briomusic
Well-known member
I am trying to find a way of evaluating all my mic pres (most of them DIY) in terms of EIN (equivalent input noise), without shelling out for any additional equipment or software. I want to stress that this is not a 'proper' test setup, but I think my 'errors' are the same for all of the mic pres under test, giving me a relative value rather than an absolute one. I just wanted to know which mic pre I should go to for very quiet accoustic signals/ribbon mics etc.
This was my test setup/procedure:
1. Connect Behringer test tone generator/cable tester to mic pre input with a -50dB signal.
2. Adjust gain to a specified output level as measured by Electroacoustics Toolbox (turned out to be -8.6 dB in my case)
3. Disconnect test tone generator and replace with dummy source (120 Ohm resistor between XLR pin 2-3)
4. Measure mic pre output using A-weighted curve on Electroacoustics Toolbox' sound level meter.
5. Repeat steps 1-4 with each mic pre.
6. EIN is measured noise level minus gain
*"EZQN" is my custom 'channelstrip' with a partial EQN (minus line input transformer and output stage) inserted into the 'trimmer insert' of an EZ1290.
My biggest surprise was the fact that my EZQN performed quite a bit worse than the Chandler LTD-1, both of them being Neve 1073/84 clones of sorts. I am happy to hear opinions and suggestions to improve my test rig/procedure. Loving the quiet gain of the SSL9K ;D
This was my test setup/procedure:
1. Connect Behringer test tone generator/cable tester to mic pre input with a -50dB signal.
2. Adjust gain to a specified output level as measured by Electroacoustics Toolbox (turned out to be -8.6 dB in my case)
3. Disconnect test tone generator and replace with dummy source (120 Ohm resistor between XLR pin 2-3)
4. Measure mic pre output using A-weighted curve on Electroacoustics Toolbox' sound level meter.
5. Repeat steps 1-4 with each mic pre.
6. EIN is measured noise level minus gain
Device under Test | Input (dB) | Output (dB) | Gain (dB) | Noise (dB) | EIN (dB) |
EZQN* (DIY) | -52,6 | -8,6 | 44 | -79 | -123 |
API 512c | -52,6 | -8,6 | 44 | -78,3 | -122,3 |
SSL9k (DIY) | -52,6 | -8,5 | 44,1 | -103,8 | -147,9 |
Chandler LTD-1 | -52,6 | -8,6 | 44 | -90,7 | -134,7 |
DRIP 47 (DIY) | -52,6 | -12,8 | 39,8 | -90,9 | -130,7 |
My biggest surprise was the fact that my EZQN performed quite a bit worse than the Chandler LTD-1, both of them being Neve 1073/84 clones of sorts. I am happy to hear opinions and suggestions to improve my test rig/procedure. Loving the quiet gain of the SSL9K ;D