I have a Technics stereo from like 15 years ago that still works great and is pretty kickin actually. I want to add some outdoor speakers to my house and run them from "Speaker B" outputs on this receiver. The specs in the manual say that it is 130 W per channel, but the "Rear" speakers are 15 W. It doesn't distinguish between "A" and "B".

So, my question is: would speakers A get 130 watts and B get something else? Do they split the power when both are turned on (there are individual switches for each set on the front of the receiver) or how does this work? I don't want to blow away my new speakers!

The model number is SU-G90, but I can't find much about it on panasonic's website or google.

9/24/2007 9:51:21 AM

I seriously doubt that it's 130W /channel all channels driven. Rotel makes amplifers like that which cost around $1000. Bottom line is I bet you'll be fine.

you could always start with the volume low too.

[Edited on September 24, 2007 at 1:02 PM. Reason : .]

9/24/2007 1:01:03 PM

your much more likely to blow away your old amplifier than you are to blow away your new speakers... that is unless of course your amplifier fails in a dead short condition and sends DC through your speakers... then your screwed...

it should have minimum impedances listed on the rear of the amplifier on the speaker outputs... and I'm not sure what type of topology it's using if it splits 130/15w b/c if it's just a shared output it would be 130/130 assuming 8ohm speakers on both...

if they were nice enough to include a seperate tiny amp for the B speakers to drive 15W then all is right in the world, short of the fact that you will most likely be under-driving the B speakers and they will sound like a dying cat


PS: I'm wasted

9/24/2007 1:35:35 PM

^ Sorry I wasn't clear. There are 3 sets of speaker outs. Main A, Main B, and Surround, surround being those with the tiny 15W amp. All of them are 8 Ohms. There are two switches on the front that can turn both A and B on individually.

Lets assume that when B is switched on by itself that they get 130W. If I am conservative or at least not retarded with the volume, will I be OK pushing a pair of Polk outdoor speakers that handle 100W (or even 80)?

9/24/2007 1:51:42 PM

absolutely. Most likely you are going to under power those polks.

Most receivers are way over rated when it comes to power, except for high end components like rotel, etc... My friend has a Rotel rated at 120w/channel all channels driven x 4 channels and the amp alone weighs 40lbs. Amps/receivers are rarely rated with all channels driven continuous power and usually rated at a higher distortion %.

Bottom line, it takes a beast of an amp to supply enough current to rate 130/channel while driving all channels. I really feel safe saying you'll be fine. You'll only have to worry about under powering your speakers.

even if you're only running the B-speakers you should be fine, in fact that's probably the only time they'll get enough power.

[Edited on September 24, 2007 at 6:03 PM. Reason : .]

9/24/2007 6:02:19 PM

most of the cheaper amps actually have only 2 main channels anyway and the 130 watts would be divided between a and b. so you shouldnt have to worry about it. but make sure that both sets of speakers are 8 ohm because the amps minimum impedance requirement is usually 4 ohms and two speakers in parallel is 4 ohms if they are 8 ohm speakers.

9/24/2007 9:59:47 PM

Quote :

"I seriously doubt that it's 130W /channel all channels driven. Rotel makes amplifers like that which cost around $1000. Bottom line is I bet you'll be fine. you could always start with the volume low too. "

This makes no sense.

Quote :

"it should have minimum impedances listed on the rear of the amplifier on the speaker outputs..."

I'd start here. Does it list anything on the back of the amp? After doing some googling myself, it appears your amp has at least one SVI-3206 module. I wouldn't expect it to have two, just for the extra B output. So when you add in your second set of speakers, you're going to lower the impedance the amp sees and make it run hotter. You're probably fine to listen to it like this at normal volumes if both speakers are 8ohms. Anything less than this ohm-wise, or anything louder than normal volumes will start to test your amps heat sinking capabilities.

I'd try and run the amp with a single pair of speaks for 10-15 minutes with some bass heavy tracks. Touch the case and see how warm the amp is. Then do it with the B speakers as well and monitor it for heat. It's possible the internal heat sink isn't coupled to the external chassis, in which case this isn't going to tell you much. But it's worth a try.

Quote :

"will I be OK pushing a pair of Polk outdoor speakers that handle 100W (or even 80)?"

Yes, of course. You can have a 1kwatt amp and speaks that can only handle 100 and if you don't crank the volume to where the speakers are obviously distorted, then all is well.

Quote :

"absolutely. Most likely you are going to under power those polks. "

Stop trying to take general concepts such as

Quote :

"Most receivers are way over rated when it comes to power, except for high end components like rotel, etc..."

and applying them liberally to something you didn't research about and then try to give advice like an expert.

Quote :

"Bottom line, it takes a beast of an amp to supply enough current to rate 130/channel while driving all channels."

For starters, this is a 2 channel amp. Furthermore, you can do 120wx4 without needing 35 pounds worth of transformers. Do you honestly think Rotel or any other "high end" amp maker could justify their hefty price tags if their amps didn't feel "solid" to the folks they are duping into buying them?

Quote :

"most of the cheaper amps actually have only 2 main channels anyway and the 130 watts would be divided between a and b. "

Not necessarily. It's entirely likely if the amp is rated 130x2 into 8ohms, and they allow a B input provided all speakers are 8ohms, then it will drive this 4 ohm load and most likely do 150-180w or so. It just depends on how tightly regulated the IC is.

9/24/2007 10:43:46 PM

If you think a $100 receiver rated at 130w is going to blow a pair of 100w polk speakers you're an idiot.

Quote :

"Stop trying to take general concepts such as Quote : "Most receivers are way over rated when it comes to power, except for high end components like rotel, etc..." and applying them liberally to something you didn't research about and then try to give advice like an expert."

If you think you are getting the wattage advertised when you bought your $150 receiver/amp then you are sadly mistaken.

If you can't tell the difference between a rotel amp with B&W speakers and a radio shack special then you're fucking deaf.

9/24/2007 11:31:03 PM

Quote :

"If you think a $100 receiver rated at 130w is going to blow a pair of 100w polk speakers you're an idiot."

Show me where I said that noob?

Quote :

"If you think you are getting the wattage advertised when you bought your $150 receiver/amp then you are sadly mistaken."

Again, you don't know shit about what you are talking.

Quote :

"If you can't tell the difference between a rotel amp with B&W speakers and a radio shack special then you're fucking deaf."

An IC delivering 130wx2 with modest thd characteristics will indeed sound different from a discrete 130wx2 amp with even better thd characteristics, but that doesn't say dick about how much power either of them can deliver.

Keep trying to test me rookie.

9/24/2007 11:35:17 PM

sure it does. They just rate the power differently. at different levels of distortion etc...

9/25/2007 12:16:15 AM

So I called the friendly folks at Crutchfield and they said most likely that amp will split the power between A and B if both are on. If that is the case then I'm not going to blow the Polk's up unless I have B on by themselves and crank it way too loud. I don't want to piss off the neighbors that much.

And FYI, this is not a $100 reciever. I don't know where you got that from clalias. I don't know how much this system cost like 18 years ago when we got it, but it wasn't cheap. The main speakers it drives have two 12" woofers, a ~5" midrange, and a 1" tweeter each. They are very loud and I've never heard any distortion or lack of power to push them. Seriously if I have the volume up too loud with A turned on and then switch to B, the Polks are going to explode sending cheap plastic shrapnel into my yard.

Anyway, they are supposed to be here in the next few days so I'll let you guys know what happens. Thanks for the help.

9/25/2007 4:14:47 AM

peak power = V^2/R... or V*I... or I^2*R

it's not very hard to make a 130w amplifier... and for multi-channel amps you just copy and paste the damn thing... it's hard to make it CLEAN with a flat frequency response...

point being, it's damn easy for a cheap amp to hit rated peak power, b/c it's just a matter of voltage rails which is the most basic and easy thing to do... so crappy amps can push just as much as expensive amps... expensive amps typically can drive much lower impedance loads, With Krells being able to drive a straight DC load being a true Current source...

[Edited on September 25, 2007 at 9:46 AM. Reason : cheap amps make the same power at 8ohms as expensive ones...]

9/25/2007 9:44:23 AM

Got the speakers in today. The power is definitely split when you have A and B on, but there is plenty to go around. I think I'll go to the trouble of putting in a separate volume control for them so it isn't so loud outside. Running the wire is going to be a bitch.

9/26/2007 5:31:00 PM

haahahah my amp is 140 * 7 rms and has a 700 watt power supply in the back good thing for big caps i guess ??

btw its past the 1k mark fairly well

a and b are typically both off the same amp and are just switchable locations

[Edited on September 26, 2007 at 9:59 PM. Reason : .]

9/26/2007 9:54:26 PM

Sounds like a waste of money to me.

Or rather, the designers know that for the life of the amp, it will never be asked to drive 140w into 7 channels at once.

9/28/2007 10:24:30 PM

my previous post I neglected to mention straight BS numbers do exist... some crappy manufacturers do not use any RMS numbers throughout their calculations and post pure peak values... so their outputs would be a factor of sqrt(2) higher than they should be...

also if the transformer/caps they are using can't feed the current requirements the voltage will sag and the power will droop during extended high volume...

this is how amps lie about their power output...

bigger transformers to supply the current/voltage needed are expensive(and heavy) and that's one of the major differences.

10/1/2007 9:21:48 PM

^ In your opinion, do you think it's a good idea to approximate the actual power of the amp based on the voltage/current rating on the power supply?

10/1/2007 10:06:07 PM

i mean if its dual channel yes.... but over 70 channels peak power will never be pulled on all 7 simultaneously and even if for a split second it happens there are 6 caps the size of my fist in there to help out.

10/1/2007 10:26:03 PM

short answer: Energy can never be created or destroyed... but it can be stored... in caps

Capacitor banks allow higher output power to be achieved for brief(or long with a large cap bank) durations but the overall average power of the system will be about what the rear rating is.

10/2/2007 11:41:49 AM

Finally got around to installing my outdoor speakers and they sound great. I'm sure I could have bought something that sounds better but I'm very satisfied for what I spent.

Oh yeah, I decided against the volume control (cheapest decent one I could find was like $50) for the price and because it would have been a total pain in the ass and really unnecessary.

10/14/2007 10:01:08 PM