OP
- Thread Starter
- #21
You can buy the normal version but use a mirror to look at it....
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Sparkos SS3602 Opamp Rolling In Fosi P4
- Thread starter amirm
- Start date
Thanks once again for the effort boss! Hopefully your efforts it won’t fall on intellectually dishonest/lazy ears this time (though I’m not holding out).
Unless the Op-Donkeys are that willfully uneducated/uninformed/lazy
Unless the Op-Donkeys are that willfully uneducated/uninformed/lazy
Well played sir! Sparkos=So-Kraps
So crap for ones wallet. Hmm, $0,47 vs about $75 for identical performance…. I know where my spare change is going
Edit: grammar
johny_2000
Addicted to Fun and Learning
Speakers and headphones are not solved.
JSmith
Master Contributor
That'd be very cool to video, shame April 1st has passed, I could title it "Reverse engineering with the new Sokraps Op-Amp - can you hear the difference?
Once more it shows how irresistible is the psychology of “if it is more expensive, it must be better”. It plays for automobiles, sparkling water, designer pocketbooks, pens and many other consumer’s goods, including electronics. Vanitas vanitatum for the ignorants and uneducated. Thank you Amir for proving once more how more expensive (160 times more) is not better. It is sad to think how $80 could be wasted in a device that has no reason of being whatsoever.
SmackDaddies
Active Member
- Joined
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sure seems like iem's are solved
Manufacturing, methods & materials:
- Integrated circuits have significant advantages over the same circuit as discrete parts:
- All of the transistors come from not only the same silicon wafer, but the same area of the same wafer.
- This mean all of the transistors in the IC behave so identically that I'm not sure it's measurable.
- Manufacturers can crank out billions of IC's with tighter part tolerances and manufacturing consistency a discrete design can't approach.
- The (monumentally) smaller distances in the interconnects between the op-amp components means reduced susceptibility to EMI/RFI and less noise.
- I mean, we're talking about centimeters of trace distance between some of the SMD components on the Sparkos SS3602 vs the µm between parts in an IC op amp.
- The distortion could quite easily be produced by just enough self EMI/RFI to be picked up by adjacent devices on the PCB. More critically - that self noise only affects part of the PCB, not all of it. Keep in mind, the distortion is, as Amir points out, negligible.
- Sometimes I think it might be useful to plot the noise floor on a linear scale vs a log scale in some cases, just to further emphasize - the difference in Voltage between -95 and -100 db is a lot smaller than the difference between -90 and -95 db.
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No, the snake oil brigade will certainly come up with something new like the type of metal used for the equipment housing.. or something even more ridiculous.
What is the bottleneck this time?
APx555? Probably not, it doesn't have that high second and third harmonic
Power supply, maybe...? PSU itself has varying impedance vs frequency. Long traces are not helping.
Passives? At -110dB, maybe?
So NE5532 is good enough that the user has to actually choose other parts properly to not bottleneck it.
APx555? Probably not, it doesn't have that high second and third harmonic
Power supply, maybe...? PSU itself has varying impedance vs frequency. Long traces are not helping.
Passives? At -110dB, maybe?
So NE5532 is good enough that the user has to actually choose other parts properly to not bottleneck it.
Not for these amps, no.
I really, really like having the OPA1641 family in my quiver, though - I have no idea if they're appropriate for Fosi's design, naturally. Likely not.
I'm particularly fond of the OPA1641 in the OPA Alice microphone impedance converter circuit, where their lower noise and lower power requirements let you use them with phantom power. The NE5532's power requirements are just too high (shocker! Old chip uses more power!)
Sure, the OPA1641 cost several times what an NE5532 does, but at ~$1.25 each @ DigiKey, at the quantities I'd buy/use, shipping is going to be the killer, not the part cost.
Now: Would the NE5532's 0.002% THD vs the OPA1641's 0.00005% THD matter? For a microphone, yes, but that's largely because it's the first stage in a string of high-gain pre-amps on the way from microphone to loudspeaker.
For a power amp? Maybe, if you're the first stage at a music festival's audio system. In a home system, with (likely) close to an order of magnitude less total amplification? Nah.
Quite a lot is left, regarding application circuits and deeper view. Below a comparison of THD vs. output voltage of op-amp swapping in the Topping D10s DAC. @amirm could repeat the test, if he had an op-amp stock available.
There will be many basic circuit where op-amp swapping would make almost no difference, and there will be many circuits where it would make a big measurable difference. Depends if your analysis is deep or shallow.
solderdude
Grand Contributor
@amirm Thanks for trying.
If the op-amp could really have mattered it would have been here as all this device is, is an op-amp with moderate gain with volume control and relays.
I assume with the tone control defeated ?
It looks a bit like there still is an op-amp in there (possibly the non-replaceable one behind the volume control) that seems to determine the performance given the harmonics.
Maybe the 5532 is still slightly better than the other op-amp (tone control circuit) that is (likely) in circuit.
In any case ... the Sparkos does not improve the performance here but because audibly the more expensive ones will surely sound better (Placebo™)
If the op-amp could really have mattered it would have been here as all this device is, is an op-amp with moderate gain with volume control and relays.
I assume with the tone control defeated ?
It looks a bit like there still is an op-amp in there (possibly the non-replaceable one behind the volume control) that seems to determine the performance given the harmonics.
Maybe the 5532 is still slightly better than the other op-amp (tone control circuit) that is (likely) in circuit.
In any case ... the Sparkos does not improve the performance here but because audibly the more expensive ones will surely sound better (Placebo™)
restorer-john
Grand Contributor
OP
- Thread Starter
- #36
Correct. And yes, you were responsible for me doing this test.
solderdude
Grand Contributor
Sorry for wasting more of your time ....Correct. And yes, you were responsible for me doing this test.
I expected small differences (which were found) where the Sparkos would perform a tiny bit worse and the Sonic Imagery would likely be slightly better (if it had fitted).
Differences were there but smaller and different than expected so wondered if the small op-amp behind the volume control might also always be in the path (but tone control bypassed).
That op-amp could also be part of the internal power supply (DC/DC converter) though.
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OP
- Thread Starter
- #38
It is the third harmonic that sets SINAD:
It is at -108 dB so after adding a bit of noise, we get to -105 dB.
The distortion amounts for the op amps are different - the spec sheets even state it outright:
| Device | THD + N at 1 kHz (typ) (%): |
| OPA2134 | 0.00008 |
| NE5532 | 0.002 |
| LME4562 | 0.00003 |
I'm personally a bit more interested int he 1 kHz frequency range than 10 kHz, but it's a continuum regardless.
The big key, though: Was the rest of the amp engineered to take advantage of the op amp's sweet spot, or are you just going for name recognition and pushing it past reasonable bounds to get that last little bit of gain?
With apologies to those who practice amp design more regularly than I: It's been a while since I've looked at power amp designs, but I seem to recall the whole point of the op amp in this case is to let you control the volume?
ie. the oversimplified version: The volume knob is connected to a potentiometer, which is one of the resistors that sets the op amp's (ie. preamp) gain. And that is what lets us increase or decrease strength of signal going to the main power amp stage?
If that's the case, then... yeah. You absolutely would want to optimize your circuit for less noise, full stop. Moreover, I'd pretty much not care about the THD when the gain is set so low the output voltage is near zero, because the amount of actual signal to distort is also near zero.
For all of the above (@ 10 kHz) , I'd probably design the preamp circuit to not exceed 0.1 V. Yes, it leaves gain on the table, but it also means owners can change the op amps at will and nothing would happen. Which, by all appearances, is exactly what Fosi has done.
solderdude
Grand Contributor
In the vast majority of cases the op-amp would just provide gain (and when a gain-switch is present would set the gain) and the (semi-log type) volume control would just attenuate the signal either in front or behind the op-amp.
In the D10 it is just a buffer/post filter that drives the output (via a small output resistor) to the RCA out and expects to 'see' a load of at least several k-ohm.
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