Master Bass Boost
Posted: Oct 8th, '16, 17:16
Huge one here...
From "the archives"...
"A couple of years ago I did some repair work on a customer's TR-909 and discovered that the DC-blocking capacitors in the final output mixer are grossly undersized. The impedance of the mixing busses (used to mix the individual sounds into left and right channels) are around 1k1. With the existing 1uF coupling capacitors (C153, C154) this makes a high-pass filter with cutoff frequency around 140Hz! Considering that the fundamental frequency for the kick and most of the toms are well below this figure, it does a good job of stripping most of the bottom-end punch out of the stereo mix outputs.
Replacing C153 & 154 with 10uF components restored the bottom-end to the stereo mix outputs so they sounded the same as the individual instrument outputs.
Maybe the bass-light stereo mix behaviour is well known to seasoned TR-909 users? ...and maybe Roland did it for some reason? Either way, i've not heard it mentioned before."
So replace C153 & C154 (originally 1uf electrolytics) with 10uf electrolytics..I personally chose to use a switch (DPDT is necessary) so I can flip between the 1uf & 10uf caps. But it is very easy to imagine many people never missing the comparatively wimpy sound of the original 1uf caps.
From "the archives"...
"A couple of years ago I did some repair work on a customer's TR-909 and discovered that the DC-blocking capacitors in the final output mixer are grossly undersized. The impedance of the mixing busses (used to mix the individual sounds into left and right channels) are around 1k1. With the existing 1uF coupling capacitors (C153, C154) this makes a high-pass filter with cutoff frequency around 140Hz! Considering that the fundamental frequency for the kick and most of the toms are well below this figure, it does a good job of stripping most of the bottom-end punch out of the stereo mix outputs.
Replacing C153 & 154 with 10uF components restored the bottom-end to the stereo mix outputs so they sounded the same as the individual instrument outputs.
Maybe the bass-light stereo mix behaviour is well known to seasoned TR-909 users? ...and maybe Roland did it for some reason? Either way, i've not heard it mentioned before."
So replace C153 & C154 (originally 1uf electrolytics) with 10uf electrolytics..I personally chose to use a switch (DPDT is necessary) so I can flip between the 1uf & 10uf caps. But it is very easy to imagine many people never missing the comparatively wimpy sound of the original 1uf caps.