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Review and Measurements of Massdrop THX AAA 789 Amp

Veri

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A small follow-up: I got a pair of these cables to replace the one I made myself which had intermittent problems (I blame the cheap RCA connectors, NOT my poor solderning skills :p)
These cables are the real deal: canare star quad cables properly wired as per hypex recommendations (pseudo-differential), Neutrik XLR connectors, Rean RCA connectors and clean solder joints.
The benchmark ones are the exact same Rean RCA and Neutrik XLR. I wonder if they are made by the same entity.
 

Roen

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I'm being friendly here. So if you don't get it just ignore it and forget it.
I think it's helpful to define what each of those terms mean so that others can understand where you're coming from.

But if you're just going to take your ball and go home, you probably shouldn't share to begin with.
 

JohnYang1997

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I think it's helpful to define what each of those terms mean so that others can understand where you're coming from.

But if you're just going to take your ball and go home, you probably shouldn't share to begin with.
First of all. This forum is very objectivity driven. Those terms are so called audiophile terms. I could only cause more problems explaining them than just let people who knows gaining from it.
Also he didn't really ask for the explanations, he was being sarcastic that those terms are nonexistent, all the difference being in my head. I was friendly, and the last but not least if someone actually experienced it, he would know immediately. If someone didn't, explanation would do anything. To people who can't hear the difference, just ignore it. There is nothing wrong with them. They should be happy about what they have. That's my approach. I guess that clears it up.
 

ReAlien

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I just tried linear PSU with THX recently. It was a custom made linear PS on a basis of some old Soviet lab-level PS with great stabilization stage and voltage level fine tuning. Maybe attempting it with more audiophile and expensive PS would bring some other results, Idk.
My impressions:

Advantages: more punchy and massive bass, on some tracks the music started to feel more emotional, in some cases, pleasant mids coloration occurred, more forward staging overall.
Disadvantages: decreased sound resolution and "airiness", the bass becomes messier, less controlled, which in most cases feels like a minus, some overtones disappear that I can hear with stock PSU, sometimes it's just more discomforting to listen overall

Out of 7 testing tracks, only one sounded more pleasing and interesting, a couple of tracks brought some mixed feelings and the rest definitely sounded worse.

As you can understand, I decided to use the stock one.)
 

JohnYang1997

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I just tried linear PSU with THX recently. It was a custom made linear PS on a basis of some old Soviet lab-level PS with great stabilization stage and voltage level fine tuning. Maybe attempting it with more audiophile and expensive PS would bring some other results, Idk.
My impressions:

Advantages: more punchy and massive bass, on some tracks the music started to feel more emotional, in some cases, pleasant mids coloration occurred, more forward staging overall.
Disadvantages: decreased sound resolution and "airiness", the bass becomes messier, less controlled, which in most cases feels like a minus, some overtones disappear that I can hear with stock PSU, sometimes it's just more discomforting to listen overall

Out of 7 testing tracks, only one sounded more pleasing and interesting, a couple of tracks brought some mixed feelings and the rest definitely sounded worse.

As you can understand, I decided to use the stock one.)
What headphones were you using for this test? I'm a bit curious.
 

ReAlien

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JohnYang1997

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HE560 mostly, but some of the A/B tests were done with Verum 1 as well.
Ok. I actually found this very interesting. I have listened to he560 to different amps and actually found something unexplainable.
Do you find the sound change similar to reduced 4khz and is overall more fluid sound? Or just being veil and lack transparency?
 

ReAlien

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Ok. I actually found this very interesting. I have listened to he560 to different amps and actually found something unexplainable.
Do you find the sound change similar to reduced 4khz and is overall more fluid sound? Or just being veil and lack transparency?
Yeah, the sound could be called more fluid but the lack of details and transparency was definitely there. I cannot tell about reduced 4khz though. Maybe will try more testing later.
 

JohnYang1997

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Yeah, the sound could be called more fluid but the lack of details and transparency was definitely there. I cannot tell about reduced 4khz though. Maybe will try more testing later.
If you can get consistent result that will be really worth noting to me.
 

Music1969

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Hi @AndrewMason

What is the maximum impedance headphones supported by THX 789, before you start to see a rise in distortion from the specs?
 

JohnYang1997

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You mean no maximum specified? This I know, hence question to Andrew.

Or do you mean there's no maximum impedance performance limit? If so, how do you know?
That's the simple answer. If you want me to elaborate, I'll do too.
If you are talking about distortion per voltage, there is no upper limit. Higher the impedance, lower the distortion. If you directly connecte the output to audio analyzer, that's what you get, usually tens to hundreds of kohms.
If you are talking about distortion per mW, that's a bit of different story. But firstly, none of the headphones on the market has high enough impedance and low enough sensitivity to trigger the problem. However, the maximum power output is limited by the voltage times the current. If you increase the impedance too much, there isn't much current, hence not enough power is generated. So if you makes the amplifier clipping, sure you will get much distortion. Except that, distortion will be very very low.
One more thing, lower impedance = heavier load, higher impedance = lighter load.
 

Music1969

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That's the simple answer. If you want me to elaborate, I'll do too.
If you are talking about distortion per voltage, there is no upper limit. Higher the impedance, lower the distortion. If you directly connecte the output to audio analyzer, that's what you get, usually tens to hundreds of kohms.
If you are talking about distortion per mW, that's a bit of different story. But firstly, none of the headphones on the market has high enough impedance and low enough sensitivity to trigger the problem. However, the maximum power output is limited by the voltage times the current. If you increase the impedance too much, there isn't much current, hence not enough power is generated. So if you makes the amplifier clipping, sure you will get much distortion. Except that, distortion will be very very low.
One more thing, lower impedance = heavier load, higher impedance = lighter load.

Thanks!

Reason I asked Andrew was because the specs provided are for 16 ohms and 600 ohms impedance.

My MrSpeakers AEON Closed are ~13 ohms but Andrew confirmed this is fine anyway. These planars need ~70mW at 13 ohm to produce something like 110dB I read somewhere.

But I was thinking of getting Sennheiser HD800-S and these can go to almost 700 ohms impedance (so past the 600 ohms specified).

From what you say, it sounds like 700 ohms distortion performance should be same as specified 600 ohms distortion performance.
 

JohnYang1997

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Thanks!

Reason I asked Andrew was because the specs provided are for 16 ohms and 600 ohms impedance.

My MrSpeakers AEON Closed are ~13 ohms but Andrew confirmed this is fine anyway. These planars need ~70mW at 13 ohm to produce something like 110dB I read somewhere.

But I was thinking of getting Sennheiser HD800-S and these can go to almost 700 ohms impedance (so past the 600 ohms specified).

From what you say, it sounds like 700 ohms distortion performance should be same as specified 600 ohms distortion performance.

Yes you are right. You won't see any distortion with hd800s but distortion is rising with 13ohm Aeon even though it's still going to be very low.
 

Veri

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My MrSpeakers AEON Closed are ~13 ohms but Andrew confirmed this is fine anyway. These planars need ~70mW at 13 ohm to produce something like 110dB I read somewhere.

But I was thinking of getting Sennheiser HD800-S and these can go to almost 700 ohms impedance (so past the 600 ohms specified).

From what you say, it sounds like 700 ohms distortion performance should be same as specified 600 ohms distortion performance.

Higher impedance is NO problem. It can effortlessly drive HD800s, same for HE-6 as long as you don't EQ it with considerable negative pre-gain. What COULD be a problem is something like the Verum planar magnetic. It has low impedance and needs lot of current, it will make the thx run hot.
 
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JohnYang1997

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Higher impedance is NO problem. It can effortlessly drive HD800s, same for HE-6 as long as you don't EQ it with negative pre-gain. What COULD be a problem is something like the Verum planar magnetic. It has low impedance and needs lot of current, it will make the thx run hot.
Well aeon should be worse in this case but shouldn't be a problem either. At normal listening volume you hardly use 100ma.
 
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