Impedance Matching

Stickman ..., Al is correct. Tom Tutay built a custom impedance buffer for my subwoofer that sums the L and R channels and also ties into the balanced outputs of my linestage.

I have a caveat that is best addressed by Al and/or Ralph. My impedance buffer only ties in the subwoofer, which is self powered. There are no artifacts between my linestage and my main amplifier. I only use the sub to supplement the bottom octave or two (below 50 or 60 Hz) where my main speakers roll off.

So, perhaps Al and/or Ralph can speak to whether inserting an impedance buffer between the pre and amp could compromise the signal.

Bruce (bifwynne)

... perhaps Al and/or Ralph can speak to whether inserting an impedance buffer between the pre and amp could compromise the signal.

Certainly inserting an additional active stage into the signal path to correct an impedance incompatibility can invoke some tradeoffs, to a greater or lesser degree depending on the quality of the buffer.

But although nothing in the preamp itself would be changed, I would view doing this as in effect amounting to implementing a design modification to the preamp, with the modified "preamp" consisting of the combination of preamp + buffer stage, and a (short) pair of interconnecting cables between them. (It would most likely be best to make the cables on the input side of the buffer as short as possible, with those on its output side as long as necessary, so that the longer cables are driven by the device having low output impedance).

Viewed in that manner, it seems to me that even apart from resolution of the impedance incompatibility, the subjective effects of adding a buffer stage would stand a reasonable chance of being an improvement, rather a degradation, although either outcome is certainly possible.

In any event, the OP indicated in his other thread that the opportunity he had to purchase the Bryston amp went away, so the question may be moot.

Best regards,
-- Al

I use a VAC Standard tube preamp as a 'tube buffer' between my digital stuff and my Bryston BP-26 preamp (to my Bryston 4B-SST² amp.
Even with the extra stage in there it sound spectacular.
And in fact the extra electronics make the CD sound really great.

Check out AUDIO COGNOSCENTI:

http://www.audiocognoscenti.com/blog.html

One of the big issues of impedance matching besides the frequency problems and other issues is the transfer of signal.

Using a very simplistic example.
Using only voltage you have a ratio of transfer. So going from 10k to 10k you would have 50% transfer. Going from 1k to 10k would give you a 1 to 10 transfer ratio and so on. Generally, so you don't have current loading issues and voltage transfer issues, it is best to have a low impedance source to a very high impedance input.

Anything else is tone control to an extent and that is why interconnects make a bigger difference on some systems then others.