difference between an active and a passive preamp?

Ts0711, you have a very sensitive amp so it won't take much to get your amp to full power. However, I would think you would lose some dynamics and high frequency response with interconnects that long. Have you tried to get your passive preamp and source close to your amp so you only have 3 feet from preamp to amp and about same from your source to preamp? I would think you would hear a noticeable difference. Your present setup may sound good to you now, but using shorter cables may significantly improve the sound.

04-12-11: Almarg
TVC's are a completely different story, that I'm not particularly familiar with. But since a transformer provides an impedance transformation corresponding to the square of the turns ratio (with attenuation or gain being directly proportional to the turns ratio), I would expect that as long as the volume control position that is used corresponds to a significant amount of attenuation (i.e., it is not near the top of its range), cable length and component impedance matching would be much less critical than for a resistive passive preamp.

I should have added to this statement that it assumes the transformer itself does not introduce significant resistance or impedance into the signal path. I have no particular knowledge of how true that assumption may be for typical TVC's.

Regards,
-- Al

Al, thanks. My understanding of TVC or AVC vs resistor/LDR volume control is that as you apply more attenuation, TVC will decrease its output impedance whereas resistor volume control will increase its impedance. That is one argument for TVC because your suppose to get better sound as you attenuate more with TVC, while you get worsening sound as you attenuate more with a resistor based volume control. At least that's the argument I heard, but I don't know if in practice this is true.

04-12-11: Dracule1
My understanding of TVC or AVC vs resistor/LDR volume control is that as you apply more attenuation, TVC will decrease its output impedance ...

True, which is why I referred to TVC sensitivity to cable length being less "as long as the volume control position that is used corresponds to a significant amount of attenuation."

As you apply more attenuation ... resistor volume control will increase its impedance.

That's not quite true. Assuming the resistive volume control is configured as a conventional voltage divider, it is true that the lowest output impedance will occur at the maximum volume position (where it will to a very close approximation be equal to the output impedance of the source). However, the worst case (maximum) output impedance will occur when the volume control is set to provide approximately 6db of attenuation, which in terms of subjectively perceived volume is not greatly different than the maximum volume position. As the volume setting is reduced from that point, output impedance will then gradually decline.

Best regards,
-- Al

I have to admit that the common detractors' rant of diminished dynamics rings true for me. For what I put into my system, however, I consider it an acceptable trade-off (for now). Plus, my system isn't perfectly optimized for a passive preamp, like the op's. This brings me back to the, more or less, main point of the thread as expressed in the original post, which is to determine when one should use a passive preamp versus an active preamp given a certain set of non-negotiable pre-existing system components.

This thread seemed to point out an Option C, however: the buffered passive. It seems that if enough gain is provided by the source output and amp(s), then a passive or buffered passive should be sufficient to accurately reproduce the source material. The only issue is impedance and possibly voltage(?). (Based on my reading here, this is my impression). If this is so, then shouldn't optimal dynamics (e.g., "attack") be achievable with a buffered passive, if not a discreet passive? For the proponents of actives, I suppose a more direct question is, what specific attribute of a proper active preamp achieves that vivid "attack" that a passive does not? Is it more than an impedance issue? If so, then what?

In short, it's clear to me that not all systems are passive-friendly, but a buffer rectifies the situation. That is, a buffer seems to be *the* Band-Aid for passive-hostile systems, based on any thread I've found on this subject. Or is it? When is a buffer plus a passive still not enough, and how common might this situation be? If this question deserves another thread, please say so and I will post anew. But this seems like a natural progression from the current conversation following from the op's expressed concerns.