Op Amp upgrade

[12bass]

Comparison recordings are available in my Eden WT-500 mod thread:

http://www.talkbass.com/forum/f15/eden-wt-500-circuit-modifications-improvements-762982/

While changing op amps may make some difference, it is only one part of the puzzle. As for the differences between TL072 and TL082, the specs are nearly the same (including distortion), only differing in input bias current and CMRR (which is worse for TL082). Even the schematics are basically the same, so I wouldn't expect much difference in the sound. Modern parts like the OPA827 and ADA4627-1 are in a different class entirely than those thirty year-old TL0x2 chips. As mentioned in my mod thread, I've gone through a lot of op amps over the years....

 

[iplay5strings]

Well def. can't wait to do the AE bypass...been playing through the effects return of the amp and the tone is SO much better. When A/B-ing the 2, the signal from the effects return is pure and full...the tone from the front input jacks with the knobs set flat sounds like some one blindy put in some hi/lo-pass filters and called it a day. There is a HUGE difference between the two and the tone from the effects return is a WAY better starting point IMO. So if that mod really takes that curve out of the preamp and makes it sound like the signal from the effects return I will be extremely happy!

 

[Jerrold Tiers]

When trying different parts, be aware that some parts have bad-for-audio characteristics..... even though they may be from teh same general family as others that are better.

FET input opamps (and some others) have had, and some still do have, nasty quirks like "output reversal", where under certain conditions of input, the output voltage will suddenly "snap to" the completely opposite polarity.... creating a sound like a very broken speaker.

This is usually visible in teh specs, but only if you know what to look for.....

 

[Bass4LifeRS]

Comparison recordings are available in my Eden WT-500 mod thread:

http://www.talkbass.com/forum/f15/eden-wt-500-circuit-modifications-improvements-762982/

While changing op amps may make some difference, it is only one part of the puzzle. As for the differences between TL072 and TL082, the specs are nearly the same (including distortion), only differing in input bias current and CMRR (which is worse for TL082). Even the schematics are basically the same, so I wouldn't expect much difference in the sound. Modern parts like the OPA827 and ADA4627-1 are in a different class entirely than those thirty year-old TL0x2 chips. As mentioned in my mod thread, I've gone through a lot of op amps over the years....

Excuse me for jumping in with absolute zero competence on the subject, but will the replacement of old op-amps with the new superior models only better the noise ratio?

 

[12bass]

Excuse me for jumping in with absolute zero competence on the subject, but will the replacement of old op-amps with the new superior models only better the noise ratio?

No. Other sonic improvements are possible as well. Better op amps can help to open up the sound via lower distortion. However, higher performance parts do not always offer a subjective improvement, as some people prefer the colorations of certain older devices, especially in things like effects pedals (see JRC4558). Also, some of the modern parts can be unstable if not carefully implemented.

 

[aborgman]

DIYable, probably. But by the time you've built/bought your test gear or taken it to a tech you'll have spent 10x as much as you've saved by buying the parts on eBay.

Depends on what you want to measure... but for audio range stuff you could probably get by with a old Tek scope, a good function generator, and a good bit of time.

 

[figuredbass]

So I just recently found out that the owner before me already changed the op amps in my amp to TL082's is this a good thing or bad thing? Should I put TLE2072's in or at least put TL072's back in or are these good/ok/better?

Changing to the TL082 is not a bad thing at all, but not an actual improvement on the TL072. As others have stated, the TL072 has slightly better specs than the 082, though in the end this is really quite negligible. I have the detailed technical spec sheets for both and there is no obvious superiority in the 072 despite it always being touted as a "low noise" version of the 082. The only noise spec that is slightly better is that of the power supply rejection ratio, which shouldn't matter if the (internal) power supply of your amp is well regulated, as amps usually are anyway in the preamp section. Other signal noise specs and distortion specs are identical in both. You can think of the 072 and 082 as being virtually interchangeable. I've never been able to detect a difference myself, either electronically or sonically.

That being said, the TLE2072 is clearly superior to either the 072 and 082 both in noise specs and sound quality! It was specifically designed as an upgrade to the TL072, with only a marginal increase in power supply current requirement. It's also fairly friendly as a drop in replacement, whereas other opamps (like the 5532) may not always be in every application and can also draw excessive current - a big problem if you're replacing a lot of them within the same piece of gear.

 

[figuredbass]

The likelihood of receiving TL072s printed as TLE2072s is most probably nil if ordering from a good company like Mouser or DigiKey.

My vote would be to put the TLE2072s in. If you decide not to make a major change, it's probably best to just put the TL072 back in rather than a TL082.

p.s. There's actually a TLE2072 in the compressor I built, shown above in my avatar photo.

 

[synaesthesia]

Hello

I don't come to TB much these days but I used to advocate a swap in ICs in SWR circuits to the point of being called a liar.
So I stopped bothering.

I preferred to use NE5532 chips over the TL072 and the actual difference was a lower noise floor; the tonal characteristics didn't change much if they did at all, and I eventually got the noise spec down to a level comparable to my Alembic and Demeter preamps, but the basic tone signature of the SWR, whilst useable certainly, was still annoying to my ear and I sold it on eventually as it was hardly used in my commercial studio. I did a lot of mods for SWR owners I came across, and it was simple demonstration of hearing the difference in the idling noise of the amp vs the lower noise floor of the modded preamp with the NE5532 chips. Tonally, no one complained that anything changed.

 

[iplay5strings]

The likelihood of receiving TL072s printed as TLE2072s is most probably nil if ordering from a good company like Mouser or DigiKey.

My vote would be to put the TLE2072s in. If you decide not to make a major change, it's probably best to just put the TL072 back in rather than a TL082.

p.s. There's actually a TLE2072 in the compressor I built, shown above in my avatar photo.

The TLE2072's are on their way and once they get here they, as well as the AE bypass, will be going in right away!

 

[iplay5strings]

The TLE2072's have arrived and have been installed! I started by only replacing the two op amps directly behind the inputs and just from doing that the noise dropped exponentially! With the TLO82's the amp hissed incessantly, even with treble rolled off. I was always getting complaints from sound techs about how loud my send was, BUT NO MORE!!! I'm so happy I did this! Standing in front of the amp now all you can hear (if it's quite enough around you) is the 60 cycle hum these amps are known for. The tone DID change, not in a huge way, but the TLO82's seem to have an "edge" to them which some people like for "phattening up" the tone of effects pedals but the TLE2072's have a more natural sound (at least compared to the TLO82's) and I like it! I replaced every op amp with a TLE2072 but the one in the very last socket on the right of the bottom board behind the volume knob(s). For some reason (current draw, or some other reason I don't have enough knowledge to know how to explain) the TLO82 created less noise/better sound than when I put a TLE2072 or even a regular TLO72 (I had a single one of these laying around) in that particular socket. Kinda interesting...but nevertheless I highly recommend doing this! My results may have been somewhat more magnified because I switched from TLO82's, but still I think this is a VERY worthwhile project, especially if you use you're head for studio recording and need the noise as low as possible. I will be doing the AE bypass tonight and will let you all know how that turns out. Thanks everyone for all their help and directing me towards these op amps, never been happier!

 

[rumblinbass]

As I recall, SWR has a "scooped" voicing when its EQ knobs are centered. That could be most of what you're experiencing. With bass gear, nothing is dead flat unless you've measured its response curve for yourself.

+1. When I had my GK700RB I ran a sweep with an Audio Precision and there was a mid scoop. AFAIK, most amplifiers/preamplifiers do not have a flat frequency response. The difference of the frequency response is what gives manufacturers there sound.

However I will disagree with those that say changing op amps will not change the tone/sound of an amplifier. It may not have as much impact as changing the speaker cab or a pickup but there is a difference.

While developing one of the products I tried a couple different op amps - the TLE2072 (already mentioned), AD823, and the OP275. They all sounded good but different. Listening environment and gear has a lot to do with it. Not sure what you would hear through a typical bass cab...

 

[rumblinbass]

I preferred to use NE5532 chips over the TL072

this is something I would be careful about.
The TL072 and NE5532 is not the best swap...results can vary depending on the circuit. The TL072 is a FET input op amp. For best results find another FET input op amp.
The NE5532 is a BJT input op amp. Great specs, been around for a looooong time and I use almost exclusively. I would not use them for an instrument input though. Considering price and performance - the best bang for the buck.
Typcally a FET input op amp not only boasts low noise but also low output offset (DC on the output). The NE5532 on the other hand does not have the best spec as far as output offset. We use caps to block that DC from getting to the next stage or pots eek. You do not want any DC on a pot. Bad news.
All I am trying to say here is just be aware.

 

[BassmanPaul]

I am glad to have been proved incorrect on this. To the OP, From one Carvin bass player to another, I'm glad that you noticed a difference for the better. Now you can start on the resistors and after that the capacitors. Who knows maybe you WILL be able to make a silk purse from a sow's ear.

Edit: that's an LB76WP in my avatar.

 

[iplay5strings]

I am glad to have been proved incorrect on this. To the OP, From one Carvin bass player to another, I'm glad that you noticed a difference for the better. now you can start on the resistors and after that the capacitors. Who knows maybe you WILL be able to mahe a silk purse from a sow's ear.

Many of the resistors have already bean changed from the brown/tan colored ones to these light blue ones by my amp tech (according to him they were supposed to be much quieter) as well as many of the capacitors. He really did a number on the power section...put these HUGE (10000 uF) caps in there so I could really get down to those low notes. (I tune a whole step down accross the board so my 5th string is an open A!). Guy is a genius and I let him dive into the more technical aspects since most of them are way over my head.

 

[rumblinbass]

Many of the resistors have already bean changed from the brown/tan colored ones to these light blue ones by my amp tech (according to him they were supposed to be much quieter) as well as many of the capacitors. He really did a number on the power section...put these HUGE (10000 uF) caps in there so I could really get down to those low notes. (I tune a whole step down accross the board so my 5th string is an open A!). Guy is a genius and I let him dive into the more technical aspects since most of them are way over my head.

resistors...quieter?
from the description (tan and blue) you went from carbon to metal film. The metal film resistors are a tighter tolerance (probably 1%) and are better suited for audio...but quieter? first I've heard. Better thermal characteristics translating to better THD maybe.
Larger caps for power supply decoupling definitely help. Helps keep from pulling the voltage rail down and filters power supply ripply. Localized decoupling also works really well.

 

[lowfreqgeek]

Many of the resistors have already bean changed from the brown/tan colored ones to these light blue ones by my amp tech (according to him they were supposed to be much quieter) as well as many of the capacitors. He really did a number on the power section...put these HUGE (10000 uF) caps in there so I could really get down to those low notes. (I tune a whole step down accross the board so my 5th string is an open A!). Guy is a genius and I let him dive into the more technical aspects since most of them are way over my head.

Resistors, opamps, caps... All can make a difference, but the trick is knowing when and where to use what and how the specific part used will make the difference. Metal-film resistors (the blue ones) have tighter tolerance and less Johnson noise (up to 40dB less!!) than carbon resistors (usually tan), but blindly replacing ALL the carbon with metal-film won't necessarily buy you much. Same for caps - the signal-path coupling caps in the SWR amps are all WIMA audio-grade Polyester. At least they used to be. While you may get better (at a price), not every cap needs to be audio-grade.

But it sounds like your tech is pretty good, so I'm sure he's familiar with what makes sense and what doesn't. The main thing is that you don't go to the expense of changing every component without understanding why/what/how it behaves.

I may try some TLEx072s in my Line6 UX2. The TL072s are very noisy with high gain (like the gain required to run a Jensen xfmr-equipped DI) and the power supply is already taxed. The 5V supply means I really need rail-to-rail to have any headroom (OP275 is out...) on the instrument input, and the supply can't give any more juice. I've already done major (really major) upgrades, but it's not there yet.

Doesn't really matter, though, as I have an RME for the "real" work...

 

[lowfreqgeek]

resistors...quieter?
from the description (tan and blue) you went from carbon to metal film. The metal film resistors are a tighter tolerance (probably 1%) and are better suited for audio...but quieter? first I've heard. Better thermal characteristics translating to better THD maybe.
Larger caps for power supply decoupling definitely help. Helps keep from pulling the voltage rail down and filters power supply ripply. Localized decoupling also works really well.

Lucas,

This is obviously from a manufacturer with an interest in sales, but here's a little reference for you: [Invalid or Expired Link Removed]

Johnson-Nyquist noise has been known for years to be lower in metal-film than carbon resistors, but - as with anything electronics - proper implementation is far more important than blindly relying on specs, so a well-designed carbon resistor circuit is going to perform better than a poorly designed metal film circuit.

I'll try to find more references.

 

[iplay5strings]

Resistors, opamps, caps... All can make a difference, but the trick is knowing when and where to use what and how the specific part used will make the difference. Metal-film resistors (the blue ones) have tighter tolerance and less Johnson noise (up to 40dB less!!) than carbon resistors (usually tan), but blindly replacing ALL the carbon with metal-film won't necessarily buy you much. Same for caps - the signal-path coupling caps in the SWR amps are all WIMA audio-grade Polyester. At least they used to be. While you may get better (at a price), not every cap needs to be audio-grade.

But it sounds like your tech is pretty good, so I'm sure he's familiar with what makes sense and what doesn't. The main thing is that you don't go to the expense of changing every component without understanding why/what/how it behaves.

I may try some TLEx072s in my Line6 UX2. The TL072s are very noisy with high gain (like the gain required to run a Jensen xfmr-equipped DI) and the power supply is already taxed. The 5V supply means I really need rail-to-rail to have any headroom (OP275 is out...) on the instrument input, and the supply can't give any more juice. I've already done major (really major) upgrades, but it's not there yet.

Doesn't really matter, though, as I have an RME for the "real" work...

My tech was very specific and intentional in the placement of the metal-film resistors...not all resistors got replaced (which until now did not make much sense to me, but obviously he new what he was doing :-D). Those 10000 uF caps are awesome! I've never had the "thermal meltdown" problems associated with the SM+900's to begin with, but the caps help the amp to stay at a "normal" operating temperature even in my skb rack case. Like I said this guy is a genius...he's just released a line of fully hand made preamps and effects pedals! (who's prototypes were built on raw computer chassies...INSAINE)

 

[iplay5strings]

Resistors, opamps, caps... All can make a difference, but the trick is knowing when and where to use what and how the specific part used will make the difference. Metal-film resistors (the blue ones) have tighter tolerance and less Johnson noise (up to 40dB less!!) than carbon resistors (usually tan), but blindly replacing ALL the carbon with metal-film won't necessarily buy you much. Same for caps - the signal-path coupling caps in the SWR amps are all WIMA audio-grade Polyester. At least they used to be. While you may get better (at a price), not every cap needs to be audio-grade.

But it sounds like your tech is pretty good, so I'm sure he's familiar with what makes sense and what doesn't. The main thing is that you don't go to the expense of changing every component without understanding why/what/how it behaves.

I may try some TLEx072s in my Line6 UX2. The TL072s are very noisy with high gain (like the gain required to run a Jensen xfmr-equipped DI) and the power supply is already taxed. The 5V supply means I really need rail-to-rail to have any headroom (OP275 is out...) on the instrument input, and the supply can't give any more juice. I've already done major (really major) upgrades, but it's not there yet.

Doesn't really matter, though, as I have an RME for the "real" work...

My tech was very specific and intentional in the placement of the metal-film resistors...not all resistors got replaced (which until now did not make much sense to me, but obviously he new what he was doing :-D). Those 10000 uF caps are awesome! I've never had the "thermal meltdown" problems associated with the SM+900's to begin with, but the caps help the amp to stay at a "normal" operating temperature even in my skb rack case. Like I said this guy is a genius...he's just released a line of fully hand made preamps and effects pedals! (who's prototypes were built on raw computer chassies and still sounded INSANE)