Why are amplifiers so different inside?

[googleborg]

i've been eyeballing the insides of hifi stuff since i was a child, anyhow...amplifiers seem so different inside, though they all seem to have a similar 'topology' (layout?).  Do these designs represent different ideologies/end sounds or are they just being different for the sake of it with end sound being the result of simple component changes?  The rega is by far the most expensive RRP yet is the simplest looking, whilst the NAD is the least expensive RRP wise iirc, yet seems the best internally to my untrained eyeball...sounds great too.  what design = what sound, is there a 'rule book' of sorts?
 
Cambridge A500 (65w) with phono modules fitted (my pic) Cambridge audio have a serious issue with silkscreen spam! has been recapped iirc.  would love to know what's under the copper box things..probably a 20p JRC opamp

Rega Brio (49w) (2000 version i think, not a brio3) not my pic...looks so beautifully simple!  my local Rega Dealer died sadly, not auditioned one, would like to hear it.

Nad C300 (25w), not my pic, but i own one. rawrr copper bus-bars, rawrr class A modules, rawrrr shielded toroidal, rawrrr all discrete...outside looks crap like all NADs

 

[Uncle Erik]

No, there are lots of different ways to design an amp. Some work on entirely different theories and use components that would not work in other designs. Each design has benefits and drawbacks, some are designed to work for certain applications, then there are cost limitations, and hundreds of other considerations.

One notable oddball is the First Watt F1. The F1 actually amplifies current, while most amps amplify voltage. The F1 works with some speakers, but won't with others.

Unfortunately, neatness of layout often gets confused with quality. People buy amps mostly on appearance. A clean build is often mistaken for a good amp. However, it's possible to take a lousy circuit and make it look neat in the box. You can also build a point-to-point amp with components soldered to tube sockets, etc. without an "ordered" appearance. That freaks a lot of people out, but that method of construction not only holds up, it can benefit the amp because the signal paths are made as short as possible.

There are many other considerations, as well, but don't judge an amp by its looks. You have to know if the circuit is good as well as if it's built right. And it's entirely possible to have a disordered-looking amp with excellent construction and performance.

 

[googleborg]

hmm i think a sony cdp i have does that amplifying current thing, a CDP-761, just read a 6moons on the first watt and it's full of innuendo, oh 6moons ...
 
anyhow thanks for the reply, as long as the amplifier designs are different for a reason other than differences sake/economics

 

[MrGreen]

Quote:

However, it's possible to take a lousy circuit and make it look neat in the box.

Hello, Grado!

 

[rohan575]

hey,
Amps can be either SS (solid state) Tube or hybrid (both) with each type a huge number of circuits are possible howerer there is a BASE circuit such as non-inverting amplifier or a biased class A mosfet driver ect... 

 

[InnerSpace]

Quote:

You can also build a point-to-point amp with components soldered to tube sockets, etc. without an "ordered" appearance. That freaks a lot of people out, but that method of construction not only holds up, it can benefit the amp because the signal paths are made as short as possible.
 

Why do short signal paths matter?  In an adjacent thread, you claim lengthy signal paths could be made out of brined and soldered paperclips and coat hangers with no audible consequence.

 

[rohan575]

 
 
Quote:

 

Why do short signal paths matter?  In an adjacent thread, you claim lengthy signal paths could be made out of brined and soldered paperclips and coat hangers with no audible consequence.

 
 
Signal paths are like antenna's, circuits own noise and induced noise from surroundings can also effect the sound quality by getting into the signal path. 

 

[InnerSpace]

>>Signal paths are like antenna's, ... induced noise from surroundings can also effect the sound quality by getting into the signal path.<<
 
Does that not apply to interconnects too?

 

[rohan575]

Yes however its the length that has greater effect not width.

 

[Driftwood]

Plus interconnects may be shielded, which can reduce the amount of noise that is picked up.

 

[jcx]

conductive braid/foil flexible shielding is only effective a intercepting electric fields and cutting capacitive coupling
 
the more common problem inside a audio power amplifier box is magnetic field coupling - it takes inches thickness of good electrical conductor to attenuate mains frequency magnetic fields
 
wire routing - physical separation from magnetic field radiating parts/wiring, geometrically symmetric signal+ref cabling that reduces differential magnetic couping are usually more valuable techniques
 
it also useful to reduce magnetic field radiation in the high current and ps parts by parts selection, placement and low loop area wiring
 
magnetic shielding requires magnetic material - air space/physical separation is the cheapest "magnetic insulator" - iron, low carbon steel are not the "best" magnetic "conductors" performance wise but still so cheap you can just use lots, combine air space and iron boxes and I've never needed exotic Mu metal foil even designing strain gage amplifiers with gain up to 8000