Review and Measurements of Massdrop THX AAA 789 Amp

[Roen]

But this is the point @AndrewMason makes above:

"The key to avoiding this is buying cables that have no portion of the cable carrying shared ground current. i.e. "4-wire""

So you need to visually see 2 cables going all the way from TRS plug to the ears -i.e V-config.

If there's a Y-config (with a split) then they are sharing ground for the majority of the length of the cable - the mechanism for crosstalk (per Andrew above).

Unless I could un-screw the TRS plug and see 4-wires, i.e. separate grounds running away from the plug (and insulated from each other) but I can't @RayDunzl

I'm only quoting Andrew above. I'm definitely no expert.

You can have 4 wires insulated under a common sheath. That doesn't mean it's 3 wire.

 

[Music1969]

You can have 4 wires insulated under a common sheath. That doesn't mean it's 3 wire.

Exactly, that’s what I meant by “Unless I could un-screw the TRS plug and see 4-wires, i.e. separate grounds running away from the plug (and insulated from each other) but I can't”

The Head-Fi comment says it is 4 wire though.

 

[RayDunzl]

I can't

Try harder.

 

[Audiodoc]

My amp is working fine with SE outputs. Yesterday made a XLR silver cable for my HD650s. Whenever I increase the volume in any of the gain modes the overcurrent protection is activated and the red led is lit. I have not used the ground pin in the XLR male plug just pin 1 left positive pin 2 left negative pin 3 right positive and pin 4 right negative.

 

[amirm]

Do you get any sound at all?

 

[wyrainer]

My amp is working fine with SE outputs. Yesterday made a XLR silver cable for my HD650s. Whenever I increase the volume in any of the gain modes the overcurrent protection is activated and the red led is lit. I have not used the ground pin in the XLR male plug just pin 1 left positive pin 2 left negative pin 3 right positive and pin 4 right negative.View attachment 18691

i made a cable for my hd800, just like you said: pin 1 left positive pin 2 left negative pin 3 right positive and pin 4 right negative.
my hd800 is ok with it, my amp is also massdrop 789 .

 

[Audiodoc]

Yes I can play the music but whenever I increase the volume the red led turns on and the sound partially or totally cuts off. With the other 2 SE outputs I can listen to ear deafening levels.

 

[Audiodoc]

I have tested the cable for continuity and everything seems fine. Have ordered and insulated XLR male plug. Will replace the current one and see if it makes any difference.

 

[mi-fu]

Yes I can play the music but whenever I increase the volume the red led turns on and the sound partially or totally cuts off. With the other 2 SE outputs I can listen to ear deafening levels.

At what volume level the protection starts to kick in? I just tried mine with balanced output. It works normal.

 

[Audiodoc]

At moderate volume levels. In SE output I can easily increase the volume level without any issues.

 

[mi-fu]

At moderate volume levels. In SE output I can easily increase the volume level without any issues.

That seems strange. But I don't have a balanced cable for Sennheiser, unfortunately. I only tried running balanced on my focal clear, which seems to be working normal.

 

[Audiodoc]

Will make a XLR cable for my Massdrop 4xx today and test for the same.

 

[Timbo2]

I have tested the cable for continuity and everything seems fine. Have ordered and insulated XLR male plug. Will replace the current one and see if it makes any difference.

You tested for continuity - did you check for a shorts as well? Also is the impedance roughly the same on all 4 pins?

 

[pkane]

My amp is working fine with SE outputs. Yesterday made a XLR silver cable for my HD650s. Whenever I increase the volume in any of the gain modes the overcurrent protection is activated and the red led is lit. I have not used the ground pin in the XLR male plug just pin 1 left positive pin 2 left negative pin 3 right positive and pin 4 right negative.View attachment 18691

I've been using a self-made balanced cable to XLR4 with no problems (Canare star quad, 6m). There's no issue at any level of playback with THX AAA, so something doesn't sound right with yours, possibly a short?

 

[Audiodoc]

You are right since I was using 8 filament silver cable one of the positive terminals was intermittently touching the ground within the XLR connectors. Heat shrink tubing will be the answer. Will revert back with the fix.

 

[Audiodoc]

Got the cable fixed with some heat shrinks within the XLR plug and now everything is working fine. Troubleshooting is a part and parcel of DIYing.

 

[skcheng]

Not sure if this is the correct place to ask. If not, I'll post elsewhere. After reading through this thread, I went ahead and purchased this amp. I also purchased the Topping DX7s through Massdrop, but that probably won't deliver till the end of January at the earliest. Is there a good balanced DAC that I could match up with this amp now? What are people using with this amp? My current setup is the Lyr 3 with Audeze LCD-2 and incoming LCD-3s. Thanks much!!

 

[helloworld]

Not sure if this is the correct place to ask. If not, I'll post elsewhere. After reading through this thread, I went ahead and purchased this amp. I also purchased the Topping DX7s through Massdrop, but that probably won't deliver till the end of January at the earliest. Is there a good balanced DAC that I could match up with this amp now? What are people using with this amp? My current setup is the Lyr 3 with Audeze LCD-2 and incoming LCD-3s. Thanks much!!

Smsl su8 v2?

 

[Audiodoc]

Not sure if this is the correct place to ask. If not, I'll post elsewhere. After reading through this thread, I went ahead and purchased this amp. I also purchased the Topping DX7s through Massdrop, but that probably won't deliver till the end of January at the earliest. Is there a good balanced DAC that I could match up with this amp now? What are people using with this amp? My current setup is the Lyr 3 with Audeze LCD-2 and incoming LCD-3s. Thanks much!!

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.

 

[wadec22]

Not sure if this is the correct place to ask. If not, I'll post elsewhere. After reading through this thread, I went ahead and purchased this amp. I also purchased the Topping DX7s through Massdrop, but that probably won't deliver till the end of January at the earliest. Is there a good balanced DAC that I could match up with this amp now? What are people using with this amp? My current setup is the Lyr 3 with Audeze LCD-2 and incoming LCD-3s. Thanks much!!

DX7s is a great option if you can wait.
SMSL SU-8v2 is also great if u can wait

See my pairing now. Depends if you are comfortable using a unit amir hasn't measured yet. I'll probably send to him for measurements in Jan
https://www.audiosciencereview.com/...msl-m10-initial-impressions.5553/#post-125911