A question of watts

[oguinn]

I’ve done a bit of googling and can’t find an answer that I can understand. I’m hoping someone here can help.

When I look at my current receiver, a crappy little Sony, I see it has an output of 100 watts per channel. When I compare that to the SEX, I see the output is about 2 watts per channel.

I’m sure that I’m missing something. Can anyone explain why there’s a drastic difference in watt output? Is it marketing? Is it unimportant?

[Paul Birkeland]

There is a drastic difference in power output because your Sony is a solid state receiver and the SEX amp is a small single ended tube amp.

Higher wattage is definitely a marketing strategy, especially with receivers.  I remember my first 120W Kenwood receiver being completely stomped by an old 30WPC Denon receiver back in the day. 

Very few people will measure or estimate actual power requirements, as it often turns out that a couple of watts is sufficient.  If you tell us more about your system, we might be able to fill in some of the gaps a bit.

[oguinn]

There's really no problem, per se, I'm just seeking to understand what specs on an amp really mean. Is it the case, then, that the more important spec would be something like impedance or sensitivity?

I asked in another thread about whether the SEX would be a better option than a Crack for my Sennheiser 6XX headphones since someone had mentioned the SEX would also power my Overnight Sensations. However, the Overnight Sensations are listed with a sensitivity of 83dB. I'd read that the SEX performs best with a higher sensitivity speaker and I wanted to understand the limits of a system that looks like this would be:

• Orbit turntable > Pluto phono pre-amp > SEX > Sennheiser 6XX/Overnight Sensations
• JDS Labs ODAC > SEX > Sennheiser 6XX/Overnight Sensations

If I'm lacking on power with that setup, would the addition of something like a Quickie before the SEX provide a solution?

[Doc B.]

The maximum output power of an amp is the point at which it begins to distort if run any harder. A SEX amp will be on the verge of clipping at 2W output. How loud the speaker plays is determined by the sensitivity of the speaker. An 83 dB speaker is not sensitive on a relative scale of speakers. However with 2 watts input it will output 86dB. We usually tend to listen at around 82 dB on average where amps are only running at a watt or two output, so most listening will be fine. To rock the house you would like more like 102dB output. That would require around 80-90watts - too much power for the Overnight Sensations anyway. To get to that 102dB listening level with a SEX amp you need a speaker with a sensitivity of 99 dB - a tall order. The bottom line is the SEX amp will work fine for average level listening with the Overnight Sensation, particularly near field on a desk top or in a small apartment living room. I would roughly equate it level-wise to using the SEX with the Blumenstein Orca, which is a very popular combination. We have often used a system with that kind of output level in the packing room at Bottleheadquarters.

Putting a preamp in front of an amp never makes it more powerful. It just amplifies the signal from the CD or phono source. There is no loudness advantage to adding a Quickie unless you can't get your DAC or phono preamp to play loud enough to clip the amp.

[oguinn]

Thanks, Doc. That's a helpful explanation.

I apologize for the basic, dumb questions - I'm just getting started in all of this - but would there be an advantage of adding a Quickie (in addition to the scenario you outlined below where the DAC or phono pre need amplification) in having a source control? Switching back and forth between the turntable and the computer, in other words.

[Doc B.]

Yup, the biggest advantage to using Quickie would be that you could switch between the two sources instead of plugging and unplugging cables at the SEX amp. Set the pot on the SEX amp so that with the Quickie turned up all the way you can just barely hit clipping with the loudest source and loudest music you play and leave it set there. Then use the pot on the Quickie as your regular volume control. That should get you near the optimum signal to noise ratio.

[oguinn]

Thank you very much! I'll get an order in for the Quickie and use it to cut my teeth before taking on the SEX I've also got coming.

[Doc B.]

Thanks for your order!

[Paul Birkeland]

I would also add that the amount of power you need depends significantly on room size and how close you are to the speakers.  My recommendation of the SEX amp to go with the Overnight Sensations was based on the assumption that your room is small (which you mentioned) and that the speakers are sitting on a desk just a few feet from you. 

[oguinn]

That also makes sense, PB. The desktop setup you described in that post wasn't lost on me; I'd definitely look for something different if I had space to fill.

Thanks for your patience guiding me through this. It's much appreciated.

[fromnowon]

I apologize for the basic, dumb questions - I'm just getting started in all of this -

I thought this was a great question.  It's not simple!