Transimpedance has too much gain?

I’m running an AT33PTG/II through an Andover Spinstage. Overall it sounds amazing but there definitely an emphasis on the 1khz region that makes some records hard to listen to. Its louder than the 20/20 and I have been swapping out parts to find the cause.

could the phonostage be adding too much gain?


In the RIAA specification, frequencies from 20 to around 500Hz are boosted with a slope of about 6db/octave. At 500Hz to 2kHz, there is a plateau; those frequencies are not boosted. Then from 2kHz on up, the boost resumes at the same slope. If you are accurate in placing the peak, then maybe there is something askew with the RIAA (there may be no plateau for frequencies between 500Hz and 2kHz due to a faulty IC or whatever), but you have also to take into account that your other LPs sound good. That really suggests that either you are particularly sensitive to the instruments and the voice on those few LPs that bother you, or that they are otherwise the source of the problem. Others might also suggest you check all aspects of cartridge alignment. By the way, not many male vocalists (except castratos, maybe) can get up to 2kHz or even 1khz. So maybe your issue is lower down in frequency than you estimate.

To amplify on what I wrote above, Mijo is correct roughly speaking to say that as internal R goes up, gain using a current driven stage goes down, but this is because the voltage output divided by the internal R gives a rough approximation of current output of the cartridge. So as R goes up, if you hold voltage output constant, current output goes down. The other factor is the actual input impedance of the current driven stage. An ideal current driven stage would have zero input impedance. But that is not feasible; if input Z is zero then the signal will go to ground. That is the equivalent of a mute switch. So, all of these stages have some finite input impedance, and manufacturers are not good at revealing numbers. The actual input impedance of the stage will have a big effect on the efficiency with which the stage is actually driven by current. Typically, the impedance is between 1-2 ohms to as high as 10-20 ohms. If you mate an LOMC with an internal R of 2 ohms to a "current drive" stage with an input Z of 20 ohms, then you get voltage drive, depending upon the sensitivity of the input to voltage. This is why I hate the term "transimpedance", which implies that impedance doesn’t matter. It most certainly does make a big difference in the success or failure of these cartridge/phono stage matches.

Thanks @lewm  I will run a couple tests tonight. 

I know little to nothing on things electrical but what you said makes sense.


should know more later.

@gochurchgo I wasn't familiar with that Love album but listening to it on streaming it is easy to see how that guitar could quickly become irritating.  I don't listen to that kind of music but I have had other preamps that produces what I call glare in that same frequency band.  It would only happen on 10-15% of the tracks I played but I couldn't stand it and I ended up selling that gear.  Sadly, all I can tell you is I'm not hearing that with my Spinstage.  Assuming you like everything else about it I would return the unit and get another one.  @lewm's suggestion that there might be a faulty part effecting the RIAA curve is plausible to me.

Also, I think the Lino C only takes balanced inputs.  No idea if your turntable supports that but it has stopped me from trying one.

pinwa, Any tonearm can be easily adapted to provide balanced output from the cartridge, because nearly all cartridges in common use are naturally a balanced source.  We use them in single-ended mode most often, but that is just because we ground one side of the output in order to use the RCA inputs on a typical single-ended phono stage. And of course, the turntable is an innocent bystander, when it comes to the signal output.  It's all about how the tonearm wires are terminated.