Drop + THX AAA™ 789 Linear Amplifier Discussions | Drop

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Drop + THX AAA™ 789 Linear Amplifier

Audiophile

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Music1978

Dec 17, 2018

Hi @AndrewMason Can the THX 789 drive planars like Mr Speakers Aeon headphones? These are ~12 ohm impedance cans (flat impedance curve). How much current can the THX 789 output into 12 ohm planars like this, while keeping the ultra low distortion performance?

(Edited)

Dec 17, 2018

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AndrewMason

558

THX Ltd. Analog & Power Engineering Expert

Dec 17, 2018

Music1978789 has no problem driving the Aeon's. In both single-ended or bal out, peak overcurrent protection ~ 0.9Apk would kick in at around 5 Watts into the 13 Ohms. MR Speakers posts 92 dB/mW closed, 94 dB/mW open. Using the 92 dB figure, 789 would produce a very loud 129 dB SPL assuming the Aeon's are still linear at that point.

Dec 17, 2018

Music1978

Dec 17, 2018

AndrewMasonThanks @AndrewMason ! I didn’t think current would be an issue in general - moreso current below 16 ohms since that is the spec for the THX 789 and the MrSpeakers measure 12-ohm (I’ve seen 13 ohm mentioned but also some one measurement where it dipped to 12 ohm so lets assume 12 ohm to be conservative). So I wanted to ask if the THX could pump out 0.9A into 12 ohm flat and still keep it’s ultra low distortion performance? Moreso as a headroom / performance question, not that I’d be listening at this level of course. I’m asking since 12 ohm is less than the 16 ohm specifies for the THX 789. Thanks again

Dec 17, 2018

jaydunndiddit

3262

Dec 18, 2018

Music1978From someone that uses incredibly sensitive IEMs, Campfire Solaris [10 ohms] and Shure SE846 [9 ohms], and the 789 handles them with aplomb. Perfectly black background and absolutely hiss-free. The low OI of the amp also ensures the FR will remain unchanged of OI sensitive gear. I used to own the Aeon Flow Closed and while they do like a bit more power, they're not a typical current hungry planar like my HiFiMan or Fostex headphones. They're much harder to drive compared to the AFC so I think in any given situation, you are going to be fine with a low gain and will have ample headroom. Even more so if you're running everything balanced. With this amp running balanced, I don't think I have gone past gain II and that's even with the voltage hungry 6XX.

Dec 18, 2018

Sean_S4126

Dec 18, 2018

Music1978I'm running a Benchmark DAC3 B with 10dB pads (17.5dBu max) on balanced XLR's to THX 789, then to Aeon Closed. I have not tried SE from the DAC3 to the THX 789. With 4-pin balanced to the Aeons, I can use the lowest gain on the 789. With single-ended TRS to the Aeons I have to use the middle gain setting to get loud.

(Edited)

Dec 18, 2018

mesaone

111

Dec 18, 2018

jaydunndidditTo supplement your info, here's nn example of current-hungry planars: I'm running a 2V DAC into the 789 SE inputs, with a pair of HE-560 (45Ω, 90 dB/mW) fed from the 789 balanced output. Plenty of power available when the amp is set to Gain 2, with room to spare on the pot. Even Gain 1 can get them to listenable levels with the pot cranked up. Granted, these aren't as hungry as some others (HE6 for one) but it's one example.

(Edited)

Dec 18, 2018

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jaydunndiddit

3262

Dec 18, 2018

mesaoneYeah, I just got balanced cabling for my HE-4XX and boy does this thing breathe something into them. Prior on SE, Gain III had to be used to get them to a consistent level I enjoy. And even then, every now and then, I could go for a bit more. With the extra power, it's absurd how good the low-end is on them. More rumble and texture than I expected.

Dec 18, 2018

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mesaone

111

Dec 18, 2018

jaydunndidditYou must prefer a much louder level than me. Gain 2 is plenty for all three of my Hifiman planars (560, 400i, 4XX) even when driven single-ended. And yeah, I agree that the 4XX can really kick with this amp.

Dec 18, 2018

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jaydunndiddit

3262

Dec 18, 2018

mesaoneOh yeah, I listen normally around 80-85 db. I do tend to listen a bit louder than most, ha.

Dec 18, 2018

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Jimster480

395

Dec 20, 2018

Music1978Yes its fine, I drive both my mrspeakers Aeon and my Oppo PM-2 at the same time all day every day.

Dec 20, 2018

G3n3r1c

216

Dec 25, 2018

jaydunndidditWith the 789 and balanced cables, my HD-600s remain below the 50% mark on Gain II. My HiFiMan HE-560s require 50% to even 75% on Gain II.

Dec 25, 2018

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