Replace OP amps. Completely pointless, or not?

[Deleted member 46664]

Why do op-amps with rail to rail capability exist if that capability is not going to be used.

Don't forget, opamps are not unique to audio. They are used in industrial, medical and aerospace applications as well and the demands there can be a lot higher than with our piddly little music signals.

 

[_thelaughingman]

Don't forget, opamps are not unique to audio. They are used in industrial, medical and aerospace applications as well and the demands there can be a lot higher than with our piddly little music signals.

I work in Medical Diagnostics field and some of the machines designed in early 80's have Op-amps on the boards that provide mechanical movements and current to motors and have yet to see one fail or have to upgrade them.

 

[egellings]

Yup, audio is a small op amp users' group. Sensors & industrial controls, to name a couple, are areas where they are widely used. Op amps are also built into mixed signal chips as well. They're everywhere! Bedawk!

 

[MakeMineVinyl]

Why do op-amps with rail to rail capability exist if that capability is not going to be used.

Every design decision is a tradeoff. You shouldn't have to design expecting idiots who don't know what they are doing to change devices for something else less capable.

On the other hand - if you put sockets into the design, and advertise to people that they can roll their own - you'd better damn well make sure your design is tolerant to typical variations between devices.

Using surface mount TSSOP packages will thwart all that.

 

[Deleted member 46664]

On the other hand - if you put sockets into the design, and advertise to people that they can roll their own - you'd better damn well make sure your design is tolerant to typical variations between devices.

Aiyima and the other "audiophile" brands aren't stupid people... They gave us a unity gain inverter to fool with opamps. In their tube enabled devices the tube is usually a cathode follower, also unity gain. These things are pretty safe to mess with and they play right into the audiophile's delusions about cables, cords and crystals. You should have seen the pileup as people wanted to but $80 discrete opamps into everything after Cheapaudioman did a video showing how to do 'roll opamps'. It was like kids in a school yard when the icecream truck pulled in...

In the end... it's all about selling stuff ...

 

[mansr]

Most audio applications employing op amps never ask for more than maybe 2Vrms from an op amp, so that requirement is easy to meet with an op amp powered on +/-15V rails.

At a preamp output stage, yes. Internally, higher signal levels may well be used.

 

[DanielT]

Don't forget, opamps are not unique to audio. They are used in industrial, medical and aerospace applications as well and the demands there can be a lot higher than with our piddly little music signals.

You already know this, and many others who write in the thread. But for those who read the thread and wonder. Basic regarding OP amps in this video. What they can be used for and how they are constructed:

 

[Deleted member 46664]

At a preamp output stage, yes. Internally, higher signal levels may well be used.

Generally no ... there isn't much advantage to boosting a signal up to 15 or 20 volts just to have to attenuate it at the final outputs.
That would both increase distortion and undermine stability.
About the highest signal levels I've seen, even in pro gear, is about 4 volts which would result from tone controls being turned all the way up.

 

[antcollinet]

Generally no ... there isn't much advantage to boosting a signal up to 15 or 20 volts just to have to attenuate it at the final outputs.
That would both increase distortion and undermine stability.
About the highest signal levels I've seen, even in pro gear, is about 4 volts which would result from tone controls being turned all the way up.

Some pre-amps can output significantly higher voltages than that.

 

[Deleted member 46664]

Some pre-amps can output significantly higher voltages than that.

Sure can ... I've worked on a couple that can produce 10vrms before clipping... but there are standards for connecting this stuff together. It's no fun if Joes Super Pre-Amp clips the inputs on Mike's Mighty Power Amp... so some agreements had to be made

First there is a definition of "Line Level" ... HERE
Next there is the digital "Alignment Level" ... HERE (Generally -18dbfs == Line Level)
There are even standards for output and input impedences... HERE

Pretty much any consumer device operating within standards will output about 800mv peak to peak...
+12db for the tone controls brings that up to about 3 volts peak to peak.

 

[Deleted member 46664]

You already know this, and many others who write in the thread. But for those who read the thread and wonder. Basic regarding OP amps in this video. What they can be used for and how they are constructed:

Thank you for this.... Earlier on I posted the actual schematic for the opamps in the Aiymia A07. Here it is again for clarity...

As we can see it's simply 4 unity gain inverters.

 

[solderdude]

Noise, unity gain or not, BW (decoupling), voltage swing, output currrent limit and input resistance are the most differing aspects of opamps.
In some cases finding a suitable replacement or an opamp that actually improves performance is not that easy to find.
There is always the possiblity performance degrades.
Whether or not all of this is audible remains to be seen.
In all cases it's the components around the opamps (and PCB layout in some cases) that determine the performance.

 

[Deleted member 46664]

Noise, unity gain or not, BW (decoupling), voltage swing and input resistance are the most differing aspects of opamps.
In some cases finding a suitable replacement or an opamp that actually improves performance is not that easy to find.
There is always the possiblity performance degrades.
Whether or not all of this is audible remains to be seen.

I think the thing most people don't really grasp about opamps is that except for exotic applications like sensor monitoring or analog computation, the larger differences between chips are pretty much neutered by feedback and the passive components surrounding them. It isn't so much "designing with opamps" it is more like "taming opamps"... to get the behaviours you need.

Audio applications are not taxing. Most circuits are low gain, low impedance, low voltage, and low frequency devices. Opamps really are a "universal hunk of gain" in almost any audio application.

That's why the change in my A07 surprised me and in the end it turned out to be a faulty socket. Now with that fixed I can flip chips all day long and it still sounds just as sweet as always.

 

[solderdude]

Most people do not realize that for a tonal change to occur the frequency response has to change in the audible band or oscillation or substantial amounts of distortion has to be there (all very measurable).

In case of opamps all of these aspects are determined by the components around the opamp which do not change when opamp swapping.

One never hears of 'transistor' rolling. Only tube rolling and opamp rolling. The reason is that it is simple to do and often the replaced parts simply work. For tubes the differences can be little to huge (depending on the circuit and tube) and folks 'believe' this has to be the case for opamps as well. Plus there are so many 'opamp rolling' threads/articles everywhere with sound descriptions and all.
The same can be said about mains cables too though.

Audio is a funny business with a wonderful opportunity to sell snake-oil and most really want to (and do) 'believe' everything makes a difference.
There are always people looking for financial gain from this and willing subjects to enable them with their wallets.

 

[DanielT]

There seems to be a lot of thinking about OP amps and their place (performance) in HiFi:

Hello,

I'm looking for some technical information on active crossover internals. Common belief is that op amps degrade the signal and that puts them out of Hifi application.

Active crossover types

Hello, I'm looking for some technical information on active crossover internals. Common belief is that op amps degrade the signal and that puts them out of Hifi application. So far I was told that signal processing is best done in digital domain. I have managed, using mini dsp Nano Digi, to...

audiosciencereview.com

 

[KMO]

Opamps really are a "universal hunk of gain" in almost any audio application.

Which is exactly why they're targetted as a "tweak". There are a range of op-amps available for a wide range of applications, but pretty much all of them will work fine in an audio amplifier gain/buffer stage. And most of them are still available in a standard DIP package. So you can swap them in and out without actually breaking anything, and then audiophiles can try to find the best flavour.

Easy-to-swap and all basically the same - the ideal audiophile subject of debate!

(Basically restating what solderdude has already said, but I had already written this as a draft...)

 

[mansr]

Generally no ... there isn't much advantage to boosting a signal up to 15 or 20 volts just to have to attenuate it at the final outputs.
That would both increase distortion and undermine stability.
About the highest signal levels I've seen, even in pro gear, is about 4 volts which would result from tone controls being turned all the way up.

Higher signal level can be beneficial for SNR.

 

[Deleted member 46664]

Higher signal level can be beneficial for SNR.

Okay ... you are not wrong.
But, there is no need to cling to a failed argument. Audio gear does not use high signal levels or even high gain circuitry. Most pre-amps are unity gain input to output. Most power amps are about 26db gain but don't use op-amps to get it.
Technically you are correct... but the things you're talking about aren't happening in audio devices.

 

[mansr]

Okay ... you are not wrong.
But, there is no need to cling to a failed argument. Audio gear does not use high signal levels or even high gain circuitry. Most pre-amps are unity gain input to output. Most power amps are about 26db gain but don't use op-amps to get it.
Technically you are correct... but the things you're talking about aren't happening in audio devices.

Now who's generalising?

A battery powered device may well be using a single 5 V rail. Some opamps, e.g. OPA1612, are perfectly happy with that while some others either will not work at all or have severely limited output swing.

 

[mhardy6647]

I find it interesting that something's reawakened the op-amp Kraken recently Maybe the phase of the moon...?
cf.

Why don't we talk about Op Amps more?

I recently decided to do a recap and Op Amp swap on a Nikko Beta 30 Pre-amp I've had collecting dust for a few years. A thread on AK suggested that upgrading the Op Amp would breathe some life into this fairly boring sounding pre. I ordered up some DIP8 sockets and OPA2132's and yeah, big...

audiokarma.org

Indeed... I wonder how many of today's (or yesterday's) op-amp rollers know that it's perfectly possible to build an op amp that is fully discrete... or even an op-amp that uses -- gasp! -- vacuum tubes instead of the reviled silicon-based life forms that the aliens told us to call transistors when they gave them to us at Area 51.