[gregorio]

The first mentioned has a DAC chip which is supposed to have a "musical" sound while the Sabre is supposed to have more emphasis on details and bass and treble. I have seen reviews of the two DAPs and this is what is claimed.

The important parts to take away from this is “supposed to be” and “what is claimed”. Yes, that is a common claim but it’s just marketing or the repeating of marketing. All DAC chips have the same “sound”, unless the designer of the DAP chooses a particularly dodgy filter or implements some other signal processing such as EQ or loudness normalisation. Unless this is the case and providing you really are hearing a difference (rather than a perceptual error/bias), then it’s some issue with the amp/IEM. The amp doesn’t have the right impedance or enough power to drive that particular IEM.

G

 

[castleofargh]

Someone called a Sabre chip cold like 2 or 3 chip generations ago when everybody would just stick one in their product without a care for Sabre's own implementation guidelines, so they could market it with the impressive specs of the chip instead of the specs of the DAP and pray for confused consumers to jump on it. Since, Sabre has been "analytical" or something along those lines.

And FIIO DAPs have been mostly called warm since the first X3 a decade ago. Once the idea is in some review and in the mind of readers, it gets regurgitated forever and gets associated with the easy stuff to remember, the brand.
Add to this all the people who mistake the impedance impact on their IEM with the "tuning" of the DAP or DAC/amp, and it becomes quite the gamble to rely on audiophile feedback. Not that it was very reliable in the first place.

 

[LarsHP]

The important parts to take away from this is “supposed to be” and “what is claimed”. Yes, that is a common claim but it’s just marketing or the repeating of marketing. All DAC chips have the same “sound”, unless the designer of the DAP chooses a particularly dodgy filter or implements some other signal processing such as EQ or loudness normalisation. Unless this is the case and providing you really are hearing a difference (rather than a perceptual error/bias), then it’s some issue with the amp/IEM. The amp doesn’t have the right impedance or enough power to drive that particular IEM.

G

The quotes you refer to are mine.

The point I was making is that these two DAPs are practically the same except for the DAC chip, which would make the two models excellent candidates for a side-by-side comparison test whether there is an audible difference between the DACs. Such a test should of course also be blinded.

I am not saying anything about if there actually is a sonic difference, just to make that clear.

 

[LarsHP]

Someone called a Sabre chip cold like 2 or 3 chip generations ago when everybody would just stick one in their product without a care for Sabre's own implementation guidelines, so they could market it with the impressive specs of the chip instead of the specs of the DAP and pray for confused consumers to jump on it. Since, Sabre has been "analytical" or something along those lines.

And FIIO DAPs have been mostly called warm since the first X3 a decade ago. Once the idea is in some review and in the mind of readers, it gets regurgitated forever and gets associated with the easy stuff to remember, the brand.
Add to this all the people who mistake the impedance impact on their IEM with the "tuning" of the DAP or DAC/amp, and it becomes quite the gamble to rely on audiophile feedback. Not that it was very reliable in the first place.

I think you are right that there was a notion that Sabre DACs were cold and analytical, but that idea isn't universal, luckily.

I don't recall reading people claiming the HiFiMan HM901S sounding cold or analytical despite the Sabre DAC it uses. The reason may be that HM901S has swappable amp cards and, as far as I remember, people have mostly discussed those, not the (Sabre) DAC chip it uses. These amp cards were then marketed as "musical" etc., which may have directed focus away from the DAC section.

 

[bigshot]

I think you are right that there was a notion that Sabre DACs were cold and analytical, but that idea isn't universal, luckily.

I have a Sabre chip in my Oppo HA-1. I did a comparison and it sounds the same as the output of my iMac.

 

[mbphotox]

Question I couldn't find an answer to so far.

Do tube amps "create" a sound signature with different headphones based on the impedance curve of the latter?
Or do headphones not have noticeable impedance curves? (is a 32 Ohm can just linear 32 Ohms?)

Where am I coming from with this?
I have an EL34 tube amp with a distinctive "sound" on my Bowers & Wilkins speakers because the speakers don't have a linear impedance across the frequency range, so the tube amp will not "amplify" all frequencies the same which changes the sound signature of the speakers quite considerably. (the impedance curve zig-zags between 2 and 16 ohms, iirc)

 

[castleofargh]

Question I couldn't find an answer to so far.

Do tube amps "create" a sound signature with different headphones based on the impedance curve of the latter?
Or do headphones not have noticeable impedance curves? (is a 32 Ohm can just linear 32 Ohms?)

Where am I coming from with this?
I have an EL34 tube amp with a distinctive "sound" on my Bowers & Wilkins speakers because the speakers don't have a linear impedance across the frequency range, so the tube amp will not "amplify" all frequencies the same which changes the sound signature of the speakers quite considerably. (the impedance curve zig-zags between 2 and 16 ohms, iirc)

The amount of variation is related to how big the ratio change is (amp/transducer) at each frequency. Speakers have their wildest impedance changes often caused by the crossover circuit between several drivers. They also happen to have extremely low impedance, which can maximize the amount of FR change when changing the amplifier's impedance.
For a single dynamic driver headphone (most headphones), you will find smaller variations as there is no cross over circuit. What's left is just one resonance at a given frequency (usually low freq). And on occasion if the headphone really has big design issues, a few other blips on the impedance curve. But those really tell you to not worry about impedance ratio and just go get another headphone^_^.
Overall it tends to be pretty stable so long as the headphone doesn't have a low impedance. If a headphone has impedance variations going from 350 to 600ohm, only a 100ohm amplifier will manage to cause a frequency response change that's worth noticing. A headphone with impedance going from 25 to 60ohm for example would be more of a concern for the final FR and how the amp's own impedance will affect it.

Dynamic driver will have the resonance(impedance bump) I mentioned. Planars tend to have an extremely flat impedance curve (they are almost fully resistive within the audible range). If you go look at IEMs and multidrivers in particular, then we're back to models more similar to speakers, with low impedance and sometimes really wild impedance variations.
So your example of 32ohm, which is usually only reliable for 1kHz where it was measured, will follow those rules of thumb for the relevant driver type.

Another possible cause for frequency variation, strictly related to impedance ratio (as there could be other reasons for a FR change), is if the amplifier also happens to not have a very flat impedance curve over the audible frequencies (depends on design, but they're usually pretty flat with some changes at really low or really high freqs, so we tend to ignore that aspect. Also, almost nobody will measure amp impedance over a frequency range. We can't be too concerned with information we can't find).

About tube amps, as they tend to have higher impedance than SS amps with strong negative feedback, they can indeed take the impedance curve of a headphone and boost the frequency area near a dynamic driver's resonant frequency (where an impedance bump would show). Some tube amp design could also exhibit some significant roll off in the subs (usually made worse with low impedance headphones). So I guess that too could count as impedance curve and impedance ratio impacts on the frequency response of the headphone.
But obviously a tube amp could also have a good deal of distortions that, without changing a frequency response graph, could change our subjective perception of something like timbre, and we might end up interpreting such changes as frequency response changes.

 

[LarsHP]

Question I couldn't find an answer to so far.

Do tube amps "create" a sound signature with different headphones based on the impedance curve of the latter?
Or do headphones not have noticeable impedance curves? (is a 32 Ohm can just linear 32 Ohms?)

Where am I coming from with this?
I have an EL34 tube amp with a distinctive "sound" on my Bowers & Wilkins speakers because the speakers don't have a linear impedance across the frequency range, so the tube amp will not "amplify" all frequencies the same which changes the sound signature of the speakers quite considerably. (the impedance curve zig-zags between 2 and 16 ohms, iirc)

Tube amps (transformer coupled, IIRC) designed with impedance selectors (for instance, either 4 Ohms or 8 Ohms) may roll off in the bass if the transducer has a much higher impedance than the amp was designed for. This will be the case even if the headphone has a completely flat impedance curve. The roll-off in the bass may be mitigated by putting a power resistor across the terminals. For a 50 Ohm headphone, a 10 Ohm resistor will change the load the amp "sees" to near 8 Ohms. Note that most of the power goes through the resistor if you do that, though.

 

[mbphotox]

The amount of variation is related to how big the ratio change is (amp/transducer) at each frequency. Speakers have their wildest impedance changes often caused by the crossover circuit between several drivers. They also happen to have extremely low impedance, which can maximize the amount of FR change when changing the amplifier's impedance.
For a single dynamic driver headphone (most headphones), you will find smaller variations as there is no cross over circuit. What's left is just one resonance at a given frequency (usually low freq). And on occasion if the headphone really has big design issues, a few other blips on the impedance curve. But those really tell you to not worry about impedance ratio and just go get another headphone^_^.
Overall it tends to be pretty stable so long as the headphone doesn't have a low impedance. If a headphone has impedance variations going from 350 to 600ohm, only a 100ohm amplifier will manage to cause a frequency response change that's worth noticing. A headphone with impedance going from 25 to 60ohm for example would be more of a concern for the final FR and how the amp's own impedance will affect it.

Dynamic driver will have the resonance(impedance bump) I mentioned. Planars tend to have an extremely flat impedance curve (they are almost fully resistive within the audible range). If you go look at IEMs and multidrivers in particular, then we're back to models more similar to speakers, with low impedance and sometimes really wild impedance variations.
So your example of 32ohm, which is usually only reliable for 1kHz where it was measured, will follow those rules of thumb for the relevant driver type.

Another possible cause for frequency variation, strictly related to impedance ratio (as there could be other reasons for a FR change), is if the amplifier also happens to not have a very flat impedance curve over the audible frequencies (depends on design, but they're usually pretty flat with some changes at really low or really high freqs, so we tend to ignore that aspect. Also, almost nobody will measure amp impedance over a frequency range. We can't be too concerned with information we can't find).

About tube amps, as they tend to have higher impedance than SS amps with strong negative feedback, they can indeed take the impedance curve of a headphone and boost the frequency area near a dynamic driver's resonant frequency (where an impedance bump would show). Some tube amp design could also exhibit some significant roll off in the subs (usually made worse with low impedance headphones). So I guess that too could count as impedance curve and impedance ratio impacts on the frequency response of the headphone.
But obviously a tube amp could also have a good deal of distortions that, without changing a frequency response graph, could change our subjective perception of something like timbre, and we might end up interpreting such changes as frequency response changes.

Hey

Thanks a ton for this incredibly detailed reply. That answers my question perfectly.

Cheers

 

[ostewart]

Ok before I confuse myself even more I thought I'd ask here.

In my Hifi setup I have the following, and was wondering if the passive pre-amp is mismatched in terms of output impedance for the power amp input - and if I need a powered pre-amp instead.

Sources:

Marantz CD-52 (200 Ohm output impedance)
Classic Audio Ltd Spartan 5 phono stage (100 Ohm output impedance)
JDS Labs Atom DAC+ (not sure on output impedance)

Pre-amp:

https://www.aliexpress.com/item/1005004416044993.html - 50k Potentiometer

Power amp:

Rotel RB-1050 (33k Ohm input impedance)

 

[castleofargh]

Ok before I confuse myself even more I thought I'd ask here.

In my Hifi setup I have the following, and was wondering if the passive pre-amp is mismatched in terms of output impedance for the power amp input - and if I need a powered pre-amp instead.

Sources:

Marantz CD-52 (200 Ohm output impedance)
Classic Audio Ltd Spartan 5 phono stage (100 Ohm output impedance)
JDS Labs Atom DAC+ (not sure on output impedance)

Pre-amp:

https://www.aliexpress.com/item/1005004416044993.html - 50k Potentiometer

Power amp:

Rotel RB-1050 (33k Ohm input impedance)

Between preamp and amp you probably don't have to worry about impedance. The matter of impedance ratio is messy between amps and headphones(or any other transducers), because headphone impedance numbers are all over the place depending on the one you get. Sources, DACs, amps, they tend to stay in line and follow the more standard system they were made to work with.

 

[ostewart]

Between preamp and amp you probably don't have to worry about impedance. The matter of impedance ratio is messy between amps and headphones(or any other transducers), because headphone impedance numbers are all over the place depending on the one you get. Sources, DACs, amps, they tend to stay in line and follow the more standard system they were made to work with.

Thanks, I'm usually ok with the whole headphones with headphone amp output impedance, but the hi-fi thing with input impedances of amps needing to be x amount higher than the output impedance of the source got me a little confused.

Just didn't know if mine were badly mismatched to the point it's severely decreasing the damping factor, or rolling off the highs.

 

[71 dB]

Ok before I confuse myself even more I thought I'd ask here.

In my Hifi setup I have the following, and was wondering if the passive pre-amp is mismatched in terms of output impedance for the power amp input - and if I need a powered pre-amp instead.

Sources:

Marantz CD-52 (200 Ohm output impedance)
Classic Audio Ltd Spartan 5 phono stage (100 Ohm output impedance)
JDS Labs Atom DAC+ (not sure on output impedance)

Pre-amp:

https://www.aliexpress.com/item/1005004416044993.html - 50k Potentiometer

Power amp:

Rotel RB-1050 (33k Ohm input impedance)

If all impedances involved are very flat in respect if frequency meaning resistive, there are no problems. High output impedance and low input impedance makes big level drop, but that's intended with passive pre-amps to have low volume level when needed.

In practise only the impedances of transducers (headphones & speakers) vary a lot with frequency for acousto-mechanical reasons so usually it is enough to worry about the impedances of headphones, speakers and amps driving them (in case of speakers the impedance of the speaker cable rather than the amp).

As always, if the sound is good to your ears you are good. If there is something wrong with it then it is time to figure out what to do to fix it.

 

[bigshot]

Phono input requires a special phono preamp if you’re plugging in to a standard aux jack. Just thought I’d toss that in since you mention a turntable.

 

[ostewart]

Phono input requires a special phono preamp if you’re plugging in to a standard aux jack. Just thought I’d toss that in since you mention a turntable.

Don't worry, I'm running a phono pre-amp