OK, so I modded my NYC BMP, recently got, to 1981 specs (as to be found here (http://www.thundertomate.com/DIY/BMP81/BigMuff1981SCH.jpg) and I absolutely love it! I performed the next mods:
- Made the diodes switchable between Si, Ge and nothing
- Added a 4 stage selector switch to switch between Stock BMP, Stock BMP + Mid boost, Swollen Pickle tone, Swollen Pickle tone + mid boost.
- Some kind of bend I always got. Now the unit does not produce nitendo sounds but oscillate like a madman. I kind of link one part of Q2 to the same part on Q3
I still have one more hole in my chassis (I drilled one too many) so I need some kind of switch (too small for a pot). Any thoughts for a last mod??
Oh, I run the unit on 18V for more volume
Maybe an input cap selector, between normal bass and extra bass for more fuzz-like tones. Or maybe normal bass and less bass, for more trebly sounds. Depends on what you like.
Luck!
Miguel
Yes, I thought so too but I noticed some tightness loss when this is done; with these caps the bass (and I use mine on bass) is very very tight (on no diodes and 18V) and I love that.......
I would love some "blue box" kind of destruction tones from it....
Ampeg scrambler type blend control. Very useful for bass.
Quote from: nelson on November 30, 2005, 03:11:15 PM
Ampeg scrambler type blend control. Very useful for bass.
Hmmmm, no.....
I play through a two channel Peavey amp; the second channel is always on and offers me that clean blend in (as I put my effects through the second channel). Both channels have individual pre-preamp FX-loops!
you could try a switch to remove the R13 resistor (the one to ground off the base of the 3rd stage) removing that resistor is supposed to give you asymetrical clipping and a warmer sound due to the transistor being misbiased.
How about using the switch to misbias one of the stages, to make glitchy gated gated sounds, like the Great Cheddar. It might sound a little more blue boxey. Boxey but good...
Looking at the schematic, if I were to take a shot in the dark how to do this, I would switch the base of q3 switch from R13, to a 100k trim pot set up as a variable resistor to ground. Maybe put a 1k resistor in series with the trim pot to prevent it from going to zero ohms and nothing coming through.
If you're going to do that (R13 mod) try it first before you make it permanent. I built a BMP with exactly that mod and couldn't hear any difference with the resistor in or out.
I'm not sure if it would be audible, but a switch could be used to add an extra diode to one or both sets of clippers for assemetrical clipping. Or add a resistor or trimpot or capacitor between the diodes and ground.
I think the tone stack response can be modified by changing just one component too. Details at AMZ I think.
Quote from: RickL on November 30, 2005, 08:07:40 PM
If you're going to do that (R13 mod) try it first before you make it permanent. I built a BMP with exactly that mod and couldn't hear any difference with the resistor in or out.
Hey RickL, did you just disconnect r13, or put in something smaller?
...how about rigging a switch to a voltage divider, so that you can run it at 9v or 18v ?
Man, I am drunk.....
OK, I tried both 9 and 18V and I liked the 18V best on the no diode section. More volume is always a pre
Will try the R13 tomorrow!
Put a rubber grommet in the hole and draw some lips around it with red marker, that'll do ya.
Left yourself wide open for that one given the BMP title, man :)
In all seriousness I would use the hole for an LDR, which would then control an amount of feedback from say, the 3rd gain stage to the first. Then you can use your foot as a half-assed feedback/wah type of thing.
Yes, that would be cool!
Shame the hole is on the back, still, for this idea I want to make another one....
Where should the LDR go then??
OH, BTW, the R13 mod does not sound that much different. I switched it from 100K to nothing and I hear only a slight change
Quote from: Bernardduur on December 01, 2005, 09:41:57 AM
Yes, that would be cool!
Shame the hole is on the back, still, for this idea I want to make another one....
Where should the LDR go then??
Anywhere there's easy foot access. You could run a wire through the hole and put the LDR on the end, like an angler fish. You'll have to put a switch to switch the LDR in/out anyway though, so there's another hole. Also I would leave some room for tapering resistors to adjust the response of the LDR.
Quote from: Bernardduur on December 01, 2005, 09:41:57 AM
Yes, that would be cool!
Shame the hole is on the back, still, for this idea I want to make another one....
Where should the LDR go then??
OH, BTW, the R13 mod does not sound that much different. I switched it from 100K to nothing and I hear only a slight change
You'd probably want a switch on this, anyway...So there you go.
Yeeee......
Sorry, I meant wich resistor should the LDR replace / change or between wich point should I put it.....
OK, I found it! I put it between R5 and R15. This is really cool; by shading it with my foot the effect is completely gone. In light the unit goes mental
Any more mods?? ;D
Quote from: Bernardduur on November 30, 2005, 12:26:04 PM
OK, so I modded my NYC BMP, recently got, to 1981 specs (as to be found here (http://www.thundertomate.com/DIY/BMP81/BigMuff1981SCH.jpg) and I absolutely love it! I performed the next mods:
- Made the diodes switchable between Si, Ge and nothing
- Added a 4 stage selector switch to switch between Stock BMP, Stock BMP + Mid boost, Swollen Pickle tone, Swollen Pickle tone + mid boost.
- Some kind of bend I always got. Now the unit does not produce nitendo sounds but oscillate like a madman. I kind of link one part of Q2 to the same part on Q3
I still have one more hole in my chassis (I drilled one too many) so I need some kind of switch (too small for a pot). Any thoughts for a last mod??
Oh, I run the unit on 18V for more volume
May i have a schematic/layout of the exact tone mods eh? If it's not too much trouble....
i'm just curious how you gots all those tone stacks in there.... :icon_confused:
Quote from: Bernardduur on December 01, 2005, 09:41:57 AM
OH, BTW, the R13 mod does not sound that much different. I switched it from 100K to nothing and I hear only a slight change
That makes sense that lifting R13 wouldn't do anything, if doing that barely changes the bias on that stage. Instead I was suggesting switching r13 to a much smaller resistance to ground, like 10k or something, to get the bias voltage on the base much lower, and make the output like a crappy noise gate, that just kind of cuts right in at a certain point in a notes decay. To try it out quick you could just solder the wiper and one of the outside lugs a 100k pot in parallel with r13.
Another mod you could try to try and simulate a dying battery, by putting a resistor in series with the power coming to the cicuit. Like switch between a 18v supply and a 4.5v supply.
Quote from: Yun on December 01, 2005, 07:25:52 PM
May i have a schematic/layout of the exact tone mods eh? If it's not too much trouble....
i'm just curious how you gots all those tone stacks in there.... :icon_confused:
OK, I've checked my notes:
A tone stack consists of five parameters. I use the schematic noted in my first post as a reference. Two parameters I leave unaltered:
- 100K (RV2) pot to control the tone
- 22k (R17) to ground resistor (they were the same in both stacks)
I use a 3P4T switch to control the other three parameters:
- Position 1: Stock BMP: R18 = 39k; C11 = 3.9 nF; C12 = 10 nF
- Position 2: BMP + mid: R18 = 39k; C11 = 30 nF; C12 = 10 nF
- Position 3: Swollen Pickle stock: R18 = 33k; C11 = 3.3 nF; C12 = 47 nF
- Position 4: Swollen Pickle + mid: R18 = 33k; C11 = 100 nF; C12 = 47 nF
The swollen pickle tonestack (both stock as mid) are now my favourite; the tone knob is a bit weird: on the lowest setting the EQ is more treble than when the knob is turned a bit. The sound basses up a bit at that point.
Second, Processaurus , I will check out your options. Thanks!
Quote from: Bernardduur on December 02, 2005, 06:02:06 AM
Quote from: Yun on December 01, 2005, 07:25:52 PM
May i have a schematic/layout of the exact tone mods eh? If it's not too much trouble....
i'm just curious how you gots all those tone stacks in there.... :icon_confused:
OK, I've checked my notes:
A tone stack consists of five parameters. I use the schematic noted in my first post as a reference. Two parameters I leave unaltered:
- 100K (RV2) pot to control the tone
- 22k (R17) to ground resistor (they were the same in both stacks)
I use a 3P4T switch to control the other three parameters:
- Position 1: Stock BMP: R18 = 39k; C11 = 3.9 nF; C12 = 10 nF
- Position 2: BMP + mid: R18 = 39k; C11 = 30 nF; C12 = 10 nF
- Position 3: Swollen Pickle stock: R18 = 33k; C11 = 3.3 nF; C12 = 47 nF
- Position 4: Swollen Pickle + mid: R18 = 33k; C11 = 100 nF; C12 = 47 nF
The swollen pickle tonestack (both stock as mid) are now my favourite; the tone knob is a bit weird: on the lowest setting the EQ is more treble than when the knob is turned a bit. The sound basses up a bit at that point.
Second, Processaurus , I will check out your options. Thanks!
Thanks, man! Much obliged, i must try this.
Let us know how it went