Limited Bandwidth
west wrote:
I built a typical phono amp with 3 12AX7s, the last tube a cathode follower
(low impedance). It has plenty of gain (70db) and can easily drive any amp
directly. I like using a 100k step resistor volume control instead of a line
amp.
My problem is that when I use any of my tube amps, the sound has limited
bandwidth. A SS amp does not exhibit this problem, if fact the SS sound is
rather impressive to me (for silicone).
With my limited know-how, I'm swagging that an impedance mismatch is the
culprit.
If my contention is correct, is there a simple cure besides using a line
amp? Perhaps some kind of buffer is called for. All comments welcomed and
thank you.
Cordially,
west
Seems like you don't know how to make your tube amps have full
bandwidth.
But all the well made tube amps have full BW, so make your tube amps
well and no problems, OK.
If the tube sound seems like there isn't full bandwidth
when in fact there is, then your statement about SS amps having more
subjective? BW than tube amps could be because
the SS has more distortion. Usually SS has less measured THD/IMD.
Have you conducted a proper AB test, set up two amp systems, one SS, the
other tubed,
and with same source from the same CD played feeding both amp systems,
then matched the level very
carefully, then switched the same speakers from one amp system to the
other?
Usually such a test reveals very little difference between tube or SS
especially if
the THD/IMD measurements are the same figures, Rout are equal, and BW is
-1dB down at 20Hz to 20kHz or better.
Many audiophiles hate this test because it tests their ability to tell
tube and SS apart,
and its a big blow to their ego when they find they cannot tell good
samples of SS and tube amps apart.
Similary, ppl prejudiced in favour of SS or who hate tubes especially
SET amps are also given an uncomfortable
lesson about reality when given the switch to switch the speakers, they
cannot tell to
which amp system the speakers are connected.
Patrick Turner.
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