Post by ninworks on Dec 5, 2022 14:53:45 GMT -5
I have been doing more recording of late for a couple clients. In the process I noticed a very insignificant noise in my setup that triggered my OCD. One of the new (rather expensive) mic preamps had an oh-so-small hum in it when I turned everything all the way up. Yeah, I know, it will never be set to that extreme level but none of the others did that and this one is further up the food chain than they are so it bugged me. It shouldn't do that.
I went on a mission to find out where the hum was coming from. I tried different audio cables to the rear of the patch bay. Nope that wasn't it. I tried different patch cables on the signal routing side of the patch bay, nope. I checked to make sure there weren't any AC power sources anywhere near any of the audio cables. I didn't think there was but I checked anyway. Nope. Running out of things to try I even changed out the AC power cable, nope that wasn't it either. For my next roll of the dice I tried swapping places with it and the two Daking compressors in the rack. DING DING DING DING. THERE it was. The preamp had been occupying the very last space in the API 500 series rack right next to its power supply. The power supply was shielded very well with metal all the way around it except for the vents in the top and bottom panels. When I put the 2 Daking compressors where the humming Great River mic pre used to be they didn't hum at all. Mission accomplished! All is well in OCD land.
The only thing I can figure is that the rather massive audio transformer in the preamp was picking up a miniscule hum from the rack's power supply and amplifying it on it's output stage. The transformer in the preamp is about half the size of a Boss effects pedal. Quite huge for an audio transformer. Stuff like that bugs the heck out of me. I had only noticed it because I had tracked one of the acoustic guitar takes simultaneously through 5 different mic preamps onto 5 discrete tracks and was really scrutinizing them on playback to familiarize myself with the different (if any) characteristics of the lot. I had them turned up pretty loud and was listening in headphones to hear any nuances they might present. There were some empty spots in the track and that's when I heard the hum. It was inaudible while the guitar was playing.
I am also happy that the Great River mic preamp was the best sounding out of all my mic pre's. The preamps I had going to the tracks were the Purple Audio Biz pre, Great River MP-500NV, internal mic pre on the RME Fireface UC interface, the Focusrite ISA428, and the API 312. Much to my surprise the API was the noisiest but was the second best sounding. I was also surprised how well the RME's internal mic pre stacked up against the others. It had the least amount of noise out of all of them and sounded very good. This was the first of many scrutinizing tests to be done. There are a number of different ways to set the controls on the preamps which, theoretically, can influence the sound. So, every time I record something that needs a mic preamp I will check my mic setup book where I log all of my settings and set them differently to see what the results are. Realisically, any of those mic preamps would have been an excellent choice. They all sounded very good. The differences were almost indistinguishable but I could hear them. I'm sure I wouldn't be able to identify which one is which in a blind listening test. Maybe after I get more familiar with them I will.
I should have been in R&D for some audio electronics company. That kind of splitting hairs is a lot of fun for me. Maybe if I were to put some flashing LEDs on my guitars I would play them more. God knows I need to.
I went on a mission to find out where the hum was coming from. I tried different audio cables to the rear of the patch bay. Nope that wasn't it. I tried different patch cables on the signal routing side of the patch bay, nope. I checked to make sure there weren't any AC power sources anywhere near any of the audio cables. I didn't think there was but I checked anyway. Nope. Running out of things to try I even changed out the AC power cable, nope that wasn't it either. For my next roll of the dice I tried swapping places with it and the two Daking compressors in the rack. DING DING DING DING. THERE it was. The preamp had been occupying the very last space in the API 500 series rack right next to its power supply. The power supply was shielded very well with metal all the way around it except for the vents in the top and bottom panels. When I put the 2 Daking compressors where the humming Great River mic pre used to be they didn't hum at all. Mission accomplished! All is well in OCD land.
The only thing I can figure is that the rather massive audio transformer in the preamp was picking up a miniscule hum from the rack's power supply and amplifying it on it's output stage. The transformer in the preamp is about half the size of a Boss effects pedal. Quite huge for an audio transformer. Stuff like that bugs the heck out of me. I had only noticed it because I had tracked one of the acoustic guitar takes simultaneously through 5 different mic preamps onto 5 discrete tracks and was really scrutinizing them on playback to familiarize myself with the different (if any) characteristics of the lot. I had them turned up pretty loud and was listening in headphones to hear any nuances they might present. There were some empty spots in the track and that's when I heard the hum. It was inaudible while the guitar was playing.
I am also happy that the Great River mic preamp was the best sounding out of all my mic pre's. The preamps I had going to the tracks were the Purple Audio Biz pre, Great River MP-500NV, internal mic pre on the RME Fireface UC interface, the Focusrite ISA428, and the API 312. Much to my surprise the API was the noisiest but was the second best sounding. I was also surprised how well the RME's internal mic pre stacked up against the others. It had the least amount of noise out of all of them and sounded very good. This was the first of many scrutinizing tests to be done. There are a number of different ways to set the controls on the preamps which, theoretically, can influence the sound. So, every time I record something that needs a mic preamp I will check my mic setup book where I log all of my settings and set them differently to see what the results are. Realisically, any of those mic preamps would have been an excellent choice. They all sounded very good. The differences were almost indistinguishable but I could hear them. I'm sure I wouldn't be able to identify which one is which in a blind listening test. Maybe after I get more familiar with them I will.
I should have been in R&D for some audio electronics company. That kind of splitting hairs is a lot of fun for me. Maybe if I were to put some flashing LEDs on my guitars I would play them more. God knows I need to.
