xnor
Headphoneus Supremus
- Joined
- May 28, 2009
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You can change the sound of an SS amp simply by increasing the output impdeance. This can be achieved by adding a single resistor at the output for each channel. 0.1 ohms sounds different from 1, 10, 20, 100 etc. But does that make the amp sound different? Well, it depends.
Some amps allow you to choose between high and low output impedance, most have a fixed one however. Some opamps need a decoupling resistor (or make use of other techniques) at the output to prevent instability when driving headphones directly, others do not. When you're forced to do so I consider the resulting coloration as part of the amp -> the amp clearly sounds different.
Other designs use buffers wrapped in the feedback loop so you get very low output impedance plus high current capabilites. I think this is one topology which Willakan refers to as well-designed.
Since the output impedance is close to zero it doesn't interact with the complex headphone impedance (see voltage divider, as mentioned before) and you can use dummy loads such as resistors to measure the performance of the amp.
Frequency response is usually flat from 20 Hz to beyond 20 kHz, distortion doesn't matter if it's 0.0001% or 0.001% because headphones will dominate this with 0.01% min. Crosstalk is no problem either as described before. Those tiny phase shifts you see in well-designed amps also don't matter since our hearing has a hard time detecting even huge phase shifts. What else is there? The noise created by jitter usually is also down below -100 dB.
All in all, I see no reason why such designs should sound differently (same goes for expensive cables).
Some amps allow you to choose between high and low output impedance, most have a fixed one however. Some opamps need a decoupling resistor (or make use of other techniques) at the output to prevent instability when driving headphones directly, others do not. When you're forced to do so I consider the resulting coloration as part of the amp -> the amp clearly sounds different.
Other designs use buffers wrapped in the feedback loop so you get very low output impedance plus high current capabilites. I think this is one topology which Willakan refers to as well-designed.
Since the output impedance is close to zero it doesn't interact with the complex headphone impedance (see voltage divider, as mentioned before) and you can use dummy loads such as resistors to measure the performance of the amp.
Frequency response is usually flat from 20 Hz to beyond 20 kHz, distortion doesn't matter if it's 0.0001% or 0.001% because headphones will dominate this with 0.01% min. Crosstalk is no problem either as described before. Those tiny phase shifts you see in well-designed amps also don't matter since our hearing has a hard time detecting even huge phase shifts. What else is there? The noise created by jitter usually is also down below -100 dB.
All in all, I see no reason why such designs should sound differently (same goes for expensive cables).