~ 0.5mV will do just fine.
12 responses Add your response
I'm not sure about that, Axel. Note that he said phono stage + preamp = 60db. So a 0.5mv lomc would result in 0.5 volts into the power amp under the usual test conditions, with the volume control wide open. That strikes me as too low for typical power amp sensitivities, and I would suggest that his phono stage and preamp are better suited to a mm or high output mc (e.g., 3 to 6 mv or so).
OK, you are then saying that he has really 40dB phono plus ~ 20dB line-stage fully open?
If so, then get an MM with ~ 3.5mV - 5mV and you are of to the races.
Fair comment I guess, just not the way I understood it. 60dB phono with unity gain (0dB) pre-amp and then 1/2 opened volume control is just fine with 0.5mV by me, it is where I'm coming from --- and might be wrong. If 60dB = 'ball to walls' why not say you got 40dB phono gain?
I'd expect that typically a 60db phono stage with a unity gain (0db) line stage would do better with a lomc than a 40 + 20. The 60db stage would figure to have better signal-to-noise ratio than the 40db stage, since it is designed and intended for use with lower level inputs.
Also, perhaps your power amp has greater than average sensitivity.
not my enquiry as it is.
But I use right now 40dB (60dB is jumper option) on phono-boards with 18dB line-pre input gain of my ML326S.
This works very well with 5mV MM cart (Empire S1000, Shure V15, EEI 500, P77, etc.)
Otherwise I use 60dB phono with 18dB line-pre and any 0.3mV MC cart, which also works fine.
Lastly 60dB phono and 0dB line-pre is good with 5mV MM cart too.
ML326S has >90dB SN which is rather quiet, yes.
So, maybe some other gear is asking for different cart outputs. I did use 0.6mV LOMC, 1.5mV HIMC, etc.
Maybe my gear is not the right stuff to make a recommendation, too flexible?
PS: ML settings are 0, +6, +12, +18dB line-pre input gain before it gets to the volume control adding the usual ~ 20 dB (balls to the wall) but I never go much past 1/2 of that.
Axel, when you mentioned you had gain options on your phono board and then I saw 326s, I had to ask myself if you had the owner's manual; because basically, with a tasty preamp like a 326s, you can use any bloody cartridge you please. I have a 26s pre + 25s phono pre -- almost as versatile as yours, definitely as quiet, which means you can use a very low output MC if you like, and get all the benefits thereof without worrying about the noise floor. AFAIC, the only SS phono stage that can beat yours or mine is the Vendetta Research SCP-2 by John Curl (whose DNA is also in the Levinson phono pre's BTW), and you're likely to see a Sasquatch before you see one of those! There's a really great old article on JC and the SCP-2 here:
Hi Nsgarch, it's NOT my enquiry, as I said on top to Al also, :-)
I know what **I** can use, but it's Jsman that asked the question.
Now before I say, go back to my first recommendations, you should have noticed I did NOT mention any HIMC...
Let's get Al to comment, as he had a point to make about SN (signal/noise) considerations. With >90dB on my rig its not an issue, so let's see what he will suggest with those figures.
(In fact, other than SN, you can use practically any cart LOMC from 0.3mV , and if you like a good MM, as Raul recommends, 3.5mV - 5mV --- it's what I mentioned in the first place).
Page 3 of the Rogue 99 manual provides a good answer to the op's question:
The optional all-tube phono section consists of two input tubes (12AX7), a passive RIAA equalization section, and an output section that can be configured in one of three gain levels to accommodate different cartridge output levels. Using 12AU7 tubes in the output amplification stage (the two tubes nearest the front of the unit) provides an overall gain of approximately 63dB. This is very satisfactory for moving magnet and moving coil cartridges with an output over 1mV. In this configuration the two small switches on the phono board should be in the l setting. An additional 10dB of gain can be realized by replacing the 12AU7 tubes with 12AT7 tubes. In this case the switches should be moved to the h position. This configuration is recommended for cartridge outputs of 0.4mV and up. 12AX7 tubes can also be used for even greater gain. It should be noted however that very low noise tubes must be used in the first gain stage (the two rear 12AX7 tubes) so that tube noise or rush is kept to a minimum.
The bottom line is that with proper tube selection low output moving coils with outputs of around 0.5mv will provide enough volume, assuming the power amp does not have lower gain than typical (0.5mv followed by a gain of 75 db and no attenuation from the volume control, i.e., volume control at max, results in approximately 3 volts into the power amp).
However, both their wording and the fact that 75db overall phono stage + line stage gain is lower than typical for lomc's suggest that hiss levels may be marginal (or worse) with low output cartridges, depending on the particular tubes which are used.
Also, as everyone probably realizes, their statement about 47K loading being suitable for most moving coil cartridges is certainly not correct. It will work, but it will result in an ultrasonic resonant peak which with many mc's will have audible adverse consequences in the treble.
My point about signal-to-noise ratio was simply that, to use the figures that were used as examples earlier, a 60db phono stage followed by a 0db line stage is likely to have lower hiss levels than a 40db phono stage followed by a 20db line stage. The reason being that the higher gain phono stage figures to have been designed with lomc's in mind, while the 40db phono stage was probably intended for mm's or homc's.
Neil (Nsgarch) -- Thanks for the interesting read about the Vendetta Research unit and John Curl. Interestingly, all three of us who have responded use Mark Levinson phono stages. I'm using the phono section of an ML1 preamplifier, accessed via the tape out jacks and going into a Classe CP60 line stage preamp. I used to use the ML1 as a complete preamp, but one of its potted output amplifier modules developed a hiss problem after 30 years or so, and replacements are just about impossible to find. The ML1 phono stage design was carried forward from the phono stage of the Levinson JC-2, designed by John Curl as one of Mark Levinson's earliest products.
First, there is a nice writeup on calculating required gain on The Absolute Sound website, http://www.avguide.com/blog/taking-the-guesswork-out-phonostage-gain. If you plug your values into the formula (works nicely in Excel) you will see how much gain you need. One variable that hasn't come up in this thread is the voltage required by your amp to drive your speakers to an appropriate level, although the TAS write-up provides an "average value."
As for personal experience, I have an ARC SP-8 preamp, ARC 150.2 amp, and Maggie 1.6QR speakers. The ARC specs say that the gain using phono inputs is 60db, and with a .5mv Benz MC cartridge, I get very adequate levels with the gain control around 12noon, i.e. at least in my set-up, 60db of gain works perfectly with a .5mv "medium output" MC cartridge.
Hi Palewin --
I found these specs on the SP-8, which confirm the 60db gain from phono inputs to preamp outputs:
I think that one reason you are doing well with that combination of cartridge, preamp, and power amp is that the SP8's noise performance for the phono inputs is much better than it may appear initially, and is much better than it may seem based on cursory comparison with numbers for other preamps:
Magnetic phono: 5µV equivalent input noise, wideband RMS (-66dB reference 10mV input) (Approximately 1µV above 200Hz or -80dB reference 10mV input)
Those numbers appear to be "unweighted," while many phono stages and preamps specify noise performance with "A-weighting" or other weighting, in many cases without making that clear.
A-weighting de-emphasises low frequency noise, and also extreme high-frequency noise, to reflect the fact that the ear is less sensitive at those frequencies than at mid-frequencies. So the 66db figure for your preamp (which is only 40db below the 0.5mv output of your cartridge) would be a MUCH higher number with A-weighting, and the 80db number would be somewhat higher as well.
The Rogue unit, by the way, doesn't appear to have any spec on noise or signal-to-noise ratio at all.