Need advice with EZ1073
« on: March 09, 2015, 11:20:18 PM »
Hi!

I have an issue with the ez1073.

I have it connected to an Alphalink converter. That's it. No computer no anything, powered through the same extension cable.

When I engage the eq on the MIC input, I get a ton of noise but not any kind of noise, if I boost the low end, I get noise tuned to this frequency, if I boost midrange, same, etc.

The signal level also raise a lot with MIC vs LINE.

Also something seem to become "microphonic". If I tap the input transformer (or anything touch the pcb) I hear it amplified. Leaking in the audio path.  A bit like the sound a mic is hearing when tapping it's mic stand.

There's no input connected, all floating (Mic and Line) except the line output. The screen of the output is connected to the pcb.

I made sure the enclosure is grounded everywhere with a ohm meter (0.3 ohm at worst), connected the power transformer's green/yellow wire , the "Mains Safety Earth" point on the pcb and the Main Ac ground to the chassis. The pots goes through the front panel and are grounded too.

When I disengage the eq the noise level drop dramatically but there's still a faint hum.

Switching to Line input everything goes quiet, even with the eq engaged.

I checked all and every soldures twice, checked with an ohm meter to be sure there's no shorts and made sure the transformers are wired properly.

Anyone have a suggestion? I think "microphonic" is the key word, maybe the inductors?  The transformer?

I have no clue so far, thanks for any help!


Re: Need advice with EZ1073
« Reply #1 on: March 09, 2015, 11:28:05 PM »
Humm found something interesting, look like it applies here!

"The reason for this is the Carnhill input transformer. If you set the gain pretty high (or maximum), any minute vibration (caused by directly tapping the input transformer, or just any vibration induced in the case, which will transfer some vibrations into the Input Transformer will cause you to "hear" the sound. Once you have a microphone connected, and loaded, you won't experience this anymore... since the microphone gain/signal will be several times more stronger than this. "

Pretty much what's happening...

Not sure why the eq is so noisy though.... will check this tomorrow I guess.

Re: Need advice with EZ1073
« Reply #2 on: March 12, 2015, 08:02:22 PM »
Ok so the real issue is when I boost the mid frequency at 380hz and 700hz,  I get a resonnance at those frequencies even if the preamp gain is at minimum.

A dynamic mic is plugged so the preamp is loaded.

It become even worse if I put the lid on the case.

Only those 2 frequencies and only on the midrange controls.

Everything else is dead quiet.

What could it be?

Re: Need advice with EZ1073
« Reply #3 on: March 13, 2015, 12:06:53 AM »
Ok so the real issue is when I boost the mid frequency at 380hz and 700hz,  I get a resonnance at those frequencies even if the preamp gain is at minimum.

A dynamic mic is plugged so the preamp is loaded.

It become even worse if I put the lid on the case.

Only those 2 frequencies and only on the midrange controls.

Everything else is dead quiet.

What could it be?

Ok got it!

It's the power transformer of the ez1073 that's leaking a +/- 320hz hum in the midrange circuit.

I placed a random steel plate in front of it and the hum dropped by half.

I ordered a sheet of mu-metal and will warp the transformer in it, should make a good improvement!

Re: Need advice with EZ1073
« Reply #4 on: May 04, 2015, 12:06:47 AM »
Well mu-metal did not work.... at all

No improvement whatsoever, look like the noise is traveling through something else than "air"...

It sounds like the eq is acting like an antena.... amplifying the noise through the selected frequency

Bad power transformer?

I double checked the assembly and everything is where it should be, any idea would be awesome...
« Last Edit: May 04, 2015, 12:13:33 AM by Dyonight »

Re: Need advice with EZ1073
« Reply #5 on: May 04, 2015, 10:36:00 AM »
Is it possible that when a certain componant is damaged it became "microphonic" or something similar?

What can act as an antenna when damaged? A condenser? The eq coil?
« Last Edit: May 04, 2015, 11:41:46 AM by Dyonight »

Re: Need advice with EZ1073
« Reply #6 on: May 04, 2015, 03:56:45 PM »
ok definitely the power transformer, I took it out of the enclosure and it's as quiet as it can be.


Bassniac

Re: Need advice with EZ1073
« Reply #7 on: May 04, 2015, 03:58:08 PM »
So

To make it easier for us, please post a picture of your units inside...

Cheers

Re: Need advice with EZ1073
« Reply #8 on: May 04, 2015, 04:15:57 PM »
Thank you Bassniac but I'll built an external enclosure.

This is a 4U rack with 21x API clones from Whistle Rock Audio.

The Avel Lindel Y23 power transformer I have for those 21 channels make A LOT of noise so I have no choice anyway.

The problems I described with the ez1073 is with the pcb out of the case. With the power transformer away it is totally quiet, so I'll just do this. I need the rack in less than 2 weeks and I'm more than tired of troubleshooting it so it MUST work NOW!  :D

ilfungo

Re: Need advice with EZ1073
« Reply #9 on: May 07, 2020, 02:26:36 PM »
Hi I have the same problem!
Yes it's the main transformer induction!!!
I want to carried it out of the case.
Just one question:
It's possible to use a single psu transformer ( the toroidal from the kit) for 2 channells?
It have enough?
Thanks!!!