The dear old 12.1s were truly gorgeous sounding but clipped fairly often. Since them I had and sold three sets of QUAD 22 and two IIs. All of them measured well, but were IMO quite disappointing, if quieter than the double mono LEAK combo. I'm more than a bit of an iconoclast, and am not persuaded that '$$$$ / raved about by 'philes rolled on virgin's thighs' caps nor R's nor inductors matter a whole lot in a feedback amplifier. Good enough IS good enough. Of course, MF plastic caps are better than NoS PIOs (and more, but they matter most in feedback circuits where commercial and then selected to 1% teflons or styros are worth the extra few $ and time, as are Holco-copper or Vishay bulk-foil R's. IME raising the wattage of selected commercial circuit R's has a far higher musical Return On Investment (ROI) - lower distortion and more stable performance but for pennies not many dollars - once you are using MF's anyway, than any expensive R in most circuit roles can do. A mixture of brands IS worth-while. Yes, I don't 'get' carbon films, OR CCRs. Another place where you can really hear good precise-value R's and caps is in phono stages, esp. passive RIAA types. JBTW, IME&O and YMMV, this is one of the few places that 12AX7s make sense in modern valve audio. BTA I do have two very sensitive power amps. ;-) Even after the mods the St20s still need SFA driving, OEM they needed just 125mv for 16w but it's more like 250-300mv now. Nor am I much convinced by SET amps, or single drivers, or VHE spkrs as 'essentials' for getting truly beautiful sound. I am convinced that controlled dispersion/directivity is 'a good thing', as is efficiency above 90dbw/8 ohm, and small PP amps given all the help that SS can give from outside the signal circuits. The ability to do justice to simply miked / 'real-stereo' recordings of acoustic instruments in real-time and real spaces, played by people interacting with each other, (and not with each other's mono 'tracks') is my reference point. Like everyone else I have to listen to a lot of these latter recordings and still enjoy them, but my heart and mind are still with real coherent music made in real spaces. Once this is has been achieved to a standard where I a continuing acoustic singer since age 9, am able to suspend disbelief and fall into the performance, that is where I say good, got it. All changes have been directed at improving on results against that reference. My latest faves are my current pair of rebuilt LEAK Stereo 20s, reviewed here at AA. Both run in 'high A' AB1. Both have big bypassed PSU caps and 4 soft-recovery SS diodes snubbed anyway. NoS Aussie AWA/AWV 6CG7 splitter-driver in long-tail-pair LTP with a single FET as a CCS. The shared input valve is now a gold-pin Tfk 6DJ8. The use of low-mu high gm valves and a FET CCS replacing the 3 12AX7s, has allowed a significant reduction in total NFB, while yet raising that of the NFB loop around the PP OPT stage a bit. S'nap ;-)! One's in pentode (20Wpc RMS 20-20K) with a passive line-level 1st-order low-pass at about 8k into a 91dbw WR mid-bass driver -3db at 3.5khz. Easy flat 8-ohm load, with R & C for Z -rise EQ. Active drive for most of what happens. The treble amp is in triode mode giving 6? watts pc driving a complex spkr-level crossover (3rd-order & Fs trap & FR Eq, padding) into large soft domes whose VC diam. matches the WR drivers VC. Flat 8-ohm load, 91db/w after 3dbw of padding R. Very quiet once I went for 'horisontal bi-amping', and added a ground strap between both chassis' -ve spkr terminals. Rear walls and side walls, slap echoes in halls, train, motorbike, and truck rumbles, entries, interplay, nuance. You are there listening on real stereo. This combo plays much louder and cleaner than 45 watts of pure-A STAX SS (Japan) power, also rebuilt. It had a cloned 'STAX Reference' amp's driver stage - and better, cleverer 'protection.' Far better bass slam, and far more bass detail! Better 3D, much nicer, and more detailed, very coherent! I'd bet the PSUs storage - in joules - is far higher in either amp than in the STAX. The only SE valve amp I have heard - through the time and phase coherent Audiosphere M3s - used 13E1 regulator valves in UL ie WITH a teeny bit of NFB. ?18 watts pc, a truly useful amount of power. Couldn't play as LOUD, and lost the plot far earlier than that. Blameless and very real but not as breathtakingly convincing as the various SE Pass ZEN with FETs iterations I have heard, through the spheres. Not as good as what I still have.
Warmest
Tim Bailey
Skeptical Measurer & Audio Scrounger
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