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Old 10th April 2010, 07:19 PM   #1
keaster is offline keaster  Canada
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Default Solid State VS. Chip Amp

I've searched all over the forum and couldn't find a answer to my question...
Just like the subject Solid VS. Chip which is better and why? I know that almost every commercial bought amp is solid but why?
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Old 10th April 2010, 07:30 PM   #2
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I think you mean discrete vs. integrated circuit...
And also for amplifier you mean that huge ,spooky metallic thing that sucks lots of current from the mains ?
From another point of view , I think ICs for their convenience,size etc. represent the nearly totality of BF amplifying devices in the world : tvs, radios, cellphones,pcs ...
BF=LF

Last edited by picowallspeaker; 10th April 2010 at 07:32 PM. Reason: traslate
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Old 10th April 2010, 07:42 PM   #3
a.wayne is offline a.wayne  United States
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Chip amp have 2 issue's ...



They come with 2 chips , one chip for the amp and the other for the owner ...... Look out ..
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Old 10th April 2010, 07:43 PM   #4
wahab is offline wahab  Algeria
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Quote:
Originally Posted by keaster View Post
I know that almost every commercial bought amp is solid but why?
Since using chip amps would be more cost effective,
the only reason that remain is that discrete designs
are simply better.
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Old 10th April 2010, 07:50 PM   #5
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Hello

I have TDA7294 and LM3886 chip amps, they sound good but very inferior to a very good discrete amp.

Chip amps need more compensations because they oscillated a lot without it, so this heavy compensations kill the sound.

The circuit of a chip amp are all on a small silicon die, the input and Vas section are too much close to the output section, that's no good and do accentuate the oscillations.

With a discrete amp you can chose a topology who will be easyer to be stable. In the Vas (voltage amplification stage) you have a capacitor between the base and collector of the transistor to stabilise the amp, if you use to big of capacitor value there, you will have a dull sounding amp, but you can reduce a lot the size of this capacitor by using a small value phase lead capacitor between the collector of the Vas transistor and the base of the negative side of the LTP input transistors. Those thing can't be done with a chip amp, you can play arround it but not inside of a chip amp.

Bye

Gaetan

Last edited by gaetan8888; 10th April 2010 at 08:07 PM.
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Old 11th April 2010, 12:05 AM   #6
satoru is offline satoru  United States
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On an IC, the transistors are formed on a single silicon wafer, apparently. It is very difficult (if it is not impossible at all) to optimize all the transistors for where they are used in the circuit. Input stage, VAS, output stage, etc, all have different requirements. With discrete design, you can pick transistors suitable for your design.

Also, all the resistors and capacitors within the IC are formed on silicon, obviously. They pose another challenge for an IC designer. As you guess, the properties of resistors and capacitors are difficult to control on IC, while it's just a design consideration/choice in discrete design. Not to mention the difference in sonics for those components (please, no flame war).

The another issue is the thermal coupling of the all the components on the IC. You don't want your input stage, or VAS thermally coupled to the output stage, for example. But on IC, you have no choice.

Here and there as these factors accumulate, there is no question why a well designed discrete amplifier could be better than the best IC amplifier. Well, there are a lot of ill-designed discrete amplifiers out there (counting mine, too, hehehe), so be careful when you pick a circuit for building your own, though.

Nonetheless, designing/building your own amplifier is always fun and rewarding experience, I believe.

Best regards,
Satoru

Last edited by satoru; 11th April 2010 at 12:18 AM.
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Old 11th April 2010, 03:42 AM   #7
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You might want to look at this thread:
So just how "good" can a chip amp be ?
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Old 11th April 2010, 09:28 AM   #8
AndrewT is offline AndrewT  Scotland
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investigate the halfway house.
National's LME49810/811/830 series are the front end of a chipamp (all the low current parts) with a discrete output stage.
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Old 11th April 2010, 02:06 PM   #9
h_a is offline h_a  Europe
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To add a little salt...

ICs have several advantages: they offer excellently matched transistors (now that do a lot of people here so it must be a good thing ;-)), transistors can be exactly optimized for their task, compensation can be made external or internal and highly optimized (i.e. done correctly). Practically no parasitic inductances/capacitances, modern processes allow extremely fast transistors (high bandwidth). Last, the chips can be produced pretty cheaply.

No reason why it should not be possible to build a high quality discrete circuit as IC.

Problem though, that commercial ICs have a power budget, means power consumption has to stay extremely low which asks for compromises. But that's not a technological limitation in principle.

Still I'm building only discretes ;-)

Have fun, Hannes
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Old 11th April 2010, 06:04 PM   #10
satoru is offline satoru  United States
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You cannot easily change the doping on IC for different transistors... You only can change the size and shape of them.

I found a lot of statements in forums here for having better matched transistors in IC. I thought the matching is usually in range of 5% and better matching is achieved by trimming here and there (please collect me if my understanding is wrong, this is a good chance for me to correct my mistakes, as usual). Of course, thermally coupling discrete transistors (if not they are a single-chip dual type) is a headache. But isn't the thermal gradient formed within IC (from output stage toward input stage) bigger headache??

I read the thread about sumaudioguy's impressive chip-amp (225dB open loop DC gain?? no way). I think this is an extreme example of how far people can push the poor little chip...

In essence, I think the general idea is that: if a chip amp is designed right, they sound good: if a discrete amp is designed/constructed poorly, they don't sound good. Chip amps are more forgiving, while discretes have more freedom in design.

Personally, I find more fun in designing/building discrete amplifiers.

Best regards and have fun!
Satoru
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