How low can you go?
How about collecting in one single thread, the specs (and features) + description + link, of all amplifier projects, finished or ongoing on this forum, instead of having them buried in thousands of pages and hundreds of threads?
1. A general Reference to easily find, compare and chose an amp for builders,
2. Motivation to design or build a better amp,
3. Competition and reward for designers,
4. Motivation to actually measure the performance of an amp objectively (virtually or physically), instead of guessing and having no clue about its actual performance, playing a Russian roulette, or relying on subjective colorful poetic words like "the best" ;)
5. Unburial of forgotten projects.
In my view, faithful reproduction is the ultimate goal for an amp (provided it is also highly stable and reliable) that means: the least altering of the input signal.
Adding 2nd harmonics for example (tubes), while might sound good to some people, it is NOT a faithful reproduction, it was NOT the artist's intention (he can take care of all that in the mastering stage, no need for the user to add more) and it can even be added artificially as a sound effect that you can switch on or off if you want, instead of having it permanently and always coloring all kinds of music you listen to.
The level of distortion and quality one can hear is unknown, it varies depending on the content, the conditions, the person, etc. so we just aim for the least distortion (=highest linearity) possible. Of course, important is also the signal to noise (SNR), power bandwidth, etc. In my experience, one great benefit when aiming for perfection is that you end up discovering new methodologies and topologies, that aside from contributing to the amp technology, they can lead to an increased overall quality (not just THD).
Suggested specs (the more, the better):
- THD % at both 1Khz and 20Khz at full output and load and at a given input voltage,
- Power bandwidth range in khz at full load,
- Bandwidth -3db,
- Max load,
- SNR (signal to noise ratio) in db (can be easily calculated from rms output noise and peak output signal): 20*log10(VPEAK/sqrt(2)/rmsnoise) -even Google can calculate that)
measured at 0 input resistance and at an average real-life value.
- Amplifier's input and output impedance (when applicable),
- Phase, Group Delay graphs for the audio spectrum,
- Gain flatness for the full audio spectrum in db (16hz to 20Khz),
- Damping factor,
- Power consumption, efficiency, Class,
- Operating temperature range (for the claimed specs),
- Other specs, pros, cons.
Also I'd suggest that all kinds of amplifiers should be welcome for this general specs-reference, despite the amp's application eg for headphone amps too, if there is no objection from the forum's admins, as the common factor here is comparison of output sound quality. For example, while I'm designing a headphone amp, I'm very interested in all kinds of amps, to find out what has/can be achieved in terms of output sound quality.
So, is there interest about a one-thread reference for-all amp specs?
If so, how about posting the specs you are proud of, either as a builder or designer, virtual, or physical, finished or in development?
A searchable database of DiyAudio amplifier projects. I like this suggestion. Very much.
I think designers and builders should NOT be afraid of comparison.
Comparisons make us all work harder for something better.
Posting here your project's specs will increase exposure, as all projects cannot be listed in the first page, especially the older ones, unless they are all mentioned in a single thread. For the history alone, it should be worth to include them here. Personally, I don't have a clue how many and what projects have been suggested in this forum.
If all users could access all projects in a single thread (specs + brief description + schematic/photo + link), many more would decide to build your projects even with less than "perfect" specs (one might prefer project A over project B due to wattage, cost, simplicity for example).
It would be irrelevant to me as most amps sound the same to me.
I have designed class A, AB and D amplifiers and cant tell between them.
I miss the gain flatness from 16 Hz to 20 kHz on your list.
Like I wrote to you in another thread, worrying about spec points sounds more like work than like hobby to me.
My ears cut off at about 9KHz now at 60 years old.
They have been abused for about 45 years as a rock guitarist and a mobile disco DJ.
I can just about hear cross over distortion when I set my amps up.
I rely on the scope to get rid of it.
And I would like to see damping factor in the spec list.
Perfection of course requires hard work, but in this case, the more perfect, the more creative it requires from you to be, which is a fun process and a rewarding end result ;)
To give you an example of how blindly optimizing spec points sometimes messes up the real-life performance:
When you design a DAC, the signal to noise ratio and dynamic range are the key specification items. The higher the numbers, the better they sell. Anything over 80 dB(A) is dead quiet under normal domestic listening conditions, but still, 130 dB(A) sells better than 129 dB(A).
As these specs are always measured with sine waves, this tempts designers to design their DACs such that they are driven as hard as possible with a full-scale sine wave. Hence, they have no headroom at all for interpolation filter overshoot and clip when you use them to play music rather than sine waves. If you back off by a few decibels from the clipping limit, practically all music will be reproduced perfectly, but the numbers measured with full-scale sine waves will get worse by the same number of decibels.
Admittedly, I don't know any such examples for amplifiers.
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