Strain Gauge Preamp/ Phono. A new standard?
I had strain gauge cartridges long ago, including the Win and the Panasonic. I saw them as quite good, but not reaching the realism of my Decca Londons. There are many benefits in the various grades of the Soundsmith phono/linestages, but it does take a commitment to this idea that I am not willing to make. |
I very much appreciate Audiogon's great coverage of the Soundsmith Strain Gauge Phono system, and for having the courtesy of posting this hopefully helpful and informative response: The Strain Gauge is a DISPLACEMNET device, not a velocity sensitive device like all magnetic cartridges. Velocity sensitive devices have a FLAT playback response, so they require RIAA EQ to invert the RIAA recording characteristic used when making masters for record production. RIAA has an interesting evolution; Mr. Galo has written a wonderful explanation of how, and why it evolved and changed over the years: http://www.smartdev.com/RIAA.html Displacement devices have an INHERENT 6dB/octave curve, very similar to the RIAA (not an accident, BYW)....they DO deviate slightly from the RIAA at two points, BUT, we do NOT correct for this, for doing so would ruin the beauty and simplicity of the device; the one super clean gain stage between you and the music we designed is almost one too many. More than one (to "fix" small anomalies) would be death to the magic. We do compensate passively for the low end roll, as required. For those who may feel that absolute compliance with RIAA is mandatory, I would suggest that they take a microphone and laptop and make a response measurement for flatness at their respective wonderful listening positions. They may find that not only does it deviate far more than "less than one dB" as we do, but that "correcting it" with additional circuitry puts so much in the signal path that they join the ranks of anti-magicians. Peter Ledermann/Chief Engineer/Soundsmith Corp. |
Hi Peter, the RIAA curve is flat from 318 uS to 3180uS. So there are about 4 octaves that will be spectrally incorrect. That is a lot bigger error than any room I've tested. BTW I've run plenty of room curves over the years- especially at shows. I agree that you see big variations, but not like this (at least not so far anyway). I've also produced a variety of LPs over the years and I've found that only 1 db variations in the test pressing can be audible (this is easy to hear over a frequency spectrum as opposed to a single frequency, BTW). So- do you offer an equalizer? |
Thank you for your comments: they are greatly appreciated. The subject of human response to amplitude and phase is an interesting one; the standpoint often determines the course of design choices for those of us in the audio design and manufacturing field. I, for one, strongly believe that the human ear is much more forgiving in the amplitude domain than it is in the time domain. After all, many amplitude deviations are the direct result of phase interaction due to resonance, both summation and cancellation, making "amplitude" perturbations audible and potentially objectionable in speaker drivers and cartridge/tone arm systems. From that standpoint, the cutter heads models also vary considerably; many require one or more frequencies to be fed back with control of both amplitude and phase to stabilize the cutter head. The phase shifts introduced by the RIAA recording curve are further modified by the varied individual characteristics of the equipment used to cut the master. So, where does that leave us? The Strain Gauge is without much phase shift at all. If one leaves out the phase shifts normally introduced by use of a playback RIAA curve, is one better or worse off?? Please also refer to the graph near the top of Mr. Galos excellent article called Figure 1; http://www.smartdev.com/RIAA.html It refers to this graph as the typical RIAA response; in reality, it is far from the ideal response that one gets from the theoretical filters due to interaction of those filters. This, not the ideal, is what we have all been listening to for years with magnetic cartridges! Superimpose a 6dB/octave curve (Strain Gauge) and you will find that it deviates less than plus or minus one dB. My experience is that severe phase perturbations over a narrow region are very audible, while those that are spread out are much less objectionable. It may well be that this is one of the positive differences one experiences when listening to the Strain Gauge. That, in combination with the general standpoint of multiple stages being inferior to a single stage, makes one think that possibly that too, is a motive for using a "simplified" strain gauge system. There are also numerous other contributors to good sound - extremely low stylus jitter being one. Although some Strain Gauge preamps in the past have been made to more closely follow the RIAA, some were not. As far as I am concerned it is an open issue that will be addressed from varied standpoints, some of which I have mentioned above. My consideration in the Soundsmith Preamp is to make it mostly flat; the decision to mainly use the inherent 6dB curve of the Strain Gauge elements is based on 35 years of listening and talking with other designers and SG owners. It also provides a standard from which one is not precluded from adding what they believe to be proper EQ to our system, or Soundsmith offering such in the future to those who want it and do not feel that it detracts from the listenability. The proof is truly in the listening; many who have listened in our rooms or who have owned our Strain Gauge or Strain Gauge systems in the past that employ flat response have enjoyed the result. If the system as I produced it was very, very wrong, I believe that there would have been many more negative opinions than positive. Again, thank you for your insightful comments - Peter Ledermann/Soundsmith |
