>the power supply cannot be greatly taxed
Indeed. My comment was just addressed to the miconception that being capable of driving headphones means it will perform very well driving a line input.
I dont have a nicemeter...
You're comparing apples and oranges. 50% is for a xfmr-loaded SE, and Push-pull class B has theoretical max efficiency of 78.5%. A resistor-loaded SE reaches 25% max. However, we all know that efficiency in line level devices is far from being a dominany factor. Particularly today, when we don't need to send +24dBu into 600 ohms.
yes youre right. SRPP has lowest THD at specific load (at which ac are symmetric for the triodes if i get it right). So such output would sound different into different loads like 10k ADC or 600ohm-input compressor. But if it is about more or less even harmonics im okay with this
The distortion produced by all output stages varies with the load and output level. It is true the SRPP produces its lowest distortion at a particular load but so does every other output stage so I am puzzled why the SRPP is singled out for special treatment.
It may be because most of the other topologies have distortion that decreases as the load lightens, when SRPP has the singularity of having an optimum, which is somewhat counter-intuitive.
That sounds like a reasonable explanation. I need to do some tests to see just how much variation in distortion with load occurs in an SRPP.
Mu follower definitely has lower distortion than an SRPP using the same tube. In fact it is probably the best way to get the lowest distortion out of a tube without resorting to the use of semiconductor constant current sources. However, it is single ended so it does not have the drive capability of an SRPP. I used mu followers a lot in my early mixer designs and one option of the classic solo mic pre is to build it with a pair of mu follower stages.
Harmonic restoration is the idea that perverted audio in the 70's and led to uncontrolled use of the Aphex processor.
This myth falls apart when the signal is complex. Nasty intermodulation becomes dominant.
Back in the early days of "audio exciters" I would try to tune in the FM radio stations better to reduce the audible distortion.
The SRPP is a two-stage amplifier. Most two-stage amplifiers (e.g. two similar cascaded gain stages) also exhibit a distortion null due to similar cancellation effects, so really there is not much difference.
Just an FYI, the SRPP usually only shows a distortion null when the lower triode cathode resistor remains unypassed.
Do they? I woud think distortion cancellation happens when two similar tubes operate in similar conditions (current, load). I don't see a typical cascaded two-stage amplifier (with largely different loads) benefiting the same advantage. Not mentioning the gain difference.
We all know that in triodes, distortion is proportional to output level (all else remaining constant). In an SRPP, the output level in both triodes is very nearly identical. In a simple cascade (two similar cascaded gain stages ), the signal level at the output of the first stage is lower than that at the output of the second stage by an amount equal to the gain of the second stage so any null is likely to be insignificant unless the gain of the second stage is deliberately reduced (e.g. REDD 47).
Interesting. I must check that out.
Yes I was thinking of an equivalent situation where the signal is attenuated between the stages, so both operate similarly. Sorry for misleading
