Skunk Wrote: > Mine is an integrated AB push/pull pentode, but I'm sure the above > applies. It runs warm even at 10% volume. The heat from the tubes is not relatied to the heat produced by running in pure class A mode. Tubes are called thermionic devices because they conduct or manipulate electrons when they are hot, so they all contain a heating element, which is what glows red hot. The heat given by the heating elements is the reason for the low efficiency of a tube AB1 amp. But a solid state pue class A amplifier has no tubes, and still makes a lot of heat, due to the class A operating mode. Class AB uses two devices or banks of devices either tube or transistor to amplify the signal voltage from line level of 1-2Vrms to 20-30Vrms in order to scale the signal to a degree that can power an electromechanical device with a lot of force, like a speaker :) The way it does this in AB is one device (tube or transistor) handles the signal when it is above 0 volts and the other device handles the signal when it is below 0 volts. They hand the signal back and forth for every cycle of the alternating current signal. When the signal is positive, the device which handles the negative side of the signal rests, consuming very low current, thus making very little heat. When it is his turn, the other amplifying device rests and cools. Even though the periods between working and resting are very small, as small as 1/20,000th of a second for a 20kHz signal, it still means the device is only working 1/2 of the time, so only 1/2 of the heat must be dissipated from its outer case or bulb, so it is more efficient and cooler running than class A
Class A amp uses a device or bank of devices, either tube or transistor, which amplify your signal all the time, both when it is input above and below 0 at the line level. How and why is for someone else to explain, but since there is only one device handling the work, any distortion introduced when handing the signal back and forth between two devices is eliminated so the sound is noticeably better. Due to the constant work, the heat builds up in Class A devices so they run hotter. A Pentode running in AB will run cooler than if you switch it to triode, even though the volume level will sound lower. Many people like triode sound better, but not me, I always opt for pentode AB in my Cary SLI-80. I just can't give up the treble accuracy and bass power that I lose in triode. Skunk Wrote: > My impression from this thread was to set volume on the SB3 to 40 to > disable all volume control algorithms. I would much rather use the SB > digital volume control if there is no manipulation of the signal, but i > assume the added bits for the volume algorithm are considered 'bad'. > Sorry for being dense, but was the verdict that for FLAC, LESS than > 100% volume(40) is better or worse? Would you always want 'more bits', > or would it depend on your DAC? Again, apologies. This is probably > covered elsewhere. Playing 16 bit files from your network you will not be able to hear any loss of fidelity by using the volume control. It has been debugged and perfected by engineers at slim and forum geniuses who found the problem and suggested how to fix. There was a problem that effected sound quality, now there isn't for any mortal set of ears. Any digital distortion induced by converting 16bit music stream to 24 bit for the purpose of controlling volume level is still within the noise floor of 16 bit resolution, meaning at least 96 decibles softer than the music that is playing (that's a hell of a lot). Your listening room has likely never been quieter than 30dBA, meaning that you could never hear the distortion outside of lab conditions, and then the limits of human hearing would challenge your ability to hear it. 20dBA is considered dead silent by most people, but you need to be able to hear something many times quieter than that, all while your favorite music, (playing at 96dB+, ouch!) is distracting you from such nonsense. Skunk Wrote: > I'm not sure if this means the digital volume is better than the analog. > Does the SB volume go from being active to passive when less than 40? > > I understood your point that an A/B amp is in class A at 100% volume > with low signal input. However, I also don't want to crank the Alps > Blue pot to 100% (if that is the same as "connecting directly to a > power amp") because of potential speaker damage. Passive volume control would be a separate component that you connect with interconnects between source and amp, it uses no electricity of it own, does not amplify the signal and thus only attenuates. It has nothing to do with the SB unit itself. Usually it is just a pot in a box with some source switching to be fancy. Most pre-amps use external power to amplify the incoming signal by 6-12dB. The SB volume control modifies the 16 bit digital stream coming from slimserver with an 8 bit coefficient containing volume control setting, to make data going into the SB DAC a 24 bit sample with volume information embedded which DAC understands. It is pure digital, and the analog of the original 16 bit music word is produced by DAC without losing anything to the signal purity. At very low volume settings there is some slight degradation, but at SB volume control levels above -35dB (#12 or #16?), the loss is inaudible. Connecting direct to your power amp would only apply if you were going to use the SB digital volume control. Then your external pre-amp or ext. passive volume control would not be necessary because the analog output signal voltage would be "attenuated" digitally by the SB DAC itself. This is the optimum way to use SB, because then you eliminate the cables and distortion inherent with passive VC or preamp and interconnect cables. I hope you are not offended if I reiterated something you already know. It can be hard to learn some of these concepts, so sometimes simple is better. The subtleties make it a fun hobby, always more to learn! Rich -- richidoo ------------------------------------------------------------------------ richidoo's Profile: http://forums.slimdevices.com/member.php?userid=3097 View this thread: http://forums.slimdevices.com/showthread.php?t=19697 _______________________________________________ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
