On 2008-07-30, Jim Lesurf wrote:
On 30 Jul, wrote:
In article
,
wrote:
I recently changed the IC's in a Quad 306 power amplifier (TI's to
Burr-Browns) playing through some Quad 988s. My wife (not an
audiophile), walked in the room and immediately asked what had
changed... "it sounded more alive" was her comment.

Comment much as above. It is a common experience that what we hear
'changes' from one situation to another. Afraid that simply isn't a
basis for deciding *why* a 'change' was heard. Far too many other
possible causes or reasons which your simple anecdote fails to deal with.

BTW I just looked at my copy of the 306 diagram. If you are referring to
'IC1' (TLC271) then you might like to note that IIUC its role seems to be
to null the dc offset of the amp. The 2M2 resistor (r33) and 680nF cap (c3)
mean it only really does much around the 1 Hz region and below.

You loudspeakers (and wife) are remarkable if they can hear this. ...

Even if a recording had content in the subsonic frequency range capable
of "fooling" the R33/C3 integrator, the input HPF formed by C2 (100 nF)
and R6 (120 kOhms) has a time constant that is about 125 times smaller.

So that subsonic content would suffer at least 7 octaves worth of
attenuation just in the 306 input stage. That's before even mentioning
Fletcher and Munson.

--
John Phillips