Which amp of these two is best for the Elac Debut Reference DBR-62?

[DanielT]

You would have to take the room acoustics into consideration also.
High impedance needs high voltage to get a minimum current across. The ASR measurements were mostly done with the 48VDC / 5A power brick. The stated opposite maximum is at 44 Ohm and 35° phase angle, which seems to provide less of a challenge because of the much lower currents (and power) needed at 2kHz.
The culprit might be the 120 Hz at which the maximum current is needed and where much of the amps power is therefore - usually - also needed.

Okay, but class d amps without PFFB (post filter feedback) that show that increase, or for that matter the decrease in FR depending on the load of the amplifier. How will it be in the higher frequencies, (when not much current is needed), and the speaker goes up to 50 Ohm? If I understood this correctly, this problem has nothing to do with how current strong an amp is, but how to implement the switching class D typology in a good way.Note, I think. Or rather, see it more as a question from my side.

 

[wyup]

Which amp of these two is best for the Elac Debut Reference DBR-62? Aiyima a07 tpa3255 vs Nad c320bee.

I have the Elacs and had the Nad C320BEE years ago but sold it.

I haven't heard the Aiyima, but I think the Nad is more suitable, more robust AB amplifier. The Elacs need current. The Nad felt powerful at 50W, and I guess it can move the Elacs.
Only thing I didn't like of the Nad is its forward sound, and volume control, difficult to regulate at low volumes. But the Elacs are lowish sensitivty and will need higher pot.
The Nad had a juicy midrange, and the Elacs are a star there.

 

[DanielT]

I have the Elacs and had the Nad C320BEE years ago but sold it.

I haven't heard the Aiyima, but I think the Nad is more suitable, more robust AB amplifier. The Elacs need current. The Nad felt powerful at 50W, and I guess it can move the Elacs.
Only thing I didn't like of the Nad is its forward sound, and volume control, difficult to regulate at low volumes. But the Elacs are lowish sensitivty and will need higher pot.
The Nad had a juicy midrange, and the Elacs are a star there.

I don't know if I agree that the Nad C320BEE would have any special sound character. Reading Amir's test it seems to amplify the signal without coloring the sound. Specified at 50 watts but in reality it has 67 watts. SINAD of 95 if used solely as a power amp. Good performance I must say.

The Nad C320BEE is now twenty years old, so it can in principle be considered vintage. Still good but of course could be in need of an overhaul, service given the age. Might be worth considering if you're thinking of buying a used Nad C320BEE.

There are probably a lot of good class AB amps in Nad's power class, which of course if they are the same age or older they may also need to be looked at,
from a service aspect that is.

The only advantage of new small cheap class D amps (Amir has tested loads of them) as I see it is that they are new, cheap and small. Fairly decisive reasons to buy such vs an older larger class AB amp.
As I see it, the disadvantage is with these small cheaper class D amps is that they are load dependent.

 

[Deleted member 48726]

I don't know if I agree that the Nad C320BEE would have any special sound character. Reading Amir's test it seems to amplify the signal without coloring the sound. Specified at 50 watts but in reality it has 67 watts. SINAD of 95 if used solely as a power amp. Good performance I must say.

The Nad C320BEE is now twenty years old, so it can in principle be considered vintage. Still good but of course could be in need of an overhaul, service given the age. Might be worth considering if you're thinking of buying a used Nad C320BEE.

There are probably a lot of good class AB amps in Nad's power class, which of course if they are the same age or older they may also need to be looked at,
from a service aspect that is.

The only advantage of new small cheap class D amps (Amir has tested loads of them) as I see it is that they are new, cheap and small. Fairly decisive reasons to buy such vs an older larger class AB amp.
As I see it, the disadvantage is with these small cheaper class D amps is that they are load dependent.

And pumped up power ratings..

 

[Deleted member 48726]

I have the Elacs and had the Nad C320BEE years ago but sold it.

I haven't heard the Aiyima, but I think the Nad is more suitable, more robust AB amplifier. The Elacs need current. The Nad felt powerful at 50W, and I guess it can move the Elacs.
Only thing I didn't like of the Nad is its forward sound, and volume control, difficult to regulate at low volumes. But the Elacs are lowish sensitivty and will need higher pot.
The Nad had a juicy midrange, and the Elacs are a star there.

The NAD is more powerful. The 50 W are continous. It is capable of substantial dynamic power into low impedance. Headroom of which class D have none.

 

[antcollinet]

There seems to be some misunderstandings about the impact of the speaker phase and impedance plots. Lets see if I can clarify it.

1 - Speakers are voltage driven devices. They are designed to ouput an SPL level that is proportional to the voltage applied - at any freqency. If the speaker imedance is high at a particular frequncy, the amp therefore delivers less current, and hence less power at that frequency. Obviously the reverse applies at dips in the speaker impedance plots - tha amp outputs more current and more power. In all cases a speaker should be outputting the same SPL. (obviously with the variation of the speakers freqeuncy response)

2 - This means that the amp doesn't need to (and in fact cannot) adjust it's ouptut voltage as the impedance curve varies. It just needs to be able to deliver the extra currnet into low impedance parts of the curve.

3 - The phase matters (especially for linear - class A or AB - amps) because - if you have a large phase shift between voltage and current then the amp will be outputting low voltage while it is outputting high current. This voltage must be reduced from the PSU rail voltages by the output transistors - which means they are operating with a large voltage accross them at the same time as a large current through them - IE they are dissipating high power. Much higher power than they would be with zero phase shift.

4 - This phase effect is made worse when the impedance dips because the output current is even higher - hence the "difficult" point on the chart circled.

5 - the phase effect is much less of a problem for Class D amplifiers, since the output switches don't operate in the linear mode. For class D amps, the reactive (capacitive or inductive) currents are pushed in and out of the PSU bulk capacitance, each cycle of the output waveform. No significant extra power dissipation in the amp (other than IsquaredR losses in the tracks/wires between the speakers and psu - and on state IR losses in the transistors - much much lower than the linear losses in a linear amp.

 

[ninetylol]

There seems to be some misunderstandings about the impact of the speaker phase and impedance plots. Lets see if I can clarify it.

1 - Speakers are voltage driven devices. They are designed to ouput an SPL level that is proportional to the voltage applied - at any freqency. If the speaker imedance is high at a particular frequncy, the amp therefore delivers less current, and hence less power at that frequency. Obviously the reverse applies at dips in the speaker impedance plots - tha amp outputs more current and more power. In all cases a speaker should be outputting the same SPL. (obviously with the variation of the speakers freqeuncy response)

2 - This means that the amp doesn't need to (and in fact cannot) adjust it's ouptut voltage as the impedance curve varies. It just needs to be able to deliver the extra currnet into low impedance parts of the curve.

3 - The phase matters (especially for linear - class A or AB - amps) because - if you have a large phase shift between voltage and current then the amp will be outputting low voltage while it is outputting high current. This voltage must be reduced from the PSU rail voltages by the output transistors - which means they are operating with a large voltage accross them at the same time as a large current through them - IE they are dissipating high power. Much higher power than they would be with zero phase shift.

4 - This phase effect is made worse when the impedance dips because the output current is even higher - hence the "difficult" point on the chart circled.

5 - the phase effect is much less of a problem for Class D amplifiers, since the output switches don't operate in the linear mode. For class D amps, the reactive (capacitive or inductive) currents are pushed in and out of the PSU bulk capacitance, each cycle of the output waveform. No significant extra power dissipation in the amp (other than IsquaredR losses in the tracks/wires between the speakers and psu - and on state IR losses in the transistors - much much lower than the linear losses in a linear amp.

Great info! I just dont understand the two bold parts correlate, first you say the amp cannot change output voltage and then you say it does because of phase. Can you explain please?

 

[antcollinet]

Great info! I just dont understand the two bold parts correlate, first you say the amp cannot change output voltage and then you say it does because of phase. Can you explain please?

The output voltage is not DC it is a sine wave. So for a fixed AC voltage output, the waveform is varying between the positive peak, and negative peak evry cycle.

Taks the drawing below...

This shows a phase shif of between voltage (blue) and current (red). When the voltage is 0 the current is near maximum. This is the outptu of the amp. Internally then when the output voltage is zero, the voltage accross the output transistor is the full rail voltage.

With a zero degree phase angle, the peak output voltage (minimum voltage accross the transisotor) would line up with the peak output current. Much Much lower dissipation in the transistor.

 

[ninetylol]

@antcollinet Thank you so much, I finally understand most of it.

Do you know how phase and impedance is in relation to each other? I read on a stereophile article those are connected somehow

the maximum phase angle never occurs when the impedance has its lowest amplitude. As both are two-dimensional projections of a three-dimensional phenomenon, they're mathematically related.

Also maybe a basic question but how does the amp know theres a impedance change so it has to output more current/power at a given speaker frequency?

 

[antcollinet]

Also maybe a basic question but how does the amp know theres a impedance change so it has to output more current/power at a given speaker frequency?

It doesn't

Just as if you have a fixed voltage (say a (perfect) battery) and connect a resistor accross it the battery will output I=V/R. If you half the resistance, the current will double (if the battery has zero series resistance). The battery has no idea what the resistance is, the current is just what will flow through that resistor when that voltage is applied accross it.


(The phase / impdance relationship is much more complex - too much for a simple post here - you need to read up on reactive (capacitive and inductive) circuit analysis)

 

[ovi]

From this article the essence seems:

So it actually seems opposite and the lowest impedance point is the hardest to drive? Is that because the amp has to push high currents which is harder to do? (from your comic: its harder to push a bigger current guy because you need more force/work/voltage)

Not wanting to hijack this thread but could someone shed a little more light on my confusion regarding this? I've been googling this issue for many months without fully understanding it. (Not looking to understand the theory and formulas behind it an ELI5 digest would be awesome).

I don't understand the expression "harder to drive" and I have read it countless times when trying to understand this matter.

Basically if I have an amp that delivers 100W at 4ohm, and we want to keep it at max. 50% power that would mean it could output:
a) 50W into a 4ohm speaker
b) 25W into an 8ohm speaker

and provided that 4ohm/8ohm is the only different value between both speakers, speaker a) would be preferable as it would be “louder”? So I am wondering why most articles on the internet suggest using easier to drive speakers with 8ohm? (Or does this suggestion not apply to an amp rated with ?W at 4ohm?) To me that sounds like: let's just use 50% of what my amp is capable of.

 

[ninetylol]

Not wanting to hijack this thread but could someone shed a little more light on my confusion regarding this? I've been googling this issue for many months without fully understanding it. (Not looking to understand the theory and formulas behind it an ELI5 digest would be awesome).

I don't understand the expression "harder to drive" and I have read it countless times when trying to understand this matter.

Basically if I have an amp that delivers 100W at 4ohm, and we want to keep it at max. 50% power that would mean it could output:
a) 50W into a 4ohm speaker
b) 25W into an 8ohm speaker

and provided that 4ohm/8ohm is the only different value between both speakers, speaker a) would be preferable as it would be “louder”? So I am wondering why most articles on the internet suggest using easier to drive speakers with 8ohm? (Or does this suggestion not apply to an amp rated with ?W at 4ohm?) To me that sounds like: let's just use 50% of what my amp is capable of.

From my learned understanding every amp has a gain setting. For example my A07 Max got a max gain of 28.5db at max volume. This means the amp multiplies a incoming voltage from Dac to your speakers (depending on volume you set). The voltage (or gain) is static on how much you set it too. If the impedance curve of the speaker changes/lowers it requires more current to push it to the same Watt I=V/R (volt is static but impedance R changes). For most amp its hard to push a lot of current.

I think the confusion comes from headphone amps, which are typically voltage limited because 1. headphones are typically much higher impedance and 2. mobile amps dont have a lot of input voltage to work from and 3. headphones use much less watt than speakers.

Phase makes this even more complicated, but thats another matter.

Maybe a pro can confirm or correct me.