Issue with THX 789 Balanced 'clicking' when high gain

[karl]

Greetings everyone,

I am going crazy. I don't know if I am just getting terrible luck or if it is something on my end and not the amp. Below is an issue I have had with two of the amps. RMA'd the first one and now maybe even the second.

When using the balanced headphone out I am getting it going from white to red and 'clicking'. This happens at roughly 50% volume on any gain channels that will allow for that volume to be reached. This happens without even a headphone plugged in. Just the cable from the amp. The cable I am using the Periapt argon balanced cable and modhouse argon mk3s. I have tested the cable with a multimeter and everything is good there. The second cable I have is an xlr headphone adapter to 2.5mm, I got a TRS 2.5 - 3.5mm to test the audio. The problem persists. I have tried the following tests to see if any option is causing it:

1. Used balanced Enog2 Pro dac with balanced out and optical in
2. Used balanced Enog2 Pro dac with RCA out and optical in
3. Used Schiit Modi2 Uber Optical in, RCA out
4. Used Schiit Modi2 Uber USB in, RCA out
5. Used different RCA cables
6. Tried different balanced to headphone cables
7. Plugged in different power strips
8. Plugged directly into the wall
9. Separated THX from dac in two separate wall outlets (different sides of room)
10. Used different computers for source (both USB Schiit Modi2 Uber)
11. Tested all steps with and without a headphone plugged

One thing is that the left channel is heard but not the right only in the adapter configuration. And when it clicks it goes from very brief right audio to no audio in but the 'full sound' is gone even with the brief dual channels. When I crank the volume the left channel does have the right volume but just cut out. Single ended output channels are OK and function great.

I have recorded an example of what is going on here. I am raising the volume on my keyboard to trigger the 'clips'.

I reached out again to Massdrop and I am hoping for a solution. Does anyone have any idea? I've spent hours trying to figure this out, I love the sound of the THX.

Thank you for your time,
Karl

 

[ke4iog]

Your testing has been well thought out. The unit is obviously going into protection, hence the relay clicking. I doubt any input variations will show any differences, but it's good to be thorough. Since you said you tested with more than one headphone cable and with no headphones plugged in, the problem seems to be internal. Since the jacks are probably hand soldered as opposed to the rest of the board, I would guess a short in the right channel, possibly from a solder blob, or some other short, or outright failure of a component. Did you try single ended? And if you did, were there any anomolies in that mode?

 

[karl]

The single ended mode is flawless, so I am enjoying that mode now. I have reached out massdrop support and am getting another replacement. I will update this post once that happens, usually takes a week or two.

 

[amirm]

The unit (or any amp) could go into protection with nothing connected if you turn up the volume. So I would not use that as an indication of other things not being wrong.

I would put my money on the cable being used. We had another member with similar issue and he thought he had tried it all until he found out the cable was problematic.

 

[karl]

The adapter I bought was on amazon and a xlr to 2.5mm (which I had to go 2.5mm to 3.5mm adapter). Ill try and find another xlr to 3.5mm plug to see if it happens to be just both cables too.

EDIT:
I also checked the cable with a multimeter and unless it was the housing causing an issue, I am not sure what could be causing it in the cable itself.

 

[amirm]

The adapter I bought was on amazon and a xlr to 2.5mm (which I had to go 2.5mm to 3.5mm adapter). Ill try and find another xlr to 3.5mm plug to see if it happens to be just both cables too.

Are the ones you are buying meant for use as balanced connection for headphones? If not, I doubt very much any of them are configured correctly.

It is best to make your own following the wiring diagram for both the amp amp your headphones. If you are not comfortable with soldering, you can use screw terminals: https://smile.amazon.com/gp/product/B076NGDR7Z/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

You can buy a 4 wire XLR cable, cut one end and strip/screw the wires to this 2.5 mm connector.

 

[karl]

If I wanted to do a 3.5mm instead that would be a 4 pin, correct?

Edit:
I forgot to link it: https://www.amazon.com/gp/product/B07PQTKMM7

 

[amirm]

Correct.

 

[karl]

Thanks! I actually found a 4 pin xlr connector and now just need to find correct wiring, do you have any recommendations Amirm. Also I forgot thank you for your help. I am very much excited about making my own cable.

 

[amirm]

My pleasure.

Tell me again what you are connecting to what and I can do a bit of searching to see which wire needs to go to what.

 

[karl]

The easier option since I am a novice when it comes to soldering is 2.5mm screw to 3.5 mm screw to the adapter. I actually realized that the 2.5mm to 3.5mm I was using was not balanced hence why I could get left channel (I think) so it actually does look like it boils down to the cable.

I am thinking of just getting the same color wire and putting tape of 1-2-3-4 on them and then just connecting one to the other just to test, once I have that down then Ill probably try and make my own XLR cable 4pin to 3.5mm cable.

 

[amirm]

Sounds like a plan.

 

[karl]

It was the cable, my janky cable sounds like crap but it works up to full volume! I let the vendor I purchased it from know that the cable is the issue with the periapt.

Thanks again for all the help!!

 

[Hemini]

Thanks for this thread!!! I have the EXACT same issue with the exact cable and headphone... and the 789. My conclusion was the cable as well, but wasn't 100% since I hadn't tested the cable yet either. Did Periapt ever get back to you? I can't get them to respond to me.