of such SUTs. What I am trying to get across is that a SUT is just a tool, not necessarily an embellishment to SQ. |
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