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As I said above, I consider the use of the inevitable step-up heads with 1 ohm, and thus sense fully embrace the approach of the Audio Research Reference Phono.
A brief aside:
Now it seems to me, "cracked" the intent that motivated the designers in the conception of the Reference Phono:
- The input impedance transformer is to head as close as possible to 1 ohm (not more than the 5 ohm).
- For all the other ... you get another entry, adjusting the value of load resistance.
The confusion arose because Audio Research says the transformer input impedance to 280 ohms, who wrote a similar thing I suppose he had drained the liquid blue of the toilet bowl, the fact is that they sent Bring a bit 'all. What, in my opinion, fared better Montanucci, while the technical Stereophile, John Atkinson, trying to juggle, he suggested unspecified compatibility issues with the Audio Precision measurement set, remedying the figure of stunned. It is easy to verify that data sheets of all processors are based on surveys Jensen Audio Precision.
End of engraved.
reiterate my concern when dealing with heads having 2.5 to 5 ohm impedance, the situation is similarly difficult cases to 1 ohm, and I understand that in many circumstances the use of step-up is preferable. But assuming a phono with gain generous, with large transconductance and clean circuit (maximum of two triode, used in purity), in this case I think that without the step-up musical performance would improve.
not forget that the step-up transformer is driven by a generator (the head) that provides voltage and current so poor as to make the matter very sensitive in all respects. So
heads with more than 20 ohm impedance, in my opinion would be only right to do without the step-up.
Although I understand that for many designers is a problem, resulting in the need for higher gain without sacrificing quality music and at the same time having to fight with greater breath (No longer reduced by the step-up transformer).
To support these considerations, I refer to the Audio Research Reference Phono above and I'm going to note that, as a pure circuit, there are doubts, even without the scheme.
I am sure that the majority like to see a device full of valves as the Eniac, but one wonders why a 22 triode phono needed only for the audio section, there are a bit 'so many?
As an MC phono two triodes per channel is more than enough for a pre-scheduled a triode is also too much for a 30W final two triodes are sufficient (as shown in a previous post) and, in case you need higher power to 150W, just add an extra triode.
Overall, the MC cartridge to the speakers, 6 triodes per channel is sufficient.
As ever with the same number of triodes in the Audio Research Reference Phono we get only half of the audio portion of a channel? (Series: I put my head on the hard review between now and 5 minutes when the music starts coming out) scheme
Without much you can not say, but, looking at a chart produced by Stereophile, we can extrapolate important considerations.
The graph shows the distortion as a function of output voltage and the typical behavior of the "magic donkey."
Normally, a donkey loaded with weights, the poor animal will work harder with increasing load.
With the "magic ass" the opposite happens, the greater the weight and do less work ... just like in the graph with the distortion of the Reference Phono, the higher the output voltage distortion and the more it changes.
This spell has a name: negative feedback * *, and given the trend of the graph, quite possibly including multi-stage closes (pain).
's why you need all those triodes! In conclusion I would agree
streamline phono circuits with short routes and natural purity and increasing performance with triodes they are low noise, fast ... and by the generous gain in these cases, it becomes possible to dispense with the step-up. It would be a definite advantage in terms of clarity and agility.
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