At least this way is more fun - but really nobody is gaining any insight from these kinds of questions & responses.
I seem to recall posting on this thread earlier, but if I didn’t: defining what is meant by ’best’ is a good place to start. There are a lot of aspects about a preamp- gain, noise, distortion, number of inputs, balanced or single-ended, what kind of coupling caps are used and so on.
I’m of the opinion that tube preamps sound better on account of the fact that tubes tend to not sound as bright. So the ’best’ preamp might be a tube preamp. Certainly bandwidth is important, to this end 200KHz is a good minimum on the high side so as to insure no phase shift components in the audio band. On the low side, 2Hz is the maximum low frequency, on the same account, so the preamp can play 20Hz without phase shift.
The preamp should be able to play at levels considerably higher than any amplifier will ever ask of it. This is just common sense, as this practice minimizes distortion and permits the preamp to convey the dynamic properties of the recording itself.
I think that balanced operation is a good idea, since if balanced lines are set up properly, they have less sonic footprint in the system, and less opportunity for ground loops (if you don’t get obvious hum and buzz from a ground loop, it might yet be interfering with the background noise). Its helpful in this regard that the balanced circuit support the balanced line standard, also known as AES48, since these benefits accrue directly from that standard! Otherwise you might have a balanced circuit that is still cable-sensitive.
I’ve found that by direct-coupling the output of the preamp, you can bypass colorations caused by the output coupling capacitor or output transformer. This is because any preamp is expected to drive a solid state amp, so if it has an output coupling cap (or a pair of them if its a balanced preamp) they have to be large enough to allow the preamp to play bass while driving that solid state amp. Despite the construction of the coupling cap, the larger the value, the more inductance is in the cap, and the more coloration as a result. By direct-coupling you get around all that- and obviously you can play bass better. But the mids and highs will be more transparent as well.
Volume controls can be built a variety of ways. The best controls have exotic materials for contacts as they are usually a multi-position switch built up from fixed resistors, which are often also exotic in nature. Care must be taken by the designer to prevent the control from interacting with the devices following it (for example a gain stage) due to something called Miller Effect, which can create a high frequency rolloff in the line stage.
Phono cartridges are a balanced source. So it makes sense to operate them in the balanced domain, since the artifact of the tonearm cable can be minimized in that fashion, and that is arguably the most important place to do that if you play vinyl. So the best phono section might be balanced.
Further, it turns out that the inductance of the cartridge and the capacitance of the tonearm cable set up an electrical resonance that can mess with many phono sections, causing ticks and pops that aren’t even on the LP surface, due to overload caused by that resonance (which can be a 30dB peak)! If the designer didn’t have this in mind when designing the phono preamp, you may have to load the input (cartridge loading) to kill the ticks and pops. The loading can cause the cartridge cantilever to be less supple- and this in turn can affect its mechanical resonance in the tonearm, affecting its tracking ability. Obviously its important for the preamp designer to deal with this issue, as it results in better sound from the phono section!
If the preamp is fully differential from input to output, it will have the ability to reject noise common to both of its inputs (inverted and non-inverted) and also the ability to reject noise in its power supplies. I would expect to see an outboard power supply so as to keep power transformers and the like from inducing noise into the preamp section due to proximity.
So if you want the best preamp these are some things to look at.
