resolved: best way to handle switching in audio pre-amp

[Mac]

In an earlier post, I asked how to handle switching of line level signals
in an audio pre-amp.

I received a lot of good suggestions, but ultimately I think I will go
with the ADG452, a quad analog SPST switch from AD with Ron = 4 Ohms. The
logic input is TTL compatible when the logic power supply is +5V, and the
performance of the analog switch is specified under single and split
supplies of various different voltages.

Thanks to all who responded and pointed me in the right direction.

--Mac

 

[Winfield Hill]

Mac wrote...

In an earlier post, I asked how to handle switching of line level
signals in an audio pre-amp.

I received a lot of good suggestions, but ultimately I think I will go
with the ADG452, a quad analog SPST switch from AD with Ron = 4 Ohms.
The logic input is TTL compatible when the logic power supply is +5V,
and the performance of the analog switch is specified under single and
split supplies of various different voltages.

I didn't see the thread, but what's the appeal of using such a low Ron
switch? Have you examined its capacitance specs? The high capacitance
of a low-Ron switch can give trouble for the driving opamp, introduce
high-frequency noise into the audio signal path from the supply lines,
and no doubt endanger the genetic pool for your grandchildren as well.

I'd start with a high-Z opamp follower after the CMOS switch, reducing
any effect from a changing Ron with signal voltage, then evaluate my
Ron spec, and avoid overdoing it. More (or less) is not always better.

For example, a 74hc4053 often looks appropriate after such an evaluation.


--
Thanks,
- Win

 

[justin]

In article <pan.2004.12.09.03.54.08.714736@bar.net>, Mac <foo@bar.net>
wrote:
I've been following this thread with interest having an upcoming
project with a simillar problem; how does one decide between a switch
and a mechanical relay? A relay will outperform a CMOS switch in every
aspect except for power.

Any thoughts?

j.

 

[Richard Henry]

"justin" <justin.c@se.net> wrote in message
news:111220040302069768%justin.c@se.net...

In article <pan.2004.12.09.03.54.08.714736@bar.net>, Mac <foo@bar.net
wrote:



I've been following this thread with interest having an upcoming
project with a simillar problem; how does one decide between a switch
and a mechanical relay? A relay will outperform a CMOS switch in every
aspect except for power.

Any thoughts?

Switching speed?

 

[Winfield Hill]

martin griffith wrote...

But when I see stuff like the TI PGA2310, I just drool in wondermunt.

Yes, –95.5dB to +31.5dB gain in 0.5dB steps, 120dB dynamic range,
0.0004% distortion at 1kHz, nice. Don't forget the original cs3310
version, although it has slightly higher 0.001% distortion + noise.


--
Thanks,
- Win

 

[martin griffith]

On 21 Dec 2004 04:53:27 -0800, in sci.electronics.design Winfield Hill
<hill_a@t_rowland-dotties-harvard-dot.s-edu> wrote:

martin griffith wrote...

But when I see stuff like the TI PGA2310, I just drool in wondermunt.

Yes, –95.5dB to +31.5dB gain in 0.5dB steps, 120dB dynamic range,
0.0004% distortion at 1kHz, nice. Don't forget the original cs3310
version, although it has slightly higher 0.001% distortion + noise.
5v rails against 15v rails for the TI part, ISTR

martin

Serious error.
All shortcuts have disappeared.
Screen. Mind. Both are blank.

 

[Winfield Hill]

martin griffith wrote...

Winfield Hill wrote:

martin griffith wrote...

But when I see stuff like the TI PGA2310, I just drool in
wondermunt.

Yes, –95.5dB to +31.5dB gain in 0.5dB steps, 120dB dynamic range,
0.0004% distortion at 1kHz, nice. Don't forget the original cs3310
version, although it has slightly higher 0.001% distortion + noise.

5v rails against 15v rails for the TI part, ISTR

Wow, a _serious_ advantage for the PGA2310, up to +/-13.5V out.
Time to get some free samples!


--
Thanks,
- Win