2. amps-preamps
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need help with impedance on SF power 2

I just get a Sonic Frontier power 2 and Genesis APM-1. On the manu, APM-1 impedance is 4 ohms and I am not sure what is the normal impedance for power 2. Is all SF power amp @ 8 ohms. I read on the manu said I have to make sure impedance match with speaker. What effect if I have 8 ohms on the amp and 4 ohms on the speaker? I felt like I need to turn up the volume quite high in order to get a good sound level. BTW, the APM-1 is 90db sensitivity.
waip7
gs5556
1,218 posts
 
The tap is set for 8-ohms at the factory. I think you have to remove the rear panel to access the tap to change it to 4-ohms to match your speaker. From what I've heard, operating the SF Power 1,2 and 3 at 8-ohms with any speaker is not a problem nor has any detraction to the sound. But at 100 watts into 90db speakers not enough volume? Maybe some power tubes are going bad or the bias is too high.
dogpile
118 posts
 
If you have the manual, just follow the instructions for load impedance adjustment. Ideally, if your APM-1 is rated 4 ohm, then the Power 2 should also be set at 4 ohm. Won't hurt to experiment, however, it's not like changing cables from terminal to terminal...you gotta' go under the 120lb amp and remove all them SCREWS!!
waip7 OP
11 posts
 
Thanks, I am going to try it. BTW, is the SF power 2 is OTL or it will alway keep the same power output(110w) in 2, 4 or 8. Which means, even I drop the ohms to 4, I still get 110w (not higher). Will that drop make the amp run not as stable or sound not as good?
msa
35 posts
 
The power will not drop, and the amp will work easier set at 4 ohms, thereby prolonging the life of your tubes.
gsselling
29 posts
 
I've been using a power 2 SE happily for a year now. I've used them with ML Aerius i's and PSB Gold i's. I found that these "4 ohm" speakers sound much better off of the 8 ohm taps. The bass isn't as tight but everything else is much improved i.e.. soundstage depth and width, separation et al. Try it for yourself. I know, it is a pain in the butt removing all of those screws though.....
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