VAC sigma vs Vac phi 200.


Need inputs from experts.

I am thinking of buying one of this amp.

I already have ARC ls 17. which one do you think has better sound?

1. Vac Integrated Sigma 160i or
2, Phi 200 with LS17 as preamp.
aprica88

Showing 2 responses by almarg

As a VAC owner (Renaissance 70/70 MkIII), and based on many comments I have read, I'm sure they are both exceptional products. Here are some additional factors that you may want to consider, though, in choosing between them:

1)The Phi 200 is spec'd as having a gain of 37 db single-ended, and 31 db balanced. Usually, although not necessarily, if the two numbers differ the balanced gain will be 6 db higher than the single-ended gain. I would check with Kevin at VAC to verify that those numbers are not reversed. See the next paragraph for the possible significance of that.

2)If you were to use the Phi 200 with your LS17, I suspect that you would want to use balanced connections between them (see, for instance, the comments about balanced vs. unbalanced in this review of the LS17). If the balanced gain of the Phi 200 is 37 db, which is quite high, and you are using digital sources having typical 2 volt or so outputs, you may wind up with excessive overall gain, causing you to operate the preamp's volume control very low in its range. That might still be true even if the gain is 31 db, given the 18 db balanced gain of the LS17.

3)The gains specified for the 160i appear to apply to its phono stage. You might want to ask Kevin what the gains of its line stage and power amplifier sections are, especially if you are using digital sources.

4)Concerning degradation of the sound by the interconnect cables that would be needed if you were to go with the Phi 200, there are several tradeoffs that are involved. Depending on how your components are physically arranged, using a separate power amp may allow you to use speaker cables that are shorter than if you were to go with the integrated. The lower the impedance of your speakers, the more important that would tend to become, and the higher the impedance of your speakers, the less important that would tend to become. The sonic effects of the interconnect cables will tend to be lessened if they are balanced, and will tend to be moderated by the fact that the LS17's output impedance, although not particularly low, is well within reason for a preamp having a tube output stage.

Good luck in your quest!

Regards,
-- Al
One more point to consider:

5)The Phi 200 provides three output taps, while the 160i provides two. Having the additional tap provided by the Phi 200 might be sonically beneficial with some speakers, particularly those having very low impedances, and possibly also with some speakers whose impedance varies widely as a function of frequency.

Regards,
-- Al