I would like to modify the bass output of my RG100ES. I would like to mod the bass so that it's not so round and fat, but rather tighter/more responsive.
If anyone knows how to accomplish this, please reply with detailed instructions and schematic references if at all possible.
Thanks in advance to eveyone that replies.
BMWFREQ-
Randalls are not exactly famous for "round and fat" bass or anything else, they are considered buzzy grindy by most.
I rather suspect speakers: what are you using it with?
If you have *too much* bass, what happens when you lower it?
Are you using any effects in the loop?
The EQ *can* be modified, just it's not my main suspect, speakers are.
I am using the 4x12 Randall cabs that I bought with the head back in '85. I believe they are 100 watt Celections?
Anyway, I really don't think it's the cabs, but rather the circuitry. The bass is way too round for me...I'd really like to tighten it up with maybe a resistor and/or cap mod.
Thanks in advance-
BMW FREQ
Have you played around with the duncan tone stack calculator?
http://www.duncanamps.com/tsc/download.html
It's a marshall-style tone stack. You can plug in values to simulate the rg100 and try switching in lower values for the bass cap. You can also simluate rotation of the pots to see response at various positions.
THAT'S AWESOME! ...I just hope I can figure out how to use and interpret this awesome program.
The program has help and instructions. It's pretty straightforward. You just click on a component to open up a window to change its value. The sliders at the bottom represent the rotation of the pots. The default is halfway, or "5" (and, sadly, Nigel, these do not go to "11" ;)). The graph is a plot of gain versus frequency, so it is telling you at which frequencies and by how much the circuit is cutting or boosting. Its like a drawing of whether you hear less treble or more bass. The caps and the resistors work together to determine the frequencies at which you start to lose gain, but generally, if you add capacitance, the effect will be to boost the bass end of things. With guitar you are concerned with the middle of the plot, from about 80 hz to about 1,000 hz. Playing with the pot and cap values for the bass should tell you what you might expect out of any tweak you are doing and then you could experiment by trying a few values yourself. The pots are easy to get at, but the caps are on the board, so you have to at a minimum lift the board up to desolder.
Also, a note on randall board: some of the caps that I replaced seem to have been cut with the world's dullest nippers when installed, they didn't want to come out of the holes, so I had to de-solder, push into the hole and nip the bottom ends, then pull back up to remove (if that makes sense?). What I'm saying is, the ends of the leads were flattened after installation. I don't know if this was intentional, or whether my board was made by a guy with old nippers, but it was annoying.
So, it sounds like you have modded your RG100ES...??? If so, what did you mod; why and what was the outcome?
Also, anyone know what the stone stack structure and values are for the new AFD100??? Anyone???
Jay-
Quotesome of the caps that I replaced seem to have been cut with the world's dullest nippers when installed, they didn't want to come out of the holes
Well, it probably was made on purpose.
Remember Randall is a serious company, they just won't use improper tools..
*There is* a special lead clipper which on purpose flattens the leg, to avoid it falling when you turn the board upside down for soldering.
I myself have un-sharpened clippers to avoid little sharp pointy leads flying all over the place.
Now they cut, say, 90% of the leg, and a small twist of my wrist finishes it, leads drop neatly inside a small convenient tray.
Quote from: BMWFREQ on March 30, 2011, 06:05:21 PM
So, it sounds like you have modded your RG100ES...??? If so, what did you mod; why and what was the outcome?
...
I didn't mod it, just replaced the electrolytics and a couple of transistors.
Quote from: J M Fahey on March 30, 2011, 11:22:37 PM.
Well, it probably was made on purpose.
I suspected as much. Once I figured out that they were like this it was easy to deal with but I did feel stupid at first pulling on the loose cap and it not coming out of the board.
This ToneStack program is AWESOME!!! Can anyone tell me what the typical values should be for the signal and load, and what they represent? Also, what are these values based on?
Thanks!
Hi,
Simple enough, just make R12 bigger, try 10k.
(Hard to read but I think it says 4.7k on the pic)
This will force a little more energy to go through the treble end of the tone circuit.
Having said that don't expect miricales as the tone stack is only one small part of the whole Amp.
There may well be other reasons why the bass is so strong.
Phil.
The million dollar question: what happens when you lower bass?
Is the sound acceptable at *any* position of the bass knob?
The bass adjustment knob doesn't really seem like it offers as much adjustment as I think it should. When I turn it to zero, there seems to be more bass remaing than most amps have. This is what I would like to change.
Also, can anyone tell me what the signal and load value should be, and how these values are determined when using the Tone Stack program? What does the signal represent, and what does the load represent?
Thanks!
The program is asking for the source impedance of the preceding stage and the input impedance or load for the next stage. I think the default value on the Marshall tone stack in the program is for a tube stage (1.3K). I'm not the most savvy on this stuff, so I am hoping one of the gurus will weigh in, but if your randall schematic is the same as my the RG 80, there is a 10k resistor, a 10K pot and a 1MFd cap coming from the preceding stage. I know cap impedance varies with frequencies, but should be smaller, relative to the resistors (maybe 1,500 to 150 ohms at guitar frequencies?). On the next stage there is a 1M resistor in front of the driver transistor and 1M in front of the op-amp going to the reverb, so maybe 500K in parallel? Also the schematic indicates the ac voltage at 1Khz before and after each stage, so someone who is good with the math can probably deduce the relative values of input and output impedance. I was playing aorund in the program with 10k-20k on the source and 1M and 500k on the load. It looks like the chief effect is to move the whole curve up or down (like adding or subtracting a constant).
Thanks for the reply - very helpful. Now if I could just figure out how to get my amp to sound the way I want it to, I'd have it made. :tu:
I came up with a mod for this if anyone is interested...
Sure thing. Please share!
I'm getting very close to having a good AFD-100 sound, but I'm still working on it. I'll post my mods as soon as I'm satisfied with 'em.
I am posting this all over the place hoping some one can help...
My RG100ES has recently started sounding loose in the bass end and sort of blah. I put new filter caps in it and the humming at idle did drop by a noticeable amount. But it just doesn't sound as good as it once did. Someone suggested the output transistors?
Any ideas what could cause the low end to start sounding flabby?
Thanks, gang.