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Phono Amp Spec’s

Hello 

Can someone please help me understand the following…

*Maximum Input Voltage
64dB = 5.7mV
70dB = 2.9mV
34dB = 180mV
40dB =  90mV
 
I would be using a Benz Micro Ruby ZH moving coil cartridge with this phono amp.  
It’s output is rated at .7mV@3.54cm/sec which I believes equates to .998mV @ 5cm/sec.  
 
1.  Am I understanding this correctly, that my roughly 1mV cartridge would be fine going into this 64dB MC input?
 
2.  Is there a way to know what would the dB overload margin would be with 1mV @1khz as well as the low, mid, and high frequencies going into this 64dB MC input?
 
Secondly,
I’m concerned about over driving/clipping the phono amp.
 
* Input sensitivity
64dB = 1.26mV
70dB =   .63mV
34dB = 40mV
40dB = 20mV
 
1.  Can you please help me understand how the input sensitivity of 1.26mV for the 64dB MC input relates to my Benz Ruby ZH with a roughly 1mV output.  
 
What exactly should this mean to me?
 
After suffering 5 major strokes, my memory of many things have been lost. So, if anyone could please help me better understand how the above spec’s would affect me, I would truly appreciate it. 
 
Best wishes,
Don
 
 
 
 
no_regrets

Showing 2 responses by lewm

lewm
13,823 posts
 

Yes I think so, but you’ll be the judge based on listening.

lewm
13,823 posts
 

With that spec showing overload occurs at 5.7mV output from the cartridge when the phono is set for 64db gain, and given that the cartridge has a nominal output of 1mV, then for a hypothetical 20db of overhead margin, you would like to see at least 10mV before overload.  5.7mV is about 15db of margin above the nominal 1mV of output. "db" are in log scale so half the voltage is not half the db.  As others have mentioned, 64db is probably more gain than you need, but the next lower gain you can select, if it is 40db, is too little gain. You are better off with 64db, IMO.  As for the rest of it, just listen. If you hear distortion on loud passages, maybe the cause is phono overload but maybe not, as distortion on loud passages can have many other causes as well.

In general, the overload margin of a phono stage is inversely proportional to its gain; the higher the gain, the lower the overload margin, but since you use high gain with cartridges that have a very low output to begin with, overload is less likely to be an issue. Also, in general, tube phono stages tend to have a higher overload tolerance than SS ones.

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