I’ve already ordered my balanced THX 789 Amp but i dont have a balanced DAC for it. I was wondering if a balanced DAC is really necessary for a balanced Amp? Is the sound that much better? I already have a Modi DAC and i was thinking of just using that. Is that a good idea?
Doesn’t the 789 also have a unbalanced headphone port? would it share the same audio quality as the balanced?
Also can i plug a unbalanced Equalizer like the Schiit Loki to the 789?
If you already have a modi and are content with it, there is really no reason to upgrade the dac. You can plug it into the unbalanced input and be just fine. You could chain the loki in as well with no issues.
The 789 has an unbalanced headphone out that still sounds great. Just a bit less power compared to balanced
The 789 converts any given signal into single ended for its volume pot and then outputs it into both a 1/4" and 4 pin XLR “balanced” connection. The balanced isnt truly balanced, so the benifit of using a balanced source would be the higher voltage a balanced DAC would offer. You will be able to use the XLR out even with your Modi
Well thats lame. I was hoping it was true balanced 
Ive heard that single ended can sound better than balanced. Maybe that will be true in this case?
But in case i decide to use the balanced ports with a balanced DAC I have the Sendy Aiva’s and they come with a balanced cable, but its a 4.4mm cable. does anyone know if the 789 has a port for that? Or will i have to get a new cable?
You can get a female 4.4mm balanced to 4 pin male xlr balanced to use it without getting a new cable
The whole not true balanced thing really doesn’t matter, as you are still getting most of the benefits of balanced anyway
And yes, I think that a good single ended amp and outperform a mediocre balanced one. The main realistic benefit of balanced is more power and a lower noise floor, not necessarily better sound quality. You just get a bit more voltage
sweet. i found these at amazon:
the one MusicTeck sells is crazy expensive. Do you think these are ok?
It should. It can be hit or miss with these adapters sometimes, as some end up with issues. But yes this is what you would want
I thought the Sendy’s came with a 4.4mm to 4 pin xlr adapter? Might be wrong though
They come with a 4.4mm to 3.5mm unbalanced
I was trying order some balanced XLR cables to connect the SMSL SU8 DAC to the 789, but i noticed the 789 has a 4 pin xlr port and the su8 has a 3 pin xlr port. but i cant seem to find a 3 to 4 pin cable. do you know of one?
On the back the 789 has two 3 pin inputs for left and right. The 4 pin is the balanced headphone out
oops! lol brain fart sorry about that 
I keep seeing that balanced is about little more than the extra power. I certainly get that a good SE design can trump a less-good balanced. But what about common-mode rejection? Do I take it that in a good balanced design there is little to reject, except perhaps on very long cable runs?
Common mode rejection essentially removes any noise from interference. Balanced sends a regular signal and a polarity inverted signal, and it then compares the signal and removes anything in common. Interference will effect both signals, so it removes that. A good balanced design is subjective, but essentially most balanced designs will be able to eliminate interference
Thanks. And what I’m asking is whether this clever interference reduction capability of balanced is of any significance as a reason to use balanced over SE. EM leakage from the source computer or from the near-by in-wall wiring or from the tangle of wires connecting and powering all the components of the system or some such?
Yes emi could cause that. If you have lots of interference issues or have to run long runs of cables then balanced might make more sense for you. Balanced might not necessarily reduce the internal noise of the amp itself, so interference could get in that way as well
It’s my understanding that the real benefit of balanced interconnects is the connection between the source (DAC) and the amp. Many smart industry folks, including the good people at Benchmark Audio back me up on this. And that the only benefit of balanced headphones is the extra power.
It makes sense to me, but what do I know?
Yes that is true. The main benefit of balanced headphones is the extra power headroom. And that ends up making more of a real world noticeable difference then balanced interconnects. But balanced components and interconnects are nice to have for long runs and more voltage, but you have to take into account people’s money and what they should prioritize. It really isn’t necessary to have a balanced dac, and if you can put that money towards better headphones or a better amp imo that’s more worthwhile. That’s the hard thing about this hobby, is that not everyone can afford to strive for perfection only had in theory.
Yeah, xlr carries a higher voltage between the source and amp. This is good for very long cable runs where rca might drop out. The extra power from the 4 pin XLR output can help drive harder to drive heapdhones. I’ve gone through all of the balanced amp/dac thing and I couldnt justify spending more on the slight difference. The extra power is very nice to have but I haven’t found myself needing it since
If we’re talking about just power, I can’t imagine needing more power than the 789 provides single ended. I keep my DAC at -12 db (long story) and use it to drive 300 ohm HD650s on the second gain stage. If I wasn’t doing the -12 DB thing I could probably keep it in the first gain stage (of 3).
And isn’t the balanced connection (with all the wattage implied) avaliable whether the DAC is connected via XLR or not?