Been messing about with this Musical Fidelity tube buffer, and while the verdict's still out on whether it's gonna be life-changing (definitely hear the effects on some things, but not others), what I have noticed is that the cables are more of a factor. I said in another post that the bass slackened when using the buffered RR2150 with my turntable, but then, when I used the Audience interconnects I had laying around while my CD player is being repaired (I was using some leftover Outlaw PCAs), the bass tightened up instantly. It surprised me, because earlier I'd said that the Audience interconnects hadn't overwhelmed me when I first introduced them into my system months ago. I keep wondering if that can be attributed to break-in…

Tubes are higher output impedance devices than anything solid state. This higher impedance can interact with cables which have varying amounts of capacitance and inductance. The difference is usually in the higher frequencies, but there could be something happening in the bass because of interaction with that cable.

It's all kinda mysterious (and fascinating) to me, Altec. I've read that the MF X10-D is a unity gain buffer with much lower output impedance, though if I understand you correctly, "low" for a tube device would still outpace something solid state.

It's very difficult for tubes to have as low an output impedance as solid state unless an output transformer is used - and even then, solid state is lower.

The tube buffer is undoubtedly a cathode follower output which is "low" impedance in the tube world, but relatively high in the solid state world.

Thanx for the info, but that brings up another question: I keep reading that upgrading the unit with an outboard 12VAC power supply or something really improves its sonic capabilities. Might your above comment have something to do with why that is? Just trying to clarify/understand stuff.

An "upgraded" power supply is utter nonsense. Think about it - does that mean that they are supplying an "inferior" supply as standard?

Any electronic device will only use the current it needs, a supply which can supply more than that is a waste of money (although one which a lot of unwary people fall into).

The power supply has nothing to do with the output or input impedances of a circuit.

Exactly…kinda what I had deduced. For what some of this equipment costs, the idea that anything on it might be substandard is a bit ludicrous, if not plain maddening. Thanx for the insight.

This cable discussion has me thinking it might be interesting to try different cables from my current Kimber PBJ's with my Yaqin buffer. From what Altec says the cables to change would be the output cables to the power amp; is that right - the 990 having a low-impedance output?

Got other stuff on my plate but I'll share my experience if I do any experimenting.

The cables coming from the output of the tube buffer would be the ones which might affect the most change. The ones going to the input of the tube buffer would not likely make any change since the output impedance of the 990 is probably quite low.

Hey psyprof1. I don't know what your cable budget is (mine's low, but I've splashed a bit in the past year), but a little bit ago I stumbled upon this site, www.usedcable.com , that discounts "high-end" cables and considers trade-ins. Haven't bought anything there yet, though. For what it's worth…