Strange reply from Polk, LSiM 703s tube amp power requirements

jdeecraigslist

Hi all,

My friend is bringing over a small tube amp because he wants see what it sounds like on my LSiM 703's. It only has 10 watts/channel power output (4 ohm), so I wanted to make sure it won't damage my speakers since Polk specifies "20-200 watts for solid state amplification". I was curious what they would say about tube power requirements, so I sent an email to Polk.

They replied: "If you're going to use a tube amplifier, it has to have a 150 watts power."

Really????!!! This seems completely incorrect to me, am I misinformed or do they just have incompetent tech support?

EDIT: 10 watts/channel @ 4 ohms

stangman67

The average Polk “customer service” agent doesn’t know jack **** about audio. They are outsourced customer service just like very other company. You need to get ahold of the people who know what they are doing at escalated levels of support to get actual knowledge.

The lsims are hungry but 10 watts will be fine, as with all sources of amplication, don’t overdrive what the amplifier is able to cleanly put out and you won’t damage the speakers

Clipdat

Hahah, that's a funny answer! No, in reality they will likely play fine with 10wpc as long as you're not trying to hit 95db.

BlueFox

I would think a watt is a watt irrespective of the source, and the issue is whether the amp can handle a 4 ohm load. The speakers might play, but I suspect not very loud. You might break either the amp or speakers trying to get some volume. Try it and let us know the result.

jdeecraigslist

BlueFox wrote: »

I would think a watt is a watt irrespective of the source, and the issue is whether the amp can handle a 4 ohm load. The speakers might play, but I suspect not very loud. You might break either the amp or speakers trying to get some volume. Try it and let us know the result.

Well, my goal is not to break either one, hence the reason I asked!

Emlyn

Tube amp power output is different from solid state amp power and the recommended power output ratings into speakers don't take tube amplification into account. 10 watts per channel from a tube amp is fine with most speakers. I'd be way more concerned about using a 20 watt per channel solid state amp than I would a 10 watt per channel tube amp.

But, to an extent the answer of how the amp will perform depends on the quality of the amp and its power supply, the type of power output tubes, the sensitivity of the speakers being driven, and a few other factors.

Hook it up and see how it sounds.

F1nut

You will get sound, but a 10wpc tube amp is not enough to bring those speakers to life. For that matter, neither will a 20wpc SS amp.

treitz3

Just for S's and Giggles, a buddy of mine and I hooked up a 10 watt amp to a pair of very power hungry Apogees. We got sound and it sounded, really, really good even though the lower registers weren't what we were used to hearing out of those speakers. They key was that you could (and very quickly) hear the tube amp exhaust itself when the volume went up, even up just a little bit.

If you're going to use a tube amplifier, it is suggested to have a 150 watts power in order to extract the most out of the speaker.

Perhaps this would have been a more appropriate response from Polk. I still think 150 watts is a bit much for those speakers and a tube amp (40-60 should suffice just fine IME). I had mine hooked up to 18 watt tubed mono blocks and it was fine for watching TV (never used it for 2 channel listening on that rig) or the wife listening to tunes on the music channels through the TV.

As for harming your amp or the speakers? What ohm taps do you have on your tube amp or if it doesn't have taps, what ohm rating can the tube amp handle? (4, 6, 8, 16 ohms?)

Tom

tonyb

I suppose if you kept the volume at low to reasonable levels, you wouldn't have a problem. You know how that goes though, every so often cranking it up is what we do. This is where you might run into problems by taxing a 10 watt tube amp too much, thus killing the tubes earlier than they should be. Depending on the tubes your using, some aren't cheap, so anything that is going to shorten their life might warrant some consideration.

mhardy6647

Actually, it shouldn't hurt the tubes (assuming a class AB push-pull amplifier designed around the optimal operating parameters for the tubes*), but as the linear range of the amp is exceeded, the sound will become (typically) strained, thin, and ultimately, yes, distorted.

___________
* Actually, in the case of a Class A (single-ended or "full-on" biased push-pull) vacuum amplfier, the amp is actually (ahem, theoretically) a bit more efficient at maximum signal output power than at idle, since at idle 100% of the power is being dissipated as heat, all of the time! In other words, a Class A tube amp's tubes could last longer at full audio power output than run at idle! Of course, in reality, that's not the case, but the 'conclusion' stands -- running the amp at high output power won't add undue strain to the output tubes (nor should it to the small signal tubes in the "front end", which are often Class A in almost all vacuum tube designs, except, perhaps, in some balanced amps).

jdeecraigslist

Update: it worked really well! The volume is definitely loud enough for my living room and the sound is great. With a really boosted signal (CD player) it was able to get super loud at only around 25% on the volume knob. With a MM phono input it was probably at around 50-60% on the knob and still pretty loud.

heiney9

Just goes to show, sometimes you have to experiment for yourself.

H9

mhardy6647

hard to beat empiricism -- although in, e.g., the case of the study being performed in @heiney9's avatar, empiricism is sometimes not the best choice if alternatives exist.