2. amps-preamps
  3. 1260904595

Can someone give me an explaination re: power amp.

So, I own a simaudio i-5 driving paradigm studio 60 v.3, and I am not happy with the sound at low volume. turn it up everything is great, but low volume has muffled sound. Everyone says the paradigms are efficient, but i go out looking for more efficient speakers, and happen to come home with a loaner power amp- a simaudio w-3 (125 wpc), and the sound at low volume sounds markedly better with the power amp. this is contrary to everything i have convinced myself to believe. i have convinced myself that a good integrated is all i need, but I cannot deny the sound. so instead of asking the age old separates vs. integrated question, i'm just going to ask- why does my system sound so much better at LOW volume with the power amp. Maybe the speakers aren't as efficient as I thought? Maybe the 70 wpc simaudio i-5 isn't as great a machine as i thought? maybe there's a technical explaination? Please enlighten me! and thanks, and merry christmas to all you audiophiles out there! (oh, and the reason I didn't come home with speakers is that i really love the full range of sound from the towers, and i couldn't find any highly efficient speaker that had the range I enjoy. not that it dosen't exist, but i just couldn't find it. I live in portland, oregon).
blazerfan

Showing 9 responses by kijanki

kijanki's avatar
kijanki
4,410 posts
 
Blazerfan - You posted your question twice so I'm posting here as well (just in case):

There is nothing wrong with Paradigm Studio/60. I had the same speakers v.2 It performed decent with integrated Cambridge amp but got much better at low volume with class D Icepower amp (Rowland 102). I found later review where they mentioned good performance of Icepower at low levels. Now I use different speakers (Hyperion 938) but low volume sound is still very good (lows, highs, clarity, dynamics, imaging). Actually, imaging is better at low volume. I have too much reverberation in my room and at low volume I get less audible reflections (echo dies faster). At high volume room brightens the sound a little more than it normally would be. Hyperion speakers are exceptional!!!
kijanki's avatar
kijanki
4,410 posts
 
Bob - I also cannot see connection between high current and low level performance. In each case (including my small class D amp) it is most likely related to particular amp design.

Blazerfan - My whole system consists of DAC with volume control and Power Amp plus very good interconnect in-between (Acoustic Zen Absolute). Music comes thru Airport Express or from DVD player (or HDTV). I listen very often at low levels at night(Duplex + wife asleep) and really like the sound.
kijanki's avatar
kijanki
4,410 posts
 
Blazerfan - I looked it up and it is very interesting amp. Very low distortion and high damping factor in an amp with very little feedback - It can be done! (I assume that Simaudio W-3 is the same as Simaudio Moon W-3)
kijanki's avatar
kijanki
4,410 posts
 
Blazerfan - Twice softer means 1/10 of the power. Four times softer means 1/100 of the power. At low sound levels power might be in fraction of a watt. Amplifiers' distortions, damping factor, bandwidth etc. are measured at relatively high level. Amp (and speaker) performance in not so good at very low levels. High performance amp might have enough of "reserves" to sound good very soft. At medium levels both amps might sound very close. At very high levels higher quality amp will outperform again.
kijanki's avatar
kijanki
4,410 posts
 
Your w-3 amp has 0.02% THD at 1W. At a fraction of a watt it might have 0.1% - still not audible while amp with 0.05% THD at 1W might have 0.25% THD at the same fraction of a watt and it might become audible.
kijanki's avatar
kijanki
4,410 posts
 
Bob - Look here http://stereophile.com/solidpoweramps/musical_fidelity_titan_power_amplifier/index5.html

Find distortions vs. power at 1kHz and it shows this u-shaped curve. Everything behaves worse at low levels. For speakers it might be mechanical but for amps and preamps it is probably noise in the system and possibly more nonlinear operation around zero output.

Most amps have the lowest distortion between 10 and 100W (dependent on max power) while distortions at 0.1W might be 10x worse. Distortions also increase with frequency by another 10x.

I don't know about tube amps - will check.
kijanki's avatar
kijanki
4,410 posts
 
Bob - I looked at two latest Stereophile reviews of tube amps and I don't see "u" shaped curve.

First: http://stereophile.com/solidpoweramps/moscode_402au_power_amplifier/index4.html

Second: http://stereophile.com/tubepoweramps/hyperion_ht-88_monoblock_power_amplifier/index4.html

In case of the second (Hyperion) it is straight line with lowest distortion at min power. That would imply that u shaped characteristic of SS distortions is caused most likely by nonlinearities (possibly output transistors) around zero. What do you think?
kijanki's avatar
kijanki
4,410 posts
 
Bob - It might be THD +S/N or some nonlinearities of output transistors in spite of feedback (there is no perfect regulator). I don't know if THD can be measured without noise. Traditional THD meter deliveres pure sinewave to the input and subtracts same sinewave from the (scaled) output measuring what left - harmonics + noise. THD + noise levels are really small - 1/100 of percent = 1/10000 (-60dB) of very small signal (0.1W). It is equivalent to about 1uV at the input. Tube amps, I looked at, had higher THD to start with, so this effect is probably hidden.
kijanki's avatar
kijanki
4,410 posts
 
Atmasphere

I agree - feedback is evil. It is less of a problem in class A amps since gains before feedback are as low as 200 but it might be big problem with class AB where gains before feedback are in order of 4000.

In class AB with most linear components available I would probably get 10% percent of THD without feedback. I would apply only enough feedbacks (avoiding global one)to bring THD down to about 0.5%. To eliminate TIM I would limit bandwidth at the input to one that amp had before feedback was applied. Low bandwidth, high THD amp might not interest too many people.
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