It is really hard to assign numbers or percentages to the difference between amplifiers.
We now have a drastically improved and very transparent A-B comparison box built and in daily use here. It allows us to connect two preamps, two power amps, and two sets of speakers all at once and switch between any combination from a remote control. Levels between any two components are matched when switching and switching is dead silent.
Using this box has taught us a few things.
For example, different amplifiers react quite differently to different speaker loads. The speakers we have connected now are a set of original Salk HT3 three way units with ribbon tweeters and a set of older B&W 801 Series Two speakers, with our crossover fix of course, and damped housings for the tweeters. Both are really good speakers and each has an easy to identify sonic signature.
The new switch box is now transparent enough to not mask differences between amplifiers or preamplifiers. It is easy to tell one design from another now.
Interestingly, when using the 801 speakers, the difference between the Synergy and Fet Valve amplifiers is more obvious. Using the HT3s, the differences are minimized.
What this means of course is that what you hear is really going to depend somewhat upon what speakers you use. The Fet Valve always comes across better, but "better worth the extra cost" is a lot less obvious if you are using B&W 801s.
Thus, my "percentages better" have no absolute meaning when the equipment is used with different speakers.
Anyway, we would suggest that the Synergy is probably 50 percent better than the Insight series. The Fet Valve amps are more like 100 percent better than the Insight series. The Fet Valve is probably 30 percent better than the Synergy driving the 801s, but 20 percent better driving HT3s. These are really wild ass guesses here, remember that.
Regarding number of output devices here is the scoop. Our heat sink sections each hold three TO3 output transistors. The big amps all use four heat sink sections, two per channel. Thus max capability is 6 TO3 devices per channel. The Fet Valve amps all use double die devices, thus adding up to 12 Exicon mos-fets per channel.
However, in the new Synergy and Fet Valve amps, two of the output devices per channel are used for output regulators. Thus these amps use four mos-fets per channel, double die devices in the Fet Valve 400 and 600, and in the Synergy 450. The Synergy 300 uses standard devices. Our long term experience with powerful mos-fet power amplifiers over many years of use tells us that our choice and number of output devices have proven to be very durable in service.
Note that using double die devices does not add to the complexity, actually it makes the layout less complex as there is less wiring needed for the same results. All of our amplifier will perform as rated with the use of single die devices only. The double die devices just add an additional safety margin to amplifiers that are rugged and quite fault tolerant in the first place.
Note also that the regulated power amplifiers all run cooler. The output devices no longer are attached directly to the high voltage power supplies. They are connected to the regulated power supplies which operate at a significantly lower voltage. The regulated power supply voltages are set to regulate up to and just past clipping. The active regulators also do not work very hard. At idle, when the see full raw supply voltage in, the are passing very little current. At full power, when the regulators must pass lots of current, the voltage across them is very low as the raw supply voltage drops with high demand. The regulators and the output devices are always run well within their safe operating windows.
No, there is no upcoming upgrades to the Insight series preamplifiers. The solid state preamps use completely different technologies than the power amps and there are no common circuit configurations. They work really well as is and would take completely new design ideas to make them better than they now are. That will be tough to do.
Finally, the new Fet Valve and Synergy amplifiers we think will make very useful improvements to your audio systems. Try one. Remember we offer a 30 day satisfaction guarantee if they do not meet your expectations.
Frank Van Alstine