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).
You just discovered one of the virtues of having a high-current amp, welcome to the club!

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!!!
RW, please explain your statement regarding a high-current amp and its impact on low volume listening. I don't understand the connection. Thanks.
okay. so it's an current/amps thing (at least in this particular situation). The thing is, I have a decent sized room, and i can handle full range speakers. for example, i listened to the ProAc Response 2.5 the other day, and I really really (i mean really) liked them. and regardless of where I go with this hobby, it's starting to look like a good high current amp is going to give me the flexibility to audition a wide(er) variety of speakers over the next few years. I think I can still get there with an integrated Kijanki, but starting to think a separate high quality amp is going to provide the most "room to move" over the next few years. I mean, lets face it, no matter what I tell myself, i'm going to be purchasing different items, micro-analyzing my system to death, for a long while- i just can't help it anymore. i give up. :)
Hi Blazerfan -
I have the same view that Bob Reynolds posted "regarding a high-current amp and its impact on low volume listening".
I do not see the connection either.

What Preamp were you driving the w-3 with??
Your Speakers do not seem to be a tough load requiring lots of power - Nominal impedance: 8 ohms. Sensitivity: 91dB/W/m (room), 88dB/W/m (anechoic).
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.
I used my simaudio i-5 integrated as a pre. The sound and low volume was much clear and clean. background instruments and vocals were audible. My girlfriend and her 8 year old son both thought the w-3 sounded much better, and they are not very critical listeners.
for the record, i don't see the connection either. if i did, i wouldn't have started this thread. i really don't understand why it is the way that it is. thus, the post.
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)
This may, or may not be of value, but my experience with Simaudio Moon integrated amps is that they don't come 'alive' until 20 steps of attenuation.

I was using Totem Sttafs and really couldn't get much out of them until I turned up the juice a bit. I understand you might be expecting something different from more sensitive speakers. If you're looking for more performance at lower volume levels I would look at different Amps than Sim/Moon. Sugden integrated amps are class A and may be worth an audition?
Maybe because the W3 is 125wpc vs the 70wpc of your integrated. My guess is that the W3 sounds better at higher volumes as well.
Some amps (a lot actually)start sound better when played louder. Some reviewers will bring this to your attention. Some times the specs the reviewers provide will show this.I like my gear to sound good at low volumes too.
Higher power nor current offer a rational explanation.

Blazerfan, how closely did you set the volume for the two amps? I mean, did you get out an SPL meter and attempt to match levels or did you just ball park the volume control to the same position?

If you just set the volume control to the same position, then voltage gain differences between the W3 power amp and the amp section of the i-5 could explain what you heard. That is, the levels were may not have been the same. I've read that even a 0.1dB level difference is audible, but will not be perceived as a level difference.
ball parked the volume issue, but feel that I over compensated (turned the volume way up) when listening to the integrated, and still experienced better sound with the w-3. with everything i know about high power and/or high current i agree they do not offer a rational explaination. however, there may be things I don't know about high power/high current that may lead to a rational explaination. this is what i'm trying to find out.
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- what do you mean by "reserves"?
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.
I've never understood why so many regard the efficiency of a speaker as a virtue. The most accurate and best sounding speakers I have heard have also tended to be the least efficient. Take sealed/infinite baffle speakers for example - you have to crank them way up to get much volume, but when you do the sound is effortless and natural. In contrast highly efficient speakers tend to sound more compressed, out of control, and have less nuance in their dynamics, both at high and low volumes. Who is pushing this notion that efficiency in speakers is a virtue in itself?
Neubilder, I'd be one of those! So far the most accurate speakers I have heard are 98 db 1 watt 1 meter. They go from 20Hz to 40KHz and have the same transparency and detail of the best ESLs but dynamic range no ESL or magnetic planar can hope for.

Additionally, amplifier power can be expensive compared to speaker efficiency. If you want realistic volume levels, it can take a prodigious amount of power to cleanly reproduce volumes of +105db without strain and distortion with speakers that are 90 db or less- assuming that the speaker can even play that loud without artifacts of its own. IMO/IME any speaker that requires more than a 200 watt amplifier is just plain impractical.
Kijanki, are you saying that if we plotted THD against input voltage level we'd see a sort of U shaped curve? Higher THD at low input voltage, dropping for some range of voltages and then rising again at higher voltages.

Can you explain why that would be the case?

I've always assumed that below some stress threshold THD differences would be negligible.
Bob - Look here

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.
Bob - I looked at two latest Stereophile reviews of tube amps and I don't see "u" shaped curve.



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, thanks for the links. I recalled the characteristic graph for solid state amps as soon as I saw it, but honestly I never paid much attention to the low end of the power axis.

From the Bryston's review:
The downward slope of the traces below 10W in fig.3 indicates that the actual distortion lies beneath the noise floor at these levels, but the Bryston is also a low-noise design.

So it's the inherent noise of the amp at low levels that's a problem. Are these relative THD+N differences audible?

From the MF Titan review, JA says:
While fig.3 reveals that the distortion rose with reduced load impedance, the Titan is still an extremely linear amplifier.

The SimAudio W8 appears to be quite linear into 2 ohm loads:

Would one expect the W8 to sound essentially the same up to a couple hundred watts?
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.
If you're after efficient speakers, try the Auditorium series speakers from Living Voice. These speakers are an easy load for amplifiers to drive; sound great at low volumes as well as at higher volumes.
Kijanki, some tube amps will make higher distortion at very low power levels just like transistors. Others (SETs for example) the distortion becomes unmeasurable.

Feedback is appearing more and more to be a poor means of ridding audio circuits of distortion. An amplifier that might not have had much beyond the 5th or 6th harmonic will suddenly have harmonics beyond the 81st when feedback is applied.

Much depends on propagation delay and how effective the circuit was as an amplifier before the feedback was applied.

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.