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Can 10 watts of Class A really drive speakers?

I been mainly running 2 tube amps lately. A 3.5w SET and a 8w PP amp into klipsch horns and it more than meets my needs.
I usually rotate gear on a weekly basis, but the tube amps been doing duty for a couple months now and my higher power SS gear has been sat aside.
I don't play real loud so I also don't have to crank the volume knob(s) way up. Low-moderate with clarity, some very nice condition vintage albums on a couple nice TTs is where I'm at now. The little Sony HD tuner gets a little duty too through a tube pre into one of the low power tube amps.
With all the receivers, separates, including Yammy & Okyo M series amps, I'm not really missing them. Well.... they do some garage use duty since my tube amps stay indoors in my man cave.
 
jsixis said:
Yes, I have a little class A 5 watt max 6AQ5 amp I use to listen to in my basement workbench. Also have a Audition 50c5 radio (less then 1 watt) that is plenty loud enough.
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If I compare SS and Tube amps that are spec'd to similar power levels, seems to me that the tubes will go a bit louder because they "clip" with somewhat more dignity (read: less harsh).

To the OP: really depends on your use of the speakers: I had plenty of fun running some small KEF 303, not super-sensitive at 87dB, with ~10W of tube power, it could play "loud enough". OTOH, I currently have ~98dB speakers and sometimes pump close to 100W into them, "kinda too loud" in my small room. :D

Another consideration is if you run EQ, especially if it is used to boost the low-frequencies, where power demands will really go up.

az
 
You must have to clip the tubes an awful lot. 3dB is just a slight increase in volume but represents 2x more power.
 
I use a 3.5 watt per channel single-ended (Class A) amplifier in the living room - no complaints with loudspeakers of better than 100 dB/watt @ 1 meter sensitivity.

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A solid state amplifier such as the Yamaha CA-800 in Class A (15 wpc, if memory serves) would be fine, as well - although an ss amp will be more dangerous to speakers if the speakers' sensitivity is borderline and the amp is pushed to clipping. Vacuum tube amps tend to compress as they go nonlinear - this will (typically) generate less potentially tweeter-damaging HF components compared to an ss amp driven to nonlinearity.

CA-800.jpg
 
I haven't liked all the Class-A I've used. A Yamaha CA-1010 left me unimpressed. I liked it, and usually ran it in Class-A, but I found it to have a 2-dimensional sound and just never really listened to it after running it for a few weeks. My Sony TA-n86 is a different story- I love that amp. About 18wpc in Class-A, its fantastic. It's not a good match for lower sensitivity speakers but I've been surprised by what it can do. The best of the lot was my friend's Bedini, though. I think it was a 25/25, but I could be mistaken.
 
OP:
Hmmm... My ADS L810 are rated at 93db and my EPI 100's at 89 db.
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Excellent spkr choices in any event. I highly regard both as being overachievers in the spkr field. Back to amps: Please understand that "Class A" is mostly a misnomer when used and usually abused by manufacturers in so-called "ratings". Class A amps tend to sound 'best', although there are plenty of variables and excellent class A/B amps challenge that very notion.

You, the OP, have a few basic factors to consider: The first could be the amount of power output that will be required for satisfying results. My estimate would be at least 30, more like about 60 to 100WPC for pleasing results. The other, somewhat less important, is the class of your chosen amps' operation. Audio power is similar to an exponential type of requirement; more accurately known as logarithmic.

To put it very basically, 1 watt is surprisingly significant, yet moving forward, greater amounts in the 10s, then 100s and even 1000 more watts are required for actually doubling to louder and louder volumes. Yes, you literally need to bring approximately 10 times more power to the table to get twice the level, then 10 more times again as the actual, desired sound ouput levels double. This is why for example, 60 watts is not far from 30 watts in much of an actual output level difference.

Note: The mix of commercial amps that claim class A along with a transition to A/B at higher power levels tends to cloud the issue. The good news is that the class of operation is only one aspect of any given amp's overall performance. If you wish to experience class A that is in fact purely class A, consider one of several Pass amp models that are in fact, actually a pure form of class A, as in one (or parallel pairs) single-ended output device per channel. I suggest this since you will likely want a greater amount of power and headroom. Others have suggested single-ended tube amps, although the power output is generally far less than that with SS, due to practical limitations.

The practical issue will not change: In order to attain pure class A single-ended operation, most of the power the amp consumes will be taken in the form of waste heat, not audio output. In order to realize 60 audio output watts, the power consumption of a stereo class A amp will require a minimum of approximately 240 watts via its power supply. That will be the consumption at all times when the amp is powered, regardless of idling, full power output swings or all "comfortable listening" points in between. That is why massive heatsinks are the norm for SS purely class A single ended amps and why 60W class A tube amps are gigantic or relatively rare in existence.

It all gets a little more technical from here, although you might want to picture it as the fact that a single ouput device in any power amp must push and pull the spkrs' voice coils entirely and equally, but wait, that's not all: Because it must push and pull, that single device has to be working hard all the time in relation to the spkrs, just to maintain the neutral, zero point the spkrs see as no current flow; then that device must do the entire pushing and pulling above and below that halfway zero point for the audio output power; hence the greater power supply consumption regardless of idle or full blast power output.
 
mhardy6647 said:
I use a 3.5 watt per channel single-ended (Class A) amplifier in the living room - no complaints with loudspeakers of better than 100 dB/watt @ 1 meter sensitivity.

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604E061111.jpg


A solid state amplifier such as the Yamaha CA-800 in Class A (15 wpc, if memory serves) would be fine, as well - although an ss amp will be more dangerous to speakers if the speakers' sensitivity is borderline and the amp is pushed to clipping. Vacuum tube amps tend to compress as they go nonlinear - this will (typically) generate less potentially tweeter-damaging HF components compared to an ss amp driven to nonlinearity.

CA-800.jpg
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Do you have a thread or more info on your speakers? Is that an EV driver?

- Woody
 
I'm a fan of the low-power/high-current philosophy (I guess that's what you'd call it... I'm no techie). That's why I love gear from the early '70's. Speakers were still being designed for use with low-powered amps/receivers, so in most cases, even the lowest-powered amps/receivers were designed/built well.

I have a fairly-small living room (listening room), so I generally-don't push the volume past 9:00. I listen a lot, so I try to be conscious of my hearing and I make sure to give my ears a rest when they really-need it (I'm a musician AND an audiophile, so my ears are everything... Overexposure to high volume-levels can make you think there's something wrong with your stereo system when in fact it's just your ears suffering temporary damage, which can become permanent if you're not careful). I like low-to-moderate background music while I'm surfing the web. With how much I listen, going any louder than that on a regular basis would surely give me permanent hearing damage.

But getting back to the topic, even 10 watts can sound great if the gear is well-designed/built and properly-matched to the speakers (class A gear or not).
 
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Since my post several months ago farther up the page I've acquired a Pass Aleph 30. 30wpc of lovely Class-A goodness that sounds better, to me, than the 400wpc amp it replaced. I'm sold. I'm on a two days in and so I should wait to form a verdict but I really love this amp. And I rarely love amps, usually thinking of them more in a utilitarian sense. Put this amp sounds great.
 
I have come close to picking up a single or a pair of the Monarchy SM-70 or SM-70 Pro's for the last few years.


One thing that has been holding me back has been a nagging reports of these amplifiers producing a audible amount of hum when used with moderately high to high sensitivity speakers. While I have hear that this can be remedied with some circuit mods or a trip back to Monarchy for an attitude adjustment, it seems to be prevalent enough that I have been a little spooked off. I even spoke with C.C. Poon about it (some time ago now) and that conversation did little to elevate my concern.

I have spoke with a few on A-gon that had these for sale and asked them pointedly about it. Only one claimed no audible hum what-so-ever but they were using speakers @92-93 dB sensitivity. The others claimed that they could hear hum from their horns speakers but you needed to be within 1-2 foot from the horn mouth to pick up on it. Seeing as how I'm in a small room and typically using speakers 100 dB @ 1w/m or more sensitivity, I've been reluctant to roll the dice and buy. Maybe some or all of this issue has been addressed with later versions of the amp and Monarchy's new offerings.

I have heard nothing but great reports about the SM-70/SM-70 PRO beyond the potential for hum with certain speakers deal. I'd more than likely be a buyer if I could audition first to make sure I had no problematic hum with what I am running here.


RC
 
Sure!

Both of my SE tube amps are 5wpc.
The both drive speakers that are rated at 90 db @ 1w/m.
I never turn the volume knob past 50%, 'cause by then it's LOUD!

Steve
 
gearhound said:
Sure!

Both of my SE tube amps are 5wpc.
The both drive speakers that are rated at 90 db @ 1w/m.
I never turn the volume knob past 50%, 'cause by then it's LOUD!

Steve
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I believe that. My receiver is 39wpc driving a pair of 50wpc speakers, and I can't get the volume past 9:00 without disturbing the upstairs neighbors. If you have big, efficient speakers and the room isn't huge, you can shake the foundations with 10 watts, class A or not.
 
I tried a SET amp (3wpc?) on a set of 89 db efficient speakers once and was very surprised at how well it worked. Obviously not ideal, but a good way to put things in perspective.
 
Im running my EV 12TRXBs (~97dB 1W/m) off of 3.5W of 6B4G goodness...cant turn it up more than 1/3rd the way or it gets much too loud for me.
 
I ran my Phase Linear 700 (350 wpc) with my 3 wpc speakers and they sounded Ok. Much better with my Sansui AU-7900 (~70 wpc). With a buddy's 3.5 watt SET it sounded very nice indeed, as a result of matching the amp and speaker ratings correctly.
 
Wow. This is confusing to me. Is there a tech paper out there explaining this subject? I had a 17 watt/channel amp and when I got a 30 it sounded louder and the 75 is too much louder to go past 12 o'clock. So how do these 3 and 5 and 10 watt/channel class A amps do it?
 
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