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kokkat
223
Jan 24, 2018
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Quoted verbatim; grammar, typos and all.
Two sets of linear power supplies Most competing products use 1x15V or etc adapter to the amplifier, this 1x15V will be convert inside the amplifier and cause noise and interference. But we use linear power adapter to provide 2x15V and 1x8V to A30, which help A30 avoid these problem. 2x15V used for high fidelity headphone amplifier circuit. 1x8V used for MCU, LED and relay. Less noise, less interference. Source: http://www.tpdz.net/en/products/a30/index.htm
Output impedance: 10 Ω (6.35 mm output) 30 Ω (3.5 mm output) <------ Why???? Source: https://www.soundphilereview.com/reviews/topping-a30-review-754/
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Eli35
653
Jan 25, 2018
kokkatHoooly 30 ohm output inpedance for 3.5mm?!?!?!? It makes no freakin' sense, since you'll probably connect low-impedance IEMs to the 3.5mm out! What a bummer...
kokkat
223
Jan 25, 2018
Eli3530 freakin' ohms! Maybe someone can explain the logic behind this.
Jimster480
395
Mar 2, 2018
kokkatIts to allow for better volume control for sensitive headphones. If your headphone doesn't have impedance response swings it should be fine anyway.
Jimster480
395
Mar 2, 2018
Eli35You know that ipod touch and stuff has a 30ohm output impedance right?
Eli35
653
Mar 5, 2018
Jimster480Which iPod? From gen 4 to now, each generation has lower and lower impedance, starting from 7 ohm (4th gen) down to 1.7 ohm (6th gen). I know there's some old gear that had high output impedance, but pairing low-impedance headphones (let's say 16 ohm) on high impedance sources will produce a massive difference in the frequency response.
Jimster480
395
Mar 5, 2018
Eli35It won't unless the headphone has impedance response swings. Many headphones these days have flat impedance response graphs.
Eli35
653
Mar 5, 2018
Jimster480Yeah that's true (phase also makes a difference), but I'd say many mid-priced headphones do in fact have impedance swings, specially IEMs with BA drivers and over the ear full sized dynamic headphones.
Jimster480
395
Mar 5, 2018
Eli35Yes I agree, many cheaper headphones do have impedance swings. But if you really look at all the headphones, it's a lower number then you think. Especially since most graphs are done with 600 ohm output impedance and the A30 has 1/20th of that.
Eli35
653
Mar 5, 2018
Jimster480Totally disagree, just for showing a few graphs: KZ ZS5 & ZS6 (IEMs, 2DD + 2BA)
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SoundMAGIC PL50 (IEM, single BA)
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Koss Porta Pro (on-ear, single dynamic)
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HD650 (over-ear, single dynamic)
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Jimster480
395
Mar 5, 2018
Eli35Yes but take a look at 1More Triple driver, 1More Over ear, Denon AH-MM400, Panasonic RP-HD10. You can find headphones that go either way. I'm not arguing here I know lower output impedance is preferable, but I am just saying that it doesn't always matter as much as you think. I have a DX7, A30, D30, M8, Fiio K1, and JDS O2... my A30 passthrough to my O2 to use headphones that are affected by output impedance. Also in the last example of yours, its an HD650... those are 250 ohm and work fine with the 10-ohm 6.35mm output. The higher output impedance only really applies to lower ohm headphones as even 80ohm beyer are all fine through the 6.35mm port.
Eli35
653
Mar 6, 2018
Jimster480Yes, there's headphones that have a rather flat impedance, and for those the output impedance is not as important. But as a rule of thumb, the output impedance to headphone impedance ratio should be always below 1:8 (10 ohm amp works fine with headphones with impedance >=80 ohm).
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