Explain difference between OP-AMPS and discrete tube gain stage?

[jrlouie]

I'm not even sure if I asked my question correctly in the subject of this thread. But it seems like I've heard notations comparing op-amps versus tube components that don't use op-amps.
Could anyone give me a run down at a high-level the difference and/or advantages to one setup versus the other? Or if you have a link that would do so, that's fine also.
I like what tubes bring to music and I'm just trying to learn more.

Thanks in advance for any feedback.

[GV#27]

Basically an opamp is gain stage that can be configured in many ways and can be made up of tubes or transistors.By far the most commonly used op-amps in audio electronics is in the form of the 8 pin integrated circuit like this. http://focus.ti.com/lit/ds/symlink/opa2604.pdf

[jrlouie]

I'm curious why some manufacturers purposefully don't use opamps. For example, the Jolida (http://www.jolida.com/catalogue/models/jd100a.shtml) (which I'm very anxious to receive in the mail) :) Note that their very first bullet states..."Unit does not utilize op-amps".
Then that's what sparks my curiousity about the two different approaches and their differences.

[disneyjoe7]

Tubes give a warmer sound then Solid State (op-amp) can. It's not to say all SS amps sound bad it's more of the design of the amp and components then anything.

[jrlouie]

Ah, I didn't realize op-amps were solid state. There we go.

For some reason or another I had the impression tube components had op-amps. Maybe there are some components that are "tube" components, but also have op-amps in them (kind of a mixed setup).

[GV#27]

Most inexpensive and even some expensive electronics including CD and DVD players are loaded with cheap noisy opamps in their gain stages.Manufacturers do this to keep the price of producing the product as low as possible without regards to sound quality.Their are some bad sounding opamps and thats why higher end companies don't use them.On the other hand their are some really hi performance (and more costly)opamps available that if used properly by a skilled designer can give excellent sounding results.For instance Mark Levinson uses the ones I linked to in post #2 in their mega buck preamps.

btw.Congrats that Jolida looks like a honey of a cd player.

[anonymouse]

Op-Amps do not technically need to be solid state. Op Amp just refers to a circuit configuration with a certain topology and properties. An op-amp could be made out of discrete transistors or tubes, but in practice doing so would not be economically attractive (at least with tubes). Op-amps are very easy to mass produce as solid state integrated circuits, so the term has come to be synonomous with this configuration.

[disneyjoe7]

Yes an Op-amp can be made from Transistors but when did a Transistor not be classified as Solid State?

[GV#27]

An opamp can be made up of discrete transistors ,tubes or dozens of transistors in the form of IC.What makes it an opamp is it has a +input and a -input and an output.The pos and inverted inputs allow it to be used in different ways.

[disneyjoe7]

Ok we are talking about op-amp as a circuit design. And I was talking about op-amp as chip thing.

[schwarcw]

An opamp is a small chip that as others have stated take the place of a number of other electronic components such as resistors. The enable the manufacturer to save some money and circuit board space. Some are good, some are not so good. The Jolida is a very good CDP that doesn't use them. There are other very nice high end machines that do use opamps.

Check out the DIYaudio forum. There are people over there rolling opamps like tubes in their CDPs. As you would expect, there is a lot of debate as to which ones are better in various applications. The BB OPA2604 is an old, but still widely used opamp, it costs about $2. Others are using the OPA2134, also cost about $2 and is very good. For the past couple of years a lot of folks have proclaimed the OPA627 as the best sounding. Others have claimed the 627 has an "acquired" taste. Meaning it sounds different, maybe not better. A lot of the mod companies like Underwood HiFi, Modright, Reference Audio Mods and others proclaim the high value added by changing out the 2604's or 2134's with 2 OPA627. The 627 cost about $27, so you need $54 for each dual opamp replaced.

The talk of "opamp tweaktown" is now the National Semiconductor LM4562. These cost about $5 and people have going wild over these. No one has these in stock yet but there are many sample out there that have found use in the DIY community and everyone is a buzz talking about the dynamics, smooth detail blah, blah, blah!!!

I've got mine on backorder;) :D

[disneyjoe7]

With all this swapping going on I think they changed out to a socket for that chip swapping.

[schwarcw]

With all this swapping going on I think they changed out to a socket for that chip swapping.

Yes! It's called a "brown dog" adaptor. Check it out HERE (http://cimarrontechnology.com/index.asp?PageAction=VIEWPROD&ProdID=24)

[GV#27]

Don't forget the OPA2107 at $11 a piece. Because of the price/performance ratio I use OPA 2134's,2604's and PMI's OP275 in my projects.I would like to try the 627 some time.

[jrlouie]

I'm starting to catch the drift. Thanks for the info!

[mlhm5]

All you ever needed to know and more. Start with the second one.

http://sound.westhost.com/articles.htm

http://www.tangentsoft.net/audio/

[reeltrouble1]

Let me be very clear about this, integrated circuits------PHOOEY. Yes I suppose 10 buck opamp trumps a 1.00 one but still not something I care much for anymore, but if it floats your boat, Rock On.

RT1

[heiney9]

OP amps are integrated circuits (silicon). They have many parts (which would normally be discrete components) in one small chip-set (block of silicon). While minaturization might be desireable in many applications; it's not a good idea in audio electronics that are amplifing a signal. Yes, there are cheap op-amps and there are expensive op-amps, but none IMO are anywhere near as good as a well designed discrete circuits with top notch parts. Is it more expensive to go discrete? You bet your ass, but the advantages far outweigh the costs.

Op-amps have there place in electronics but should never be used in the signal path!

H9

[disneyjoe7]

Let me be very clear about this, integrated circuits------PHOOEY. Yes I suppose 10 buck opamp trumps a 1.00 one but still not something I care much for anymore, but if it floats your boat, Rock On.

RT1

Don't worry Ted I wasn't about to break out my Soldering iron.

[Early B.]

Op-amps have there place in electronics but should never be used in the signal path!

OK, but from a practical perspective, where can we find "affordable" (i.e., <$1K) CD players, DVD players, receivers, SS amps, etc., without op-amps?

[jrlouie]

Being novice to op-amps, I only know of one. The Jolida CDP (JD 100A) (http://www.jolida.com/catalogue/models/jd100a.shtml) does not have op-amps and retails new under $1,000.

[heiney9]

OK, but from a practical perspective, where can we find "affordable" (i.e., <$1K) CD players, DVD players, receivers, SS amps, etc., without op-amps?

Seeing as my current cdp is 10 years old as well as my DAC I can't help you there. My amp and pre are 20 years old. None of this equipment to the best of my knowlegde employs op-amps in the signal path.

Op-amps have become a necessary evil in audio for their cost effectiveness as well as space savings and next to no heat output comparatively to discrete circuits and in many instances just make plain good sense. It's a tough feat to try and purchase equipment that doesn't employ op-amps in the signal path. I'm sure I'll be asking myself the same ?'s when I need to replace my current equipment.........I'm not looking forward to it.

You just have to look a the design of a certain piece of equipment and then understand what you are gaining and losing in that design and then decide if the compromise is worth it in the overall big picture.

Again some will care that there are op-amps some won't give a rat's a$$.

H9

[billbillw]

Sometimes opamps are in there, even when you think they are not.
I recently picked up a B&K Pro10 preamp.
The literature gives this description:

"Thank you for selecting B&K Components, Ltd.’s PRO10 preamplifier. The PRO10 is designed for the discriminating audiophile. The PRO10 is a DC coupled preamplifier that has been designed using all discrete circuit topology with a switchable head amp on the phono stage. Gold-plated premium connectors have also been utilized to minimize degradation in the signal path. The PRO10 has an external power supply that should be connected to an unswitched AC source. In order to obtain maximum performance from this unit, Please read these instructions very carefully."

I opened it up and had a look. Low and behold, I found 4 opamps on the board. Albiet, they were good ones, and they are mounted in sockets for easy replacement (haven't yet checked to see what upgrades are available if any).

When I looked closer in the literature, there was a line that followed the above description:
Also:
Direct output capability
All discrete predriver circuitry
Premium gold-plated connectors
Separate source and record selectors
Balanced outputs standard

So, it can be deceiving. The preamp sounds damn fine to me, regardless of the opamps. They have mostly gotten a bad rep from their overuse and cheap implementation.

EDIT: I should have mentioned, by looking at the board, I believe that two of the opamps are used for the MC phono gain, and the other two are used in the linestage, only in active mode. So, I should be opamp free when in passive mode, with a MM cart.

[GV#27]

Big improvements have been made in IC Opamps the last few years in the areas such as lower noise and distortion ,faster slew rates ,wider bandwidths etc.The newer hi performance opamps are actually light years ahead of the ones produced in the 70's and 80's and in the hands of a skilled engineer can be made to sound as good as discrete circuits.For instance some of the DIY designs by noted Opamp guru Walt Jung sound marvelous.Even Mark Levinsons ultra expensive preamps use them in the signal path.So yes while the cheap Opamps littering the insides of inexpensive components made in the Far East can sound pretty nasty, the better ones implimented properly with good power supplies etc,can sound very good indeed.