2. analog
  3. 173827-37344

Phono stage and preamp overload

I’m in the process of setting up my first analog rig (i.e. trying to rely upon my digital gear for ease and building an analog system that’ll offer a different experience).  I’ve read as much as possible without asking some questions, so here goes…Basically, I’m trying to understand how to set the phono stage at an appropriate gain such that my line stage is not “overloaded”.  

 

Here is my relevant gear and numbers:

Line Stage - Bel Canto Pre3 (input voltage overload = 10 vrms; gain = 20 db)

Phono Stage - Pass Labs XP-17 (gain of 50/60/70 unbalanced or 56/66/76 balanced)

Cartridge - Dynavector 20x2 (0.5mv)

Amp - Pass Labs x250.8 (2.24 v at full gain; not sure if this is relevant or not)

 

I’ve read that dB gain = 20 log (Vout/Vin).  How do I calculate the appropriate phono gain so that I retain a reasonable amount of headroom and don’t overload my line stage?  My simple math leads me to setting a phono gain of 66, or 20xlg(1/0.0005), but I have no idea how that relates to the input voltage seen by the line stage nor do I understand whether or not Vout = 1 is the correct value).

It seems easy, but I remain perplexed…please help an analog newbie escape digital!

mikek1
ghdprentice
6,946 posts
 

My experience has been to plug the components together, start with the lowest gain. Given the low output of your cartridge you will probably need the highest setting on your phono stage. But how much you need to turn up your volume control on your preamp will answer the question. 
 

I suppose one could learn how to do the math, but I normally leave that for work.

russ69's avatar
russ69
3,497 posts
 

The XP-17 features gain adjustable from between 56dB and 76dB; a range sufficient to allow successful operation of not only high output moving magnet cartridges, but also the lowest output moving coil cartridges without the use of an auxiliary step-up transformer. This extremely low noise / high gain structure of the XP-17 is capable of cleanly and quietly delivering in excess of 0.5V line level signal output with a phono cartridge input of 80 micro-volts.

It doesn't look like you will have any worries. 

hdm
1,062 posts
 

Are you sure your Dynavector outputs .5 mV? If it does I'd go with balanced and 56 dB of gain, loading the cartridge between 50-100 ohms as it appears to have an impedance of 5 ohms. 

But it also appears to have an output of .3 mV from what I can see. If that's the case I'd run it single ended into the Pass Phono preamp with 60 dB of gain, again loaded at 50-100 ohms. 

Either way, but especially if it is .5 mV, 66 dB of gain is a ton of gain and very likely contributing to making your ears bleed. 

mikek1 OP
13 posts
 

re: Cartridge.  My mistake.  It’s actually 0.3mv…not 0.5.

More to discover