advertisement


Phonostage gain optimisation

The only variable is how much input voltage your system needs to have the volume you prefer.

For "normal" systems and "normal" volumes, it's about 40dB for MM and 60dB for MC.
 
Right, that’s 87dB to run a Audionote IO without a step up.
Then again my 0.2mV SPU needs 73dB by the “this way” calculation and it’s fine on a standard superline with 64dB.
A Decca by the same lines needs 45dB but I run one with a 35dB phonostage.

I maintain its the digital device’s output that’s too high, especially those things from Chord, vinyl was here first.
 
yeti42 said:
Right, that’s 87dB to run a Audionote IO without a step up.
Then again my 0.2mV SPU needs 73dB by the “this way” calculation and it’s fine on a standard superline with 64dB.
A Decca by the same lines needs 45dB but I run one with a 35dB phonostage.

I maintain its the digital device’s output that’s too high, especially those things from Chord, vinyl was here first.
Click to expand...
Sure, I also set my phono preamp s with gain adjustment to lower values than standard.
 
It seems "we" don't care... much...

The internal gain distribution of a phono stage is very important, the RIAA eq making it especially so, but the overall gain, as being discussed here, is generally of much less importance and mainly a convenience thing ie whether you need to set the vol control hugely differently for phono compared to other sources. The main exceptions to this are of course those few cartridge "flyers" of way higher or lower output than normal.
 
I use trial and error and a 12" 45rpm single or two.

I crank it up until it distorts slightly and then back down one level. :)
 
Welcome back Jez.

Disappointed not to have inspired any neurotic anxiety with this one, have to say. Guys, what if you’re doing it wrong and not getting the best out of your cart?
 
I find the KAB calculator tends to suggest just a bit too little, but I think the other one you linked was suggesting 1V, which seems humungously high. I know KAB suggests 64dB for a 0.2mV cartridge, and in fact I have a 0.2mV cartridge which I use with a 64dB gain phono stage. However I did find that this was slightly limiting on very quiet classical recordings, so I had the designer tweak the circuit slightly to give a tiny bit more gain. I'm currently using a 0.4mV cartridge with the same phono stage and I have loads of headroom. I think 64dB does very well for 0.3 - 0.4mV. For a 0.5mV cart I think I might want a little bit less. Are you asking in relation to the ART9 Sean?

These are my findings. It's all relative to the general gain structure of the system, I suppose, and I'd like to understand more about the signal to noise ratio that Graham mentioned.
 
Elephantears said:
I find the KAB calculator tends to suggest just a bit too little, but I think the other one you linked was suggesting 1V, which seems humungously high. I know KAB suggests 64dB for a 0.2mV cartridge, and in fact I have a 0.2mV cartridge which I use with a 64dB gain phono stage. However I did find that this was slightly limiting on very quiet classical recordings, so I had the designer tweak the circuit slightly to give a tiny bit more gain. I'm currently using a 0.4mV cartridge with the same phono stage and I have loads of headroom. I think 64dB does very well for 0.3 - 0.4mV. For a 0.5mV cart I think I might want a little bit less. Are you asking in relation to the ART9 Sean?

These are my findings. It's all relative to the general gain structure of the system, I suppose, and I'd like to understand more about the signal to noise ratio that Graham mentioned.
Click to expand...
That's interesting Andrew. Yes, it was the Art9 that set me off: according to the KAB calculator *both* the settings on my Rega Aria are too high: by the Absolute Sound one, one is too high and one too low. I think I prefer it through the *really* high setting. I'm having to do all sorts of tweaks to get the cart sounding right through the new speakers.
 
Signal to noise ratio is exactly as it sounds. You pick an output level that can be considered "standard" /"normal" for a specific unit, lets say output for an input of a "standard" 5mV for a MM cart, and then remove all input signal and measure the noise over a specified bandwidth (the wider the bandwidth the higher the noise level hence the worse S/N ratio), often 20Hz - 20KHz, and then express the two in dB and voila that's yer S/N ratio. Often it will be expressed as a weighted figure, "A" Weighting being the usual standard used in hi fi. An A Weighted figure looks loads better than an unweighted figure hence it's so often used.... A Weighting takes into account the sensitivity of human hearing to various frequencies between 20Hz and 20KHz and hence concentrates on the midrange where our ears are most sensitive to sound (noise here). It means that mains hum at 50 and 100Hz is largely ignored (not entirely though) from an A weighted figure.
 
I'm with G, put the gain in the device with the best snr, and only have as much gain overall as you need.
 
The first stage, and in fact the first amplifying device in the first stage (and its supporting components and power supply), is where all the action is. Within reason, nothing matters after that when it comes to low noise as this sets it all in stone.

After that, dynamic range is the issue ie the difference between the minimum usefully discernible signal above the noise floor and clipping point (for this is the technical definition of dynamic range). The fact that a phono stage has 100 X more amplification at 20Hz than at 20KHz and records are cut 100 X louder at 20KHz than at 20Hz is where all the fun in between happens and why gain distribution AND type of EQ technology within the phono stage are important.

Total gain, as in the context being discussed in the main part of the thread, is mainly irrelevant... within reason anyway.
 
You must log in or register to reply here.


advertisement


Back
Top