Tube Amps / Music Electronics
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|8/6/1999 12:43 PM|
||Re: BassBalls schematic - seek no more|
Sorry to spoil your learnig-process, but shoul you want it, I put it up at
Enjoy. (and donīt yall start kicking my butt for telling! ;-p)
|8/6/1999 1:03 PM|
What does the Bassballs do? I see the schematic has a fuzz knob, so is it a bass guitar distortion box?
|8/6/1999 3:31 PM|
It was an envelope-triggered filter for bass that made the filtering a little more pronounced by adding harmonic content to an otherwise dull bass sound (assuming one wasn't playing a Rickenbacker with new strings and bright speakers).
|8/7/1999 12:50 PM|
Looking at it a bit more, it is essentially two parallel Doctor Q circuits, with the range setting capacitors (.022 in one case, and .0047 in the other) set roughly two octaves apart. The envelope detection circuitry is pretty much like the Dr. Q, with attack and decay set by the usual R/C combination. The "fuzz" switch selects betwen two sources for filtering: the buffered input signal (which is what the output sees in bypass mode), and a boosted signal coming from the stage used to drive the envelope detector. The fuzz is not explicitly clipped in any manner other than running out of headroom, and is padded down to provide signal balance betwen straight and fuzz when switching.
The schematic comes from EH, so I shouldn't challenge its accuracy, but I will note that the 2.2M input resistor on the the envelope detector op-amp stage seems ridiculously high. Moreover, since the circuit is essentialy a double Dr. Q, I will point out that the feedback resistor for the same op-amp element in the Dr. Q is 2.2M not 220k. Bottom line: possible there is an accidental reversal of parts here (input resistor should be 220k, feedback should be 2.2M). As always, there are probably design quirks that I'm naive about, so take these suggested changes skeptically.
Areas for mods....
1) A true fuzz might give a livelier sound, so try sticking the textbook diode pair to ground, just ahead of the 100k resistor going to pad "E". Given that the diode pair will reduce the signal level to a half volt or so (depending on diode type selected), the padding at E will need to be adjusted to provide balance between straight and fuzz. This will likely involve reducing the 100k resistor to reduce the overall attenuation.
2) As with the Dr. Q, the attack/decay parameters can be tweaked by varying the resistor and capacitor following the diode. Values greater than 100 ohms will slow the attack a bit, and capacitors greater than 4.7uf will result in longer and smoother decays.
3) The trimpot in the Dr. Q can also be used to "tune" the range of the filter by attenuating some of the envelope-triggered control voltage coming from the first 2N5088, and the same rule applies here. This also means that the staggering of the two filters and sweep width of each can be played with by tweaking the two trimpots. Anyone who builds one of these may want to chasis mount them for playing with, although you should note that only part of the range is actually useful.
4) STEREO, BABY, YEAH!! There are two versions. One involves running the direct signal available at G to one amp and the effect signal available at H to another. A second involves having the 2.7k resistor from each filter section connect to its own output via a 1uf cap and 47k resistor to ground. Send each effect out to a different amp and voila. Naturally this introduces the question of effect bypassing, which I haven't quite figured out yet.
5) Single or multiple sections. Piece of cake, here. If you're running in mono, run each 2.7k resistor to a SPDT on-both-on toggle switch, and you'll be able to have the lower, upper (standard Dr. Q sound) or both filter sections.
See, now THIS is why I like analog.
|8/8/1999 12:02 AM|
I have an original (made in USA)
Hard to describe. Originally I think they were intended for bass guitars, but some one found they sounded great with guitars too.
If you find one, try it. Once you hear one (at least the originals...) you will recognize it's great sound anywhere.
It's capable to be selective-sensitive to the attack, so if your attack is soft, it sounds more or less like a phaser or flanger. BUT! if you dig hard... it's like the guitar is kind of talking while making bubbles ore something like that.
|8/10/1999 4:14 AM|
The Craig Anderton "Bi-Filter Follower" worked on a similar principle - two dynamic bandpass filters with their centre-frequency staggered apart. The original had the filters relatively colse together to get a thicker sound. I found that making the higher bandpass filter a little higher (about 2 or more octave above the lower filter) could get me phase-shifter-like sounds when the sensitivity was set just right and the effect fed with a slightly compressed signal.
The extra spacing simulates the multiple discernible peaks of a phaser. Making the gadget hover around threshold would get pick-sensitive sounds that weren't dramatic enough to feel like a touch-wah.
I mention all of this because the same logic applies to the BB; lowering the uppr filter section (the one with with the smaller cap values) will get you a "thivker" sound, while keeping the filter sections at leats 2 octaves apart can get you phas-ey sounds.
|8/6/1999 10:01 PM|
I must give the guy who mailed me that schem credit, but Iīm afraid I forgot who did it... Thanx anyway!
I also must learn to type correctly when typing fast.
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