Impedance Matching


Would you even consider running a tubed preamp with an output impedance of approx 2,500 ohms into a lower impedance solid state amp, say if the amp had a value of 15,000 ohms?
stickman451
Unfortunately I cannot 'try before I buy' but the price is very, very, good and hard to pass up. Magnepan voices and runs their speakers with Bryston gear because (1) it sounds good to them, (2) the Brystons NEVER break driving the DIFFICULT Maggies.

At the bargain price I almost wonder if it would be worth picking up a good SS pre to drive them and just keeping the Hovland too!
At the bargain price I almost wonder if it would be worth picking up a good SS pre to drive them and just keeping the Hovland too!
Another possible approach, although it would result in having an additional active stage in the signal path, would be to buy the Bryston, and if the Bryston/Hovland combo proves to be unsatisfactory purchasing and installing a separate active buffer stage in between them.

I'm not sure if the Burson AB-160 buffer is still being made, but if you can find one new or used that would probably be a good choice. Also, A'gon member Bifwynne (Bruce) has had a custom buffer stage made for him at a modest price by Tom Tutay of Transition Audio Design, I believe in Florida. Tom is reported to be an outstanding person to work with, and Bruce reported excellent results with the buffer stage.

Either of those devices would provide a very high input impedance and a very low output impedance, just what you need.

Regards,
-- Al
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
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