What am I missing? Pre/power gain and input sensitivity.


I’ve read a few posts about power amps with lower gain needing a pre with additional gain, but no one seems to mention input sensitivity in those conversations. If my source outputs 2V and my power amp input sensitivity is only 1.2V then whether the power amp gain is 16dB or 26dB my pre amp is attenuating the signal and the amount of gain on the pre doesn’t matter at all. With a given set of speakers, to get the same SPL with 2 different amps they should just need to output the same voltage, regardless of how they get there.

Am I missing something?

cat_doorman

Showing 2 responses by cat_doorman

Thanks for the confirmation, guys. No matter how much I read and think things are obvious, I start to doubt myself.

With standard digital outputs being so high it almost makes sense to use a lower gain amp so you don't need to attenuate the signal so much (all other things being equal).

I guess what I was missing is how different things are with analog. I didn't fully appreciate just how much gain MC phono stages need just to get some of those low output cartridges amplified to 300mV. So with an analog system of course you would need some gain in the preamp. While at typical listening levels you may not need it, it would be a shame if your system was limited to only what you absolutely needed.

I do know I have a big blind spot when it comes to vinyl. As a kid, once I got a Walkman, I switched to cassettes over 45s on a Fisher Price record player. I started collecting CDs in college and am now streaming more than I ever thought I would. Couldn't bear to listen to a cassette the last time I even bothered connecting my tape deck. My main objection to vinyl is the ticks, pops, and noise. I'm easily distracted. The nicer systems with well cared for records may sound incredible (haven't had the pleasure), but the price of entry to get to that level is quite a barrier (as well as not owning any records).

Right now I'm using a Schiit Saga+ (unity gain) as an inexpensive interim preamp while I explore some different power amp and speaker types. I think as long as I don't try any really inefficient speakers or go for face melting SPL I should be okay. For now. 
@switlikbob I recently got Omen DW (97dB, 12 ohm), too! Pretty impressed so far. It’ll be interesting to see what I think after a few months acclimating when I finally get around to switching back to my Dynaudio Audience 82 (87dB, 4 ohm) again to compare. I’m using a Primaluna DP HP (26dB, 1.2V max in) so my pre needs no gain from my ~2V sources - Oppo BDP-105, Bluesound Node 2i. I’ve been lusting after a First Watt F7 (14.5dB, 2.7V max in) but was running the numbers first. At my listening position I rarely hit 90dB and most of the time am <80dB. So both of these amps would probably be at ok with any of the speakers I’m interested in.

I’ve been making too many changes all at once lately - cables, speakers, amp, streamer. So I’ll probably leave upgrading my pre until later. I still haven’t even played with tube rolling the Saga+ yet. I’ve been making a list of preamps to look at eventually. There’s a recent thread that has a bunch of 6SN7 based options.