Phono Stage upgrade to complement Dohmann Helix One Mk 2

@rauliruegas 

So, I set up the AnalogMagik software today, and it did help me adjust the azimuth.  I was able to get the Lyra Atlas cartridge to have a -28.4 cross talk in both L and R channels.  Oddly, the VTA didn't work with the Lyra Atlas, as it read 6-8%, and the software says that if the reading is above 5%, it might not work for that cartridge.  (The Koetsu was down around 2%).  Another oddity was the gain selector on the AnalogMagik software:  it selected 15db also, but that's only because the CLIP SIGNAL light went from green to red on the USB Phono Plus computer interface machine when I selected 20db. . . I suppose that's the same reason that the CH P1 software also stopped at 15db.  Would I hear anything adversely by having the gain so high that the clip signal light turns red on that computer interface machine?
Thanks. 

So here's some follow up on the CH Precision P1 (run in current mode) gain settings from the Analog Magik software:  at 15db gain, the SNR = 21db; at 20db gain, the SNR = 23db; at 25db gain, the SNR = 20.5db.  

At 20db gain, sometimes the CLIP SIGNAL light would flicker green, but was mostly red.  Apparently, Analog Magik favors a 20db gain. . . I'll have to play some more with this.  

Dear @drbond  : "  Would I hear anything adversely by having the gain so high.."

The best for you is to ask  directly to AnalogMagik.

 

In the other side that " oddly " VTA with the Atlas is something that you have to ask for too. I don't know if that could means that you have to " play " a little with the cartridge VTA till be inside that 5% range limit even that you set up the Atlas VTA where you like it the more.

 

R.

Interesting - I don't profess to know much about AnalogMagik, but a cursory look raises a few issues that I think could be cause for concern -

AudioMagik believes the optimal gain level is the one which yields the highest Signal to Noise ratio."

This is not right. You need to look at gain in the context of the system.

There are 2 aspects to consider.

Cartridge interface to phono

It is quite easy when matching low output mc cartridges with high gain phono stages, to overload the phono, particularly at ultrasonic frequencies - leading to sound quality issues that are more about gain matching than cartridge set up.

Even if the overloading is at ultrasonic frequencies supposedly outside the "audible range", artefacts of ultrasonic overload may impact back down in the audible range.

Therefore you only want enough gain in the phono to obtain the optimum balance between low noise floor, decent headroom, natural dynamics and enough output to drive the next stage at its optimal level. Remember the line stage optimum level is also dependent on the sensitivity and load characteristics of the succeeding stage - in this case power amp.

Phono to Line Stage

Too much gain into the next stage could lead to overload. So for example, you might have a high SNR from a phono using high gain, but at a cost.

Ordinarily it should be hard to overload a competent line stage - however if a phono is outputting distortion at ultra high frequency into an active line stage with poor overload margins at those frequencies - hey presto you have a problem - and the optimum in this case may be lower gain, giving up SNR, may be of benefit.

Similarly if driving a passive line stage, insufficient gain may cause other issues down the chain - loss of dynamics for example, poor signal to noise ratio into the power amp.

In my view you should use Analogmagik as a guide, for better understanding of whats going on, but ultimately should select gain by ear, balancing low noise versus adequately driving each succeeding stage without overload nor insufficient load.

In @drbond s case, experimenting with the CH Precision gain in tandem with  his line stage may yield an optimum result above or below the CH recommended gain.

Trust your ears - if I'm looking to find optimum gain settings between components I am looking for the most natural presentation - not dull, not hyped.

Same with their loading suggestions -

AM has you play pink noise (noise with equal energy per octave) and displays the frequency response, both raw and smoothed, between 20Hz and 24kHz. In the graph, muddy will be indicated by elevated bass or low mid frequencies. Bright will display as elevated treble. AM's 'just right' loading is when the smoothed frequency response graph is flattest.  

Again there is an assumption that flat frequency response is optimal.

It may not be. There may be downsides of trying to flatten the frequency response, the cure may be worse than the remedy. 

Analogmagik may be a useful tool to understanding your system and system set up  for loading, gain etc, but ultimately you have to trust your ears. I don't see it as gospel, more an analysis tool to help understand your system. 

In this case @drbond has 2 arms and cartridges - so he can compare the behaviour of changing the parameters of each cartridge/phono set up - this is useful.

I would encourage him to try out the voltage gain option as well at some stage to get an understanding if voltage vs current mode for each of his cartridges. This will vary dependent on cartridge of course and can't be used for a generalised conclusion.

 

 

@dover 

Thanks for sharing your insight into the potential weaknesses of the analog software.  

I think the record that CH Precision offers for gain testing is essentially a small version of the Analog Magik software.  The Analog Magik software works by taking the output cables from the phono stage, and plugging that into a USB Phono Plus phono pre-amp circuit (which itself could have some limitations), which is connected to a computer running the Analog Magik software, while the Analog Magik test LP's are playing. 

In a couple of months, once my ears are used to the sound from the current settings on the CH Precision P1, I'll experiment with the voltage settings. 

Thanks again.