Question about selecting appropriate phono preamp gain

I usually like to be within about two dB of ideal usually a touch over. Too little gain an you get column fine but small details and dynamics are sucked out. I'd usually rather be two deciles over than under. It takes quite a bit more to overload most preamps and amps.

 

I agree. I can go up or down more than that even. The key is like you and others have already said, let your ears guide you. They're there for more than holding your hat up.

 

Okay, so I finally had time to play with the settings last night. The 42 dB setting was pretty much equal to my CD player in terms of volume. After a lifetime of having to turn things up when listening to a record, that was pretty surprising. I did find everything a little harsher overall than I was hoping. The dynamics seemed flattened as well. The 30 dB setting required me to turn the volume on the amp up more, but I think I liked the presentation of the music much better. I didn't even bother trying the 48 dB setting.

I'll let this break in a bit before I finalize my conclusions, but I think the 30 dB setting is where I'm going to end up. It's nice to have so many options on a preamp that goes for $130.

Thanks again, everyone, for all your help!

 

After a couple of days of living with this, I really like this little preamp. First off, it is quiet. I find that I never notice noise floor issues until there's been an improvement. This thing is dead silent. The top end seems a little tamed, but not in a bad way; sibilance is decreased overall. (I have stuck with the 30 dB setting.) This is my first purchase of a Schiit product, and so far I'm very happy with it (and again, it's a really good value for the money).

 

Just got my Schiit Mani delivered, it's -1c here (Scotland) and the little unit was freezing when i took it out the box! Set it up at 42db with a 2m Bronze, initial impressions are good, should sound even better when it heats up!

 

Not a bad idea to let them sit a while at room temp before powering up, if for no other reason than internal condensation.

 

I couldn't wait! It's blowing away my 640p but there is a slight buzz and hiss, the Cambridge was dead silent.

 

Math tells me 53.98
KAB tells me 55
Nova II set at 56dB for the Delos.......brilliant.

 

@Wounded Land I'm a complete mathematical failure, in life generally, never mind this stuff!

Is a spreadsheet or similar possible here with some of this stuff? For example I've been trying to work out the Mani gain setting for weeks! 48dB gain sounds OK during my limited play with my AT440Mlb cartridge, but intrigued to know more...

AT440MLb Dual Moving Magnet Cartridge (DISCONTINUED) || Audio-Technica US

 

My calculations come out to 31 db, so you should try the lowest setting on the Mani (30 db of gain).

.15 (input sensitivity of the analog ins of the line stage (not the phono stage) of your amp / .004 (output of your cartridge)
take the log
multiply by 20

31. 48

 

Wow, wasn;t expecting that low!

I tried that setting a while back, it really did need to be cranked up to be heard.

My amp registers Sensitivity at 150mV / Impedance 50kohms S/N: 100dB, whatever that means!

My normal CD volume level listening position on the amp ranges between -35 and -30dB's (its how it is measured on the Sony amp STR-DA5300ES). The volume with the Mani set that low is about -11

 

I have my Mani set at that setting as well. I definitely have to turn my amp up more than when I'm listening to a CD, BUT the sound of the LP is so tactile and three-dimensional at 30 db. The higher settings are more "in your face" but I found them fatiguing and having a "flat" presentation.

 

Yeah, I tried the other formula and came up with 66db for my lyra skala, which was too high.

 

I've since realized I was doing it wrong. It's actually better than KAB, but you have to do the maths right. WHO KNEW! lol

 

I'll give it a shot again later tonight. My worry, by having the amp too high, is that it will start to produce more background noise, which I can hear when the amp gets to around -10dBs and onwards (or downwards, upwards, depends on your view! )

 

Yea. I just read the post about using input sensitivity which gave me 62db, which is more reasonable as I use 60

 

This is what I generally find with preamps. Lower gain sounds best as long as it is adequate overall. So for MM phono, I generally prefer something in the range of 35 - 40 db for MM and 60 - 63 db for LOMC. Some preamps can sound as good with a touch more gain, but when it gets too high, the top end gets brittle and harsh sounding and it's just not to my liking.
-Bill

 

Exactly. I hear it on loud moments, with horns, etc. The formula tells me 43 db gain is ideal and I can get away with 44 db depending on the loading. It's like you want those transients to bite just a tiny bit or almost and still get bass that projects.

 

I use a 5mV output MM cartridge with a 48dB MM phono stage with no issues at all. It's obviously louder than the DAC but not a bit brittle or harsh sounding. I suppose these issues may be cartridge and system dependent but you surely can have a normal sounding system with what would be defined as too much gain according to the formulas.

 

I realize this reply is a bit late, but I just wanted to explain where the formula in the original post comes from.

Gain expressed in decibels refers to power gain - how much more power is going to be obtained from a given circuit/settings. What the formula does is first determine how much the cartridge's output voltage at a standard stylus velocity of 5cm/s has to be multiplied to reach a desired voltage. Power for a specific voltage is related to the square of the voltage. For example, the power generated in a given resistance is E^2/R where E is the voltage and R is the resistance. So the formula begins saying "find out how much your cartridge's output voltage has to be multiplied to produce 1V".

Now you don't have to use 1V, but that's a common assumption for what a reasonable "line input voltage" is on many power amps. Ideally, you would want to use the voltage that actually produces your amp's rated RMS output power. But let's continue with 1V for the moment, because if everyone uses it, then at least everyone can agree.

So you obtain a voltage multiplication factor, which you'd like to convert to decibels. Now a Bel or a deciBel (1/10 Bel) is the logarithm of a ratio, so the first thing you do is take the log of the voltage ratio. That gives you a voltage ratio in Bels. 1 Bel = 10 dB, so you multiply by 10 to get a voltage ratio in dB. But you want a power ratio (because that's the standard way dB are used in the industry). That means you want the square of the voltage ratio. The way logarithms conveniently work (by design, I might add) is that to express the square of the original ratio, you just multiply the log by 2. So you're doing this:

* Finding a multiplier that will produce 1V from the cartridge's output at a stylus velocity of 5cm/s
* Taking the log to convert from this raw voltage ratio to Bels
* Multiplying by 10 to get deciBels from Bels
* Multiplying by 2 to get the square of the voltage ratio, which gives us the power ratio

This formula isn't magic, it's simply following the definition and conventional use of dB, but makes an important assumption: that the voltage that you want to obtain from your cartridge at 5cm/s stylus velocity is 1V.

Having explained the formula, there are a lot of reasons why you shouldn't put too much stock in it, only one of them being the voltage that will cause your amp to produce its rated RMS power. Cartridge output isn't linear: if the input signal (the waveform of the groove) doubles, it doesn't mean that the cartridge's output will necessarily double. It may be more or less than double. And that varies by frequency! It could be more than double at one frequency, exactly double at another, and less at still another. Cartridge nonlinearity is probably the biggest variable affecting resulting frequency response and distortion. This causes a variety of interactions with a phono preamp's input circuits (even it appears to be a pure resistance), not to mention small but measurable capacitive contributions of the cables.

The net of all of this is that there's no perfect formula for generating the exact settings that will produce the best result for a given combination of cartridge, phono preamp and power amp. The best way to get optimal results would presumably be to try various settings and measure the results using a known test record with laboratory test equipment. Since this isn't available to most people, the next best thing is to use your ears. And, interestingly, while not as "scientifically correct" as using calibrated test equipment, it makes a lot more sense, since your personal preference may not be for laboratory precise audio reproduction, anyway. I know that I prefer listening to vinyl records with vacuum tube electronics of my own design and construction. I know for a fact that this doesn't produce laboratory-flat audio reproduction, but I don't care. And neither does anyone who's listened to my system. It's enjoyable, and that's what matters.

So my suggestion for this thread is: (1) email Schiit, ask what they recommend for your cartridge, and try it; (2) if you don't like it or want to see if you like something else better, try different settings. I came here looking for Schiit's recommendation for my Shure V15 Type V-MR and found this thread, which didn't have the answer, so I'll probably just follow my own advice: email them, then try various settings. I'm betting I'll fall back on Schiit's recommendation (unless it *really* sounds bad).

 

One last point: I already followed the advice in the Schiit Mani user guide and I don't like the sound - the midrange seems to be missing, the upper midrange seems too forward, and the top end is again missing. The resulting sound is "shrill". I can compare albums where I have both vinyl and well-mastered CD and consistently hear this, so I know it's not my imagination, or just one record (or my electronics). Maybe it's the Mani phono preamp, but I'm not prepared to blame that product without giving it the benefit of trying everything else, first.

 

At what gain level were you at? For my 3.6V Virtuoso V1 Wood cart, I've been going back and forth between 42db and 48db. My amp (Marantz PM7005) line inputs are 200mv input sensitivity. Both of these gain levels could fall in range of where a CD would be, depending on how loud the CD is, while the 30db clearly requires the amp volume to be increased quite a bit. I think that the final solution is going to be somewhere between 42db and 48db. But I wouldn't be surprised if after a few more dozen or hundred album sides that I might find one level preferable to the other. 42db is probably the safe bet for most MM cartridges and music, but 48db does sound very good on many albums so far.