ez1073 "Addon EQ" issues

[tronnyjenkins]

Hello, I recently finished up an AML ez1073 preamp and then the Add on EQ module. The preamp seems to have gone well (calibration was a little unusual as I had to use my oscilloscope) but I think I got it into spec. Sounds great. Also did their PDI module and it's fantastic.

However, I plugged in the EQ and I 'might' have a couple of issues. Firstly, my LED is constant on, regardless of the EQ IN switch. Not sure that is normal, but I am guessing not. Also, while the EQ functions all seem to work, if I have it set "flat" my signal from my preamp seems hotter and as well (at least with a loud test vocal) it seems to clip before my digital equipment. As in flattened top of waveform. But then if I switch it back out, preamp goes back down and no clipping. Any ideas where to start if no obvious soldering boo boos? Thanks in advance!

 

[tronnyjenkins]

Just double checked my tp1-tp2 voltage and it’s 23.8mV which is in range.

 

[JMan]

The LED is always on. It’s a little weird at first, I agree, but nothing is wrong there.

Sorry I don’t have a suggestion regarding the level jump, mine worked fine right out the gate and as such I never did much of a deep dive into the circuit.

 

[tronnyjenkins]

The LED is always on. It’s a little weird at first, I agree, but nothing is wrong there.

Sorry I don’t have a suggestion regarding the level jump, mine worked fine right out the gate and as such I never did much of a deep dive into the circuit.

Thanks! That’s at least good to know. I’ll play with it again today. I also wondered- one of those middle of the night problem solving dreams- if the circuit is just different enough with the EQ inserted that the gain would just need to be adjusted. My test singer was belting some eighties style vocals and my setting wasn’t as conservative as usual.
That, or maybe my preamp isn’t calibrated as well as I thought and it’s somehow clipping in the EQ stage…

 

[fragletrollet]

I have the line amp instead of the mic amp with my eq's. Following the calibration guide one should trim gain to match the front panel. No clipping here, something is probably wrong in the eq. First verify the preamp works as it should, then add the eq and troubleshoot that if necessary.

 

[tronnyjenkins]

I have the line amp instead of the mic amp with my eq's. Following the calibration guide one should trim gain to match the front panel. No clipping here, something is probably wrong in the eq. First verify the preamp works as it should, then add the eq and troubleshoot that if necessary.

Thanks for your reply. I tested some more today. The preamp has never clipped, before digital input clipping would occur at least. Here is where it gets interesting. If I arm up a condenser and have the level at say 35dB, when I insert the EQ, there is a 2-3dB gain increase. Not sure if that is part of the EQ circuit or what.
I didn’t actually check for the eq clipping phenomenon again today. I just tested my voice with all the filters and they seem to work great. So of course I am puzzled.

 

[fragletrollet]

Check your preamp with a test-tone, verify that all gains levels are right. Are you sure the pre-amp is 100% ?

Then, move on to the EQ.

A vocal is usually a very dynamic source , use a steady tone instead for testing.

 

[oongbac]

Mine has 2-3dB of level boost too!