Apogee vs Soundlab

Dazzdax, its normal for transistor amps to sound that way on the Sound Labs, due to the low impedance at high frequencies. Sound Labs do not expect the amp to double power as the impedance is halved. see
http://www.atma-sphere.com/papers/paradigm_paper2.html

So when you put a transistor amplifier on the Sound Labs, the result is too much treble energy and not nearly enough bass. That's why tube amplifiers are preferred; they will try to make the same power regardless of the impedance- that gives you a more tonally neutral sound on the Sound Lab.

Bottom line is that they can be very extended and smooth yet still aggressive if the music calls for it, IOW quite neutral :)

The Cat is fairly neutral, so I doubt it to be the culprit. The fault must lie elsewhere. I think Atmasphere is right. I have tried several highly reputable transistor amps on my SL speakers and they all sounded flat generally and nasty in the highs. Like the Quads this speaker needs a good tube amp to show off its mettle. Albert Porter in another thread reports of several, which sounded right to his experienced ears. Amongst those were the big VTLs and Atmas. I've settled with Atmas.I am extremely sensitive to highs not reproduced properly and am very happy with how the Atmas reproduce my music.

Ralph, what would happen if I'm using a 10 ohms resistor in the treble section of the Soundlab (instead of using the "brilliance" control rheostat)? Would that prevent for the solid state power amplifier to "double" power? Whay don't I hear the same treble characteristics with the Quad ESL 63?

Chris

Chris,
this is purely personal experience and hence highly subjective:
I've owned Quads for decades and was never really satisfied with their high end. In the olden days I put Sequerra ribbons on top of the 63s to get the highs I liked and later the aCapella plasmas. I still have those, but feel no need to use them with my Sound Labs where I have the control rheostat at full tilt boogie.
Curious to hear what Ralph will say to your idea.
Wondering if your trouble couldn't also possibly be room dependent and if I, because of my age, should stop talking about the high end response of speakers, because my ears won't hear it no more anyway.......

Chris- check out what Jafox used in a mod on his speakers:
"I also replaced that horrible "brilliance" rheostat with a gold plated double-contact selector switch of 6 resistance values (values 0-> 2 ohms range). Treble clarity significantly improved. And with an occasional treble-hot recording, being able to attenuate the treble a little bit is mighty nice. It was amazing how much treble grain existed with the original rheostat."Maybe this will help out your situation.