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Hi all I did this layout mod to my ruby... but i have some problems and confusions...
1. which "VOLUME" can i eliminate and how can i do that? example if the 10k volume so 47n + 10k to the ground?
2. is this the right place to insert the tone stack? or put it in pin 5 = pin 5 - the 18 watt tone stack - 10ohms to the ground 220 uf - Speaker?
Thanks in advance
A2
The 386 is wired as an inverting amplifier it needs to be decoupled from the volume and it needs some series resistor to define input impedance.
Google might help?
Or go build what has already been done.
You can't just hang anything in a circuit,, ie in this case use a tube amp type tone circuit in front of the 386 and expect it to work identical to a valve circuit.
Phil.
Thanks Phatt.. I just did what the Beavis Guys did to Noisey Cricket :D its good... but anyways i tried my modification and i have some problem with the volume pot if set it to 5 oclock it has some oscillation also the volume doest work properly
Thanks again
Quote from: phatt on June 10, 2011, 05:07:14 AM
The 386 is wired as an inverting amplifier it needs to be decoupled from the volume and it needs some series resistor to define input impedance.
Nope: The chip's inputs are internally ground referenced, no need for coupling. The chip also has internal 50K input reference resistors, no need for such either. The gain is also internally set so additional components for that are optional.
But I agree: overall the design depicted in the schematic is a poor one.
If you really want to do something about it, get rid of the 500K volume pot. Not only is it totally unneccessary, it's also a poor match to 50K input impedance of the LM386. You want to impedance bridge circuits by factor of 1 to 10, not the other way around.
Now, the 50K input of the chip can actually be used to replace the 500K load presented by the second volume control pot, but you need to "scale" the tonestack's component values by factor of 10 to match up. So, resistors and pots are decreased to 1/10th of their current value, capacitances are increased by factor of 10. Now it's the same response but a lower impedance circuit working better with the LM386.
Thanks Teemu, Whoops!
I assumed they where much like the average,, obviously internally different :-[
Phil.
Depending on how much distortion you need, you might want to add a gain stage.
(tone stacks lower signal level)
If you play mostli clean-ish, the teemuk's advice should work nicely ;)
I've built quite a few ruby amps (my first diy projects). I did add various tone stacks, but my best one, which I still use sometimes, is a "two channel" amp without any tone controls. First channel is a Fetzer Valve, second channel is a Mockman 2.0 (switchable). I still have a mockman channel sample (http://www.box.net/shared/3064zojj8y).
Not bad for a battery powered amp smaller than a cigarette pack, I think :)
@Teemuk Sir! that's a good explanation! i really love to do what you had said but unfortunately can get a picture out of it. . . . whta do you mean in factor 1 - 10? is this math are you talking about? sorry for this question. in my head is the .01uf = .1uf? 500k = 50k? is this correct? thanks again
alexius - i really want very clean amp because the distortion that's coming out to this amp is very minimal.. so i need some distortion in front.. i've tried adding SHO + Ruby in one bred board it oscillate like hell! mmhh i wonder why? also i did perf the ruby and add the sho also in front " breadbord" still oscillations!
Thanks guys!!
PS phatt thanks also
Alexius II your link is super kick ass! what's your rig hear? wow its super nice!
Well, thanx :)
That recording was done with the second mini-amp I've done. It's the right one on the photo (the "Mk.II").
(http://www.shrani.si/f/44/HH/4kcfu1Qg/mk1mk2.jpg)
Setup was: guitar > amp > 4x12 cabinet > mic > pc soundcard (one left and one right track)
ps: your math is correct, you have to multiply caps by 10 and divide resistors by 10... and remove the second (500k) volume.
Wow! nice mini amp! any chance for the Schematic? the modified one? nice distortion you have in recording that mini amps generating that distortion? what software did you used for recording?
PS - ohh im right in math! hahaha how about the 500k? change it to 50k resistor to the ground? :D
A2
Nice job, dude. :tu: I bet those come in handy, Especially when you're travelling. Those would surely be alot lighter. Are they difficult to build?
I do not have the exact schematic, but as far as I remember, the fetzer valve and mockman are switchable (input and output) and share the volume pot, which then goes into the ruby. Ruby is built without volume pot, since there is volume control after preamps, so the buffer is connented directly to the chip.
And yeah, the whole guitar sound is generated inside the amp. Mind that mockman is basically a distortion pedal circuit, without any gain control. Fetzer on the other side is a clean gain stage, but very capable of nicely overdriving the ruby.
Well, considering I had absolutely non electro-knowledge prior building my first ruby, I thought it was easy :tu:
I later learned It was VERY easy, compared to creating something from scratch, and make it not crap-sounding ;D
Hm, I believe Sonar was used to record this.
Congratulations. :tu: