Hybrid systems (valve and solid-state)

This is not to say that the components would not work together. The audio industry does have open architecture and a common interface between components. However what can happen with disparate impedances is that there could be substantial frequency response roll-off between the two components, particularly in the low frequency bass region. This is only potentially a problem when considering a valve preamplifier to drive a solid state amplifier, as many valve preamplifiers have very high output impedances, (designed to drive high input impedance tube power amplifiers) and most solid state amplifiers have low input impedances. Sometimes a high output impedance preamplifier can be very sensitive to the capacitance of the interconnect cable, which tends to roll off the high frequencies also.

AK, I am not an EE either, but from what I have read and seen discussed in various places:

Impedance mismatching MAY cause problems; the variation in input/output impedances of various manufacturers equipment (both valve and SS), is too great to provide a general answer.  

Some combinations may work brilliantly and others dismally or not at all.

Many people seem to use valve preamps with a combination of valve and SS amplifiers in systems utilising active crossovers and multi-amped speakers, the tendency is to use valve for the tweeters and mids with SS for the bass.

More people seem to use valve preamps with SS power amps than the reverse.

It is possible, by using an active buffer stage between components (like the Burson Audio Buffer) to lower the output impedance going forward to the next stage.

The sort of sound tailoring that you seem to be interested in obtaining (from your other comments and enquiries) might well be best achieved by programmable equalisers such as the Behringer Ultracurve DEQ 2496 (relatively inexpensive), the TaCT DSP or the DeqX system - the latter two are quite pricey but are primarily intended to provide active crossover and room equalisation abilities and, by all accounts, are extraordinarily effective.

In my understanding, a low output impedance driving a high input impedance is a good thing, a high output impedance driving a low input impedance is not - in very general terms.

Afterthoughts, I would expect a SS preamp to work better with a valve amp than the reverse.  Your previous quote actually covered most of that I think although some of it seemed, to me, more applicable to a valve preamp stage in a hybrid amplifier than to standalone separates.

One other aspect occurred to me, somewhat of a digression but related, perhaps Graham has thoughts on this.

That aspect was the notion that if equalisation is achieved in the digital realm (as per the equalisers mentioned) then the issues of "insertion loss" and phase anomaly are of no consequence, eg non-existent.

Those thoughts arose from the consideration that what we essentially have is a fixed gain device from which we wish to have a variable gain that is frequency related.  The only way to achieve this is to attenuate the complementary frequencies of the incoming given signal since we cannot add to that signal only take away from it.  If, however, the signal is digitised, it can be manipulated with impunity prior to reconversion to an analogue waveform.  Or so my thinking ran, simplistic ? - heretical, likely 

Does this digital "sleight of hand" obviate the "phase issues" Graham is outlining above ?

I would be interested in comment on that aspect.

Thank you for those thoughts.

I think that, indirectly, you have very adeptly illustrated the point that, like, I suspect, many, if not most, of your customers, I most often half understand, half of what you are saying, half of the time.

I am probably being generous to myself there