A couple years back I wanted to change the stock tubes in my Korg EMX-1 to see how more expensive tubes would sound. I ended up recording and measuring the results for the Electribe forums over at: http://electribe-forum.com. However, I still get a lot of questions on it, so I wanted to sort of archive it by reposting to my blog. Here’s the article in it’s entirety:
I wanted to create a quick and simple test to see how much of an audible difference replacing the tubes in my new Korg EMX-1 would make. After looking into what tubes to replace the stock 12AX7 tubes with, I decided on a pair of matched triode JJ ECC83S which I bought from Eurotubes.com:
I wanted to see how much difference there would be in level (volume) between the tube types, as well how much the distortion varied as well. The first thing I did was create a simple 1 bar pattern with a held sine wav to measure the output of the EMX using the stock tubes. The EMX-1 main outs were then routed to the inputs of my MOTU Ultralite soundcard, and I used Ableton Live 7.07 and the plug in Inspector XL from EAS to measure the levels. Inspector XL was set to use the K-14 meter scale, which is my preferred metering scale. I recorded the RMS meter readings at 5 difference positions of the Tube Gain knob on the EMX-1.
Here are the readings I obtained with the stock Korg tubes:
Knob Position 0 = -11.30dB
Knob Position 2 = -9.50dB
Knob Position Half = -0.55dB
Knob Position 8 = 3.67dB
Knob Position Full = 3.93dB
Here are the readings I obtained with the JJ ECC83S tubes after the swap:
Knob Position 0 = -17.20dB
Knob Position 2 = -15.80dB
Knob Position Half = -6.49dB
Knob Position 8 = -2.22dB
Knob Position Full = -2.00dB
As you can see, the JJ tubes are quieter by roughly 5-6dB at all knob positions. Next to the tubes in the EMX-1 are pots to adjust the output levels of each tube, but there was not enough range to successfully match the levels of the two tube types, so be aware that swapping your tubes will potentially lower the output level of your EMX-1.
My next step was to record audio examples of the two tubes in action so people could hear the differences with a more real-world example. For this test, I used an 8 bar EMX-1 pattern from my last song, “Puled” which you can read about here:
I recorded 8 bars of audio from the EMX-1 into Ableton Live 7.07 using the same Tube Gain settings listed above. Live was set to record 24bit/44.1kHz wav files, and these were then converted to 320kbps MP3’s once I was done to save on traffic on my site. I think even the MP3’s make the differences plain to hear, so likely nothing would have been gained anyway by posting wav file formats. Here’s the audio examples:
Knob Position 0:
Knob Position 2:
Knob Position Half:
Knob Position 8:
Knob Position Full:
As you can hear, not only are the stock tubes louder, but they also distort much more at higher Tube Gain settings on the EMX-1. As to which tube type is better, I’ll leave that for you to decide, as it really depends on how you use the tubes and the sound you personally prefer.
Hope this was helpful to people. Thanks for taking the time to listen, and feel free to let me know if you have any questions on the testing I did.