Static from Neutrik XLR/TRS

A

asher67

New member
My Alto preamp has begun to produce static, regardless of which of the two channels is being used. The inputs are Neutrik XLR/TRS, the combined XLR and 1/4" jack. The outputs are separate 1/4" and XLR jacks per channel. It began slightly a couple of weeks ago, and now it has become full-blown static and hissing, not predominant, but enough that it can be heard.

Here's the interesting part - if a 1/4" plug is in the input, then that channel no longer gives static, while the other one will be noisy until a 1/4" is put in (no cute jokes, now). Using an XLR will not stop the noise.

Has anyone else experienced this with these combo jacks? I'm tempted to replace them, just because it seems like the least costly solution, assuming that there is something wrong with these. I'll call Alto's service department (yeah, it's out of warranty), but I figured I would try the brain trust here first. If it matters, the unit is an Alpha Mictube preamp.
 
I doubt that both connectors went south at the same time. It could be that the TS connection follows a slightly different signal path then he XLR... A high Z TS instrument level as opposed to the mic input of the xlr. Same results with and without phantom power?
 
MOFO Pro said:
I doubt that both connectors went south at the same time. It could be that the TS connection follows a slightly different signal path then he XLR... A high Z TS instrument level as opposed to the mic input of the xlr. Same results with and without phantom power?
Click to expand...

Yes, same result. Engaging phantom power by pressing the button slowly will stop the static for a second, followed by a more generous amount of static. However, the static is present even without anything plugged in and regardless of whether phantom power is engaged.

As for the signal path, the input signal for the channel goes to both the 1/4" and the XLR outputs for that channel. If an output for each channel is connected to the mixer, then static will be heard unless a 1/4" plug is inserted into both inputs. If only one channel is connected to the mixer, then it takes only a 1/4" in the input of that channel to stop the static. It doesn't matter whether the the 1/4" or the XLR output is used.
 
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it may be hard to trace down... for a start i would take a blank xlr and grnd each pin one at a time... make sure the phantom is OFF !!! this should tell you if it's predominantly in which signal path... it could be a simple as a bad grnd... did you notice anything else happening when it degraded???
 
dementedchord said:
it may be hard to trace down... for a start i would take a blank xlr and grnd each pin one at a time... make sure the phantom is OFF !!! this should tell you if it's predominantly in which signal path... it could be a simple as a bad grnd... did you notice anything else happening when it degraded???
Click to expand...

Thanks. I'll try that tonight. As for noticing anything else - I noticed my blood pressure rising and that voice in the back of my head that says "To hell with all this, just play your guitar."

Actually, the only other thing is that the first couple of times it happened, the unit was quiet until I turned on the phantom power. The mic was connected, there was no static, and engaging the phantom power was followed by a bit of static. The first few times, it went away after a few minutes. Now, it starts regardless of whether the phantom is on, and it starts when the tube warms up. For the record, I have swapped out a variety of 12AX7, 12AT7, and 12AY7 tubes, some Jan/Military, some not. The result is the same with each.
 
After following through on Dementedchord's excellent suggestion, I'm in the same place as before. I have a call in to Alto's tech, to see whether this is a unique problem. As much as I like what this unit does, though, I doubt that the cost of a repair is worthwhile, given what a used replacement will cost.

Thanks for the suggestions. I'm open to any others. I'll do a follow-up post in case anyone is interested, once I get a solution.
 
I've had stuff that is not worth the normal repair route too. Sometimes cars are like that.

One thought is to pull the cover off of the unit on the off-chance that there is a visibly defective component.

If you're the type to do this like I am, you could experiment with running a new ground from one spot on the pc board to the XLR's ground.

If it works with a 1/4" plug, I guess you could use XLR to 1/4" cables to plug mics in. Although it wouldn't be balanced it would probably be ok.
 
Something I just thought of:

THE most common fuck-up I've seen, over and over again, on gear in the last 20 years is hands down:

pc mounted jacks that develop cracks around their "legs"

I've repaired my SoundCanvas, Yamaha VL70-m horn module, and countless CD players that had this problem. They mount the jacks (like a headphone jack for instance) on a pc board and after you use it for a while the wobbling makes the solder crack. Often you need to use a magnifying glass to see the cracks, and you might need to remove the pc board for access to do the repair.

I can't tell you how many times I've done the breath control jack on my horn module. My guess is that most of the broken VL70-m's lying around only need that.

The repair is usually simple - just heat up the solder and apply more if needed.

This is so common I'm amazed that it isn't discussed more. My guess is that 90% of portable stereos are thrown away because of this.
 
Thanks for the suggestion, Dintymoore. A good one, but it didn't solve the problem. Alto will look it over without charge, so I'm giving it a chance. I'm still open to suggestions, while awaiting a return authorization from them.
 
dintymoore said:
Something I just thought of:

THE most common fuck-up I've seen, over and over again, on gear in the last 20 years is hands down:

pc mounted jacks that develop cracks around their "legs"

I've repaired my SoundCanvas, Yamaha VL70-m horn module, and countless CD players that had this problem. They mount the jacks (like a headphone jack for instance) on a pc board and after you use it for a while the wobbling makes the solder crack. Often you need to use a magnifying glass to see the cracks, and you might need to remove the pc board for access to do the repair.

I can't tell you how many times I've done the breath control jack on my horn module. My guess is that most of the broken VL70-m's lying around only need that.

The repair is usually simple - just heat up the solder and apply more if needed.

This is so common I'm amazed that it isn't discussed more. My guess is that 90% of portable stereos are thrown away because of this.
Click to expand...

I bought one of these back in 1993 and still have laying unused. Never bothered to get it repaired-never bothered getting another one. It worked great for a few months when I got it then one channel crapped out - then the next. Like people have said, it was a pretty musical sounding box and I did get some great recordings at the time. Anyways I found it today while having a clean out - will try the suggestions regarding the solder joints. Will post my results.
 
Thought I'd post a follow-up, for anyone interested. The tech department at Alto said that there were too many things wrong with the unit to repair it. No details, but they said that it was defective. They replaced it with a new unit, and that works perfectly. Already done some tracks with it, and they sound great.

While this unit is for the budget-minded home studio user, it is very musical. It has a warm presence on vocals, which is really all that I wanted from it.

Thanks again to all who tried to help me figure out the problem.
 
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