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Ampeg Scr-di mods
- Thread starter abracadunphy
- Start date
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- Tags
- ampeg distortion fuzz mods scr-di
I like the Scrambler in the SCR-DI, however I use it just to impart the slightest bit of grind.
A major difference to me between the DI and the Classic preamp is that the Classic can be hissy while the DI has a much lower noise floor. EQ is slightly different too. See the respective manuals for specs.
A major difference to me between the DI and the Classic preamp is that the Classic can be hissy while the DI has a much lower noise floor. EQ is slightly different too. See the respective manuals for specs.
Yeah, that's what I use it for as well sometimes- not as an all out distortion/overdrive, but just to add some "hair" to the sound. By itself, it really isn't that good, and I wonder why it DOES drop some low end out of the signal. In contrast, my Earthtone Pi (Big Muff) and Rusty Box don't lose any lows whatsoever (in fact, I think they emphasize it, due to the compression inherent in them)...
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Anything ever come of this project? Love everything about my SCR-DI except the Scrambler. I'd love to mod it make it usable!
What I have found, is to use the Scrambler (on the SCR-DI) for the most, is for that "just at the edge of breakup" SVT sound- I've been running the scrambler's drive and blend both at 50%. I'm also pretty heavy handed on the EQing anyway (bass @2 o'clock, mids @ 10 o"clock, treble a@2 o'clock, AND the Low Contour ON!).
And while I haven't had a chance to actually start tearing apart circuitry (recording and playing too much lately to take it "out of service"!), I have had the SCR open and took some photos. The level pad control seems pretty basic. Other bits and such I'll have to start tracing with the o-scope and a Function genny...
Resistors R69, R71, R76 make up part of the level pad. It looks a little unconventional though (multilayered PCB perhaps?)...
The overall "guts" of the SCR-DI...
Stay tuned...
I personally find the blend circuit of the SCR-DI interesting...
Scrambler output is coming from R6 and Clean signal is coming from C43.
For those of you that actually are into electronics (or are techs, engs, etc...), do some math here and see just what that network of R25,R26 and C15 actually do across R8... Hmm.
Scrambler output is coming from R6 and Clean signal is coming from C43.
For those of you that actually are into electronics (or are techs, engs, etc...), do some math here and see just what that network of R25,R26 and C15 actually do across R8... Hmm.
Always nice to find a thread that appears to be exactly what you're looking for...
My volume pot is way loose compared to the other knobs, just feels bad. If I'm looking at the schematic right, the volume pot is R9, a 50kA?
My volume pot is way loose compared to the other knobs, just feels bad. If I'm looking at the schematic right, the volume pot is R9, a 50kA?
Basscapes didn't log in for a while, so does anyone else have a schematic with a better resolution?
Has anyone figured out how to fix the low output on the 1/4" line-out?
Ampeg have added a useless 6dB pad to the 1/4" out i'd like to remove.
My very limited understanding of electronic schematics tells me it's probably something to do with R72. Can someone maybe confirm this?
Ampeg have added a useless 6dB pad to the 1/4" out i'd like to remove.
My very limited understanding of electronic schematics tells me it's probably something to do with R72. Can someone maybe confirm this?
Very interesting. Mine seems to be at unity gain at 12 o'clock. Have seen some folks complaining about clipping but can't remember if that was Line Out, XLR, or both.
The clipping people talked about is a different problem. Thats when you use a active bass, you clip the input of the pedal. the 15db pad jumper inside removes the life out of the sound.
This is about the line output. the XLR output is just fine at around 12 oçlock on the volume knob, but then the jack output is so low my ampeg optocomp wont trigger. I have to raise the volume knob to 3 o'clock or above to get some useful input on the compressor. but this gives a very hot signal on the DI out and adds a little distortion i don't like.
More people have complained about this when driving a power amp for instance.
I hope bridging the 1k R72 resistor on the line-out wil remove the 6dB pad ampeg is talking about in the documentation. although that's a bit of a guess, it seems logical to me a series resistor is just to lower the output. read something about increasing impedance with a series resistor.
i'm seriously thinking about just bypassing it with a drop of solder and see what happens, although i'm a bit scared to do so, don't want to destroy it.
Ok i went ahead and bypassed the resistor and it seems to have done exactly what i was trying to do!
I'l have to test this a bit more later on, maybe i'm missing something, but this could be a very easy fix for a problem people are having with their pedal.
I'l have to test this a bit more later on, maybe i'm missing something, but this could be a very easy fix for a problem people are having with their pedal.
Bdw, took a look at the schematic again and i think your right. It says 50kA.
I have mixed feelings about the mod i did.
I feel it may have helped a little, but I'm not quite shure atm how much actually. I could just have the volume pot a tiny bit higher maybe somewhere in my signal chain the gain staging is a tad different. I've changed some pots in my bass. Maybe just fooling myself.
Bit of a bummer i haven't been very scientific about it. But at the same time the pedal still seems to work fine and i feel the compressor after the pedal gets triggered a bit easier(has no threshold, just ratio control).
So all in all i can't really say this mod works, although my situation seems to have improved a little.
If there's no experts around to maybe shine some light on this, I may try to remove the resistor and put a switch in between to really A/B both situations but I'd have to borrow/buy a hot air soldering station for SMD soldering. Very busy atm so probably will look into this some time in the future
I feel it may have helped a little, but I'm not quite shure atm how much actually. I could just have the volume pot a tiny bit higher maybe somewhere in my signal chain the gain staging is a tad different. I've changed some pots in my bass. Maybe just fooling myself.
Bit of a bummer i haven't been very scientific about it. But at the same time the pedal still seems to work fine and i feel the compressor after the pedal gets triggered a bit easier(has no threshold, just ratio control).
So all in all i can't really say this mod works, although my situation seems to have improved a little.
If there's no experts around to maybe shine some light on this, I may try to remove the resistor and put a switch in between to really A/B both situations but I'd have to borrow/buy a hot air soldering station for SMD soldering. Very busy atm so probably will look into this some time in the future
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