Attenuator opinions?

[tsmith1315]

Hi all.

I'm looking to add an attenuator into an automotive preamp I'm designing.

After mixing or switching the inputs from cass/CD, the first stage will be a follower with gain of 10 or so. I'm using an Analog Devices AD 797 for this, and to capitalize on the low noise aspect of this op-amp I'd like to use a stepped attenuator to provide constant input and output impedances. Frequency compensation is a viable option with this arrangement as well.

Looks to me like I'm going to need a 2-gang switch per channel to achieve the desired constant Z. Therefore, a 4-gang switch will be needed for two channels. This limits switch choices to about 6 positions. In light of this, I'm thinking of using a second switch (rotary or toggle) with 10dB steps or so like the old Pioneer SPEC-1 did.

Am I making things too complicated?

I have some *very* nice components to mate this with, so extra effort in design and construction will be worthwhile.


TIA,

Tim Smith

[Petter]

Do a search in the Trading Post area for the Apox discussion which should be completely enlightening.

Petter

[hifimaker]

If you are looking for a simple rotary attuenator, this guy cannot be beat. I already bought one and the qyality is awesome! He will build any value you like.

http://cgi.ebay.com/ws/eBayISAPI.dll...tem=3063320842

-David

[tsmith1315]

Petter suggested:

Do a search in the Trading Post area for the Apox discussion which should be completely enlightening.

Whoa... 1100+ replies. Interesting reading, this may take some time.


and David plugged:

If you are looking for a simple rotary attuenator, this guy cannot be beat.

Not quite what I'm looking for, but a very cool design and at a great price. I wonder how many of them switches he has.

I can't spend a bundle of money on this, but time and effort aren't a problem. It's beginning to look like I'll be scavenging for used parts and working around the parts I find.

Thanks for the help!

Tim