Why no Spectral phono stage?

A Spectral dealer told me they did, but this was about a year ago.

Some of their older preamp models provided optional built-in phono stages, but I am not aware of any separate phono stages they have produced. And I believe that those built-in phono stages provided somewhat lowish gains, that were only suitable for use with LOMC cartridges by virtue of the relatively high gain provided by the line stage in those preamps.

Just guessing, but perhaps one reason they apparently have not produced a separate phono stage might be that application of their ultra-wide bandwidth philosophy and circuit expertise to a phono stage might result in significant design challenges related to avoiding RFI (radio frequency interference) issues, given the very low signal levels that are involved. And also given that the frequency response of LOMC cartridges typically has a resonant peak somewhere in the RF part of the spectrum, resulting from the interaction of cartridge inductance with phono cable and load capacitance.

I don't doubt that they could have overcome those challenges if they chose to, but perhaps they felt that it wasn't worth the effort given the competitive landscape.

Regards,
-- Al

There will be a phono preamp this year; it's been in development for over a decade, and rumor has it the specs and sound are extra-ordinary as usual. Suggest you join the Spectral forum at whatsbestforum.com

Al, the forum would also welcome your technical expertise and in-depth understanding of fast, wide-bandwidth designs used in the Spectrals

Given Dr. Johnson's role in digital recording technology, (HDCD, etc.) perhaps focusing on analog playback strategically isn't of interest to Spectral.

Cheers,
Spencer

Ack, thank you. My knowledge of Spectral's designs is limited to what I've read at their website and in reviews. You may find the comments by me, Atmasphere, and a number of others in this thread to be of interest, if you haven't seen it already.

An excerpt from one of my posts in that thread dated 2-6-15:

... slew rate, risetime, and bandwidth will in the case of many designs extend well beyond the point of being overkill with respect to effects that may have DIRECT audible significance. The Spectral amplifiers being extreme examples in that respect. As I'll get into in a moment, though, that does not necessarily mean that the only benefit is to those who write marketing literature....

So why have I put the word “directly” in caps? Well, I would presume the designers feel that by designing ultra-fast circuitry they can avoid or minimize effects which may be audibly significant. For example, they may be able to realize the benefits of increased amounts of negative feedback while avoiding or minimizing what would normally be its adverse effects, such as transient intermodulation distortion. Or the higher speed circuitry might help to minimize crossover distortion, or the effects of unwanted energy storage in devices, etc.

So what can be said about that? Well, it’s an approach, and a philosophy. As is usual in audio, how good or bad the results are will depend on quality of implementation, system matching, and listener preference.

In the case of their power amplifiers, my speculation would be that the main contributor to the subjective perception of speed that is generally attributed to them is the avoidance or minimization of TIM (transient intermodulation) distortion that might otherwise be a consequence of the use of negative feedback. Rather than the perceived speed being a consequence of the ultra-wide bandwidth in itself. Reduced TIM means "cleaner" transients, and it would seem expectable for that to correlate with subjectively "faster" performance.

Designs having ultra-wide bandwidth have their potential downsides, however, certainly in terms of additional challenges that have to be faced in the design process. And perhaps also in terms of additional challenges that might have to be faced by the user, to the extent that there may be increases in sensitivity to RFI, speaker cable capacitance, AC power quality, etc.

The potential benefits of their ultra-wide bandwidth approach seem to me to be mainly applicable to power amps, though. I'm not sure what the benefits of ultra-wide bandwidth might be for preamps or phono stages (as opposed to bandwidths of say 200 kHz or thereabouts, that being a factor of 10 greater than the supposed upper limit of human hearing, and therefore arguably high enough to eliminate the possibility of audibly significant phase shifts). But I don't doubt that with sufficiently good engineering excellent results can be obtained for those kinds of components with their approach, while also being obtainable with other approaches.

Regards,
-- Al