Do I need a sut?
http://www.ebay.es/itm/332504231804?rmvSB=true Not sure of the overall quality of the specific transformer, but a reasonable price and should be an almost ideal match in terms of gain (28 dB) along with the 48 dB from the Herron MM input. |
Everyone needs to keep a gain cascade calculator handy 😉 28dB plus 48dB plus 14dB gives 1.58v out for .05mV in which is probably half what most power amps like to see (if we know your amps input sensitivity that would help) another 6dB is ideal to get you up to 3V hence the T2000 or XG-5 at the 32dB up level Anyway if the OP can give some insight into his power amp that would be helpful |
Depends on the gain calculator you want to use. ;) In multiple systems over the years, I've found the KAB calculator to be pretty much dead on and it suggests a phono gain of 76 dB for a .05 mV cartridge. FWIW, using line level gain in the calculation is foolhardy in most cases IMO (with the exception of pretty unusual systems-those with passive preamps would be one). Users of fixed gain phono stages or a combination of a fixed gain stage combined with a fixed gain head amp or SUT will never realize how absolutely critical gain matching is because they do not have the ability to adjust gain "on the fly" or have infinitely variable gain available. With a high quality stage with infinitely variable gain, one can realize just how critical and narrow the optimum gain window really is and how 1-2 dB variances in gain can be substantial in terms of performance with low output MC's. And how it can actually even vary from record to record, depending on how they were cut, if one wants to take it to audiophile nervosa extremes Line level gain only serves to amplify further what the cartridge/phono preamp has sonically "created"; if that is not "correct" one is just further amplifying problems and the mismatch, (unnecessary noise, possible overload issues etc.) It cannot magically correct for either too little or too much gain at the cartridge/phono pre interface. Plus the Herron MM gain is relatively high at 48 dB and the T2000, while it was designed to be used with the MC 2000, was probably designed with a much more traditional MM stage in mind, probably one offering a more typical 38-40 dB of MM gain. Hence my recommendation of the Ortofon SUT above with lower gain. I'd be trying that at a reasonable price first before shelling out a couple of grand for the T2000 and very possibly having too much gain and a pricey piece of equipment to resell. Then again, I'm a cheapskate. |
Regarding the adequacy of 76 db of SUT + phono stage gain, that is 7 db more than the OP presently has. For a typical rotary volume control, which when viewed as a clock dial can be adjusted between limits of say 6:30 or 7 o’clock at min and 5 or 5:30 o’clock at max, and is used in the upper half of its range, a 7 db difference probably corresponds to a bit more than 45 degrees of rotation. For example, see the dial calibrations shown in this photo, although the photo is of an MFA passive (not active) preamp. So **if** the volume control on the OP’s Herron preamp has similar rotational limits (approximately 6:30 or 7 o’clock and 5 or 5:30 o’clock or so) he should be able to approximately judge the effects on noise level of 7 db of additional gain by reducing the volume control setting by a bit more than 45 degrees, and seeing how that change in setting affects noise levels when no music is playing. Also, I agree with Folkfreak that it in general it would be wise to assure that the combination of cartridge output rating, SUT gain, phono stage gain, and line stage gain is adequate to drive the power amp to full power. Even if the most power that is ever used is say half of the amp’s capability, that would only be 3 db less than full power. So if full power can’t be obtained even with the volume control at max (which is the position at which the preamp will provide its rated gain), 3 db less than full power may not be attainable at any volume control setting either. And regarding the KAB calculator, it can be important to note that the calculations of phono stage gain which it provides are based on boosting the cartridge’s rated output to only 325 mv. Regards, -- Al |
