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Topping B100 Amplifier Review
- Thread starter amirm
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Class A vs AB vs D amplifiers
Hi all Iv always been under the impression that class A AB amplifiers sounded better than class D , however less powerful at same cost etc.. Now days with modules like the purifi , some say the class D exceeds the latter classes... in what respect are we talking, and how does this relate to...
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staticV3
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A pair of B100 Monoblocks can output 100W per channel at 4Ω, or 70W per channel at 8Ω.
If you're asking what kind of speakers these can drive, that depends on numerous factors. There is no simple answer.
This http://www.hometheaterengineering.com/splcalculator.html
and the Dezibel X App may help you to find out, if this is enough power.
The Topping B200 has the same SINAD specs but twice as much power for twice as much cost.
The Fosi V3 Monos have less SINAD but are exactly in the middle between these Topping gems if you are asking for „enough“ wattage.
And this guy explains exactly why power is „nearly everything“ that counts in case the amp has at least a few other qualities…… He likes it to have 450 Watts at 8 Ohms (and I strongly recommend his video!):
I just watched from where your link begins and have objections right away.
THD < 0.1% inaudible? really??
Sound is about cone acceleration not THD and that is is justification for needing high power and high damping factor? In fact, it is the best argument for current drive, because a = F / m and F is proportional to the B-field which is proportional to the current. There go all his arguments for high damping factor.
Seriously, if the source has a certain max level and the amp a certain gain, if the resulting output is within the linear range of the amp, no amount of extra headroom or current capability of the power supply will make a difference.
For some systems that may be appropriate. For others, that is overkill. There are numerous factors that affect how much power is needed. Yesterday I started a thread and posted a link to a spreadsheet to do some rough calculations to determine the minimum amount of power a system should have.
Spreadsheet for Calculating Power Amplifier Requirements
The question "how much power do I need?" sometimes is asked. But, the correct answer is dependent on numerous variables. To help, I have created a spreadsheet for calculating amplifier power requirements and made it publicly available at the following link...
audiosciencereview.com
Is slew rate / high Bandwith an indicator for good acceleration? I am no expert.
Damping factor is needed to make frequency range / and how the frequency response is independent from the Ohms (Resistence fluctuation) of the speaker. So very nice to have.
Sorry having to agree with you.
It is very easy to calculate the necessary slew rate for a given frequency and desired RMS output voltage. A little extra does not hurt, in the case of an Class B, AB, or A amplifier to keep the input stage reasonably balanced but loads of extra slew rate have no benefit.
Bandwidth, are you talking about closed loop bandwidth or unity gain bandwidth? With input filter or without? The input filter should be somewhere around 30 to 50 kHz so you still have a flat frequency response at 20 kHz, but you don't want to amplify EMI. The amplifier behind the filter can have higher bandwidth which is an indication for having lots of loop gain in the audio band, but not necessarily, depending on the frequency compensation technique employed.
Slew rate is a time domain measurement pertaining to how fast an output signal is able to move between voltage rails, e.g., when testing step response of an amplifier. Bandwidth is a frequency response measurement. Bandwidth may have some correlation to slew rate, but not necessarily a direct correlation. As long as they are adequate for the frequency range over which the driver is operating, I don't think they have much impact on cone acceleration. But, I have not looked too deeply into it.
Damping factor pertains to how well an amplifier is able to control overshoot of a driver. It generally is a concern more in the bass region than the higher frequencies. It does not pertain to frequency response, but instead how well the amplifier is able to control the driver.
With regard to resistance of the speaker, it depends to which you are referring. If you are referring to a driver directly connected to the amplifier with minimal resistance (e.g., low resistance speaker cables) and you have an amplifier with a low output impedance, you are correct (EDIT: with regard to better bass). But, if there is a passive crossover in the circuit, then the assertion would be incorrect. Properly determining the damping factor includes considering the total impedance from the input/output leads of the woofer's voice coil all of the way back to the amplifier's output stage, including the amplifier's output impedance. Good amplifiers usually have a low output impedance. So, the passive crossover becomes the prominent factor in determining the damping factor (something that too often is overlooked when people discuss damping factor). Inductors with high DC resistance and/or high core losses should be avoided if damping factor is a concern. On my speakers I removed the passive crossovers all together and went all active. This made an audible difference - the bass sounds much tighter.
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Ah, the old myths about damping factor. Depending on how well you crossover is designed, you can probably get away with a few tenths of an Ohm of series resistance, e.g. 0.2 R total resistance of amp output, terminals and cable will result an a damping factor of 30 in an 8 Ohm speaker (which will be around 6 R) without having significant impact on the frequency response.
As far as bass goes, series resistance changes the Q of the driver and hence the alignment of your bass box, no metter whether it is closed, bass reflex or transmission line. So whether you have a damping factor of 50 or 200 is probably not going to matter much, but eliminating the passive crossover can change the alignement which is audible. This is not about better "control" but different frequency and transient response.
If you were out to minimize harmonic distortion, you'd want as high as possible source impedance. This is actually what Purifi recommend in their white paper for the alu cone drivers: have a series resonant circuit that increases the series impededance exactly at the frequency that would have its harmonics amplified by the cone mode.
As far as bass goes, series resistance changes the Q of the driver and hence the alignment of your bass box, no metter whether it is closed, bass reflex or transmission line. So whether you have a damping factor of 50 or 200 is probably not going to matter much, but eliminating the passive crossover can change the alignement which is audible. This is not about better "control" but different frequency and transient response.
If you were out to minimize harmonic distortion, you'd want as high as possible source impedance. This is actually what Purifi recommend in their white paper for the alu cone drivers: have a series resonant circuit that increases the series impededance exactly at the frequency that would have its harmonics amplified by the cone mode.
No myths from me. From you, maybe?
A few tenths of an ohm of series resistance for a crossover used in an 8 ohm speaker is very low, especially for a 3-way speaker. Measure yours, you might be surprised. When I pulled my crossovers out I measured the DCR of the two inductors in series with the woofer. One measured 1.2 ohms and the other measured 0.4 ohms, for a total of 1.6 ohms in series with the woofer.
It doesn't change the Q of the driver itself, but instead changes the Q of the system including the driver.
I agree that a change in damping factor from 50 to 200 isn't going to do much. But, a change from about 3.6 to about 28.7, which is what I achieved by removing my passive crossovers, made a significant difference.
Here is an article that explains DF pretty thoroughly: https://sound-au.com/biamp-vs-passive.htm.
I think you misunderstood what they are saying. I haven't read the white paper, but a series resonant circuit has minimum impedance at the resonant frequency. A parallel resonant circuit has maximum impedance at the resonant frequency.
Please read what I wrote. A few tenths for the total of amp output impedance, terminals, cable, NOT crossover.
About Q, it is still about the driver inside and out of the box. Series resistance will make it behave like it had a higher Q_es. And yes, that changes the alignment of the system.
About the white paper, I think you missed my point completely. It is an example where a manufacturer that takes HD seriously proposes using series inductance to lower HD. In that case, only for one frequency, but applied across a broader band, it would also lower distortion across a broader band. However, you'd still have to think of something to do about the fundamental resonance of the driver...
But you are right, I was a little sloppy. They used a resonant circuit in series with the driver to increase source impedance at the critical frequency.
About Q, it is still about the driver inside and out of the box. Series resistance will make it behave like it had a higher Q_es. And yes, that changes the alignment of the system.
About the white paper, I think you missed my point completely. It is an example where a manufacturer that takes HD seriously proposes using series inductance to lower HD. In that case, only for one frequency, but applied across a broader band, it would also lower distortion across a broader band. However, you'd still have to think of something to do about the fundamental resonance of the driver...
But you are right, I was a little sloppy. They used a resonant circuit in series with the driver to increase source impedance at the critical frequency.
But the crossover in a passive speaker is the predominant factor in determining the damping factor. Unless somebody is using an amplifier with high output impedance, e.g., a tube amplifier, the output impedance of the amplifier is negligible.
Yes, the Q of the system changes, and thus the alignment of the system. That is a separate issue from the damping factor of which I was discussing, which pertains to the amplifier's control over the woofer. Adding resistance in series with the woofer decreases the amplifier/speaker system damping factor.
That's fine for a midrange or tweeter, but to do so on a woofer will decrease the damping factor. It is a compromise. In my opinion, it is not a compromise worth making on a woofer that is going to be used to play low-mid bass.
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Can you tell me what HD means?
harmonic distortion
Thanks!
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