The Opamp thread

[Rob43]

..... In my particular amp, opa1692 has narrower sound stage than opa1656, as 1692 is designed for portbable use with trade-off (low power draw).

I'm saying this to everyone:

For me personally, I'd rather listen to Full/Great sounding music for a shorter amount of time, vs music with a narrower sound stage for a longer amount of time.


Rob43

 

[HeyManslowdown97]

I'm saying this to everyone:

For me personally, I'd rather listen to Full/Great sounding music for a shorter amount of time, vs music with a narrower sound stage for a longer amount of time.


Rob43

In response and because I started this assault on the Opa1692. It’s not that much of a night and day difference in terms of wider soundstage and actually you only notice it on longer listening seshes. It’s just that the details aren’t as pronounced but you don’t “miss” any details. Opa1692 actually has a lower CMRR anywhere from 120-140 dB (according to Mouser) vs Opa1656. It’s also a lot quieter and has a faster slew rate (I believe). I believe that range is determined by the DAC chips specs so that’s a factor!

Also it’s goes beyond just listening for more hours, if you have a battery powered music player the less current you use the more output current you have for an output stage op amp for current hungry iems. It also gives a lot of portable option especially if it’s not you main op amp as MOST balanced, Line out or SE go through stages.
When you get more of understanding of How circuits affect op amps and what the correlation they have with add components like op amps “act” in certain circumstances you start to realize there’s no all encompassing holy grail op amp.

This does take some experience and hands on work and reading others’ theories and takes helps with your own blindspots and sometimes disagreements (totally normal).

For instance, many in the diy don’t like adding caps to circuits because it changes the op amps sound which to me is a benign argument.

In my view you add caps with ESR or ESL to a op amps in either the in put or out put to improve biasing and filtering. Sure, if you take too much off aliasing it will sound worse but if experiment with caps and coupling you can get op amps to maximize or even Exceed their own benchmarks improving the sound of a said op amp you like. If so, congrats you made something special sounding to your ears!

Also, some mediums like Vinyl requires a pre Phono set up and some solid state op amps outputs are already cleaner have lower noise levels than the distorted median so there’s no need for extra caps.

the point I’m trying to make is to always keep an open mind. The more you experience in this hobby the more your perceptions will shift...

 

[Rob43]

In response and because I started this assault on the Opa1692. It’s not that much of a night and day difference in terms of wider soundstage and actually you only notice it on longer listening seshes. It’s just that the details aren’t as pronounced but you don’t “miss” any details. Opa1692 actually has a lower CMRR anywhere from 120-140 dB (according to Mouser) vs Opa1656. It’s also a lot quieter and has a faster slew rate (I believe). I believe that range is determined by the DAC chips specs so that’s a factor!

Also it’s goes beyond just listening for more hours, if you have a battery powered music player the less current you use the more output current you have for an output stage op amp for current hungry iems. It also gives a lot of portable option especially if it’s not you main op amp as MOST balanced, Line out or SE go through stages.
When you get more of understanding of How circuits affect op amps and what the correlation they have with add components like op amps “act” in certain circumstances you start to realize there’s no all encompassing holy grail op amp.

This does take some experience and hands on work and reading others’ theories and takes helps with your own blindspots and sometimes disagreements (totally normal).

For instance, many in the diy don’t like adding caps to circuits because it changes the op amps sound which to me is a benign argument.

In my view you add caps with ESR or ESL to a op amps in either the in put or out put to improve biasing and filtering. Sure, if you take too much off aliasing it will sound worse but if experiment with caps and coupling you can get op amps to maximize or even Exceed their own benchmarks improving the sound of a said op amp you like. If so, congrats you made something special sounding to your ears!

Also, some mediums like Vinyl requires a pre Phono set up and some solid state op amps outputs are already cleaner have lower noise levels than the distorted median so there’s no need for extra caps.

the point I’m trying to make is to always keep an open mind. The more you experience in this hobby the more your perceptions will shift...

I'll give you this, you like to write a lot...

I would tell you to also keep an open mind.

So when talking about inexpensive parts like the Op Amps we're discussing, the best sounding part gets the job every time . Even if this means the length of play is reduced.



Rob43

 

[HeyManslowdown97]

I'll give you this, you like to write a lot...

I would tell you to also keep an open mind.

So when talking about inexpensive parts like the Op Amps we're discussing, the best sounding part gets the job every time . Even if this means the length of play is reduced.



Rob43

There’s short hand when discussing this stuff with platitudes, anecdotal evidence and being passive aggressive guised as keeping an open minded because of your chosen style of brevity for thread contributions is unwelcoming and can seen as bullying.

 

[Rob43]

There’s short hand when discussing this stuff and being passive aggressive guised as keeping an open minded because of your chosen style of brevity for thread contributions.

Sure, if you believe that I say you should run with that.


Rob43

 

[HeyManslowdown97]

Sure, if you believe that I say you should run with that.


Rob43

Fair enough, do yourself a favor and please select the “ignore” and censor yourself from long hand thread contributions like mine. Clearly you are well above them.

 

[Rob43]

Fair enough, do yourself a favor and please select the “ignore” and censor yourself from long hand thread contributions like mine. Clearly you are well above them.

Thanks, I'll take that into consideration...


Rob43

 

[HeyManslowdown97]

Here’s a great article comparing opa2156 CMO vs opa1612. My understand if noise isn’t a problem the opa1656 is great alternative to the opa1612. Both (I believe have Fet-inputs)

There’s also 2189 CMOS audio op amp has impressive specs of an impressive was designed for MUX friendly DACs and multichannel dacs!

https://quantasylum.com/blogs/news/opa2156-hifi-in-cmos

datasheet fro opa2156 CMOS op amp. Slightly better specs/= to Opa1656 for audio purposes.

https://www.ti.com/lit/ds/symlink/o...42125&ref_url=https%3A%2F%2Fwww.google.com%2F

 

[morpheus620]

what do you say about OPA1632 or OPA1637?

 

[HiFan]

Have you tried Opa2156? It too is CMOS audio amp. I plan on getting some soon!

... I've actually used CMOS LDOs designed for audio ...

I have opa2156 sitting aside to be installed onto adapters. I have been a bit lazy but will try it out this weekend.

In my collections, actually opa2228 isn't bad. I put it into one of my little DACs and use it for output. The warm presentation (due to higher 2nd harmonics distortion) pairs with my current Alessandro Ms Pro very well. I noticed no difference in details when comparing with opa2111. In the same position, opa1656 sounds flat with slightlty wider soundstage, but I feel sound is a bit weird (cannot properly discribe it).

A side note on LDO. I recently have been probing and tweaking circuits using LM340/LM78xx. Their noise performance is medicore compared with many newer ones, but with oscilliscope I see it barely affects output noise level as opamps actually have ripple rejection. BUT, I found out that many devices were designed to use low ESR or high capacity output capacitors behind them, which is actually bad application. So I have been modding them to use 10uf tantalum output capacitors, and received positive results. According to application notes from TI, LDO output caps are only used to improve transient response of the LDO, and won't do any good to lower output ripple. Large caps actually will confuse the LDO's interal voltage differential error amp, and make LDO less responsive to voltage drop across the load.

 

[HeyManslowdown97]

l. I noticed no difference in details when comparing with opa2111. In the same position, opa1656 sounds flat with slightlty wider soundstage, but I feel sound is a bit weird (cannot properly discribe it).

Actually it makes a lot of sense. The opa2111 is one of 3 op amps that has Burr Brown “Bifet” design. The two others are opa2107 and opa627. However, it doesn’t sound like those two chips at all! It’s very musical imo.

You are not “wrong“ in describing the Opa1656, it is recommended to be used in portable devices I/V stage because it has a input fet like the opa1612 and the opa1642. It has to do with the load capacity limitation be under a certain load capacity of 50 ohms. (I believe).

Because Audio is mostly an AC application LDOs are used to allow current to travel via the circuit. I totally agree with you on the higher valued caps around them. They do stop the flow when the values are too high. Lots of people believe that the higher values in caps (everywhere in the DAC) increases VREF but that’s only true when the values are highest at the DAC chips in sigma delta modulator which are made mostly today in CMOS requirements are met. (R2R designs are be far more sophisticated and requires a lot of attention to details. They are simply an “art” to do with precision counterpointing resistance values and caps).

Personally, I am still “lost” when it comes to coupling caps with resistance series. That requires experiment “off board” but a lot of Sigma Delta modulators are pretty basic to implement, are cheap to make & also have their limits.


LDOs will ALWAYS produce noise (no question) but attempting to the lessen the noise, muzzle them or attempt to push the noise outside of the noise signal usually requires a cap of anywhere from 1-2uf ceramic caps based on data sheet recommendations so you can’t go “rogue” with the values.

Caps are all constructed differently and use different materials that often affect the sound. The same is true for resistors, Op Amps. The best are film caps because they do a great job filtering out DC noise which allows the audio signal to be stronger which are of lower values and are pretty large. Personally, I’m still trying to fully understanding coupling especially with caps and resistance.

The main objective always in 99% of all modding is the lower noise levels.

Since many DAC chips are CMOS like the AKM449X series it may make sense to use CMOS based parts like LDOs and Op Amps??? Because they sound better “natively” in short length circuits and power limits per sections of the DAC?? (not sure).

A lot of times you just have to wing it and take calculated risk or use threads to see if anyone has attempted what you are doing. As DIYERS we are not privy to endless R & D funding so a reliance on a community of hobbiest is parliament! A lot times, diyers in Audio proven methods for a problem aren’t totally scientifically proven but work. Haha

 

[HeyManslowdown97]

Thanks, I'll take that into consideration...


Rob43

Rob43,

Wanted to apologize, I want back a re-read you initial comment. At first, I mistook it as malice (which it wasn’t).

I do go on some tangent sometimes and can’t help it. Haha

Sorry everyone for the double post, just wanted to get that in there.

 

[HiFan]

Actually it makes a lot of sense. The opa2111 is one of 3 op amps that has Burr Brown “Bifet” design. The two others are opa2107 and opa627. However, it doesn’t sound like those two chips at all! It’s very musical imo.

You are not “wrong“ in describing the Opa1656, it is recommended to be used in portable devices I/V stage because it has a input fet like the opa1612 and the opa1642. It has to do with the load capacity limitation be under a certain load capacity of 50 ohms. (I believe).

Because Audio is mostly an AC application LDOs are used to allow current to travel via the circuit. I totally agree with you on the higher valued caps around them. They do stop the flow when the values are too high. Lots of people believe that the higher values in caps (everywhere in the DAC) increases VREF but that’s only true when the values are highest at the DAC chips in sigma delta modulator which are made mostly today in CMOS requirements are met. (R2R designs are be far more sophisticated and requires a lot of attention to details. They are simply an “art” to do with precision counterpointing resistance values and caps).

Personally, I am still “lost” when it comes to coupling caps with resistance series. That requires experiment “off board” but a lot of Sigma Delta modulators are pretty basic to implement, are cheap to make & also have their limits.


LDOs will ALWAYS produce noise (no question) but attempting to the lessen the noise, muzzle them or attempt to push the noise outside of the noise signal usually requires a cap of anywhere from 1-2uf ceramic caps based on data sheet recommendations so you can’t go “rogue” with the values.

Caps are all constructed differently and use different materials that often affect the sound. The same is true for resistors, Op Amps. The best are film caps because they do a great job filtering out DC noise which allows the audio signal to be stronger which are of lower values and are pretty large. Personally, I’m still trying to fully understanding coupling especially with caps and resistance.

The main objective always in 99% of all modding is the lower noise levels.

Since many DAC chips are CMOS like the AKM449X series it may make sense to use CMOS based parts like LDOs and Op Amps??? Because they sound better “natively” in short length circuits and power limits per sections of the DAC?? (not sure).

A lot of times you just have to wing it and take calculated risk or use threads to see if anyone has attempted what you are doing. As DIYERS we are not privy to endless R & D funding so a reliance on a community of hobbiest is parliament! A lot times, diyers in Audio proven methods for a problem aren’t totally scientifically proven but work. Haha

TBH, i do appreciate your input, but IME it is all decided by peripheral circuit rather than the opamp. To date I only roll in opamps that has similar reference design to avoid issues.

I have built several amp myself and got the chance to test out things extensively, including using recordings to check upon spectrum. It turns out my head is influencing my preception a lot more than the actual chip.

LDOs doesn't like ultra low esr ceramics in the output. You can use it in adj pin to stablize reading of the error amp, which actually is what determines the noise. It is going to resonate if you use that as output. TI has many writings on that. Here is an easy report.

 

[HeyManslowdown97]

LDOs doesn't like ultra low esr ceramics in the output. You can use it in adj pin to stablize reading of the error amp, which actually is what determines the noise. It is going to resonate if you use that as output. TI has many writings on that. Here is an easy

except I’m using ADI/LT LDOs Not TI

 

[HiFan]

except I’m using ADI/LT LDOs Not TI

You still have to check datasheets. LT makes some chips based on similar designs of TI and onsemi. For example, LT1085/LM317/LM340 (these have on-semi counterparts) are actually "the same" chip. Most LDOs don't like ultra low esr in the output and they typically will specify what to use. I found 10uf Tantalum (non-smd type) to work very well.