2. analog
  3. 1073433382

Sonic Frontiers Phono One: Gain too high?

Hello,

I'm trying to help a fellow 'phile troubleshoot a problem with his Phono One. He claims that he cannot use anything except very low output cartridges with his Sonic Frontiers phono stage because he has the "high gain" version. Evidently there were three different versions of the SF Phono One: a low gain, normal, and high gain? I looked through the manual and on page eight it describes how to set the dip switches for various cartridges, even has two user defined positions (using add-on resistors and capacitors). No idea why he couldn't fiddle with these settings to dial in the step up.

So... can a "high gain" Phono One be set up to accomodate high output moving coil or moving magnet pickups???? Thanks much, Jeff
jeffloistarca
sayas
181 posts
 
gain was as stated not readily adjustable unless a tech removed and added the necessary ??????.

gain of 62 58 or 54db were the three hardwired choices offered by SF
aroc
760 posts
 
Why Kenny? If my math is correct wouldn't 0.6mv with 62dB gain only be 0.75v? Isn't line source 2.0v? Wouldn't a 1.5mv cart be 2.0v after 62dB of gain? It always seemed that phono stages needed more gain to me. Else don't you have to relay on your linestage to provide a bunch of gain?

dB gain = 20 * log (V1/V0)
10^(dB gain/20) = V1/V0

I have a Hagerman Bugle with 40dB gain and a dynavector 20x-h with 2.5mv output, and I'm considering changing the gain to 50 or 60dB with a resistor change.
hagtech
99 posts
 
I don't believe the issue is gain, but rather overload. The 1.5mV cart would probably overdrive the inputs (or second stage) when set to high gain. If opamp-based circuit, will likely be hard clipping, which is pretty easy to hear. Once signal is past EQ then you can add more gain without saturation.

The Hagerman Bugle can handle the 2.5mV at 50dB, but not at 60dB. It's best to run minimum gain for maximum headroom. Also true with linestages; attenuators sound best when not used.

jh
Ag insider logo xs@2x
kennyb
117 posts
 
Yes the issue is overload. I have one LP in particular that is cut very hot. This LP was unplayable using my .6 mv Clearaudio Victory because of distortion. I had no such problem playing the LP with the .5 mv Helikon.
sayas
181 posts
 
now that you state 1.5mv i would have to agree that there is too much gain, howevere if you went to the resistor that gives the lowest gain 54db that would likely be about right
More to discover