Better amp for low impedance?

[PurpleAngel]

10x as a minimum? Or for optimal/best performance?

I think of 10X as a good guideline (for damping control.), up until you talked about the 50X, I had never heard of that before, or seen it talked about on Head-Fi.
So as far as my brain is concerned, 10X is fine with me, even 5X is OK with me.

 

[CT007]

I think of 10X as a good guideline (for damping control.), up until you talked about the 50X, I had never heard of that before, or seen it talked about on Head-Fi.
So as far as my brain is concerned, 10X is fine with me, even 5X is OK with me.

Would be interesting to set up a test for this, where A) a blind test is done between various impedance/DF matchings, and B) an impedance formula is made, where you can reliably hear a difference.

If I plug my AD700X (38 ohms) directly into my Modi MB(75 ohm impedance) instead of my Vali 2(1.2 ohms), for example, I can't say I've noticed a difference yet.. Not that AD700X is anything exceptionally transparent or difficult.

 

[PurpleAngel]

Would be interesting to set up a test for this, where A) a blind test is done between various impedance/DF matchings, and B) an impedance formula is made, where you can reliably hear a difference.

If I plug my AD700X (38 ohms) directly into my Modi MB(75 ohm impedance) instead of my Vali 2(1.2 ohms), for example, I can't say I've noticed a difference yet.. Not that AD700X is anything exceptionally transparent.

Headphones like the ATH-AD700X usually sound good no matter what jack they are plugged into.

 

[castleofargh]

Would be interesting to set up a test for this, where A) a blind test is done between various impedance/DF matchings, and B) an impedance formula is made, where you can reliably hear a difference.

If I plug my AD700X (38 ohms) directly into my Modi MB(75 ohm impedance) instead of my Vali 2(1.2 ohms), for example, I can't say I've noticed a difference yet.. Not that AD700X is anything exceptionally transparent or difficult.

B already exists. the at least 1/8 ratio that serves as a vague rule of thumb is in part based on how it should ensure less than 1dB of frequency response change. but that's with the assumption that your headphone has a fluctuating impedance response and that the value you use for the 1/8 ratio is the lowest impedance of the headphone. not just the impedance at 1kHz like is usually the case in specs.
I use a basic formula all the time to estimate DAP impedance at a given frequency. it goes something like this: voltage X headphone's impedance / (headphone's impedance + amp's impedance) = voltage at the headphone.
you have to use that a few times to get relevant points of reference. like say the minimum impedance value for the headphone calculated with 2 different amps, and then same thing for the maximum impedance of the headphone with those same 2 amps. so you end up with 4 voltage values, showing that one amp, due to a different impedance output, will make the headphone more boosted by a given amount at the frequency where the max impedance of the headphone is located. or something along those lines.
and to go from voltage variations to dB variations, I'm lazy so I almost always enter the values here http://www.sengpielaudio.com/calculator-gainloss.htm ^_^

with all said an done, those stuff won't really tell you how 0.6dB boost at 1700Hz will feel. and even those values can turn out to be significantly inacurate if the way the specs were measured wasn't all that accurate. me for example, for a long time I was off by about half an ohm because like a moron I didn't include the extra cables I used to measure. when measure my HD650, who cares about 0.5ohm right? but when measuring IEMs that go as low as 5ohm and checking variations between amps that had sometime just 0.3ohm between them, well let's say that my calculations didn't mean crap in such circumstances. which is too bad because of course it's with IEMs that the biggest fluctuations are to be expected.

with all that said, you would be wrong to assume that a simple impedance number is the cause and answer to any question about audible differences, or why a given headphone may kind of suck with a given amplifier. ultimately it's but one variable, so while making sure you have a reasonable damping ratio is never a bad idea IMO, there is no rule saying that the lower the impedance of the amp, the better it will behave with a low impedance headphones. what you've been concerned about so far is the well being of the headphone in a way, but amps have needs too and I'm afraid that short of having them measured into the load you plan to use, you will have a hard time figuring out how well an amplifier will manage to drive a low impedance headphone/IEM. for some 30ohm or more and relatively high sensi, most amps will work just fine(except maybe some OTL designs as they're not very fond of low impedance loads), but below that, unless the designer explicitly says that all is good with low impedance IEMs and stuff like that down to Xohm, again it would be better to find actual measurements(which is often easier said than done).


leaving people with no clear answer and many more questions, that's how I roll!
sorry ^_^

 

[castleofargh]

I feel like I need to add this late disclaimer: I'm talking as a, and for nitpicking perfectionists. most people never bother about all that and live happily ever after with the amp they got because they liked the color of the front knob.

 

[CT007]

Awesome! Thanks : )

B already exists.

So, what are some amp+phone pairings where you notice the problem? Something affordable, perhaps ;p

Perhaps there is a special high impedance headphone cable you could use, in place of a high output impedance amp? (Assuming detachable cable feature)

Is it dangerous to the headphones to operate with such a mismatch..?

more boosted

So if there's a significant impedance mismatch, it means you basically get less volume(at least in one frequency range or another)?

 

[castleofargh]

wall of words!!!!

So, what are some amp+phone pairings where you notice the problem? Something affordable, perhaps ;p

which problem? if you're talking about the frequency response change that could be caused by using an amplifier of different impedance output, then many IEM can change audibly simply by going from maybe 0.5ohm to a 2ohm amp section. typically multidriver IEMs where you have the impedance curve going from very low impedance to pretty high or the other way around, or even have several back and forth due to crossovers.
you can see some examples of using the same IEM on amps with different impedance in my post here https://www.head-fi.org/threads/feedback-about-gears-stop-doing-it-wrong-impedance.866714/
my JH13 aren't the worst and you see that you need pretty substantial impedance output to make a relevant change in signature. but if you were to check the same impact on IEMs that go as low as 4 or 5ohm at certain frequencies, like the Shure SE846, then the variations would be much bigger and even a few ohm would be audible as a frequency response change.
for headphones, on my HD650 the impedance curve has a pretty serious bump around 100Hz. so when you use a high impedance amp, you can see measure that area being boosted a little. but as the lowest that headphone ever reaches is already several hundred ohm, you won't get a big bass bump by switching a 0.5ohm amp with a 3ohm one. because both already offer more than enough when it comes to damping ratio, ensuring minimal change in frequency response.

so it really depends on the impedance curve of the headphone/IEM when they become part of the complete circuit. but low impedance headphones/IEMs automatically are more likely to be more affected because it's about damping ratio.

two warnings:
- here I'm specifically focusing on headphone's frequency response variations due to impedance. in reality there could be other differences aside from FR, and even for FR, other causes could affect it. different amps may be different in many ways.
- we're often assuming that the best damping and amps with lowest impedance are best, but subjectively you might find situations where you'll just prefer the sound from a higher impedance amp.

Perhaps there is a special high impedance headphone cable you could use, in place of a high output impedance amp? (Assuming detachable cable feature)

we can do that of course, adding one resistor to each channel, or even creating a little voltage divider. but you have to remember that it's "seen" as a change for both the amp and the headphone. the amplifier "sees" the headphone+cable as the load, while the headphone "sees" the amp+cable as the source's impedance. so by adding a resistor in series, you will worsen the damping ratio, while reducing the volume level(that the amp will have to be able to compensate). once again, it's a case by case thing to consider, but overall, it's not the answer IMO.
when it could be good:
- if your amplifier simply can't handle the current flow because your IEM has too low an impedance, by adding a resistor you reduce the current flow and could help the amp work nominally again despite still using that IEM. you'd just have to check that the possible change in signature doesn't displease you. but that's a pretty extreme situation, usually such a thing just doesn't happen unless the headphone has both stupidly low impedance and low sensitivity. a few planars or something like that maybe, but usually when you have such difficult headphone to drive, you know about it and get the amp for that specific job. I'm only listing what could exist, not saying that it's the norm.
- when you simply like the sound better with extra resistance. the most famous example of this would be the Etymotic ER4. the ER4S that the vast majority of users prefer to the ER4, is an ER4 with 2 75ohm resistors in the cable(one per side). it reduces the entire listening level, but because of the impedance curve of the ER4, the attenuation is slightly bigger in the low and mid range compared to the trebles. so once you've finished matching the volume back to your preferred listening level, the trebles are slightly louder and Ety fans usually like that.
- another use that has nothing to do with impedance, is to simply reduce the listening level with the hope to also reduce background noise. and hopefully when you increase the gain on your amp, that noise won't increase back with the music.

so once again, different circumstances create different needs/choices.

Is it dangerous to the headphones operate with such a mismatch..?

no.

 

[CT007]

so by adding a resistor in series, you will worsen the damping ratio, while reducing the volume level(that the amp will have to be able to compensate). once again, it's a case by case thing to consider, but overall, it's not the answer IMO.

I guess that's the result I was looking for, haha. Creating a strong mismatch, by using a high resistance cable(if that even exists on the market), to hear/tell a difference.

Also, Stax > Pringles

 

[PurpleAngel]

I feel like I need to add this late disclaimer: I'm talking as a, and for nitpicking perfectionists. most people never bother about all that and live happily ever after with the amp they got because they liked the color of the front knob.

Yea. that makes sense to me.
I just bought a duffel bag to use as a carry on for flying, at the store, I could not decide on the size or features of the carry on bag, but I saw a purple one and that made it the deciding factor.