Phono Preamp. With transformer or fully active

In order to add a bit to the road Mike went down his first audition was with two pair of identical 1:20's, one in silver and the other in copper.  Initially the silver was preferred and after a few weeks he found that the internal SUT's to the CS Port offered some benefits over the 1:20's he had in system.  A little bit of sleuthing turned up the distortion spec of 0.1% @ 0.76Vrms output.  Working this number backwards from the 40dB of gain this translates to 7.6mV of input.  The Etsuro Gold has 0.56mV of output and fed to a 1:20 that will be slightly above the 7.6mV level.  It turns out that the CS Ports internal SUT had 3dB less gain which using simple math put the output right at that published distortion number which is why I suggested that mike try a 1:10.  I sent him a copper 1:10 for his 4Ω Etsuro and things improved over the internal SUT.  Replacing the copper with silver was the icing on the cake that he is currently consuming.  

I think the important thing to note about this is the high frequency overload characteristics of phono playback is typically not pretty.  At high frequencies many phono stages seem to have a more abrupt transition into distortion where the higher order artifacts show up and quickly dominate.  This high order high frequency distortion only happens at dynamic peaks nearing the highest possible groove velocities.  Holman notes a worst case 105cm/sec peak @ 7Khz on  Woody Herman Verve V-5885 and that represents 26dB above the standard 5cm/sec velocity referenced to 1kHz.  Granted the 7kHz signal receives 10.7dB less gain but that still leaves a 15dB dynamic peak above the 1kHz baseline.  It is these periodic events tickling the abrupt onset of distortion that I find gives a "something is not right but I'm not sure what it is" type of feeling.  It is the periodic occurrence at dynamic peaks that make it so elusive.   The trend as of late is for MC carts with 6dB or more output than their predecessors which simply translates to a 6dB loss of high frequency dynamic headroom when considering a MC stage built with a 0.2mV SPU in mind.  10 years ago a 1:10 was an anomaly and today with MC outputs in the 0.5mV to 1mV range it is slowly becoming the norm.

dave 

Dear @intactaudio :  From some years now LOMC cartridge designs comes with higher output levels than in the past.

That healthy higher output makes a more easy way for phono stages to handle LOMC designs, especially tube electronics but that healthy output comes with a trade-off in the overall cartridge quality performance levels.

If that Etsuro Gold instead of 0.56mv came with say 0.15mv I have no doubt that @mikelavigne  will be even more happy that with his already great Etsuro samples quality performance.

Problem is that 0.15mv can be a problem even for SS phono stages. Nothing is perfect but normally lower output mv means less wire in its coils with more powerful magnets as neodymium ones.

Lyra is a good example about when JC started with his Atlas/Etna models and latter on he presented the new same models in low output fashion and owners and reviewers gone with a smaLL PREFERENCE FOR THE LOWER OUTPUT MODELS.

I remember what happened in the past with some of the LOMC cartridges I owned, example: AT MC 1000 that was marketed along its dedicated SUT AT 1000T for its low 0.1mv output or the Ortofon MC2000 that appeared along its dedicated SUT T-2000 for its very low output of 0.05mv and the same was with Audio Note design. 
All those cartridges came with very high quality level performance but not easy to handle for phono stages, certainly not tubes designs.

Latter on I remember my first Colibri with a not so lower but certainly not something approaching the Etsuro output, this Colibri had 0.21mv and performed excellent in quality kind of sound. Latter I bougth two other Colibri samples but VDH only offered with higher output and I have to say that nothing like the " original " 0.21mv polymer cartridge body.

Anyway, good that both of you are satisfied with.

R.

It is interesting to note that as the frequency response approaches flat at 20kHz the phase shift increases further down into the audio band. In this case it becomes the choice of the lesser of two evils. Since no two people hear the same, it is no wonder loading of cartridges is such a hotly contested subject when it comes to transformers. It is my belief that often times when you adjust cartridge loading via the secondary of a SUT, the sound (and measured response) of the transformer is what is heard. This change in sound is then falsely attributed to the cartridge seeing a different load.

@intactaudio Why would you want to adjust the cartridge loading? I agree entirely though that loading the transformer is for the benefit of the transformer and not the cartridge- what it appears you're also saying here. That is what I was saying earlier as well, if that was not clear.


An SUT that has troubles making it to 20KHz it is a bit troubling- I would expect 50-70KHz at least on a part with that little power requirement. But that is of course ignoring the inductance of the cartridge... But your graph didn't suggest anything about that. 

This is kinda off track , but transformer, based 

Mac amps ?  Claim they are “ auto-transformer” coupled.

what does that mean ?

jeff

ps: what is sound difference between a preamp with & without transformers?

Ralph,

Cartridge loading is another hotly contested subject that is best to save for a new discussion.  It seems we both agree that applying a load through the secondary of a SUT has a much greater chance of changing the SUT behavior in an audible way than the cartridge behavior.

The inductance question can be answered by looking at SUT behavior when driven from various cartridge impedances.  The plot linked below is the 4722 wired 1:18 driven from 2Ω to 100Ω and at 100Ω the -3dB point is ~10Hz which translates to 1.6Hy.

http://www.intactaudio.com/images/SUT%20white%20paper/4722%20cart%20z.png

I chose the 4722 because it is a known device that represents the typical behavior of a microphone transformer pressed into SUT usage.  I agree that the top end behavior of this device leave a lot to be desired. When paired with an EMT or a Denon 103 into a 47K load it is -1dB @ 10Hz and 20kHz and has what many call a "vintage" sound.  As an aside, Bell Labs did a lot of work on voice transmission and intelligibility and found that linearity in the phase domain was far more important than linearity in the amplitude domain.  They considered the range from 600hz to 4Khz the critical range and found that phase shifts creeping down below 4kHz tended to muddle the voice.  I agree that the audio bandwidth is much larger than that required for voice but it is interesting to note that the phase shift of the 4722 does creep down into that "sacred area" that Bell Labs found had an impact on intelligibility.   I just measured some 900:900 Western Electric repeat transformer that had a specified frequency range of "Voice" and 425Hz-1615Hz was mentioned.  When fed from a 50Ω source and left unloaded the -1dB points were 18Hz and 2.4Mhz.  I don't think the crazy high top end bandwidth was an accident and the phase stays flat to 100Khz.

http://www.intactaudio.com/forum/files/phase_385.png