ASR/amirm has opened my eyes.

[VQR]

I'm banned on both btw, and i don't mind at all.

It's tough sometimes holding back my inner millenial troll.

 

[fpitas]

I'm banned on both btw, and i don't mind at all.

Good work!

 

[voodooless]

I've also got to school myself on Op amp selection.

Replace OP amps. Completely pointless, or not?

Why do so many OPs change amps in, for example, the amplifier AIYIMA A07 TPA3255? What's the point of that? Does not modern OPs amps amplify the signal completely linear straight(if the construction they sit in is well constructed, and made to fit OP amp X)? Do not modern OP amps have a...

www.audiosciencereview.com

 

[Doodski]

It's tough sometimes holding back my inner millenial troll.

I don't bother with that sort of stuff. I have in the past when young but now I consider it silly and a waste of time and energy that I can use doing productive things. I'm not a good troll anyway...LoL.

 

[VQR]

I don't bother with that sort of stuff. I have in the past when young but now I consider it silly and a waste of time and energy that I can use doing productive things. I'm not a good troll anyway...LoL.

I don't know your background, but I grew up trolling online. I'm dating myself with that comment of course. I can be good at trolling if needed.

 

[Doodski]

I don't know your background, but I grew up trolling online. I'm dating myself with that comment of course. I can be good at trolling if needed.

My first 3 pooders starting at a P75 I think it was where for gaming and IRC as a OP. So I had no time for trolling LoL. It was chat, chat, chat and a bit of OPing as required.

 

[Killingbeans]

I've also got to school myself on Op amp selection.

The choices for this Apollon purifi are Opa 1612, Sonic Imagery 994 Discrete and Sparks SS 2590 Pro. From least to most expensive. I guessing the Opa 1612 for no additional charge is the common choice. I haven't the slightest idea.

Sticking to the "cheap" OPA1612s is probably a very sensible choice. Fancy opamps are nothing but jewelry, if you ask me.

Implementation is king. A good engineer can design circuits, that function like the fabled wire-with-gain in any practical sense, using "pleb" opamps. And a crummy engineer can easily wreak havoc with the fancy boutique ones.

Discrete OpAmp Review: Sonic Imagery vs Sparkos

Recently I reviewed the Nord Three SE 1ET400A Dual Mono Stereo Amplifier. That unit came with the Sonic Imagery's 990ENH discrete operational amplifier ("opamp") in the buffer stage (pre-amplifier). The owner then ordered a set of Sparkos Pro SS2590 discrete opamps. This gave me a chance to...

www.audiosciencereview.com

 

[Waxx]

It's tough sometimes holding back my inner millenial troll.

I was not trolling, just telling facts with proof that they didn't like....

 

[AdamG]

I'm dating myself

Now that’s a novel way of beating the Dating scene.

 

[afinepoint]

Have you downloaded the data sheets for these OP amps and compare them?

I will. That's my plan. I try to keep a realistic approach as in whether I can hear the difference. Why pay for upgrades I can't use.

Amir did a Sonic to Sparko comparison in Dec 2019. Not sure how valid those results remain. What I got out of it was stick with Nord's basic Op amp.

The Opa data alone is 34 pages of highly technical jargon and graphs. I can see my comparisons will be crude. I'll pick out the graphs that match amir's.

 

[Doodski]

I will. That's my plan. I try to keep a realistic approach as in whether I can hear the difference. Why pay for upgrades I can't use.

Yes, and there is a ton of information in those data sheets that is transferable and some shows the differences or not between the Op amps. Usually the original design is a mix of what is economically applicable and what is the best performance and has the right circuit parameters for the final design of the OP amp circuit. Then the designer chooses the feedback and gain and calculates the proper peripheral components for the topography. So... Sometimes swapping a OP amp may change the sound but that does not mean it is better.

 

[afinepoint]

Ok I need help with this one. Under "Noise Performance " in the OPA 1612 data sheet it states, " The low voltage noise of the OPA 161x series op amps make them a good choice for use in applications where the source impedance is less than 1k ohm."

The Purifi stats states, "High Input Impedance 100K."

Are these different impedances?

Amir?

 

[Doodski]

Ok I need help with this one. Under "Noise Performance " in the OPA 1612 data sheet it states, " The low voltage noise of the OPA 161x series op amps make them a good choice for use in applications where the source impedance is less than 1k ohm."

The Purifi stats states, "High Input Impedance 100K."

Are these different impedances?

Amir?

Yes, they are very different. One is the resistance of the output feed going to the OP amp's input and the other the resistance of the OP amp input. To have a very low output resistance is good and to have a high input resistance is good. So it's low to high is the best choice for audio applications. If other applications this may change.

 

[afinepoint]

Yes, they are very different. One is the resistance of the output feed going to the OP amp's input and the other the resistance of the OP amp input. To have a very low output resistance is good and to have a high input resistance is good. So it's low to high is the best choice for audio applications. If other applications this may change.

I thought it must be considering the large delta.

Thank you for the lesson. Now back to it.

 

[Doodski]

I thought it must be considering the large delta.

Thank you for the lesson. Now back to it.

Usually for audio applications look for at the least a 1:10 ratio between output R and input R. It's very common to use this general rule or to better it.

 

[afinepoint]

Usually for audio applications look for at the least a 1:10 ratio between output R and input R. It's very common to use this general rule or to better it.

So 100:1 definitely betters it.

 

[Doodski]

So 100:1 definitely betters it.

O' yeah that's a fine ratio to have. Keep in mind the feedback network which can be a resistor, a inductor, a capacitor or all three of them or more is effective at circuit changes gain and such too. So with keeping those feedback elements in mind the gain across the hearing spectrum is sometimes changed and the OP amp that is used in circuit has been calculated for optimal operation and expense. So I suggest looking at the gain specs for each OP amp (At the beginning of the data/spec sheet.) that is to be rolled and then you can see if one has more gain than the other(s). The gain is really what is occurring when rolling OP amps because they all have such a good slew rate that the rise time and resulting frequency response exceeds the needs of the audio circuit and so a gain difference is sensed as louder and better.

 

[afinepoint]

Is Magnitude (db) and Gain (db) the same thing? The two graphs both have frequency as the x axis.

And what is Open Loop Voltage Gain which is also expressed in dB?

 

[afinepoint]

Looking at the curves in the data sheets:

Opa - 100 db @ 1k Hz . Expressed in Gain (db)

Sonic Imagery 994 Discrete - 94 db @ 1k Hz Expressed in Gain (db)

Sparkos 2590 - 125 db @ 1k Hz Expressed in Magnitude (db)

Amir reviewed a Sonic and Sparkos op amp.

Discrete OpAmp Review: Sonic Imagery vs Sparkos

Recently I reviewed the Nord Three SE 1ET400A Dual Mono Stereo Amplifier. That unit came with the Sonic Imagery's 990ENH discrete operational amplifier ("opamp") in the buffer stage (pre-amplifier). The owner then ordered a set of Sparkos Pro SS2590 discrete opamps. This gave me a chance to...

www.audiosciencereview.com

Per his review the Sparkos had higher distortion (>10db).

Per amir "Both appear to lose to stock Purifi implementation so not sure if either is worth the premium."

The Sonic is a $224 upgrade. The Sparkos twice that at $448. I'm leaning towards going with the standard Opa 1611.

 

[Doodski]

I'm leaning towards going with the standard Opa 1611.

Good choice.