2. amps-preamps
  3. 1325552222

Active or passive preamp

Hey guys,

I need some advise as to whether I should go active or passive on a preamp. Although I have several digital sources, I'm running all of them through an Emotiva XDA-1. It's nominal voltage output is 1v with a max of 7v. Its output impedance is 1K ohms.

My amp is an Aragon 2004, with an input sensitivity of 150mv for 1 watt. Its input impedance is 22K ohms.

Although I've been doing as much reading up as I can, I'm still not sure that these components will be a good match with a passive preamp.

What do you guys think?

Thanks.
tonyangel
tonyangel OP
309 posts
 
Just for purposes of understanding, would you say that an amp with a higher input impedance would be better? Why?

Thanks again.
brownsfan
1,508 posts
 
Yes, an amp with a higher input impedance would be preferable. There is a rule of thumb that the input impedance of a component should be at least 10 x the output impedance of its upstream component. I'm about 38 years removed from my last physics class, so I defer to someone else to provide you with the math. Failure to observe the 10 x rule can result in attenuation of the signal at frequency extremes.
Since I like to use passives, I tend to stick with amps that have ~ 50-100 K ohms where impedance mismatch is not an issue. Then the only consideration is making sure you have sufficient gain.
tonyangel OP
309 posts
 
I really appreciate the information. I just ran across a NAD C162 preamp for sale. Based on the info that I got and my previous experience with NAD equipment, I went ahead and grabbed it.

Thanks.
ngjockey
1,042 posts
 
For the record, TVC's have an output impedance below 100 ohms for all but the highest 2 or 3 steps. In fact, the first half is usually under 1 ohm. S&B removed their website that showed this.
brownsfan
1,508 posts
 
Ngjockey,
Thanks so much for that information! I have looked high and low for output impedance on TVC's to no avail. All I ever got was a nonspecific "lower than resistor based designs." Is that true for all TVC's, or only the S&B's?
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