Amir's TODO thread

[drconopoima]

The very low sensitivity headphones range from 16Ω to 50Ω.

There are also some 8ohm IEMs and the Audio Technica ATH E-40 that are 12 ohm.

 

[RayDunzl]

Is there something else at play here that I may be missing?

Your Ohm's Law example seems to be holding the voltage constant, not the delivered power level.

"Sensitivity is how effectively an earphone converts an electrical signal into an acoustical signal. Sensitivity indicates how loud the earphones will be for a given level from the source. This measurement is given in decibels of Sound Pressure Level per milliwatt, or dB SPL/mW." - http://www.shure.com/americas/support/find-an-answer/understanding-earphone-headphone-specifications

Higher impedance would require a higher applied voltage for the same (1mw) power level dissipated at the headphone for a sensitivity test.

 

[drconopoima]

Your Ohm's Law example seems to be holding the voltage constant, not the delivered power level.

I had understood that voltage is what should be held constant because that's what the amplifier does, I mean to get to a certain voltage (amplification of 2X, 6X, 10X, etc). I converted the power I obtained to dB using the Digizoid calculator.

 

[amirm]

power = voltage (V) * current (I)
We don't know the current so let's convert that to ohm that we do know: I = Voltage/R (impedance of headphone)
Plug that in above we get:

Power = Voltage * Voltage / R (impedance of headphone)

So if R climbs, our ability to produce power goes down. To drive high impedance headphones then, we need to have an amplifier that has high output voltage.

 

[RayDunzl]

voltage is what should be held constant because that's what the amplifier does

No. There is a Volume knob (which adjusts the signal voltage applied to the amplifier to be amplified by its gain factor - 2X, 6X, 10X, etc) somewhere in the chain.

 

[drconopoima]

No. There is a Volume knob (which adjusts voltage applied to the amplifier to be amplified) somewhere in the chain.

Yes, but the voltage when the volume knob is maxed out is constant, if the input voltage doesn't change either. Whichever headphones are quieter at that maximum level are harder to drive than the others, right? So, the 600 ohm version of the Beyerdynamic 880/990/discontinued 770 would be quieter in any amp than the HE560, wouldn't they? (at least based on power calculations)

 

[RayDunzl]

I had understood that voltage is what should be held constant ... using the Digizoid calculator.

That Calculator has two choices:

Constant Power or Constant Voltage

I suppose there isn't agreement by the manufacturers/user how to specify "sensitivity", so it lets you use both.

 

[drconopoima]

That Calculator has two choices:

Constant Power or Constant Voltage

I suppose there isn't agreement by the manufacturers/user how to specify "sensitivity", so it lets you use both.

Certainly a 43 ohm headphone that had a sensitivity of 90 dB SPL/V would be harder to drive than the Beyerdynamic DT880 600ohm with a sensitivity of 96dB/mW. But the HE-560 are rated by HiFiMan at 90 dB/mW (although, Innerfidelity measures needing 2.53 mW for 90 dB).

 

[mindbomb]

With a lower impedance, the amplifier will be generally outputting more power, thus being under more stress, will have worse performance. So the way I view it, if a low impedance thd curve is good, then you can infer that all higher impedance ones will be generally better.

In my experience with the headphone community, having enough voltage gain is rarely a problem. It's gotten to the point where a common refrain is that headphone amplifiers aren't just about volume, because people aren't having volume issues even with high impedance headphones.

 

[Candlesticks]

There are also some 8ohm IEMs and the Audio Technica ATH E-40 that are 12 ohm.

They are very high sensitivity though. Output impedance and crosstalk would be the most important measurements. I think there should be an exploration of whether balanced is worthwhile with low impedance, high sensitivity IEMs to reduce crosstalk. I've noticed that it is quite common for IEMs to have high amounts of crosstalk due to poor cable design and that 3.5mm male to female extension cables increase audibly crosstalk.

 

[drconopoima]

They are very high sensitivity though. Output impedance and crosstalk would be the most important measurements. I think there should be an exploration of whether balanced is worthwhile with low impedance, high sensitivity IEMs to reduce crosstalk. I've noticed that it is quite common for IEMs to have high amounts of crosstalk due to poor cable design and that 3.5mm male to female extension cables increase audibly crosstalk.

Yes, I misread what you said (you were already talking about low sensitivity headphones). I mentioned that the ATH-E40 are 12 ohms because the other worthwhile test for amps is determining whether any channel imbalance will be possible to affect any headphones at hearing volumes. If a channel imbalance is unnoticeable with the ATH-E40, it is certainly unnoticeable with anything even if it is measurable.

 

[Candlesticks]

Yes, I misread what you said (you were already talking about low sensitivity headphones). I mentioned that the ATH-E40 are 12 ohms because the other worthwhile test for amps is determining whether any channel imbalance will be possible to affect any headphones at hearing volumes. If a channel imbalance is unnoticeable with the ATH-E40, it is certainly unnoticeable with anything even if it is measurable.

That's a good point. Measuring the point where the channel imbalance stops on the potentiometer used would be useful for high sensitivity IEMs. Fiio amps normally have 0dB gain as low gain but even then a DAC outputting 1.5Vrms can lead to a moderate listening volume for very high sensitivity IEMs being in the channel imbalance range. It's also a problem for the Schiit Magni 3 where 6dB gain is the low gain. It makes digital volume control required just to avoid the channel imbalance when using high sensitivity IEMs.
https://www.amazon.com/Earbuds-Headphones-Isolating-Earphones-Controller/dp/B072XDPM3J

 

[Candlesticks]

I'll add the Schiit Mani onto the list as well as it is a cheap phono preamp and hopefully a good one. On top of that a good ADC that isn't high cost would be worth finding for vinyl rips. There is the Schiit Jil. I wouldn't consider these high priority.

Building a list of quality budget DAC and amps that can cover all use cases is more important. A lot of people ask on a daily basis what to purchase and being able to point to a list of verified equipment with known limits would be invaluable.

Fiio products tend to be good recommendations because they are a DAC and amplifier with line out functionality which means that if in the future someone wants to purchase an amplifier with higher power output they don't have to buy another DAC. Someone could start out by buying a Fiio Q1 and in the future they can buy a Schiit Magni 3 while still using the Q1 as a DAC. They can then disconnect the Q1 from their home desktop setup and take it with them to work or connect it to their smartphone.

 

[Rthomas]

Hi Guys,

I went on holiday and now I'm back as a Patron! Happy to support the excellent work by Amir.

I have a suggestion. A R2R vs DS DAC shootout.

Take a ''top of the line'' FOTM R2R Dac like the Schiit Gungnir Multibit and compare it against a solid DS DAC like the new RME ADI2-DAC.

I know that both of these are higher than Amir's usual budget but Schiit has a 15 day trial with a restocking fee and I'm sure the ADI-2 DAC will be available at large pro-audio retailers with generous return policies.

I'm happy to contribute towards the costs of such a shootout. I think a lot of us who frequent such forums are willing to spend reasonably high amounts for set it and forget it performance ($750 to $1500). Come on guys let's help make this happen

 

[amirm]

I have a suggestion. A R2R vs DS DAC shootout.

Thank you so much for the kind donation. This is the most often requested comparison. And I am anxious to do it. Cost has been a barrier toward getting it done as you said. At $1,300 even the restocking fee with Schiit can be significant.

 

[Sylafari]

I may be willing to lend Amirm my RME, but it will have to be a few months down the line (I love it too much currently )

 

[Rthomas]

Thank you so much for the kind donation. This is the most often requested comparison. And I am anxious to do it. Cost has been a barrier toward getting it done as you said. At $1,300 even the restocking fee with Schiit can be significant.

Hi Amir,

An idea (don't know if it is any good) is to create a seperate thread for the shootout and then give an approximate cost to get it done adding up shipping and any restocking fees/ loss on resale etc....

The interested members can share the expenses?

That sounds fair especially as you're spending the time to do the testing. Maybe that'll work?

 

[bobhol]

Good news. It got the purchases it needed to hit $179 so there is good demand for this. Will be a very interesting comparison to Topping D30.

The SMSL m8 is getting closer. I also ordered one and today I got an email the they had printed the label! ROTFL

 

[amirm]

The SMSL m8 is getting closer. I also ordered one and today I got an email the they had printed the label! ROTFL

My notice says it will ship Feb 19th. If it is coming from China we need to add another week to two to that.

 

[DonH56]

Here's one I've thought about off and on: I usually click on "new posts" and read from there. When I do that, I'll click the first post, read it to the bottom, then have to scroll back up to the top to hit "new posts" again (usually I just hit alt-left arrow to return but that does not reduce the list by the thread I just read). How about adding the "new posts" button to the bar at the bottom of the forum page as well?