John Byrns wrote:

In article , Patrick Turner
wrote:

Overkill is better. Tube amps have typically 100k input Z and
CF output from preamps = 600 ohms.
SS pres have opamps, maybe Ro = 20 ohms, but usually
they place a 470 ohm R in series to the output terminal which
stops the opamp fusing itself dead if a shorted output occurs.

What is the typical input Z of a modern SS amp. both pres and integrated?

Quad 405 Rin = about 20k; many SS amps tend to be around this figure,
including preamps, and this keeps them a little quieter, since noise is worse
with
high Rin with nothing connected.

Rout is typically less than 0.1 ohms from power amps because
often there is 110 dB of local and global NFB applied,
and what actually makes up the 0.1 ohms may be the LR zobel network
and the fuse soldered into the output circuit if there is one.
( it does need to be soldered in, not clipped in, since fuse clips and fuse
holders are notorious
for increasing thd from 0.001% to to 0.01%.

Rout from preamps is often between 220 and 600 ohms, and is made up with the
opamp
with Ro less than 100 ohms, and a series R added to protect the opamp from
shorts.


Patrick Turner.





Regards,

John Byrns

Surf my web pages at, http://users.rcn.com/jbyrns/