Transimpedance has too much gain?

Atmasphere described this. Most current drive phono stages use an op amp input stage which provides a “virtual ground” the impedance between the inputs and the virtual ground can be zero. But there is also a true ground, and the impedance between hot and real ground cannot be zero. Many manufacturers admit to a finite input impedance in their fine print. Up front they like to say”zero”. None of this means they can’t sound good, but because there is some input impedance the sound seems to vary more unpredictably with cartridges having different internal resistances, albeit the lower the better .

pinwa

IF many LPs sound ’right’, you do NOT need to change the connectors on your Tonearm. No 1K prominence on many LPs, just some Rock, makes no logical sense.

I have that VPI junction box, mini-din in, RCA out. VAS rewired my tonearm. I like it a lot except it’s price, but over time ....

To use it, you need to change the connector on the tonearm wires (which evidently are NOT a problem now).

KISS, you could buy a returnable MC Phono EQ from Amazon, use it to ’prove’ it is the current phonostage, and to prove your cartridge/arm/cable are not the culprit.

This brand may not be respected, but it has variable settings, find answers, return it

@pinwa 

Key word is "overpriced." A pair of gold Neutrik male XLRs cost a whopping $10.00.  

@mijostyn @lewm Thanks for that info on converting a tonearm to balanced.  I also discovered VPI sells a somewhat overpriced junction box that you can use to replace the RCA box on their turntables.

@lewm 

I said Ideally. Output levels are still in play. The Spinplay has an input impedance "effectively Zero ohms" 
@gochurchgo 

I have a Channel D Seta L Plus and am very pleased with it. The coolest thing though is recording records with Channel D's Pure Vinyl program. The Channel D units all have pass through outputs, outputs without RIAA correction which is then done by the computer. It is like taking your photos in Raw format. I get to raid all my friend's record collections! Recorded in 192/24 digital you can not tell the difference between the recording and the original unless I kick in the pop and tic removal tool. This one really works. It removes the pop and fills in with the preceding 10th of a millisecond of music. 

@pinwa 

The only turntables that use a single wire ground are the Regas. Otherwise, all you have to do is is remove the RCAs and solder on XLRs leaving pin 1 blank. Pin #2 is positive and #3 is negative. Channel D will also sell you RCA to XLR adapters. I do not like any unnecessary contacts in the way of the cartridge, but if you do not have a soldering iron this is a viable option. 

Send the spinstage back to the manufacture to check.

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.

@pinwa  thanks. I may do that.

@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.

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.

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.

@mijostyn ​@lewm  unfortunately I DK t have another cart to test.  The album I specifically mentioned I’ve owned in cassette, cd, Lp in several versions/masterings. It’s always been a good sounding album. It still is a good sounding album other than this issue. I have been trying to see what interaction is causing this.

i have a few things I’ll try tonight when I get home. 
 

after that, not sure what to do.

Could it be that those LPs actually sound bad when accurately reproduced? Have you tried a different LOMC cartridge? I disagree with Mijostyn that the internal resistance of the cartridge must be 2 ohms or less; most current driven stages work fine up to around 10-12 ohms and many use them happily with even higher internal resistance cartridges. In any case that issue is probably not a cause of your problem. Maybe there is an issue with the RIAA correction filter in your unit, if indeed what you report is real. Try another cartridge and compare it using the Sutherland vs the Spinstage.

@gochurchgo 

I had a look at the AT's specs, imp 10 ohms, output 0.3 mv. You definitely do not have a gain problem. That impedance is at the upper limit for a transimpedance stage. As impedance goes up gain drops. I assume other sources do not have this problem? Have you tried other cartridges? Make sure cartridge set up is right (miss tracking). You might also have a look at cartridges with lower coil impedance, ideally you want < 2 ohms. The Spinstage has uniformly great reviews, perhaps you got a defective one? 

@pinwa they sound more alike then different but the Spinstsge is more lively. I like it a lot otherwise I’d just send it back. What it does right it does beautifully. What it does “wrong” keeps me up at night.

I bought the ipower SMPS but also tried a LPS. They did relax the sound but not how I wanted.

i bought it as I was curious about current injected phonos. I was pondering the Lino C but now not sure what to do.

the few dozen jazz LP’s I have sound great, as do the handful of classical. But rock music where lots of guitar and vocal fall into that 1khz to 2khz zone sound annoying. The Cult’s Love album. Ian’s vocal is right in that pocket as is lead guitar. It’s annoying.

The Andover Spinstage is about 71 dB of gain if I am remembering correctly and that is more than most MC Phono Preamps.  But I don't hear any tonal emphasis on mine.  It just sounds much much better than it should for the price.  But you might find a benefit from using a linear power supply rather than the wall wart they supply.  I felt it sounded a bit smoother and perhaps less dynamic with a linear power supply and I'm guessing you would find that more pleasing.  Of course even a cheap linear power supply will set you back about half the cost of the Spinstage.

But how do you think it compares to the Sutherland 20/20 in general?  It is nearly a 10x difference in price.  

Thanks @mijostyn  it’s definitely in the 1k - 2k region. The Sutherland 20/20 doesn’t have this forwardness and after going through everything I can only think maybe the gain is off or a cart mismatch.

I have been using a transimpedance stage for almost a year. Too much gain is not a characteristic I have encountered. If anything I would not mind even more. "Hard to listen to" usually occurs in the 3 to 4 kHz region where sibilance is a problem.