#1
so i've decided to build myself an amplifier, but i want it to be usefull to me. Happens to be i'm a basist and there aren't a lot of resources on the topic of building a bass amplifier, especialy when it commes to something my level (basic to say the least). So how would i make something like the Ruby Amplifier or the little gem Little Gem suitable for low frequencies? its probably got to do with replacing or removing a couple of capacitors, letting more low end pass trough, but this is confusing me.
maybe the circuits are ok as they are
#2
ruby looks ok to me =)
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#4
what about the bassman mod? isn't it supposed to sound more like a bass amp then (altough it could be in the sense of the '59 reissue guitar amp)?

the woofer idea is great, i'm certainly going to look into it!

also, how do i feed this? low frequencies usualy use more power, so i'm probably gonna need some kind of adaptor of some kind, maybe something like a recycle wall wart, or would that give issues with the sound?
#5
*Double the input and output caps.
*Use a 386 that can take a higher voltage (I think the LM386-N4 can handle up to 18V).
*Power the thing off a wall-wart that can supply well-filtered DC at the maximum rating of your IC.
*Look up the 386 datasheet and for where it talks about a low frequency boost. You might want to implement this as stock.
*Do the Bassman mods. You lose a bit of versatility, but at least you'll get a smoother sound more suited to bass.
"Everybody, one day will die and be forgotten. Act and behave in a way that will make life interesting and fun. Find a passion, form relationships, don't be afraid to get out there and fuck what everyone else thinks."
#6
Quote by the_random_hero
*Double the input and output caps.

so that means i'm gonna have to use a 94nF (aprox 100nF) and a 440pF capacitor, or something in that area
Quote by the_random_hero

*Use a 386 that can take a higher voltage (I think the LM386-N4 can handle up to 18V).

any lm386 can take up to 15v, the lm386n-4 can take 22v max, so i figure any model is gonna be ok, but the n-4 the best
Quote by the_random_hero

*Power the thing off a wall-wart that can supply well-filtered DC at the maximum rating of your IC.

how would i make sure it is filtered? could i mod it safely so that it becomes filtered?
Quote by the_random_hero

*Look up the 386 datasheet and for where it talks about a low frequency boost. You might want to implement this as stock.

i've seen the graph of the frequency response when the bass boost is used, and its a straight line with a peak in the low end, is that good?
Quote by the_random_hero

*Do the Bassman mods. You lose a bit of versatility, but at least you'll get a smoother sound more suited to bass.

i've been thinking that maybe i could still use a potentiometer instead of the fixed resistor for gain, it wouldn't realy change anything, would it?

anyways, thanks guys for the advice you already gave me, all other input is welcome!
#7
Quote by mithrilglove
so that means i'm gonna have to use a 94nF (aprox 100nF) and a 440pF capacitor, or something in that area



Sure 0.1uf (100nf) will be perfect for an input cap. On second thoughts, you won't have to change the output cap. It's way higher than I remembered, so it's not doing much tone shaping.

Quote by mithrilglove
any lm386 can take up to 15v, the lm386n-4 can take 22v max, so i figure any model is gonna be ok, but the n-4 the best


I thought that some models could only take 12V?

Quote by mithrilglove
how would i make sure it is filtered? could i mod it safely so that it becomes filtered?


You can buy a regulated and filtered power supply, or build your own based off a 12VAC adaptor. I can make a schematic if you want.

Quote by mithrilglove
i've seen the graph of the frequency response when the bass boost is used, and its a straight line with a peak in the low end, is that good?


A peak means greater 'volume' in that frequency area, hence the term 'bass boost'.

Quote by mithrilglove
i've been thinking that maybe i could still use a potentiometer instead of the fixed resistor for gain, it wouldn't realy change anything, would it?


Not particularly. I'm a huge fan of the Bassman mods and I've found I can set the level of distortion by playing with my guitars volume pot. Either way, it's still going to be fine.
"Everybody, one day will die and be forgotten. Act and behave in a way that will make life interesting and fun. Find a passion, form relationships, don't be afraid to get out there and fuck what everyone else thinks."
#8
Quote by the_random_hero

I thought that some models could only take 12V?

i checked the datasheet and you are correct, my bad


Quote by the_random_hero

You can buy a regulated and filtered power supply, or build your own based off a 12VAC adaptor. I can make a schematic if you want.

my dad said he didnt care me working with the 240v mains, so i'm probalby gonna build a psu myself, but if you know about somewhere where i could find schematics for a regulated and filtered 12v psu, that would be great.
#9
The hardest part of this will be getting the speaker to sound good. Don't take my word 100% for this as this isn't really my area, but from what I gather a big part of bass cab design is the actual box. All bass speakers and sub woofers that I've seen have been in ported or sealed boxes. Something to do with the frequencies becoming increasingly hard to reproduce under 100 hz, and so you need to tube the box to get it to efficiently reproduce those frequencies. If you try and put low frequencies through a speaker without a properly tuned box, it'll (apparently) die. I suspect that this is a large part of the reason you can't put bass through guitar amps and some pa cabs.
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#11
Quote by xifr
The hardest part of this will be getting the speaker to sound good. Don't take my word 100% for this as this isn't really my area, but from what I gather a big part of bass cab design is the actual box. All bass speakers and sub woofers that I've seen have been in ported or sealed boxes. Something to do with the frequencies becoming increasingly hard to reproduce under 100 hz, and so you need to tube the box to get it to efficiently reproduce those frequencies. If you try and put low frequencies through a speaker without a properly tuned box, it'll (apparently) die. I suspect that this is a large part of the reason you can't put bass through guitar amps and some pa cabs.


i'm not sure, but i think that it wont kill the speaker if you put it in a badly designed cabg, but i'm gonna do my best to make it work, altough i'm not looking for the perfect sound, just something that will let me play amplified for practice so i don't need to have my roland 150w amp at home.

also, to the guy demanding the pics, i'd love to show you, but i don't have any, its still in the design fase, but the moment i have them i'm gonna start a decent project thread, and there'll be plenty of pics. and trust me, it's gonna be something special!
#12
Yeah, Conrad's right on this one, cabinet design plays a big role, there's tons of theories on porting and such out there.
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#13
This is from wikipedia:

When a vented bass-reflex design is used, an opening is cut into the cabinet and a tubular or rectangular conduit is typically mounted in the opening. These tuned openings increase the speaker cabinet's efficiency and output, and reduce the movement of the cone near the port tuning frequency, which lowers distortion. One disadvantage of using a vented design is that there is no air pressure difference to help limit the driver cone excursion at frequencies below port resonance. As a result, infrasonic (very low-frequency) signals such as those caused by fingers hitting strings may cause very large and potentially damaging movements of the speaker cones. Ported systems can suffer from port noise or "chuffing" due to turbulence in the port, and poorly designed ported systems may ring excessively at the resonant frequency they are tuned to, which may give a boomy or "one-note" sound.

Essentially what it's saying is that ports are tuned to a frequency (usually 40 hz for 4 string basses, 30 hz for basses with a low b), so that the speaker is more efficient at lower frequencies, but when you go below the tuning frequency of the port you over exert the speaker which can cause damage. If you don't want to try and get the port frequencies right you can build a sealed cab, but you're going to need a much more powerful amp to be able to get the same volume out of a sealed cab than a ported cab.



EDIT: it seems building a sealed cab isn't so easy:

Output falls off below the cabinet resonant frequency (Fs), which can be determined by finding the peak impedance. The designer must balance bass response, flatness of frequency response, efficiency, and size of enclosure.

Though the manufacturer might tell you what volume the inside of the box needs to be (after deducting things that reduce from this such as the speaker itself etc.)

"A wise man once said, never discuss philosophy or politics in a disco environment." - Frank Zappa
Quote by Jinskee
Don't question the X.
<Frenchy> I'm such a failure
#14
i think i'm gonna make a little change in plans. i've found out that i can buy speakers relatively cheap from thomann, so i was thinking about designing a cab around this one:
$http://www.thomann.de/gb/eminence_delta_15.htm
does anybody have any good resources about building a bass cab that doesn't involve any specialised equipment (just stuff like screws, glue, a saw, not cnc routers and other s**t)