Pass Labs X250.5 - Manual (Page 7)

7 X250.5 Owners Manual
The Pass Laboratories™ X250.5 is optimized for loads nominally rated
at 4 ohms and above. You can run the amplifiers into a lower nominal
impedance without difficulty, and we are not aware of a speaker on the
market that presents unusual difficulty with these amplifiers.
The X.5 series amplifiers do not care particularly about the reactivity
of the load. Reactive loads typically will have slightly less distortion
at a given voltage/current level than resistive loads, but will make the
amplifier run a little hotter. The X.5 circuit was designed to be quite
happy driving electrostatic and other difficult speakers.
When driving transformer-coupled loads directly, as in some elec-
trostatic and ribbon designs, some attention must be paid to the DC
character of the situation. If the transformer primary is being driven
raw with no protection from DC and your source has DC voltage, or
in cases where the small offset of the power amplifier is still too much,
you may create distortion in the transformer and get less than optimal
performance from it. Generally this is not the case with transformer-
coupled loudspeakers, but it does occasionally surface. In these cases,
take special care that the source does not contain a differential DC
component, and confirm the differential DC offset of the pre-ampli-
fier is sufficiently low. This differential voltage is easily adjusted by a
qualified technician armed with the appropriate service documents.
We have a general recommendation about interconnects, which is that
they should cost less than the amplifier, and be flexible enough to work
with. We have tried a lot of products and most of them work well, but
as a practical matter we cannot make blanket recommendations.
The amplifier is not sensitive to source interconnects or ground loops.
It is also not sensitive to radio frequency pickup, which allows some
flexibility in choosing source interconnects without shields, though
shields are always in good taste.
We prefer speaker cables that are thick and short. Silver and copper
are the preferred metals. If you find any cable made of gold, please
gift us a couple hundred meters.
Fortunately the amplifier is not sensitive to the capacitive/inductive
character of some of the specialty speaker cables, so feel free to ex-
periment.
We have found that about 90 per cent of bad sounding cables are in
reality bad sounding connections, and we recommend that special at-
Speaker Interface
Interconnects and Speaker
Cables