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100W+ solid-state amps known for beautiful mids

Quad 909 back in the day had a reputation for the best mids running up to $5000. I've used it in the past and I would definitely say that the mids were the highlight on that amp. It wasn't overly coloured, a hint of warmth, but it had a purity and sweetness to its mids. Unfortunately, mostly everything else was okay at best, kind of rolled off at both ends and congested stage-wise.

I'm looking for that same purity and sweetness without sacrificing the rest of the sonic traits. What have been your guys' contenders for 100W+ solid state power amps with the best mids?
128x128hedonism

Showing 2 responses by atmasphere

atmasphere's avatar
atmasphere
11,632 posts
 
The best part though? The Quad 405-2 cost me $400. I've generally had in my mind that price correlated with quality (though not ironclad), but this recent pick up is seriously challenging my beliefs.
High end audio isn't about price, its about intention. Since that amp is ticking the boxes for you, if I were you I'd be looking into (if its older than 25 years) making sure that the filter capacitors in the power supply are good so that the amp remains reliable.
atmasphere's avatar
atmasphere
11,632 posts
 
@hedonism  What you are looking for is an amp with the right distortion signature. The warmth of the Pass is caused by a 2nd harmonic for example- similar to a lot of tube amps. If you talk to Nelson you'll find he's very aware of how the distortion signature affects the sound of an amp.

If you want solid state you're up against a real problem. Here's the engineering difficulty:
When you apply feedback to an amplifier circuit it will make distortion of its own while suppressing distortion in the amp. The added distortion is audible as harshness as brightness since its all higher ordered harmonics which the ear interprets in that way since it converts all forms of distortion into a tonality of some sort.


Now tube amps actually have more higher ordered harmonic distortion, but it is masked because tube amps also make a significant 2nd and 3rd harmonic which masks the presence of the higher orders. Getting a solid state amp to do this is a bit of a trick with traditional amplifier design.

However it turns out that class D offers a means around this- it turns out that if you used the right encoding scheme, that and the dead time used in the class D amp tend to result in lower ordered harmonics. A lot depends on the design! But if its done right, the result will be an amp with a distortion signature that masks the higher ordered harmonics, allowing for a very smooth midrange and highs with overall lower distortion than you can get out of a tube amp. IMO IME you're better off looking for such an amp- one example is the AGD Audion, which does make over 100 watts into 8 ohms so it should be enough power.
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