[robzy]

Hey, To be honest, i dont 100% know what im talking about, but i do know that an opamp is basically a collection of transistors, and that before opamps were around amplifiers were based on transistors.

So I was just thinking, is there any benifits to be gained by using full size transistors and everything instead of using an opamp?

 

[rickcr42]

on paper no but in actual use yes.A discrete opamp will sound better and can be optised for the intended use and you can choose the topology-

all jfet class-A,tube/mosfet,discrete transistor,mosfet,jfet/bipolar,all tube

at each stage you can choose the operating points from class-B to A/B to A or anything in between (class-A up to a pint then a/b),cascodes.parallel devices....

But this means more work in DIY and the single chip all in one solution works best for most hobby buiders-no real math just buid it

 

[rickcr42]

couple of discrete opamp examples :

http://www.passdiy.com/pdf/diyopamp.pdf

http://www.borbelyaudio.com/adobe/hybrid.pdf

http://www.forsselltech.com/schemati...et%20Opamp.PDF

http://www.forsselltech.com/Great%20River%20Opamp2.pdf

 

[The Speaker Guy]

On an IC level, the parasitic capacitance and inductance is reduced. The devices are very close to thermal equilibrium, and all devices within a single die match each other quite well.

Discrete designs allow more current in each stage as the power dissipation is shared across many packages. Discrete designs allow the mix and match of various processes.

 

[rickcr42]

like I said,on paper the single chip is superior.But since this is audio and far more a subjective thing,the discrete version more often sounds better if properly implemented.

but most here would have difficulty designing or using a discrete design unless the boards were available and the partds pre-selected and identified.Even the above examples are no easy thing to actually build unless you know where you are going with it and what the end use is.

IC opamps are essential though if you want portability and compact size.The "package" details are already worked out and optimised to a certain power vs output point.

Could portable amps be discrete designs ?
Yes.but they would not be an optimal use.In order to do it right you want voltages and currents above the norms used in battery operated gear and any discrete design would be a comprimise being mostly at best low level class A sliding towards A/B and finally Full class B plus the DC offsets would be considerable without large coupling capacitors or DC servoes.
You could match every part to cancel any DC componant and then add a Dc balance pot to get the last bit of DC output gone but as parts age they drift and this would be a constant adjustment.

But when it comes to home use and personal preference i can honestly say there is not one single I.C. opamp in the audio signal path unless the TV feed is counted,and the only monolithic i have in the path is an LH0033 unity gain buffer and that has only four parts-two jfets and two transistors internally so in essence is as close to discrete as it gets

 

[robzy]

thanks rick & TSG, it all makes sense.

I guess i will be sticking with opamps then

 

[Garbz]

That said Gilmore's all discrete desgins blow any IC out of the water! (personal opinion)

 

[TrevorNetwork]

Agreed. The Dynahi is amazing

 

[ppl]

Quote:

Originally Posted by Garbz That said Gilmore's all discrete desgins blow any IC out of the water! (personal opinion)

I would be carfull about sutch general statements like that. The Difference between any two High quality amps is real small and after having listened to Both OpAmp and discrete component Amps side by side and both good quality Amps showed slight differences and once you move to a discrete output stage from a Monolithic IC 90% of any sound improvement will happen just because the output transistors in the Discrete component output stage are Larger and handel more current and have a Hfe that holds up well at moderate currents while the small Die and High Bandwidth of the Output transistors used in most IC op amps and IC Monolithic Buffers are low current devices that have an Hfe falling rather quickly at modest output currents. More over when you also consider that most Monolithic output stages are Biased way low most often Class B its easy to see the limitations of an IC output stage.

Now the voltage gain stage is quite a different matter Perfectly matched input transistors and as The Speaker guy ststed a constant operating tempature across the entire circuit that will remain so if the Output stage driving the load is a separate device housed in a different Package from the Op Amp. Also constant current source loading of the opamps output stage asures that small current changes resulting from the constantly changing input currents of the output stage with the Load are not going to add to great Die tempature changes of the Driving Op Amp. The DC precision of Monolithic opamps are soo good that DC blocking capacitors and servos are not required to maintain low DC offset voltages.

In conclosion Audio just like anything elce in life has no absolutes and every thing is a compromise.

My 2C worth

 

[Sovkiller]

I have some questions here:
Why my PPA sound so good, and why the Blockhead sound so good, or the Meier Prehead, they are not discrete designs at all....I have heard a few discrete designs, that will not hold a candle against them.....and considered very good designs....parts in an IC are computer trimmed and matched, I strongly doubt that you could do that with any multimeter by hand......the topology? Well what if the topology offered by a commercial chip, is the one you want? They are proved to work for years, and years, and not choosen at random, don't forget that....

 

[Earwax]

But you replaced your IC buffers in the PPA with the discrete diamond buffers, right?

So, that seems to support ppl's point about using larger transistors instead of chips for higher current parts.

Is it because discrete parts are inherently better, or just because the market for buffer ICs for audio is so small that little developement effort is going that way?

 

[Sovkiller]

Quote:

Originally Posted by Earwax But you replaced your IC buffers in the PPA with the discrete diamond buffers, right? So, that seems to support ppl's point about using larger transistors for higher current parts.

And this improved the sound, clearing it up a little bit, but the nature remained the same.......OTOH, I will not replace OPAmps, until I hear one better made by transistors, or tubes, to the date, I have not heard any.......
But if you read again the tittle of the thread "OPAmps Vs. transistors" and looking at my amp, you will notice now that I replaced the "buffers" not OPAmps (the buffer is an impedance matching device)...period, not the nature or sound of the amp itself, if tomorrow I find one Buffer better then the Elantec, I will not hessitate to go back to ICs again.....

 

[rickcr42]

any design method using either I.C. opamps or discretes well engineered will beat a design using the same or opposing design done poorly.

you can find great examples of all methods and get superior sound but in my opinion a great discrete optimised to all class A will beat any monolithic chip design.i base this on one factor mainly-

with the I.C. you only have control of what surrounds the device and any topology decisions are pre-made for the designer according to what the engineer who designed the chip was after.

but someone talented in discretes and knows the what and the why will be able to optimise each and every stage of the opamp to get the end result he desireswith no comprimisee due to being locked in to what is on the chip

Just my opinion and you can decide for yourself what you prefer,what DIY audio is all about-choices

 

[Sovkiller]

Quote:

Originally Posted by rickcr42 any design method using either I.C. opamps or discretes well engineered will beat a design using the same or opposing design done poorly. you can find great examples of all methods and get superior sound but in my opinion a great discrete optimised to all class A will beat any monolithic chip design.i base this on one factor mainly- with the I.C. you only have control of what surrounds the device and any topology decisions are pre-made for the designer according to what the engineer who designed the chip was after. but someone talented in discretes and knows the what and the why will be able to optimise each and every stage of the opamp to get the end result he desireswith no comprimisee due to being locked in to what is on the chip Just my opinion and you can decide for yourself what you prefer,what DIY audio is all about-choices

I agree, but what about if what is inside the chip is the optimal solution for the kind of application you are looking at.....There are chips very simple BTW, OTOH discrete designs have some other problems due implementation, soldering joints, traces close to noise sources, different temperatures inside the case, differences in the tolerance of the parts, etc.....

What I was trying to say is that it is not an absolute truth, you can get any, and sound good, they won't sound good just becasue they are made by IC, or transistors, or tubes......you can get a good sound from any method, if it is done properly.....

 

[bpribadi]

Quote:

Originally Posted by rickcr42 ...LH0033 unity gain buffer and that has only four parts-two jfets and two transistors internally so in essence is as close to discrete as it gets

Where did you get those information? Couldn't see it on the datasheet. Thanks!