Review and Measurements of Massdrop THX AAA 789 Amp

[wadec22]

I am using the topping D50 and SMSL M8. I also have the ODAC and a few other DIY DACs using burr brown and wolfsons ICs. I also have a dragonfly DAC. None of my DACs is balanced but the thx 789 is not fully balanced internally. The topping D50 is the best one when we compare pure specifications.

Using the balanced inputs is still preferential to eliminate any noise from the mains.

That said, the d50 does pair with it well, I was using them together for awhile.

 

[skcheng]

Smsl su8 v2?

Thanks!! I'll look into this unit. I've already ordered through MD the DX7s. And the remote from ePay.

 

[skcheng]

I am using the topping D50 and SMSL M8. I also have the ODAC and a few other DIY DACs using burr brown and wolfsons ICs. I also have a dragonfly DAC. None of my DACs is balanced but the thx 789 is not fully balanced internally. The topping D50 is the best one when we compare pure specifications.

I think the D50 looks great!! Was just hoping for a balanced DAC option while waiting for the DX7s to arrive. And yes, I did read that the 789 isn't fully balanced. But I want to satisfy my own neurosis by giving things a try. Worst case scenario, I go back to my trusty 1/4" plug

 

[skcheng]

Using the balanced inputs is still preferential to eliminate any noise from the mains.

That said, the d50 does pair with it well, I was using them together for awhile.

I did read from Andrew that the first best option with the THX 789 is balanced DAC input. Thanks!! Looks like the SMSL balanced unit isn't readily available now? Amazon or other?

 

[wadec22]

I did read from Andrew that the first best option with the THX 789 is balanced DAC input. Thanks!! Looks like the SMSL balanced unit isn't readily available now? Amazon or other?

The M10 is available on Amazon now and has XLR but has not been tested by amir. If you trust SMSL's own measurements - its around 108db SINAD (so basically the same as the D50, without the ESS hump). If you prefer to wait for amir to test it - better off waiting.

The v2 of the SMSL SU-8 is available through Amazon if you select the SMSL store AND order the one that ships from China - you just won't get it until January.

 

[Roen]

Can always use Aliexpress as well.

 

[wadec22]

Can always use Aliexpress as well.

if you are talking about the SMSL SU-8 - maybe.... Through SMSL's own rep here we have confirmed the SMSL store via amazon when you select from china is shipping v2. Outside of that, any other vendor or method - you probably want to confirm with the retailer prior to ordering.

 

[skcheng]

The M10 is available on Amazon now and has XLR but has not been tested by amir. If you trust SMSL's own measurements - its around 108db SINAD (so basically the same as the D50, without the ESS hump). If you prefer to wait for amir to test it - better off waiting.

The v2 of the SMSL SU-8 is available through Amazon if you select the SMSL store AND order the one that ships from China - you just won't get it until January.

I just looked at the M10! Looks nice. Would you think this DAC is of better quality/sound than the SU-8? BTW, PM sent!!

 

[wadec22]

I just looked at the M10! Looks nice. Would you think this DAC is of better quality/sound than the SU-8? BTW, PM sent!!

according to SMSL's own specs - they put the SU-8 measuring slightly better. They list the SU-8 at 110 SINAD (which is accurate in v2 per amir) and the M10 at 108 SINAD. the difference between the two would not be audible. It depends on which you prefer for function, feature and aesthetic.

 

[Schackmannen]

Finally got my unit yesterday, I was surprised that i didn't have to pay any import fees but I won't complain . I connected the amp to my Topping D50 and my HD6XX to the 3.5 mm output and it was working perfectly with great sound quality yesterday. However today i noticed a very faint noise in the left channel, it sounded like an electrical buzz if that makes any sense. It went away for a while but then came back louder than before, although still not that loud. I tried turning off the amp and unplugging and replugging all the cables but the buzz comes and goes and after a while it switched to the right channel. Could this be caused by ground loops since I'm using the unbalanced input? And if so is there anything i can do to get rid of it other than getting a DAC without balanced outputs? Or could the amp be faulty? I really don't want to have to send it back considering it took a month to get here Maybe @AndrewMason got any helpful advice?

 

[skcheng]

Finally got my unit yesterday, I was surprised that i didn't have to pay any import fees but I won't complain . I connected the amp to my Topping D50 and my HD6XX to the 3.5 mm output and it was working perfectly with great sound quality yesterday. However today i noticed a very faint noise in the left channel, it sounded like an electrical buzz if that makes any sense. It went away for a while but then came back louder than before, although still not that loud. I tried turning off the amp and unplugging and replugging all the cables but the buzz comes and goes and after a while it switched to the right channel. Could this be caused by ground loops since I'm using the unbalanced input? And if so is there anything i can do to get rid of it other than getting a DAC without balanced outputs? Or could the amp be faulty? I really don't want to have to send it back considering it took a month to get here Maybe @AndrewMason got any helpful advice?

Did you figure this out??

 

[skcheng]

Any other DACs that members are using with the THX 789? I just purchased the Topping D50, which I figure I'll eventually use for a coffee table setup in my living room along with hopefully an A50 amp. Looking at the SMSL DACs currently. They seem reasonably priced.

 

[rajapruk]

Finally got my unit yesterday, I was surprised that i didn't have to pay any import fees but I won't complain . I connected the amp to my Topping D50 and my HD6XX to the 3.5 mm output and it was working perfectly with great sound quality yesterday. However today i noticed a very faint noise in the left channel, it sounded like an electrical buzz if that makes any sense. It went away for a while but then came back louder than before, although still not that loud. I tried turning off the amp and unplugging and replugging all the cables but the buzz comes and goes and after a while it switched to the right channel. Could this be caused by ground loops since I'm using the unbalanced input? And if so is there anything i can do to get rid of it other than getting a DAC without balanced outputs? Or could the amp be faulty? I really don't want to have to send it back considering it took a month to get here Maybe @AndrewMason got any helpful advice?

Can you test a balanced dac, i.e use xlr input?

Test other signal-cables.

 

[Roen]

Any other DACs that members are using with the THX 789? I just purchased the Topping D50, which I figure I'll eventually use for a coffee table setup in my living room along with hopefully an A50 amp. Looking at the SMSL DACs currently. They seem reasonably priced.

Tone Board

 

[Schackmannen]

Can you test a balanced dac, i.e use xlr input?

Test other signal-cables.

I don't have access to a balanced DAC at the moment so i wouldn't be able to test balanced input. I guess i could buy a better pair of RCA cables and see if it helps. But for the most part the amp is dead quiet and i don't think i've heard any buzzing during playback so it's not a huge issue for me, just a small annoyance.

 

[AndrewMason]

Finally got my unit yesterday, I was surprised that i didn't have to pay any import fees but I won't complain . I connected the amp to my Topping D50 and my HD6XX to the 3.5 mm output and it was working perfectly with great sound quality yesterday. However today i noticed a very faint noise in the left channel, it sounded like an electrical buzz if that makes any sense. It went away for a while but then came back louder than before, although still not that loud. I tried turning off the amp and unplugging and replugging all the cables but the buzz comes and goes and after a while it switched to the right channel. Could this be caused by ground loops since I'm using the unbalanced input? And if so is there anything i can do to get rid of it other than getting a DAC without balanced outputs? Or could the amp be faulty? I really don't want to have to send it back considering it took a month to get here Maybe @AndrewMason got any helpful advice?

Hi @Schackmannen . Try a few things to see if you can get the buzz to change or go away. That'll help us figure out the root cause.

- swap the L and R RCA cables going into the 789 but don't touch them at the DAC output. Does the buzz change ears? If so, could be a cable or Lch DAC issue.
- unplug the RCAs from back of the 789. Does the buzz go away? Then definitely ground loop related.

If you're suspecting a bad cable, try a new 1 ft RCA-RCA with braided shield. http://a.co/d/0sDdF9N . The braid and short length mean the impedance of the shield is minimal, so hum caused by cable Z is reduced.

Or even better, a properly built RCA to XLR cable that keeps ground current separate from the signal- wire: https://benchmarkmedia.com/collections/cables/products/benchmark-rca-to-xlrm-adapter-cable.

 

[Roen]

Hi @Schackmannen . Try a few things to see if you can get the buzz to change or go away. That'll help us figure out the root cause.

- swap the L and R RCA cables going into the 789 but don't touch them at the DAC output. Does the buzz change ears? If so, could be a cable or Lch DAC issue.
- unplug the RCAs from back of the 789. Does the buzz go away? Then definitely ground loop related.

If you're suspecting a bad cable, try a new 1 ft RCA-RCA with braided shield. http://a.co/d/0sDdF9N . The braid and short length mean the impedance of the shield is minimal, so hum caused by cable Z is reduced.

Or even better, a properly built RCA to XLR cable that keeps ground current separate from the signal- wire: https://benchmarkmedia.com/collections/cables/products/benchmark-rca-to-xlrm-adapter-cable.

Blue Jeans Cable will make the same type cable as benchmarkmedia for a lower cost if you choose 1 ft, as long as you tell them how to make it properly.

 

[pos]

Another alternative: https://www.amazon.co.uk/dp/B07B3GC...colid=W25DX4NAX94B&psc=0&ref_=lv_ov_lig_dp_it
They do have 30cm/50cm/75cm/1m variants.

 

[skcheng]

While we're on this topic, I need to connect my incoming D50 to this amp. I'm hoping these cables will work okay?

https://www.amazon.com/Monoprice-Co...4822955&sr=8-7&keywords=rca+to+xlr+male+cable

 

[Schackmannen]

Hi @Schackmannen . Try a few things to see if you can get the buzz to change or go away. That'll help us figure out the root cause.

- swap the L and R RCA cables going into the 789 but don't touch them at the DAC output. Does the buzz change ears? If so, could be a cable or Lch DAC issue.
- unplug the RCAs from back of the 789. Does the buzz go away? Then definitely ground loop related.

If you're suspecting a bad cable, try a new 1 ft RCA-RCA with braided shield. http://a.co/d/0sDdF9N . The braid and short length mean the impedance of the shield is minimal, so hum caused by cable Z is reduced.

Or even better, a properly built RCA to XLR cable that keeps ground current separate from the signal- wire: https://benchmarkmedia.com/collections/cables/products/benchmark-rca-to-xlrm-adapter-cable.

Thanks Andrew for the quick reply! Since i got back from work today i have barely heard any buzzing at all after using it for ~6 hours straight, just a little bit for a few seconds after turning it on and maybe a tiny amount here and there but it's so quiet it's almost impossible to hear over the background noise from my computer fans. But if the noise returns i will try your suggestions and post the results, it wouldn't surprise me if it's the cable's fault since it's 2 meters long i think and as cheap as it gets.