Hiss on Phono

[f1eng]

Hi Frank,

Thank you for your recommendation for using a SUT with an MC cartridge. The noise floor is really low and I hear next to no hiss even with my ears close to the tweeter.

My cartridge is an Ortofon MC Quintet Black with output voltage specified as following: Output voltage at 1000 Hz, 5cm/sec. - 0.3 mV
I had a slight hiss when I used the MC stage of Devialet. So I got a step up transformer, Ortofon ST-7 so that I could use the MM stage of the D200. 
The gain of the SUT is Gain: 24 dB at 1 kHz and Recommended load of 47 kΩ // 200 pF
This gives excellent performance however I wanted some help on the setting I should aim for. If I set the load to "high" the noise floor as indicated by the meter on the D200 is > -80dB and I also get clipping (red dot blinking) on certain records during dynamic passages. So I have set the load to 460ohm which ensures there is no clipping and the noise floor is between -90db and -80db . But with the max voltage level set to around 4.4MV (which is the equivalent of 24dB voltage gain on 0.3mV) the volume level of the Devialet needs to be cranked up high (> -10dB on the volume indicator) for quiet records for normal listening. So I have set the max voltage to 1.8MV which results in a normal listening level of -20dB for most records.

What is the preferred setting- Keeping the max gain high and cranking up the volume or keeping it low? Thanks in advance!

Best regards,
Sandeep.

For a level frequency response the load definitely needs to be set to high. I am using an Ortofon A90 and ended up with voltage level set at 7.7mV to avoid clipping on the LPs I checked it with. That is over double what I had expected, unlike digital max recording level on LPs is not a fixed quantity!

I have a background noise level of around -80dB with these settings, and about -60dB on the run in groove of a clean LP.

Thank you Frank. I have updated the settings and currently playing around to get the right voltage level set! You mentioned in an earlier thread that you have the Ortofon T3000 SUT which has a 30db gain so wouldn't the output voltage from the SUT be 8.54mV given that the A90 is rated at .27mV? Wanted to understand what the starting point should be for trying out the voltage levels in my scenario. Apologies if I am getting some of the basics wrong

You are quite right about the gain, my mistake.

OTOH the limiting factor here is that what is taken as 0dB on an LP is nominal 5cm/sec at 1 kHz, and records exist modulated a fair bit more than this, and with varying level content with frequency (and often scratches some of which give huge output) whereas digital 0dB is the maximum level possible, all bits on.

That means setting the gain to avoid clipping the ADC is a hit and miss affair. Generally I go for a safety margin when recording microphones since 24-bit is way more than needed. On the Devialet phono input I have not 'finalised' my gain setting yet either! Maybe I never will. Adjusting with each LP to avoid clipping is probably the only way to iterate to a suitable setting.