2. analog
  3. 1261350841

Convert cartridge output voltage to db gain

Happy holidays everyone. I hope that you may help me with a problem. I have re-configured my system, preamp and amp gone, I'm now using a integrated amp. I still have my phono stage and cartridge. My cartridge has a 0.24mV output, my phono stage has 66 db of gain. This used to sound fine, but now I notice that the noise floor is too high for me. So I'm debating on whether to look for a higher gain phono stage, or more likely, a higher output cartridge.

So now my question, how much more output would give me how much more gain? Should I be looking at a 0.5, 1.0 or 2.0+ mV output cartridge? I think I need at least 10 db more gain, and there are not many 76db+ phono stages out there. So what do you analog experts think? Is there any table out there that can show me how to convert voltage output to gain increase? TIA.

Cheers,
John
128x128jmcgrogan2
sidssp
1,077 posts
 
66db phono amp should be more than enough for 0.24mV cart. What kind of noise are you talking about? If it is groove noise, higher gain isn't going to help. If the phono amp itself is noisy, it is more of a quality problem than gain problem.
jmcgrogan2's avatar
jmcgrogan2 OP
6,346 posts
 
Thanks for the input so far. Well I assumed it was a gain issue because I have to turn the volume knob up to around 2 o'clock to get satisfactory listening levels. When I play CD's, the volume knob is around 10 o'clock for the same listening level. In my old preamp/amp setup, I did have to turn the phono up louder than the CDP, but it wasn't as drastic. Phono was about 11 o'clock, CD around 9 o'clock.

FWIW, previous amp was 75 wpc, the amp section in my current integrated amp is listed as 80 wpc.

Sidssp, the phono stage is solid state, and was not noisy in my old preamp/amp setup. It does seem like surface noise, but my cartridge, speakers, and phono stage have not changed. I sold my preamp and amp (both tubed), bought an integrated amp, then I noticed the change. CD's play with no noise issue. The integrated amp has a tube line stage and tube power amp sections.

Kal, where would I find V1 and V0?

Cheers,
John
Ag insider logo xs@2x
uru975
684 posts
 
My cartridge is low enough, about .35mV that to get it to sound the same as the CD player the volume has to be turned up. Paul Marks, the phono preamp creator said it was a matter of the gain of the phono preamp combined with the cartridge output that made it necessary. A slightly higher one, .65mV was mentioned, would obviate that necessity.
So some part of it is the gain issue, but not the noise issue.
jafox
1,457 posts
 
Actually, the equation is: db = 20Log10(Av), where Av is the voltage gain (Vout/Vin). Vin is the input signal (your cartridge output of 0.24mv) to the phono stage. Ultimately you want a line level of 0.5 to 1.0v from the phono stage's output to match the same same level from the CD Player.

If you are aiming for 0.5v output from the phono stage, Av = (0.5v / .24mv) = 2083.3 Plug this into the "db = " equation and you have a db value of 66db, needed by the phono stage to achieve that 0.5v signal into the line stage.
kr4's avatar
kr4
3,685 posts
 
So, by that calculation, he has adequate gain in the phono stage despite his protestations. As I said, it is the noise level, not the gain that needs to be addressed.

Since he is turning up the gain (reducing attenuation) in the in the integrated amp to attain the same (subjective) output with the same phono stage, I suspect the input stage on the new integrated.

Kal
More to discover