On 11/19/2021 12:22 PM, bad sector wrote:
http://dlcdnet.asus.com/pub/ASUS/Audio_Card/Essence_STX_II/E9122_Essence_STX_II_User_Manual.pdf
I bought this card like in another life because the Crosshair mobo
(also bought in another life) onboard 1/8" audio connectors aren't
worth a shit (continuous crackling and things) making music work
IMPOSSIBLE. This card has the 1/4" jacks as well!!! Going through
my things I just found the bundled pair of small pliers and these 3
chips. Very nice idea for the pliers, maybe other makers could start
bundling other computer-handy tools, bits-&-pieces, cpu-paste and stuff :-))
BUT...
p-11 says the (supplied) 3 chips will "change the tonal characteristics" without so much as giving a hint as to in what way, something one
would want to know BEFOREHAND! Are all manufacturers this freakin'
stupid?
Some commercial DAC chips, have high impedance outputs. Like
one megohm to ten megohms. This means for the next circuit in
line in the chain, they have no "driving power". An opamp with
FET inputs and 10^12 input impedance, helps quell any
audio rolloff.
---- 1 megohm ---+-----> instrumentation amp ---> and so on
| unity gain follower
Cin
|
GND
When you substitute a 741 in the circuit, it sounds
like a phone booth on the output. All the high frequencies
disappear.
At a guess, the "tonal characteristic" is "low pass filter".
If they offered you anything, it could have been a chip
puller for some 8 pin DIPs. It was popular at some time
in past years, to be swapping out opamps and seeing if
there was less effect on higher audio frequencies.
There might be a web page or two on this topic out there.
There are probably more opamps in SMT format than DIP,
which means the variety of opamps available might be
limited in some way. But there would be no way for
an end user to "insert" a surface mount opamp, and so
this hobby of amp swapping would need adapters of some sort.
Instead of 8 pin DIP, the surface mount ones might
have five contacts (diff in, out, VCC, GND). The 8 pin DIP
had enough pins on it, to do dual opamps in one pack.
If someone hands you an 8 pin DIP, it could be
a single op amp or a dual op amp.
Opamps come in a variety of operating voltages. In the
old days, the supply limit was +/-18V, for a total of
36 volts between VCC and GND. But later on, there were
some (ostensibly) 5V opamps, where the opamp had a charge
pump inside to make a negative bias, and the opamp could
"swing to the rail". The old 18V bipolar opamps, the
output might swing +/-15V and the amp could not
"swing to the rails". There are some opamps for things
like cellphones, where VCC = +1.0 volts and the amp
has a very low range of output voltages. These might
be used in hearing aids.
As a result of this, at least a bit of care is required
in vetting amps to shove in the hole :-) Don't be shoving
the one volt item in there, or there will be magic smoke.
The sockets presented, will have no armament to protect
from catastrophe. You have to know what you're doing,
and the damn documentation should explain stuff like this
if the intent is for the user to be running off to
Radio Shack for Opamps.
When I was in school, one afternoon I had a lab, and it
had to do with high frequency rolloff. And we were given
a 741 each, to play with. So what I did, is left the lab
and ran across the street to the Radio Shack, and got
a CMOS amp with 6MHz gain bandwidth, and I did my lab
with that :-) That's why I tell these little jokes about
Radio Shack, because I've actually done that in a real
world situation (play the part of an opamp snob :-) ).
Paul
--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)