Just a comment from my experience. I have never considered anything but sound quality in choosing preamps and amps in the over fifty years I have pursued high end audio. In that time and more than a dozen preamps and more than a dozen amps never had an electrical mismatch of any kind.
Preamp advice
Hi, I am quite new to this hobby.
I currently have a MC 275 mark 6, running with Klipsch La scalas and Sansui AU9900 as preamp. I know the MC tube preamps are a dream machine to pair with the MC 275 but i need recommendations on any other non MC solid/ tube preamps which can be used with my setup.
Always grateful for your recomendations.
Thank you
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This thread might be helpful on matching preamp and amps. I'm also trying to sort this out. If you have amps with an input sensitivity of 2.15 Vrms, and a preamp with maximum output of 22 Vrms, would this not be a good match because you can only take use the first 2.15 Vrns from the preamp, and this would reduce your signal to noise ratio? So in this case, a low gain preamp would be a better mach to this 2.15 Vrms amp?
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@redlenses03 "Could you expand a bit on this. More specifically, maybe provide an example for a good match vs. a bad match WRT gain matching a pre and amp (stereo or monos)" Amplifiers provide gain, either in voltage (typically preamps) or in current (power amps). Amplifiers also all generate some degree of noise, have an input sensitivity, and a maximum output level before clipping. Signal to noise ratio is typically measured as the noise floor below some reference level, e.g. 1 volt for preamps,1 watt for power amps. Dynamic range is measured from the clipping level to the noise floor. Similar, but not identical. Since the OP was asking about an MC-275, I’ll use that as the example. The McIntosh MC275 power amplifier has an input sensitivity of 1.2 volts unbalanced and 2.5 volts balanced. The MC275 also has an input impedance of 90,000 ohms unbalanced and 180,000 ohms balanced. This means 1.2 Volts of output from the preamp will drive it to full rated power - 75 Watts. That's roughly 19dB of gain. OK, here’s where it gets a little tricky. Suppose your preamp has 10dB of headroom above the 1.2V needed, that’s 12 V. The noise floor is (lets say) 60 dB below the1.2V, so that then becomes the maximum dynamic range for the system. Worse, the S/N relative to 1 W output is reduced by the 19 dB to 41dB. If I turn the input sensitivity of the MC-275 down, to where it takes all 12 V from the preamp, the noise floor stays the same on the preamp, but because I have to drive the amp with a higher signal level, my S/N improves by, in this case, 10dB to a more respectable 70 dB. Now, if you’re driving LaScalas with 100dB 1W sensitivity, it doesn’t take much signal to make an audible noise, and 41 dB below 100dB is 59 dB. easily audible in a typical listening room. So, a poorly gain-matched system can easily be heard as noise, or hum, or both. Reducing the input sensitivity on the amp and driving the preamp harder moves the entire signal further above the noise floor and the system is quieter to the ear. There’s more to consider, however. If you’re listening to vinyl, there’s another preamp stage - the phono preamp, and it’s gain structure needs to be accounted for. Worse, if you have a low-output moving coil cartridge, whose output can be .5 millivolts or less, you need another pre-preamp stage which carries its own noise levels and dynamic range, and that must be adjusted for the output of the particular cartridge being used. So you can see how it’s very easy to end up, even with very high end components, an improper gain stage design that results in an audibly noisy system. In recording studios, engineers routinely lose sleep over their signal chains trying to maintain proper gain-staging and a quiet environment. And this is before you consider grounding issues and environmental electrical noise on powerlines, or introduced by inadequate power supply filtering. There are whole books and courses on this subject, and for good reason. However, I’m going to stop here. Hopefully though you see the basic idea - raise your signal above the noise floor, without clipping the upstream source, at every opportunity. The best you can do with your ears is keep the input levels on your amp down, and drive the preamp harder, but not so hard it clips before the power amp. Doing this accurately however requires some degree of technical savvy, and test equipment, including signal generators, dummy loads, and most importantly an oscilloscope so you can see the noise and clipping levels. |
I also run a MC275VI with modded Cornwall IV's. I tried a number of tube pre amps starting with a C2300, then C500T, both were blown out of the water by a Modwright LS100. To say I was shocked is an understatement. I could have easily lived with the LS100, but in my large dedicated listening room, I found the lack of a volume readout to be a PITA. I purchased a Don Sachs II from Don just prior to him signing on with Spatial Audio and my pre amp journey is over. It is an outstanding match. Uncharacteristically there are 2 or 3 "used" DS II's on the market currently as some users have moved up to his new offerings thru Spatial. I also auditioned Schiit Freda+, Rogue RP9, Aesthetics Calypso. Didn't work for me in my room. Enjoy! |
+1 ^^^^^^^^^^^^^^^^^ Given the price limit specified and the preference for valves, you might try the Schiitt Freya + preamp. It is selectable between a passive setting, zero gain, a "buffered" solid state stage and a tube stage (octal, 4 tubes) with 12dB gain. It is well-reviewed and reasonably-priced. Schiit has a direct sales distribution but their warranty service is good.
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Given the price limit specified and the preference for valves, you might try the Schiitt Freya + preamp. It is selectable between a passive setting, zero gain, a "buffered" solid state stage and a tube stage (octal, 4 tubes) with 12dB gain. It is well-reviewed and reasonably-priced. Schiit has a direct sales distribution but their warranty service is good. |
The lower the power amp gain, the higher the preamp voltage required for a given output. The higher the preamp voltage, the farther it is above the noise floor, and that equals improved signal to noise ratio for the system overall. This is called gain-staging, and is something many high-end separate systems of ’blended parentage’ get wrong - they are improperly gain staged and are noisy as a result. This is especially helpful with high-sensitivity speakers like La Scalas. This is not a failure of the amp or the preamp, this is a failure of the owner to properly set up the system. That said, there are many great vacuum tube preamps out there, ARC, Mcintosh, VAC, BAT, Cary, amongst them. They all have their fans and detractors, but they all are in actuality very nice pieces. Just don’t plug them in without some understanding of their gain structure and expect great results. |
@p05129 +1 Totally agree. |
Guys he's running LaScala's he doesn't need more gain he's already got 65wpc more than he needs. he need a good quality preamp that's not hi gain and that's very quiet. If you have the funds look at the matching Mac preamps, they are dead quiet even the tube ones and have many features that are quite handy. The volume control will give you a good range of use with your hi efficiency speakers as well. Also the MC275 is a balanced amp and runs balanced, the single ended input is immediately converted to balanced so your better to run it balanced, one less tube in the circuit. If your running it balanced the first tube closest to the inputs is not critical as its only used in the heater circuit. It's for converting the single ended signal to balanced for the amp. I have a C2700-MC275 and the paring is excellent. I will say though get the JJ tubes out of the amps/preamps and find something better sounding that's the limiting factor in the new mac tube gear the factory tubes are not the best but they are reliable. |
Tubesound247, I just went on a preamp listening tour, and listened to quite a few preamps in person: Rogue Audio RP9, BAT VK-80, Backert Labs Rhumba 1.4, Backert Labs Rhumba Extreme 1.4, used ARC REF 5SE. Of those my favorites were the BAT VK-80 and Backert Labs Rhumba Extreme. I could have lived with the Rogue RP9, had I not heard the BAT and Backert. In the end I ended up buying an Aric Audio Motherlode XL preamp, the idea of a point to point wired and easily upgradable preamp (along with only amazing reviews), and having heard another of Aric's preamps.....was the deciding factor. |
Many people are underwhelmed with the sound of the MC275 because it has too little gain to sound its best with most preamps. Its 20 db gain is a full 9 or 10 db less than most amplifiers. Get a tube preamp with higher than usual gain and you will be happy. I recommend the Cary Audio SLP 98 which has 20db gain, an awesome sounding preamp. The higher gain will give the 275 a shot of energy and wake it up with life like dynamics and drive. I found this out with my 20db pass labs amp, it was a perfect match for my Cary SLP 05 preamp with 23 db gain. Low gain amps thrive on higher gain preamps. |
@tubesound247 Your amp has balanced inputs so I would consider a balanced preamp as the amp itself will work better simply on that account. If you consider going that direction, there is a balanced line standard known as AES48. This standard helps eliminate colorations due to the interconnect cable and has been in place since the inception of balanced line. A lot of balanced equipment in high end audio does not support the standard. If the standard is not supported by the equipment, two important benefits of balanced line operation are not realized: the first I explained, the second is immunity to ground loops.
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