A stiff power supply is needed to get deep and tight bass from a power amp. But there is another parameter that seems equally important.
It all started when I had my 100W Class AB power amp PCB´s on break-in with a 12 Volt PSU. I got curious how it would sound as a headphone amp. Said and done, I hooked up the headphones and put on some music. I was stunned by the immence power and control in the bass range compared to what I´ve heard from stand-alone headphone amps. OK, 16 pcs of 15A Sankens for a stereo headphone amp is quite an overkill, but I was totally surprised that the sense of power and control was still there even if just milliamps was delivered by the amp. Damping factor should not matter when driving 300 ohms, right ?
Theory says that a tiny amp will perform equally well when driving an easy load like a pair of headphones, but this is obviously not the case. If amplifier A sounds more powerful on speakers than amplifier B does, it will sound equally more powerful with headphones. This is counter-intuitive since damping factor really should be a non-issue when driving 300 ohms with a power amp. But the difference over headphones is real and very easy to detect - if fact just as easy as when listening to the speakers. Interesting indeed.
I have a range of power amps I´ve designed and built over the years. They all have a very stiff power supply (typically the transformer is 8 times rated power and the electrolytics are 180.000 uF or more). But they all have different "power" in the bass range. As can be guessed the smallest amp (with the smallest output devices) sounds smallest. All of them have a very tight bass, only the sense of "power" differs.
The observations has led me to the following conclusions:
- The stiff power supply gives bass control, i.e. the amp will be able to control what is there. If the output stage is small the sound will be slender, but still, very well controlled. I recall that builders of the Hiraga 8W "Monster" like the bass. Surely the control comes from the stiff power supply.
- The sense of bass "power" is a function of the output devices and is, it seems, INDEPENDENT OF THE RATED POWER OF THE AMP. My headphone experiment confirms this.
Class A amps are often praised for their powerful bass. I think that these amps would have the same powerful bass even if biased in Class B. The reason for the deep tight bass is probably the stiff power supply and the output stage, not the bias mode.
These findings suggest that a stiff power supply is simply not enough to achieve powerful bass. There is an absolute need to use powerful output devices. And it also suggests that a 10W power amp can outperform a 100W amp if the latter has a "smaller" output section. The rule is simple: use more (or bigger) output devices and the sense of bass "power" will improve (all of course given that everything else in the design is done right).
Kind regards
Syl
It all started when I had my 100W Class AB power amp PCB´s on break-in with a 12 Volt PSU. I got curious how it would sound as a headphone amp. Said and done, I hooked up the headphones and put on some music. I was stunned by the immence power and control in the bass range compared to what I´ve heard from stand-alone headphone amps. OK, 16 pcs of 15A Sankens for a stereo headphone amp is quite an overkill, but I was totally surprised that the sense of power and control was still there even if just milliamps was delivered by the amp. Damping factor should not matter when driving 300 ohms, right ?
Theory says that a tiny amp will perform equally well when driving an easy load like a pair of headphones, but this is obviously not the case. If amplifier A sounds more powerful on speakers than amplifier B does, it will sound equally more powerful with headphones. This is counter-intuitive since damping factor really should be a non-issue when driving 300 ohms with a power amp. But the difference over headphones is real and very easy to detect - if fact just as easy as when listening to the speakers. Interesting indeed.
I have a range of power amps I´ve designed and built over the years. They all have a very stiff power supply (typically the transformer is 8 times rated power and the electrolytics are 180.000 uF or more). But they all have different "power" in the bass range. As can be guessed the smallest amp (with the smallest output devices) sounds smallest. All of them have a very tight bass, only the sense of "power" differs.
The observations has led me to the following conclusions:
- The stiff power supply gives bass control, i.e. the amp will be able to control what is there. If the output stage is small the sound will be slender, but still, very well controlled. I recall that builders of the Hiraga 8W "Monster" like the bass. Surely the control comes from the stiff power supply.
- The sense of bass "power" is a function of the output devices and is, it seems, INDEPENDENT OF THE RATED POWER OF THE AMP. My headphone experiment confirms this.
Class A amps are often praised for their powerful bass. I think that these amps would have the same powerful bass even if biased in Class B. The reason for the deep tight bass is probably the stiff power supply and the output stage, not the bias mode.
These findings suggest that a stiff power supply is simply not enough to achieve powerful bass. There is an absolute need to use powerful output devices. And it also suggests that a 10W power amp can outperform a 100W amp if the latter has a "smaller" output section. The rule is simple: use more (or bigger) output devices and the sense of bass "power" will improve (all of course given that everything else in the design is done right).
Kind regards
Syl
