High power amp for low level listening?

[KEW]

I've got the upgrade bug!

Currently, my Emotiva UPA-2 is my most powerful amp. I don't listen loud and doubt the UPA-2 has ever been wanting, but I always wonder if I might be missing something in the headroom category.

I was considering the XPA-2 (could get for $700) - Definite overkill, but solid insurance that I would never run out of headroom. However, when I read the Audioholics review of it, I saw the following:

I ran FFT distortion plots at various power levels to determine how clean this amplifier really is. At 1 watt, the spectral distortion was good with the second order harmonic being (9.007 + 67.533)dB being 76.54dB down from the fundamental or 100*alog^-1(-76.54/20) = .015%. While this is a respectable measurement, it is no way near as pristine as what I’ve seen on their RPA-1 demonstrating a measurable trade off between higher sustained power of the XPA-2 versus measurably cleaner low power of the RPA-1. If you tend to favor low listening levels, you may opt for an RPA-1/ RPA-2 over the XPA-2.

I do tend to favor lower listening levels and am concerned that going from the UPA-2 to the XPA-2 might actually be a step backwards in SQ (similar FFT distortion specs are not available for the UPA-2).

I don't really understand the FFT distortion spec. Is this a S/N ratio?

I'd appreciate any comments on whether I should be concerned about these FFT distortion levels and if there is an amp which might give an optimal low level performance, but ample power reserves to feel confident the amp isn't "topping out" (without breaking the bank).

I'd like to do this for under $750, but appreciate any suggestions.

Thanks!

 

[Seth=L]

I can't imagine the UPA-2 lacking in headroom. It's total block capacitance is 40,000uF, which is quite substantial. The triple darlington output stage, properly implemented, gives you an excellent range of driving ability (they are often stable into very low impedances and can deliver large amounts of power when impedance dips occur).

The transformer is rated 300va, which seems a tad small, but certainly up to the task. As long as the capacitor voltage is high enough dynamics should never be an issue.

The UPA-2 has 4 output transistors dedicated to each channel. I had a Niles SI-275, which had 6 output devices dedicated to each channel and I believe the transformer had a higher va rating as well. It also had 40,000uF block capacitance. It was rated down to nearly 2 ohms for safe operation. I never felt that amplifier was lacking in dynamics.

 

[vikebrian84]

At low listening levels you probably wont even be able to tell the difference between the two amps. I mean unless you really just have 700$ burning a hole in your pocket I would say to stay with the upa-2. If not then sell me the upa-2

 

[KEW]

I can't imagine the UPA-2 lacking in headroom. It's total block capacitance is 40,000uF, which is quite substantial. The triple darlington output stage, properly implemented, gives you an excellent range of driving ability (they are often stable into very low impedances and can deliver large amounts of power when impedance dips occur).

The transformer is rated 300va, which seems a tad small, but certainly up to the task. As long as the capacitor voltage is high enough dynamics should never be an issue.

The UPA-2 has 4 output transistors dedicated to each channel. I had a Niles SI-275, which had 6 output devices dedicated to each channel and I believe the transformer had a higher va rating as well. It also had 40,000uF block capacitance. It was rated down to nearly 2 ohms for safe operation. I never felt that amplifier was lacking in dynamics.

You are right, neither the UPA-2 nor the SI-275 has ever caused me to sense headroom was missing. However, these old articles from Axiom which have me wondering.

http://www.axiomaudio.com/power.html

http://www.axiomaudio.com/dynamicheadroom.html

The one thing I have noticed is that my active Focal Solo6 Be speakers outperform my Paradigm S-2's and Songtower RT's when it comes to transients. It may be a headroom issue or just the nature of having an active crossover system before the internal bi-amping that makes this difference. I like all of these speakers, but it would be really great if I could get the same type of attacks out of the Paradigms and Salks as the Focals provide.

FWIW, for me "maximum loud" is 90-92 dB peaks on my RS meter using C weighting. I assume that the C weighting is a form of dampening such that the transients actually exceed that.

 

[PENG]

FWIW, for me "maximum loud" is 90-92 dB peaks on my RS meter using C weighting. I assume that the C weighting is a form of dampening such that the transients actually exceed that.

In my opinion if you like classical music and listen to average SPL or 75 to 85 dB then it is worth upgrading to the XPA, but you said you want it for low level listening? In that case you should keep the UPA.

 

[KEW]

In my opinion if you like classical music and listen to average SPL or 75 to 85 dB then it is worth upgrading to the XPA, but you said you want it for low level listening? In that case you should keep the UPA.

I should probably rephrase that. I listen around the 70dB level 85% of the time and crank it to 80-85dB for the other 15%.

 

[Pyrrho]

You are right, neither the UPA-2 nor the SI-275 has ever caused me to sense headroom was missing. However, these old articles from Axiom which have me wondering.

http://www.axiomaudio.com/power.html

http://www.axiomaudio.com/dynamicheadroom.html

The one thing I have noticed is that my active Focal Solo6 Be speakers outperform my Paradigm S-2's and Songtower RT's when it comes to transients. It may be a headroom issue or just the nature of having an active crossover system before the internal bi-amping that makes this difference. I like all of these speakers, but it would be really great if I could get the same type of attacks out of the Paradigms and Salks as the Focals provide.

FWIW, for me "maximum loud" is 90-92 dB peaks on my RS meter using C weighting. I assume that the C weighting is a form of dampening such that the transients actually exceed that.

90-92 dB peaks? How far away from the speakers are you, and what is their rated impedance and sensitivity? Most likely, you will get nothing from a more powerful amplifier (other than a more empty wallet and a higher electric bill), but it does depend upon what speakers we are talking about.

 

[AcuDefTechGuy]

Once you have the upgrade ITCH, aka Upgraditis, it is no longer about what you NEED.

I don't think you will hear any difference either, but then again, does it really matter at this stage of this ILLNESS?

Would this be a Stage 1 (beginning) of the Upgraditis Sickness, or is it Stage 10?

 

[Pyrrho]

Once you have the upgrade ITCH, aka Upgraditis, it is no longer about what you NEED.

I don't think you will hear any difference either, but then again, does it really matter at this stage of this ILLNESS?

Would this be a Stage 1 (beginning) of the Upgraditis Sickness, or is it Stage 10?

I think if one has a desire to upgrade, one should put one's money into something that will make an audible difference. For example, better speakers are almost always possible (keeping in mind that a subwoofer is also a speaker).

 

[AcuDefTechGuy]

I don't really understand the FFT distortion spec. Is this a S/N ratio?

I believe it refers to THD.

Most people say a THD of <1% is inaudible.

Of course, Audioholics standards is < 0.1% THD.

 

[KEW]

I believe it refers to THD.

Most people say a THD of <1% is inaudible.

Of course, Audioholics standards is < 0.1% THD.

Unfortunately, as presented in college, FFT held little interest and it was clear that it was not a key aspect to the lab class we used it in, so I used the results without really understanding the theory behind it.

 

[KEW]

90-92 dB peaks? How far away from the speakers are you, and what is their rated impedance and sensitivity? Most likely, you will get nothing from a more powerful amplifier (other than a more empty wallet and a higher electric bill), but it does depend upon what speakers we are talking about.

I listen at about 10' away.
I have three pairs of speakers which I might use interchangeability with this amp:
Paradigm Signature S-2 - Sensitivity - Room / Anechoic 91 dB / 88 dB
Impedance Compatible with 8 ohms
Salk SongTower RT - Sensitivity - 88db (dB/2.83v/1M)
Impedance 4 ohms minimum 6 ohms nominal
EMP 41SE/Be - Impedance 8 Ohms
• Sensitivity 86dB (2.83V@1m)

 

[Pyrrho]

I listen at about 10' away.
I have three pairs of speakers which I might use interchangeability with this amp:
Paradigm Signature S-2 - Sensitivity - Room / Anechoic 91 dB / 88 dB
Impedance Compatible with 8 ohms
Salk SongTower RT - Sensitivity - 88db (dB/2.83v/1M)
Impedance 4 ohms minimum 6 ohms nominal
EMP 41SE/Be - Impedance 8 Ohms
• Sensitivity 86dB (2.83V@1m)

I think your Emotiva UPA-2 should have no problems with them at the volumes you are talking about, assuming that the ratings are reasonably accurate. It is impossible to know exactly how much of a drop in SPL there is in your room from 1 meter to 10 feet (though you could measure it with your meter, that would still not give us an exact figure to work with, because your room is probably not anechoic and therefore not going to be giving us a number we can perfectly use with the ratings, but it should give a ballpark figure to work with [their room ratings are a total unknown, as we do not know what their room is like]), but if it is 6dB, you still should be able to get 92 dB continuously out of any of those speakers with less than your amplifier's full rated power. (Assuming a drop of 6dB due to distance, with your least sensitive speaker, you should get 80dB with 1 watt, 90dB with 10 watts, and 100dB with 100 watts. And your amplifier can deliver more than that continuously, not to mention whatever more it can do with peaks. And your amplifier is fine with 4 ohm loads, being capable of delivering even more power into that impedance than 8 ohms, so that is not a worry either.)

I really doubt that a more powerful amplifier would do anything more for you than empty your wallet and give you a higher electric bill, though very often the placebo effect works wonders on one's perceptions, so you might like it more anyway, even if it does not actually make an audible difference.

 

[ichigo]

I've noticed power draw from the wall swings fairly widely depending on the type of music, even at similar SPLs. This I assume has to do with impedance swings the speakers provide as well as repeated transients during a song. For example, a drum hit that comes every 2 or 3 seconds.

I've got an Onkyo TX-SR805 and during Overture 1812 go from 1.7A from the wall to 3.5A (during the finale), which I believe would be equivalent to 100W/channel+ (assuming 1.7A is 1W/idle power).

So if you plan on listening to Overture 1812 repeatedly...I would get a bigger amp. But for most music, at regular listening levels I haven't seen power draw exceed +0.8A (or about 50W/channel) during louder passages. With pop music the most I've seen is +0.4A which would be 25W/channel...easily achievable by any regular amp assuming regular listening levels.

I listen around 10 feet and I typically listen at lower volumes (~75dB SPL) with speakers that are about 85dB sensitivity.

 

[KEW]

I've noticed power draw from the wall swings fairly widely depending on the type of music, even at similar SPLs. This I assume has to do with impedance swings the speakers provide as well as repeated transients during a song. For example, a drum hit that comes every 2 or 3 seconds.

I've got an Onkyo TX-SR805 and during Overture 1812 go from 1.7A from the wall to 3.5A (during the finale), which I believe would be equivalent to 100W/channel+ (assuming 1.7A is 1W/idle power).

So if you plan on listening to Overture 1812 repeatedly...I would get a bigger amp. But for most music, at regular listening levels I haven't seen power draw exceed +0.8A (or about 50W/channel) during louder passages. With pop music the most I've seen is +0.4A which would be 25W/channel...easily achievable by any regular amp assuming regular listening levels.

I listen around 10 feet and I typically listen at lower volumes (~75dB SPL) with speakers that are about 85dB sensitivity.

Interesting!
How do you measure amp draw at the wall?

 

[PENG]

I've got an Onkyo TX-SR805 and during Overture 1812 go from 1.7A from the wall to 3.5A (during the finale), which I believe would be equivalent to 100W/channel+ (assuming 1.7A is 1W/idle power).

If it draws 1.7A idling, another 1.8A from the wall outlet at 120V probably represents less than 50W output per channel after factoring in the power factor (consine of the phase angle between current and voltage) and efficiency assuming we are talking about class A/B amps.

 

[ichigo]

If it draws 1.7A idling, another 1.8A from the wall outlet at 120V probably represents less than 50W output per channel after factoring in the power factor (consine of the phase angle between current and voltage) and efficiency assuming we are talking about class A/B amps.

Depends on amplifier efficiency, it could be anywhere from 40 to 60W x2. Trying to actually achieve 100W of power output at the terminal posts you would need about 200-250W of draw from the wall. This isn't including resistive losses like the the material of the binding post or banana plugs--gold reduces conductivity by 30%.

At the end of the day getting 100W to your speakers takes a lot of effort. If you are talking about actually getting 100W to reach your crossover network, there isn't an AV receiver on the market that can pull that off.

 

[indcrimdefense]

KEW, are your S2 v1 or v2? I've had the S8 v1 for 3 years, and have heard the S2 multiple times over the years at the dealer on multiple system setups, from macintosh down to a marantz integrated.

 

[KEW]

KEW, are your S2 v1 or v2? I've had the S8 v1 for 3 years, and have heard the S2 multiple times over the years at the dealer on multiple system setups, from macintosh down to a marantz integrated.

Mine are S2, v2.
I'm not sure the efficiency number I gave was right (although they are definitely more efficient than my worst case 86dB EMP's).
Unfortunately Paradigm doesn't seem to have the specs for the older versions on their site.
They didn't change much between v2 and v3, but I do think one of their arguments for dropping the phase plug from the mid-bass driver was it increased efficiency a little.

Edit: So do you have any comments on what you heard regarding MacIntosh to Marantz? Did you have a chance to make any comparisons in a good A-B setup?

 

[KEW]

I think if one has a desire to upgrade, one should put one's money into something that will make an audible difference. For example, better speakers are almost always possible (keeping in mind that a subwoofer is also a speaker).

I agree that speakers have the best goody/$ ratio. My wife won't go with treatments (though I have done what I can and pull the drapes closed for critical listening).

I'm pretty happy with the passive speakers I have. My best speaker is the Focal Solo6 Be which is an active studio monitor. It has a 150W rms, BASH amp to drive the mid-bass and a 100W rms, class AB amp to drive the tweeter.
Here is a link for the curious:
http://www.focalprofessional.com/en/sm6-line/solo6-be.php

It is quicker (more articulate) than the passive speakers I have, but also has more power (I presume) so I was wondering if the a bigger amp might close some of the gap. In the end, it is probably the active configuration which really makes the Solo's different. I'd especially welcome any comments on this!

I would certainly entertain any ideas on speaker upgrades, especially active speakers.
But it is pretty difficult to get higher end speakers in a true A-B scenario.