Review and Measurements of Massdrop THX AAA 789 Amp

[Hemi-Demon]

I have found the photo of the Focus internals on the Nazar's forum: http://www.audio-perfection.com/forum/showthread.php?tid=608

Great off to read, Thanks

 

[RickSanchez]

If it's helpful to anyone on this thread, here's a comparison of the 789 to the Monoprice 887 and the SMSL SP200:

• https://www.audiosciencereview.com/...-amp-measurement-comparison.9952/#post-268559

 

[Blur]

I picked one of these up for review and to pair with my Topping D90. I'll try and drop my brief review in here as the measurements have already been well documented.

 

[zepplock]

I have found the photo of the Focus internals on the Nazar's forum: http://www.audio-perfection.com/forum/showthread.php?tid=608

Isn't it cheaper to do binaural in foobar? (if you use foobar, of course.)

 

[Viper Necklampy]

I picked one of these up for review and to pair with my Topping D90. I'll try and drop my brief review in here as the measurements have already been well documented.

What a pairing! Let us know how it sounds, the d90 is really interesting

 

[Viper Necklampy]

Does thx aaa 789 comes with 1 year warranty by MassDrop, or just 30 days?

 

[Rusty Shackleford]

Does thx aaa 789 comes with 1 year warranty by MassDrop, or just 30 days?

The Monoprice model comes with a three year warranty.

 

[Blur]

Does thx aaa 789 comes with 1 year warranty by MassDrop, or just 30 days?

Massdrop has 1 year

 

[Viper Necklampy]

1 year? That's awesome, i thought it was just 30 days..
Can i ask a easy question? With 32ohm, how can i get the balanced signal of 6W of power? With XLR Dac to amp, with XLR on just headphones, or it need both?

 

[JohnYang1997]

1 year? That's awesome, i thought it was just 30 days..
Can i ask a easy question? With 32ohm, how can i get the balanced signal of 6W of power? With XLR Dac to amp, with XLR on just headphones, or it need both?

You always have that regardless of the dac or headphones etc. It's the amp itself that has the amount of power.
Are you going to put the volume on maximum all the time and blast it? If the answer is yes, sure you need to have both. If the answer is no, then you don't worry about it just listen to music. Simple.

 

[YSC]

You always have that regardless of the dac or headphones etc. It's the amp itself that has the amount of power.
Are you going to put the volume on maximum all the time and blast it? If the answer is yes, sure you need to have both. If the answer is no, then you don't worry about it just listen to music. Simple.

For a electronic noob question, I saw some amp spec their output of different impedance and SE/Balanced max power in W differently, doesn’t the input V and the load ohm affect the maximum power output?

 

[Viper Necklampy]

You always have that regardless of the dac or headphones etc. It's the amp itself that has the amount of power.
Are you going to put the volume on maximum all the time and blast it? If the answer is yes, sure you need to have both. If the answer is no, then you don't worry about it just listen to music. Simple.

So to have all the 6W at x6 gain the only way is to have them both XLR? If i put a single XLR instead of all single ended, no benefit? Need both XLR then?

If you also know guys, if 6W is at Max gain x6 gain which is power output at medium Gain II x2 gain?

 

[JohnYang1997]

For a electronic noob question, I saw some amp spec their output of different impedance and SE/Balanced max power in W differently, doesn’t the input V and the load ohm affect the maximum power output?

Balanced output gives extra voltage output but no extra current output. For higher impedance, say higher than 150ohn or 50ohm or 30ohm depending on the amp, it does give 4 times the power output. For lower impedance it's basically the same as SE.

For maximum output specification, it's normally independent to the input level. Meaning, it's common to have specification using much higher than standard 2V input (4V for XLR). They may use 5V input signal to get the maximum output power spec. This is called input sensitivity. IMHO, it's not a very important spec for headphones. Higher input sensitivity requires higher gain thus causing higher noise and possibly worse distortion. For normal use, it's ok to have less output power than spec with 2V input.

Load on the other hand is very important in the specification. For different loads, they requires different current and voltage. Lower impedance load generally needs more current than higher impedance. If the amplifier has small current output, the output power with low impedance it's going to be small. If the amp has small supply voltage, the output power for high impedance is going to be small.

 

[JohnYang1997]

So to have all the 6W at x6 gain the only way is to have them both XLR? If i put a single XLR instead of all single ended, no benefit? Need both XLR then?

If you also know guys, if 6W is at Max gain x6 gain which is power output at medium Gain II x2 gain?

The maximum power output doesn't mean anything if you are not using it. And the "headroom" doesn't change with the input either. It does change with the output tho. Balanced output will give more power with high impedance. For normal use, the balanced connection's benefit is not the power but the immunity to interference. It is inherently more noisy than single ended if there's no interference. The input circuitry is much more noisy than just two buffers of single ended, generally in the order of 2-5 times. The balanced output is at least 1.4 times more noisy than single ended output.

 

[Viper Necklampy]

So to have all the 6W at x6 gain the only way is to have them both XLR? If i put a single XLR instead of all single ended, no benefit? Need both XLR then?

If you also know guys, if 6W is at Max gain x6 gain which is power output at medium Gain II x2 gain?

The maximum power output doesn't mean anything if you are not using it. And the "headroom" doesn't change with the input either. It does change with the output tho. Balanced output will give more power with high impedance. For normal use, the balanced connection's benefit is not the power but the immunity to interference. It is inherently more noisy than single ended if there's no interference. The input circuitry is much more noisy than just two buffers of single ended, generally in the order of 2-5 times. The balanced output is at least 1.4 times more noisy than single ended output.

Allright, so i guess all xlr or nothing for the full power output
2-5 more noisy, but with THX AAA 789 with ''0,0000x'' level of distortion, i guess is it not noisy at even near audible level? Or i am wrong?
Also, this 'noise' has something in common with gain multiplier? 3,3x gain or x6, doesn't it add more kinda compression to get the loudness and get fuzzy or noisy, but as we walking super transparent amp is not audible?

 

[JohnYang1997]

Allright, so i guess all xlr or nothing for the full power output
2-5 more noisy, but with THX AAA 789 with ''0,0000x'' level of distortion, i guess is it not noisy at even near audible level? Or i am wrong?
Also, this 'noise' has something in common with gain multiplier? 3,3x gain or x6, doesn't it add more kinda compression to get the loudness and get fuzzy or noisy, but as we walking super transparent amp is not audible?

Ok. Now let me talk practical. With 789 there are attenuation, 0db, +6db gain 3 settings. Use 0db as much as you can. If it's too loud, use attenuation. If you don't get enough volume even when you max out the volume knob then switch to high gain. Don't use high gain as long as you can get away with it.

In terms of 789's power supply. It's a pretty terrible SMPS. It has fair bit amount of mains leakage which degrades the single end performance. The mains hum is pretty high comparing to balanced input or output.

If the XLR/RCA output of your dac is earthed, then when you connect the XLR/RCA input, you creates a path from the 789 to earth which will eliminate the mains hum even when you still have the single end input selected.

If you use the balanced output then regardless of which configuration you will have the mains hum eliminated you just get 1.4 times the noise.

So with this analysis I actually recommend single end input and balanced output. This way the noise degradation is the least and you have extra free 6db gain due to balanced output itself.

 

[Veri]

So with this analysis I actually recommend single end input and balanced output. This way the noise degradation is the least and you have extra free 6db gain due to balanced output itself.

Interesting. Is SE in SE out still good though? You mention bal has 1.4 times the noise?

 

[JohnYang1997]

Interesting. Is SE in SE out still good though? You mention bal has 1.4 times the noise?

The SMPS's leakage current ruined the objective performance.
Best power supply design for single ended performance that I am aware of is external transformer like Atom.
However I do not know how Geshelli Archel2 made low supply noise from SMPS. (still 6-10db higher than external transformer tho, atom doesn't have the best performance from this method)

 

[Veri]

Best power supply design for single ended performance that I am aware of is external transformer like Atom.

I see. Thanks

 

[Giulio]

The SMPS's leakage current ruined the objective performance.
[...]

Where do you see this leakage from Amir's mesurents?