[rollo]

  Why ? Are Op amps really a better solution ? Is cost or space the reason or are they better sonically than circuitry ?
 



charles

[NekoAudio]

An op amp is an integrated circuit that provides a very useful function, and is able to perform that function very well for intended uses. They are an extremely good building block for solving lots of problems. Not only from a cost/space stand point, but because they are a complex building block. It's a lot easier to build something, and build it correctly, if what you're putting together is more functional (e.g. high-level programming languages versus assembly).

But of course real op amps are not perfect. So there's a difference between the theory of an ideal op amp and their use in practice. You have to work with what the universe and our technology gives you.

That's my long-winded way of saying it all depends on what you're trying to do. Op amps are still circuitry, just packaged differently.

[richidoo]

IC opamps use huge amounts of negative feedback to achieve their low distortion. This is necessary to achieve extremely low distortion specs despite the tolerances that accumulate inside a complex, mass produced IC chip. That much negative feedback robs the music of openness and life, and some opamps sound worse than others, despite their excellent "performance" specs. Some opamp ICs sound "good" but there is no comparison to the sound of a class A triode with no feedback, even if the triode's distortion is 10,000x higher.

A discreet circuit can be designed to tighter tolerances for inherently low distortion before correction. There are methods of correction other than negative feedback which are just as effective but do not rob the music of life, but these are not found in common opamp ICs.

Belleson Audio demonstrated a prototype discreet opamp at the Charlotte Can Fest in 2010. It sounded really excellent, but I don't know if it had the usual 100dB open loop gain requiring 90-100dB negative feedback. It might have been no/low feedback design. He is quite a clever designer.

[sts9fan]

Who said they are better?  I think it is strictly a cost deal.

[rollo]

  OK its a still circuitry, thanks for that clarification. No techie here, obviously. A discrete circuit is what I was curious to know. It would cost more to design and implement in a product.
  So if one had a choice cost no object it would be discrete design not op amp ? For the Manf. of say a DAC would the cost differential be worth the effort ? For the DIY crowd ?
  Appreciate the learning experience, thanks


charles

[richidoo]

Depends who they are marketing to. Ultra fi gain stages are always discreet. Consumer electronics are all opamps. But there is a gray area in the middle where many excellent sounding products have opamps (like Vista phono pre) and some mediocre hifi products are discreet. Pass B1 is a popular discreet buffer circuit for DIY. But it's single ended, not an opamp, can't do the tricks an opamp can do.

[Steve]

I think it is interesting to note, that from conversations I have had, many if not most, or even all DAC chips use push pull class B in the analog output from the DAC chip. I wish it were class A, but supposively too much current thus heat.

However, if they would increase the size/length for more dissipation capability, they could run class A operation.  But what are the odds?

Hopefully the newest ones are run class A.   

Cheers.

[HAL]

There are ways to make an opamp run higher Class A/B output stage operation.  You need to add a current sink at the output to force the bias up.  There are a few companies that have done this over the years to make an opamp sound better.  Adding a heatsink to the opamp will help with heat dissipation.

[NekoAudio]

  So if one had a choice cost no object it would be discrete design not op amp ? For the Manf. of say a DAC would the cost differential be worth the effort ? For the DIY crowd ?

Different manufacturers design and build DACs with different goals in mind, even within their own product line. So asking if any cost increase would be worth it is kind of a moot point because the final price point and marketing would be set to achieve a profit to match the increase in cost.

A DIY design will be based on whatever resources (time/money/research) that person wants to put in. In my experience, most DIY designers tend to like a challenge and look for more interesting solutions (e.g. discrete component circuits) that might provide better sound quality. Although afterwards it's rare to see actual measurements take place. And what one person subjectively thinks is amazing another might think is mediocre.

Plus, it's always a good idea to remember that sometimes designs and features are based on what markets well or is subjectively pleasing to the ear, rather than what may actually be "better".

(FWIW, I designed the D100 for myself as a cost-no-object DIY project to get what I wanted. I did not plan to sell it.)

[Steve]

There are ways to make an opamp run higher Class A/B output stage operation.  You need to add a current sink at the output to force the bias up.  There are a few companies that have done this over the years to make an opamp sound better.  Adding a heatsink to the opamp will help with heat dissipation.

Are you saying that one can increase the current in the output transistors in the digitial to analog chip itself?

Cheers.

[HAL]

This is adding a current source at the output of an opamp to force it into higher bias Class A/B in the output stage.  This is not for the DAC.   

[Levi]

I find some discrete OPA to sound very nice. They need a good stable voltage to sound their best. An excellent implementation of non OPA circuit will beat a good OPA in my experience.  To each his own.

[SET Man]

  Why ? Are Op amps really a better solution ? Is cost or space the reason or are they better sonically than circuitry ?
 



charles

Hey!

     Yes, it is all about cost and spac saving. Opamp can be stamp out in hundreds on waffer while discreet circuit need to have each resistors, resistor and etc components soldered one by one.

     Anyway,some opamp based stuffs can sound good depnding on chip model and how they are implemented but personally I do preferred to have discreet circuitry. 

Take care,
Buddy 

[NekoAudio]

The inside of an op-amp is the same stuff that you could use in a discrete component design. So, you could reproduce the entire internals of an op-amp using discrete components and more board space but it would questionable to say you've definitely created something better than the op-amp.

[lounge Audio]

The first op-amps were made with tubes. http://www.tayloredge.com/museum/museum/opamp.pdf

Op-amps in the 50's were basically in the exclusive domain of analog computers.

There are some ways to get today’s IC op-amps to sound quite good. Mentioned already here is the use of current sources to bias the op-amp further away from class B to class A operation.

Believe it or not a way to get a more natural sound from an op-amp is to use a slightly squishy power supply. A simple way to do this with the basic 3 terminal regulators is to add a series R of about 2 ohms and then a shunt cap not to large in value like about 10uf to feed the dc power to the op-amp. Be careful this method can cause some cross talk if sharing L and R channels so separate R-C sections should be used for stereo circuits.

The high-speed op-amps with Linear Technologies being the fastest voltage op amps and Analog Devices and Texas Instruments both making serious speed demon current op-amps all sound much more resolving than then the standard bi-polar or jfet op-amps.