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Problem with buzzing noise in my THX 789 amp

Schackmannen

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So I have this issue where randomly the amp will start to produce a faint noise in the left channel that sounds like electrical buzzing if it makes any sense. It can go days without happening or it can happen multiple times a day. It's been like this since I got the amp about half a year ago but figured it might have been ground loop related since I used the unbalanced input with some very cheap RCA cables. However during the summer I now have my ADI-2 DAC and the THX amp in the same place so I ordered some XLR cables to try the balanced output from the ADI-2 DAC, but a few days later the buzzing returned.

Is the amp faulty or could there be an issue with the power supply or something like that? The buzzing happens on both the 6.3 and 3.5 mm output at the same time and if I press the button so the amp switches from balanced to unbalanced input (which should be the same as disconnecting the XLR cables?) it still remains. Turning the amp off instantly makes the noise go away but it almost always returns if i power the amp on again. It's not a big deal since it's only audible if nothing is playing and it doesn't happen very frequently but it would still be nice to get it fixed if possible.
 
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Schackmannen

Schackmannen

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That's what I suspected, only problem is that I live in Sweden so shipping mine to the US would probably take a while and cost a bit if I have to pay for it. And they might not even have replacements to send out given how popular the amp is. Not sure if this issue is worth all that hassle but I guess I'll contact the support and see what they say. Maybe @AndrewMason could offer some help?
 

maxxevv

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Some suggestions to troubleshoot:

i) You could try changing your playback source. See if you have the same issues.

ii) Do you get the same issue with a different amplifier?

iii) You could try bringing your setup to a completely different location to try.
 
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Schackmannen

Schackmannen

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Some suggestions to troubleshoot:

i) You could try changing your playback source. See if you have the same issues.

ii) Do you get the same issue with a different amplifier?

iii) You could try bringing your setup to a completely different location to try.
i) Do you mean connecting everything to something other than my PC? Because the noise happens even with nothing playing.

ii) I never hear this noise with the ADI-2 DACs headphone amp but I've heard it on the THX both when I had my Topping D50 or ADI-2 DAC driving it.

iii) Other than changing what USB port and electrical socket I use to connect everything I can't really change anything about my setup.
 

maxxevv

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i) Yes, connecting to something other than your PC for playback. Ok, seems that you have answered that in (ii).

ii) you answered in (i)

iii) Maybe give that a try. Especially for the power plug of the 789. Swap it for some other plug if possible.

But you specifically mentioned that its only in 1 channel ? If what you did so far hasn't solved it, its likely that something is wrong with 1 channel.
 

Jimmy

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If you are a bit handy, open the case and visually inspect (if you have a magnifying glass it's ok to use it, combining it with a phone's flash in torch mode), and see if you can find any visible defects that you can fix by yourself, you may be surprised with what you can find sometimes, quite often companies try to reduce costs to the absolute limits and this has consequences, I've seen true aberrations even with expensive electronic equipment (which proves that they didn't even do any kind of basic QC).

Anyway no matter the case I'm sure Massdrop will honor the warranty, the problem is as you say shipping overseas, that's why I never buy expensive equipment outside Europe (or even in other countries), quite often warrantly claims are a nightmare.
 
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Schackmannen

Schackmannen

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If you are a bit handy, open the case and visually inspect (if you have a magnifying glass it's ok to use it, combining it with a phone's flash in torch mode), and see if you can find any visible defects that you can fix by yourself, you may be surprised with what you can find sometimes, quite often companies try to reduce costs to the absolute limits and this has consequences, I've seen true aberrations even with expensive electronic equipment (which proves that they didn't even do any kind of basic QC).

Anyway no matter the case I'm sure Massdrop will honor the warranty, the problem is as you say shipping overseas, that's why I never buy expensive equipment outside Europe (or even in other countries), quite often warrantly claims are a nightmare.
Yeah I've thought about opening it up and see if I (or you guys) can see anything wrong but that would void the warranty right?
 

amirm

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Yeah I've thought about opening it up and see if I (or you guys) can see anything wrong but that would void the warranty right?
There is no way for them to tell if you are very careful and don't scratch the case, or strip the screws in any way. Use the right size driver for the screws and put a lot of force down and carefully loosen the screw.

That said, I don't remember if I had to take the feet off and such to open it. If so, they may be able to tell from that.

Personally I don't think you are going to discover anything. Given how much demand there is for these units, I would bite the bullet and send it in for repair.
 

jontehmon

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Hey did you ever figure out what was wrong with your Massdrop THX 789 or how to fix it? I have the exact same issue where I've hooked up multiple DAC's and also no DAC's at all, and I can hear a slight buzzing/clicking noise on the left channel from both XLR Balanced and SE outputs. This is when no music is playing and no DAC is connected or powered on at all.

Bummer because I bought this unit second hand and I am not sure if Massdrop will honor its warranty or repair/replace this unit.
 
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Schackmannen

Schackmannen

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Hey did you ever figure out what was wrong with your Massdrop THX 789 or how to fix it? I have the exact same issue where I've hooked up multiple DAC's and also no DAC's at all, and I can hear a slight buzzing/clicking noise on the left channel from both XLR Balanced and SE outputs. This is when no music is playing and no DAC is connected or powered on at all.

Bummer because I bought this unit second hand and I am not sure if Massdrop will honor its warranty or repair/replace this unit.
I contacted their support and they very quickly responded giving me two options, either return it for a full refund or get $20 back and keep the unit as is. They had no replacement units available nor could they repair it. For me the issue was too small to bother sending it to the states from the EU so I kept the unit. Not sure how it works when you bought it second hand but I would contact them and see what they say.
 

March Audio

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I contacted their support and they very quickly responded giving me two options, either return it for a full refund or get $20 back and keep the unit as is.

They had no replacement units available nor could they repair it. For me the issue was too small to bother sending it to the states from the EU so I kept the unit. Not sure how it works when you bought it second hand but I would contact them and see what they say.

o_O!
 
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Schackmannen

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Here's what the customer support said in the email: "We only order the exact quantities needed for each run, which means there is no extra inventory available to send as a replacement. Our business model is based on group purchases, so we do not have the ability to procure individual replacements from the vendor at this time."
 

Swtoby

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Here's what the customer support said in the email: "We only order the exact quantities needed for each run, which means there is no extra inventory available to send as a replacement. Our business model is based on group purchases, so we do not have the ability to procure individual replacements from the vendor at this time."
Reading this makes me appreciate good customer support from a company like JDS Labs. I've used Drop, but stuff like this makes me leary and a company that backs their products counts for a lot in my opinion.
 
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Schackmannen

Schackmannen

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If you bought the unit with a bank card that allows you to dispute transactions, you might try raising a dispute with Massdrop through the bank. (I realize this is unlikely in the EU, but it is very common with U.S. credit cards.) Thank you for reporting your experience here--I think that a lot of us will avoid Massdrop after hearing of experiences like this.
To be fair they did offer me a full refund if I returned the unit and I think I wouldn't have to pay for shipping it back either which I think is perfectly fine.
 

Soniclife

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To be fair they did offer me a full refund if I returned the unit and I think I wouldn't have to pay for shipping it back either which I think is perfectly fine.
Why didn't you take them up on this when you also had the RME?
 
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Schackmannen

Schackmannen

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Why didn't you take them up on this when you also had the RME?
I have 2 setups at different places so I use the RME at one place and a Topping D50 + the THX at the other. Had the issue been more frequent and annoying I would have taken the offer.
 

jontehmon

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Thanks a lot for your responses! I messaged the person I bought it from and he was kind of enough to offer me a full a refund in case Massdrop cannot replace it. Disappointing because I really wanted to enjoy the unit and thought it was an issue with my previous DAC (Fostex HP-A4) being USB-powered only, but my Topping D70 showed the same issue when it arrived too (both XLR and RCA inputs, and XLR and SE outputs). The issue is present even when no DAC is connected as well...

I'm wondering if it could be a power supply issue? My EL amp plugged into the same outlet shows no problem.

Just sucks that I may have to wait until November to receive a new unit, if I decide to buy another one.
 
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Schackmannen

Schackmannen

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I'm wondering if it could be a power supply issue? My EL amp plugged into the same outlet shows no problem.
I'm definitely not the right person to answer this but I was thinking the same thing but I'm not sure where I could find another power supply to try and see if it fixes anything. Now that I've decided not to return the amp I might open it up and see if anything looks broken inside.
 

jontehmon

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So I've been listening to the Massdrop THX AAA 789 for the last 7 hours so far and it hasn't shown any of its noise from before. The one difference I made was that I plugged the power supply to its own wall outlet instead of to the Belkin power strip, which was connected to two monitors, PS4, Xbox One, Nintendo Switch, DAC, speakers. So far so good, so I think the main difference is that the amp is plugged into its own outlet (even though the power supply does not have its own ground).

Actually, a few hours later I plugged the THX AAA 789 back into the Belkin power strip and it's still working perfectly... Another difference is that I plugged the power strip to a separate wall outlet from my desktop PC (which is connected to the DAC via USB). One thing I did notice initially was that the noise was present when the computer/hdd was "thinking/working" so the fact that the noise is not present when the PC is working now is a good sign. Maybe it was the power strip or wall outlet all along. I'll try this setup for a few more days and will let you guys know the result.
 
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