Op-amp Rolling Using Sparkos on Fosi V3 Mono

[solderdude]

So, how do I match level of View attachment 4420372 integrated amplifiers with responses at "flat" setting like this? At 1 kHz? Really?

Does it really matter ?
Do you even for 1 second think (I know you don't as you have more than enough experience !) that there is a single frequency or overall average 'level' where you can not tell these curves apart when listening to it nor nulling it ?
This kind of difference is audible and measurable. Period.
What does it have to do with level matching at 1kHz or 3kHz in this particular case ?
The outcome will never be 'no difference detected' when matched at 1kHz, 3kHz or any other frequency of choice.

 

[danadam]

Are the number of frequency points (or bins) used, for the frequency range (20-20K), generally 32, 36, 40 then a straight line drawn between them, to ask?

Not sure I understand the question, but the number of bins in the range from 0 to half the sampling rate is half the FFT size used. The FFT size is usually a power of 2 and in the order of tens or hundred of thousands. REW for example gives options from 8'192 (2^13) to 4'194'304 (2^22).

 

[KL....]

Not sure I understand the question, but the number of bins in the range from 0 to half the sampling rate is half the FFT size used. The FFT size is usually a power of 2 and in the order of tens or hundred of thousands. REW for example gives options from 8'192 (2^13) to 4'194'304 (2^22).

FFT (Fast Fourier Transform) is a mathematical algorithm used to analyze signals by converting them from the time domain to the frequency domain, while REW (Room EQ Wizard) is a software tool that utilizes FFT to analyze room acoustics and system performance. REW/FFT is designed for room acoustic measurement, loudspeaker measurement, and audio device measurement. It helps users optimize the acoustics of listening rooms, studios, or home theaters.... is that correct?

In the context of FFT (Fast Fourier Transform), the Frequency Points and Bins are essentially the same measurement points, representing the discrete intervals of the frequency spectrum. The frequency spectrum is divided into a finite number of intervals/bins which represent specific frequency ranges. Each Bin corresponds to a specific Frequency Point, and the FFT provides amplitude and phase values for each of these points. If you perform an FFT with a size of 100, you'll get 100 frequency points/bins representing the frequency spectrum.... is that reasonable?

 

[danadam]

REW/FFT is designed for room acoustic measurement, loudspeaker measurement, and audio device measurement. It helps users optimize the acoustics of listening rooms, studios, or home theaters.... is that correct?

Basically yes. Personally I rarely use it for acoustic stuff and mostly use its RTA tool for DACs measurements.

If you perform an FFT with a size of 100, you'll get 100 frequency points/bins representing the frequency spectrum.... is that reasonable?

In the most general case, i.e., in case of complex-valued signals, yes, that's true. You will get 100 points representing frequencies from -0.5 * sampling rate to +0.5 * sampling rate. But in case of real-valued signals, the negative side is just a mirror of the positive side and is usually not shown.

 

[pma]

Ideally, when there are stronger differences than 0.1dB/20deg then simple level matching is impossible and A/B comparison will very likely be dominated by those differences.
That is, you can A/B those different frequency responses directly, without any DUT or with the same DUT eq'd and will get detectable differences from that alone.

That means, to compare two different DUTs, their frequency responses must be minutely matched first to remove this variable. And the variable itself can be checked independently.

I had one prominent case where people heard difference between a DAC output and the original recording but the "DAC output" actually was emulated only by its associated frequency and phase response and no other effects, no actual conversion.

Sure. The main question is if you want to hear the difference in linear transfer function or not. If not, then you may EQ. But in case you are interested in linear transfer differences as well, then you must not equalize them. And if they exist, you hear them and it is the fact, you cannot deny it. BTW, linear differences are much more audible than the nonlinear ones, in fact linear differences are key to perceived differences.

 

[SIY]

The main question is if you want to hear the difference in linear transfer function or not.

In this thread's context, the question being asked is "Can one hear the difference between device A and device B?" And if the frequency responses are sufficiently different, one can.

Your question is a different one which requires a different experiment. This is why it's extremely important before designing an experiment to specifically define the question to be answered.

 

[xNORgate]

I wonder why we went from 'tube rolling' straight to 'op-amp rolling' and skipped the whole 'transistor rolling' thing...
Wouldn't that be fun...

No... but any of these three have got to be more enjoyable than the - non-optional - firmware/software updates for audio 'hardware'.
FW/SW updates have become the 'way of the future, way of the future' in audio.

 

[wwenze]

Software is the biggest pain that is somehow unspoken

When I was forced to upgrade to Windows 11 my UMIK returned such weird measurements that I thought it was broken

Then months later I went to control panel and disabled a bunch of "enhancements" and it was working again

 

[xNORgate]

FWIW: Unlike op-amp rolling; tube-rolling had a purpose.

I asked googleGemini about sonic differences between KT88 and 6550 tubes when used with the McIntosh MC-275 tube power amplifier.
Some of the requested 10 bullet-points Gemini provided were strangely close to what I recall of those years of attempting to hear their differences... but never could prove.

Here's a summary of how they generally compare in audio performance:
1. Power Output: KT88s generally have a higher plate dissipation rating, potentially allowing for slightly more power output in a well-designed circuit. However, in the MC275, the difference might be minimal.
2. Bass Response: 6550s are often described as having a slightly more powerful and deeper bass response with a bit more weight. Some listeners find the KT88 bass to be tighter and more controlled.
3. Midrange: KT88s are often praised for a smoother, clearer, and more detailed midrange. Some describe the 6550 midrange as having a touch more "grain" or a slightly different character.
4. High Frequencies: KT88s can offer a more extended and delicate high-frequency response, sometimes described as "sweeter" and more refined compared to 6550s.
5. Overall Tone: KT88s are often characterized as having a more "hi-fi" sound with greater clarity and a wider soundstage. 6550s can offer a more robust and muscular presentation.
6. Headroom: Due to their higher voltage and dissipation capabilities, KT88s may provide slightly more headroom before clipping, potentially leading to a cleaner sound at higher volumes.
7. Distortion Characteristics: When driven hard, 6550s might exhibit a different type of distortion, sometimes described as "snarlier," which can be desirable for certain musical genres. KT88s tend to remain cleaner for longer.
...
Experimentation Recommended: The best way to determine which tube is preferable in your MC275 is to try both types and listen for the differences in your own system.

Quad match sets of KT88s were more pricey than 6550s. I used to think that it may have been my implicit bias to prefer the KT88s.

 

[SIY]

Unlike op-amp rolling; tube-rolling had a purpose.

I'd question that.

 

[KL....]

FWIW: Unlike op-amp rolling; tube-rolling had a purpose.

I'd question that.

Thank you, yes, but Tubes/Valves are very much a Material tech and applyed via a Electronic/Electrical Tech, aren't they? Opamps are similar/same but/and especially they are much more able to control the Material/Electronic/Electrical characteristics via proximity/application/etc, aren't they? For a type of Tube/Valve application, Nuvista is a good example of proximity/application/etc, with the example showing the characteristics of better/improved speed/control via proximity/application/etc, aren't they?

 

[xray]

I asked googleGemini

I've been using AI at work for about a year now. It's helpful about 50% of the time. The other 50% of time it's very wrong. If you don't know enough to tell the difference it's a dangerous tool.

 

[roog]

I don’t think this will affect most audiophiles beliefs, theywant to hear a difference too badly.
When you think about it, operational amplifiers were designed to do analogue computations, if they did anything wildly different they wouldn’t be much good as op amps!

 

[SIY]

Thank you, yes, but Tubes/Valves are very much a Material tech and applyed via a Electronic/Electrical Tech, aren't they? Opamps are similar/same but/and especially they are much more able to control the Material/Electronic/Electrical characteristics via proximity/application/etc, aren't they? For a type of Tube/Valve application, Nuvista is a good example of proximity/application/etc, with the example showing the characteristics of better/improved speed/control via proximity/application/etc, aren't they?

I am unable to understand what you're trying to say. The use of the word "proximity" is also totally puzzling. "Speed/control" is even more puzzling. Aren't they?

 

[solderdude]

tubes age and can go bad pretty quick. That's why you can easily exchange them.
Also the Vin/Iout characteristics vary a lot between tubes. Depending on the circuit (amount of feedback) the distortion can be quite different.

 

[SIY]

Also the Vin/Iout characteristics vary a lot between tubes.

Not nearly as much as, say, FETs, where a 5:1 variation in transconductance and 3:1 in pinchoff voltage are the norm. For example, in my phono preamp (no overall feedback), the largest effect of tube swap is in the second gain stage, and the worst tube clocked in at about 0.05% second harmonic, which I seriously doubt is audible. In my power amp, which uses EL84, changing from one brand to another barely budged the distortion needle.

Worn out tubes are a different story, but I don't classify that as "rolling." Ditto swapping pin compatible but vastly different tube types (e.g., ECC83 for ECC82). That's not really rolling, it's breaking.

 

[CedarX]

That's not really rolling, it's breaking.

Good point! Also true for opamp: if you remove the opamp altogether, it does make a noticeable sound difference (as… “no sound”).
If one “breaks” things enough, it’s going to impact the sound.

 

[xNORgate]

I'd question that.

I am near certain that you've owned tubed audio gear.
Or, maybe you are questioning my liberal use of 'tube-rolling', instead of the necessary and periodic 'tube-replacement'.

[op-amps] When it is broken (which in practice never happens) and even then a $ 1.- opamp is already more than good enough in this amp.

[tubes] not so.
In my use-case, their life-expectancy hovered around a year or so.
I must have performed about a dozen "tube-rolling" events, during the 30+ years of a MC275 ownership.

 

[amirm]

I am near certain that you've owned tubed audio gear.

He is an accomplished tube designer! Better have your act together before challenging him.

 

[amirm]

Here is my test of tube rolling confirming what @SIY post.

Tube Rolling: Does it Make a Difference?

I recently reviewed the Mhdt Pagoda tube DAC. Owner was kind enough to send me three other tubes to test with it. Here are the set of tubes I received: Let's start again with the tube supplied with the unit (GE 5670) Now let's switch to Tesla 6CC42 (GA): Other than slightly more mains...

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