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Why so much TL072 ?
MUFF WIGGLER Forum Index -> Music Tech DIY Goto page 1, 2, 3  Next [all]
Author Why so much TL072 ?
JediDJ
I noticed that some big DIY projects, you name it, still engineering their modules with heavy TL072 usage.
This is shitty outdated opamp that's so lame and frustrating at specs.
And it costs not that cheap at Mouser.
Years go by but for some reason this awful IC is still seen in major schematics.

Economy or habit ?
Or "vintage" IC sound ?? ))
MapacheRaper
Cause its cheap as chips (outside the mouser multiverse) and sounds fantastic in a helluva proven designs to date? Dead Banana

Just for curiosity, which ones are your preferred ones?
sduck
Because it works perfectly for a large number of applications in the modular world?
JediDJ
In audio signal path it can do bad things.
Very limited ability to drive a load.
Latching due to input overload or power rails proximity.
Sure it depends on a source impedance.
But overall I don't see a point of using one these days.

For audio usage even old 5532 is miles better, quieter.


Outside of a Mouser world ?
Where ?
Asia is all over fakes.
That are only 0.3V-3V uSec vs 13V stated in a datasheet.
I don't think there is another trusted source to buy ICs these days except major like Mouser or Digikey.
Other cheap places are like Russian Roulette.
Especially Tayda and Aliexpress (most pirated one).
aabbcc
JediDJ wrote:
In audio signal path it can do bad things.
Very limited ability to drive a load.
Latching due to input overload or power rails proximity.
Sure it depends on a source impedance.
But overall I don't see a point of using one these days.

For audio usage even old 5532 is miles better, quieter.


Outside of a Mouser world ?
Where ?
Asia is all over fakes.
That are only 0.3V-3V uSec vs 13V stated in a datasheet.
I don't think there is another trusted source to buy ICs these days except major like Mouser or Digikey.
Other cheap places are like Russian Roulette.
Especially Tayda and Aliexpress (most pirated one).


Arrrow for one, almost all the IC's I usually need are like 30-60% cheaper at arrow smile
Luap
27 to go? meh
Jaytee
I mean, TL072 is hardly the crappiest, most obsolete part sDIYers use. wink
JohnLRice
Newark maybe? hmmm.....

https://www.newark.com/texas-instruments/tl072cp/op-amp-3mhz-13v-us-di p-8/dp/60K6988

Quantity/Price each
1+$0.80
10+$0.67
100+$0.432
500+$0.389
1000+$0.346
2500+$0.313
10000+$0.281
arthurdent
Luap wrote:
27 to go? meh


thumbs up thumbs up
fuzzbass
JediDJ wrote:
In audio signal path it can do bad things.
Very limited ability to drive a load.
Latching due to input overload or power rails proximity.
Sure it depends on a source impedance.
But overall I don't see a point of using one these days.

For audio usage even old 5532 is miles better, quieter.


My impression after five years of building is that TL072 is widely available, inexpensive, and adequate. They do seem to dissipate some heat, so scaling up designs with lots of op amps one should look for improved efficiency. Most of us are building modules with only a few op amps each.

Can you reference a DIY circuit that might be improved by replacing the TL072?

I have built a bunch of TTSH with the even worse on paper LM301. I have done testing with better, audio marketed chips such as Burr Brown, and some AD chips that were near to Burr Brown specs. My observations was that upgraded chips made no difference in almost all cases, but in one case changing LM301 to TL071 improved the circuit (LAG), and in another case the improved chips made things worse (triangle shaper).
JediDJ
Luap and Arthurdent.
Do you think Wiggler is so cool tramplin for sales ???
If I wanna sale I most preferably go to ebay or reverb.
Don't you think ?

So you can put your sarcasm in some other place seriously, i just don't get it
JediDJ
fuzzbass wrote:


Can you reference a DIY circuit that might be improved by replacing the TL072?



I'm yet not a specialist in modular synth DIY.
But had an experience on reworking mixing consoles.
And the difference after changing 072 to 5532 or BurrBrown (with some resistor correction) was always night and day.

So I assume in Eurorack world changing 072 can also put out the muddiness and reduce noise.
tobb
JediDJ wrote:
fuzzbass wrote:


Can you reference a DIY circuit that might be improved by replacing the TL072?



I'm yet not a specialist in modular synth DIY.
But had an experience on reworking mixing consoles.
And the difference after changing 072 to 5532 or BurrBrown (with some resistor correction) was always night and day.

So I assume in Eurorack world changing 072 can also put out the muddiness and reduce noise.


By the whole AMsynths range he uses BB all over the places.

Or buy the whole Cwejman range,its all over That chips in there..
UltraViolet
The real answer to your question is because generating sounds is not the same as applications like mixers and pro audio equipment where distortion is a bad thing. The noise and non-linear behavior is a part of the sound and can be a good thing in some cases and isn't a big problem in the rest.
arthurdent
JediDJ wrote:
Luap and Arthurdent.
Do you think Wiggler is so cool tramplin for sales ???
If I wanna sale I most preferably go to ebay or reverb.
Don't you think ?

So you can put your sarcasm in some other place seriously, i just don't get it


OUCH! I guess we touched a soft spot. So it's not to get count up for B/S/T, he's just trolling. Must be a slow day over at Gearslutz...
NV
JediDJ wrote:
fuzzbass wrote:


Can you reference a DIY circuit that might be improved by replacing the TL072?



I'm yet not a specialist in modular synth DIY.
But had an experience on reworking mixing consoles.
And the difference after changing 072 to 5532 or BurrBrown (with some resistor correction) was always night and day.

So I assume in Eurorack world changing 072 can also put out the muddiness and reduce noise.


Op amps have an enormous variety of uses, and audio amplification is only a subset. An op amp that is bringing microphone levels up to line levels carries a very different set of design concerns than an op amp serving as a buffer for control voltages.

Many if not the majority of times you see op amps in synth circuits they are not handling audio signals, but instead serving any number of other functions. Upgrading every $0.20 TL072 in a circuit to $5 Burr-Browns will quickly highlight the problems with doing so.
tobb
L-1 has also few kits using hi Q That vca's

a couple are direct Cwejman 'inspired'

https://synthcube.com/cart/l-1
guest
the 072 is a really good bang for the buck for an all-around opamp. sure, its not the lowest noise or distortion thing on the planet, but its good enough for most things. it can handle +/-15V rails, it has output protection, and pA level input bias currents. this last one is super critical for a lot of synth applications. and its 0.27$ @100, whereas things like the 5532 (which have monstrous bias currents) are 0.59$ @100.

if you go to digikey, select all the opamps that can handle high voltage rails and have low bias currents, and then sort by price, its pretty much the TL0x2 series exclusively. and, of these, the 072 is the best for audio applications. the next thing pricewise are some of the new OPA RRIO opamps, which are absolutely amazing (eg OPA1678, 0.59$ @100, 16MHz, 4.5nV/Hz noise, 0.0001% distortion, etc). so, when im designing circuits, i first grab an 072, and if that doesnt meet peformance criterion, then i start shopping around, and usually end up at these new OPA opamps.

when designing for production, its cost effective to limit the number of different parts on the BOM. so if you can get away with one type of opamp, even if it isnt the ideal amp for each particular use in the circuit, its better to do so. and, although 0.30$ extra for a part doesnt seem like much, its typically 4x parts cost to the consumer, so thats an added 1.20$ per opamp at the sale point. use 4 of them in the circuit, and its 5$ more cost. and when designing for DIY, availability is king, and almost everybody has a drawer of 072s kicking around.
ricko
Basically, ignore anything on the Internet from audio people talking about slew rate and noise and op-amps. Line level is only about 1.2 V, while synthesizers run much hotter. This translates to more proneness to slew-rate problems but less noise (often). And slew really is only an interesting issue if you are using designs from before about 1974, AFAICS *OR* you are using the op-amp in a specialist role, such as in the integrator/comparator of a saw VCO.


Slew

The TL071 family has a JFET input and an advertised slew rate of 13 V/
μs (Typical). According to the Electronics Notes slew rate calculator, if we have a maximally large wave for a Eurorack system (+12 to -12) then the TL071 can handle up to 80kHz. At +/-5Hz, it goes up to 119kHz.

So TL071 actually have a good slew story compared to many other cheap op-amps.

We can turn it around, and ask, say, what is the minimum slew rate for a high-fi sampled Eurorack system at its loudest: so lets say a sample rate of 96k and the +/-12V full swings? That requires a slew rate of 7.2 V/µs. So that leaves out a few things like OPA171. TL071 are OK for slew.

We can also ask what slew rate would someone with tin ears even start to experience problems: lets say where a 7.5k wave in a hot wave of +/-7.5V is not handled (so it gets softer and harmonics at 15k are introduced)? Basically you have to be under .7V slew to have a problem there. That only excludes the low voltage op-amps like NJM2732, for modern opamps, AFAICS.

So an op-amp with over 7.2 V/µs. is OK even at the most demanding, but even lesser specced op-amps won't have any real problems in real life, as long as they handle more than .7 (because no-one will really run have such a high frequency wave at such levels). For example, an LME49726 is really high specced, but with a relative slow slew rate of 3.7 V/µs, but really it should be fine in any normal system.

So I think you have to try pretty hard to have a slew rate problem for Eurorack audio rate systems, unless you go out of your way. This *was* a problem in the past, because the 741 has a slew rate of .5, so it was not quite good enough for a system with hot signal levels. Moreover, older modular synths that ran +/-15V could could run their signals hotter, and so were prone to taxing op-amps with poor slew-rates even more.

So the golden rule: never use a 741 (unless you are deliberately recreating an antique circuit, or there is some particular thing that makes it desirable.) But I don't think this has really been an issue for 30 years.

The other gotcha is with antiques is LM301 op-amps as used by early ARP and ETI: its slew will depend on the external compensation capacitor: for audio, I just replace 301s whenever I find them (cut out the compensation cap) and have definitely experienced clearer signals.

Phase reversal

So it seems to me that slew rate problems will not happen on eurorack systems with TL071 in the audio path for another problem: if you start to get large signals, you run the risk of going up to rail, and then you get lock-up (phase reversal) before you even get a chance of significant slew problems ;-)

Indeed, the TL071 family may have a CM IFR of -11V, according to the data sheet. So for a eurorack system, tit might freak out at negative signal more than -11V, not just at the rail. So this makes a potential problem in three situations in eurorack: on inputs to the module, where you might have hot signals; directly after unity gain mixersthat mix a number of fullstrength signals; and in filters with high resonance that have hot internal signals.

Thumbs rule?

Do people think this is a fair rule of thumb?: when is a TL071 OK in eurorack modules?

* inside circuits guaranteed to have in-spec AC signal level (i.e. 10V PP or max 20V PP)
* in slow DC positive circuits for control voltages rather than audio, where linearity is not a pressing concern
* where price is critical but some noise and distortion and linearity are not important

Does this mean that we are better off not having TL07x for audio input buffers (unless there is a voltage divider?) and in VCFs and audio output buffers (because of the new generation of passive LPGs etc might like better drive capabilities)? In which case, why not just say only use TL07x for CVs and not the audio path, if we don't want to think too much and are happy to over-engineer sometimes?


But what else can we use, that won't cost the earth with unnecessary high specs? What the best modern jellybean replacement for a TL071,2,4 is: in particular what is there at a comparable price (i.e. under 50c for dual or $1 for quad in small numbers) with no phase reversal issue?

I am gravitating to using LME49790 quadsmore instead of TL074s for end-of-chain audio buffers for best clarity, which works out to about 75c per op-amp. but they are not jellybean price.
medbot
I built a few CGS/Serge panels a while back and used lots of OPA2134 (which are at least a dollar more on Tayda than they were back then :0 ). I can't speak for the audio path necessarily because I didn't spend a lot of time doing A/B tests, but there was absolutely a noticeable difference in several modules where the OPA was better than a TL072.

The DUSG in particular was night and day when using it as a filter - the OPA opened the filter much more than the TL, which sounded pretty dark/filtered even when wide open.

I wish I could remember which module it was (maybe the wave folder? Don't quote me on that...), but there was also one where I clearly preferred the TL chip to the OPA, which kinda surprised me.

I used OPA and LME chips through the entire audio path (and avoided electrolytic caps), but I don't actually know how much difference it makes because it's hard to A/B dozens of parts across dozens of modules. I like to think it makes the system sound nicer, but I also liked the flavor of the snake oil I bought from an audiophile forum, so...
JimY
I heard the TL07x are better with high impedance inputs & so popular in guitar fx & preamps. I don't know why they would be a good pick in many synth circuits with high signal levels, since they have small input and output signal swing and don't sound too nice if those specs are exceeded.

Don't forget that many designs that are developed DIY often start with breadboard friendly thru-hole components. So types that are so recent that they have no DIL package don't get considered at all.

I've always found any op-amp with an OP or AD prefix is far too expensive to experiment with - at least buying in small quantity. I'm sure the big users get much lower prices or they would sell very few.
When I have spent the money on them, I've really not benefitted from the improvements. In most cases, it's really been a matter of choosing the right jellybean cheap type for the job, not the most highly specified super chip.
col
I usually substitute any TL07x found in the audio signal path with either OPA213x or LM4562 ( LME49720).

Iv'e noticed in a lot of pro-audio consumer devices they use LM4580 it seems to be the current bang4buck opamp for signal path duties. Iv'e tried substituting these with OPA213x or LM4562 ( LME49720). You really can't tell the difference.
slow_riot
Opamps have much more to do with context than anything else.

We tend to take them for granted but they are complex and made up of many internal stages, and there are many different design techniques used internally to achieve the results needed from each stage.

Discussions about specific parts rarely address these nuances. Any discussion based on audible differences when swapping out a single part is a waste of everyone's time. We might be making devices for the purposes of art but meaurements under a range of conditions are easy in the age of SPICE (even if you need to take into consideration the possibility of flaws in the model) and almost limitless access to information online or textbooks.

Most of the discussion around opamps can be focussed on the choice of JFETs or BJTs for the inputs. That accounts for the big difference in noise (notable for mixing consoles as mentioned). Also input impedence and bias currents - essential for integrators and why JFET input opamps are ubiquitous in synths.

Not mentioned so far, is distortion in JFETs when used as followers (not inverters) due to capacitance on the gate channel. This can be mitigated completely either by design or by running the amplifier in inverting mode with a virtual ground. This problem does not exist in BJT input opamps. Also, some designers like Grant Richter of Wiard deliberately use this distortion in the signal path, so it's not always a question of specsmanship. Grant is also, shall we say, a big fan of the TL074!

There are other discussions around amplifier stages, such as compensation, gain. These are all better addressed in the literature sent out by the manufacturers.

Some of the places where the ubquity of the 07x really shows are in exponential converters. JFETs have much higher offset voltage, which drifts with temperature.

Overall I think it's possible to design a perfectly interesting synth based around 80% TL07x, and it's foolish to write off any device which uses them, because design is much more complex and nuanced than expense of part. Worth remembering that Moog, Buchla, EMS designed legendary synths out of totally crap discrete BJTs, rarely with on-die matching, and would have probably pushed their mothers under a bus to get their hands on a TL07x in the 1960s!
JediDJ
Arrow and Newark. Do they certainly selling genuine ones ?
Somebody measured the samples ?
Cause in my country it's becoming harder to get original ones.
Asia is all over here.

I know that full slew rate ability is rarely needed.
But.... it will be nice if a product matches the description.
If 13V stated, then it must be so.
No need to sponsor fakes !

If I need a fake, I shall probably buy 100 of them for 5$ on Aliexpress.
But when some official traders sell these for 0.8$ a piece, I need quality.
kassu
guest wrote:
(eg OPA1678, 0.59$ @100, 16MHz, 4.5nV/Hz noise, 0.0001% distortion, etc).

Thanks, looks like good specs for a very reasonable price!

On the original topics, I find that TL072 is sufficient for most synth uses. Noise on these levels is not an issue in synths - with typical 100k input impedances in modular synths thermal noise is usually bigger than the 18nV/sqrt(Hz) input noise of the TL072 anyway. Even distortion in the audio path is hardly a big deal, it will be covered up by all the "classic" circuits such as discrete circuits or OTAs that distort orders of magnitude more than the opamps.

One thing I would appreciate is an affordable (cheap) opamp with lower offset voltage. I'm now starting to use OPAx197, which is very good but certainly not cheap at around 2 euro per piece.
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