Post by lousymusician on Jan 4, 2017 4:21:33 GMT
Hi, I'm Bill, I'm new to this board but not to audio. After some years (decades, really, but with long gaps in between bouts of activity) of building tube and SS amps and speakers and trying to learn what I can about audio reproduction in general, I have lately started playing with headphones. Looking at amps to power my current phones (AKG K240M, beyerdynamic DT880-250 Pro) and whatever phones come next (HD6x0?) led me to Garage1217 and to this forum with a couple of questions.
I have read through most of the main DIYAH site and cruised through the forums here, but one topic I have not seen addressed directly is the choice of a Class A mosfet output device (Sunrise, Horizon) vs. an opamp output (Ember, Polaris, Solstice). I'd be interested to hear more about why those topologies were chosen and the tradeoffs and sonics of each. I have my beliefs and guesses, but there's always more to learn. What would happen if you coupled the Fet input of the Polaris to the mosfet output of a Sunrise? Sunrise and Solstice both run 24V rails and have comparable input sections (save the autobias in Solstice). Do they sound different due to their output sections?
Thinking about the mosfet outputs reminds me of the Zen and Firstwatt amp designs of Nelson Pass. One of the thoughts behind the Firstwatt designs is that most of the music played through a loudspeaker takes less than a watt to reproduce (particularly through a sensitive speaker), and that a huge amp throttled way down may not perform as well as one designed to run optimally at low levels. This seems to me to be even more true with headphones. For my beyers, for instance, 1 mW is good for 94 dB, and my average listening levels are well below that. First-milliwatt, anyone?
In that light, for most headphones most of the time an amp like Polaris is loafing along at a milliwatt or two, far below it's maximum capability. It has tons of reserve, yes, but we have a mosfet that can swing 40+ volts. At full output it's capable of damaging eardrums and/or voice coils, whichever gave out first. Not that we would try to play that loud, but accidents do happen. In normal listening I'd never even see a 1V swing. So, the question - is there a tradeoff between ultimate power output for hard-to-drive phones and ultimate low level linearity and detail when driving more sensitive phones? How much headroom is too much for those of us not running power-hungry ortho phones?
Apologies for the LONG first post, and thanks,
Bill
I have read through most of the main DIYAH site and cruised through the forums here, but one topic I have not seen addressed directly is the choice of a Class A mosfet output device (Sunrise, Horizon) vs. an opamp output (Ember, Polaris, Solstice). I'd be interested to hear more about why those topologies were chosen and the tradeoffs and sonics of each. I have my beliefs and guesses, but there's always more to learn. What would happen if you coupled the Fet input of the Polaris to the mosfet output of a Sunrise? Sunrise and Solstice both run 24V rails and have comparable input sections (save the autobias in Solstice). Do they sound different due to their output sections?
Thinking about the mosfet outputs reminds me of the Zen and Firstwatt amp designs of Nelson Pass. One of the thoughts behind the Firstwatt designs is that most of the music played through a loudspeaker takes less than a watt to reproduce (particularly through a sensitive speaker), and that a huge amp throttled way down may not perform as well as one designed to run optimally at low levels. This seems to me to be even more true with headphones. For my beyers, for instance, 1 mW is good for 94 dB, and my average listening levels are well below that. First-milliwatt, anyone?
In that light, for most headphones most of the time an amp like Polaris is loafing along at a milliwatt or two, far below it's maximum capability. It has tons of reserve, yes, but we have a mosfet that can swing 40+ volts. At full output it's capable of damaging eardrums and/or voice coils, whichever gave out first. Not that we would try to play that loud, but accidents do happen. In normal listening I'd never even see a 1V swing. So, the question - is there a tradeoff between ultimate power output for hard-to-drive phones and ultimate low level linearity and detail when driving more sensitive phones? How much headroom is too much for those of us not running power-hungry ortho phones?
Apologies for the LONG first post, and thanks,
Bill