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Review and Measurements of Massdrop Alex Cavalli Tube Hybrid (CTH) and JDS O2 Headphone Amps

Blank Verse

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Thank you Amir for your excellent reviews. I just got my first headphone amplifier recently (a JDS Labs O2) and in great part I did it thanks to your endorsement. I don't plan to power anything too demanding (like HE6). I'm planning to use this with HD600 mostly, though I was thinking about the K240 Sextett or K240DF. I know these cans are demanding, and I wonder if any people have tested them with the O2.

I am no audiophile, but to my ears the O2 is a golden amp. Extremely clear and detailed. I can't believe the amount of resolution and details I can hear, even with my lowly MDR-7506. On the negative side, a lot of my material now seems to have glaring flaws I didn't notice before.
 

Jimster480

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Thank you Amir for your excellent reviews. I just got my first headphone amplifier recently (a JDS Labs O2) and in great part I did it thanks to your endorsement. I don't plan to power anything too demanding (like HE6). I'm planning to use this with HD600 mostly, though I was thinking about the K240 Sextett or K240DF. I know these cans are demanding, and I wonder if any people have tested them with the O2.

I am no audiophile, but to my ears the O2 is a golden amp. Extremely clear and detailed. I can't believe the amount of resolution and details I can hear, even with my lowly MDR-7506. On the negative side, a lot of my material now seems to have glaring flaws I didn't notice before.
It is always a slippery slope as more quality = more flaws revealed.
I also have a JDS O2 (mine is a custom unit) and I loved it for a few years. Now I don't use it anymore ever since I got the THX AAA789 because i just have one amp on my desk. However I will likely use it again when I build a second setup for my other desk.
I never had any issues with it and JDS Labs really stands behind their products!
 

Blank Verse

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It is always a slippery slope as more quality = more flaws revealed.
I also have a JDS O2 (mine is a custom unit) and I loved it for a few years. Now I don't use it anymore ever since I got the THX AAA789 because i just have one amp on my desk. However I will likely use it again when I build a second setup for my other desk.
I never had any issues with it and JDS Labs really stands behind their products!
Yes, you are absolutely right. It makes me wonder what kind of equipment some engineers master with HAHA. But it is like cleaning a window which hasn't been cleaned in years, everything is more clear and if, say, it allows you to see the hobo down the street taking a leak in a corner more clearly, too bad for you I guess. ;)

Yes, even though I bought my unit second hand I contacted JDS a few weeks ago and I have never had such a pleasant interaction with a retailer/manufacturer since I was a kid with the icecream truck man. A really standup company.

Using the O2 as a secondary unit makes a lot of sense because it is so compact. Mine has the AC and line input in the front which makes it a little more unwieldy, though. But it is still worth it for the results. BTW, what cans have you used the O2 with?
 

Jimster480

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Yes, you are absolutely right. It makes me wonder what kind of equipment some engineers master with HAHA. But it is like cleaning a window which hasn't been cleaned in years, everything is more clear and if, say, it allows you to see the hobo down the street taking a leak in a corner more clearly, too bad for you I guess. ;)

Yes, even though I bought my unit second hand I contacted JDS a few weeks ago and I have never had such a pleasant interaction with a retailer/manufacturer since I was a kid with the icecream truck man. A really standup company.

Using the O2 as a secondary unit makes a lot of sense because it is so compact. Mine has the AC and line input in the front which makes it a little more unwieldy, though. But it is still worth it for the results. BTW, what cans have you used the O2 with?
Yea my customizations are to have everything on the back like a traditional amp and just have the headphone jack in the front (I did a 3.5mm because that is what I have the most of) and I have a 1x/3.3x gain instead.

I used it with my Denon AH-MM400, 1More Triple Driver Over-ear & Quad Driver IEM & Triple Driver IEM (the last 2 are lost now at an event) and Panasonic RP-HD10K, Oppo PM-2 and MrSpeakers (now Dan Clark Audio) Aeon Flow Closed.. we have tested out various other headphones like Hifiman Ananda & HE6 and LCD2, Aeolous etc at headphone meets in the past too. It didn't have an issue driving basically anything we connected it to.
 

Blank Verse

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Yea my customizations are to have everything on the back like a traditional amp and just have the headphone jack in the front (I did a 3.5mm because that is what I have the most of) and I have a 1x/3.3x gain instead.

I used it with my Denon AH-MM400, 1More Triple Driver Over-ear & Quad Driver IEM & Triple Driver IEM (the last 2 are lost now at an event) and Panasonic RP-HD10K, Oppo PM-2 and MrSpeakers (now Dan Clark Audio) Aeon Flow Closed.. we have tested out various other headphones like Hifiman Ananda & HE6 and LCD2, Aeolous etc at headphone meets in the past too. It didn't have an issue driving basically anything we connected it to.
Thank you for the details. That's quite some variety. What I heard before is that HE6 were not driven very well from the O2, but it's good to know that the results are at least acceptable, because those have to be some of the hardest cans to drive.

I'm looking forward to getting a few headphones (HD540, K240DF, etc) with the security that I won't have trouble driving them.
 

Jimster480

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Thank you for the details. That's quite some variety. What I heard before is that HE6 were not driven very well from the O2, but it's good to know that the results are at least acceptable, because those have to be some of the hardest cans to drive.

I'm looking forward to getting a few headphones (HD540, K240DF, etc) with the security that I won't have trouble driving them.
The HE6 required my 3.3x gain and the knob to be pretty cranked, however it was definitely possible to listen to.
 
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