Someone was throwing away a perfectly good Sony subwoofer, saw it sticking out of a trash can, so WTH took it home.... 75W RMS, 28-200 Hz range. Ran my SigGen into it (unit has an RCA for line level in), and boy that reflex port moves some air at 30Hz. Want to add a little preamp for guitar-to-line level, maybe give it a tone control.... whaddya think?
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Yeah, you're right, I need to reproduce higher frequencies to sound anything close to good...I'm just excited about getting something to play with for FREE....Have perused this forum on bass guitar frequencies, lots of good info. This would be an amp for home or garage use, it does have 75W RMS, maybe a medium horn (not piezo) with a crossover. Stuff the preamp inside the subwoofer, tone knob out the back, horn on top. Do horns have to be enclosed? I think not...may be wrong....
You might want to look at the whole fEARful world for inspiration, then try a cheap 6 or 8 incher with a proper crossover, or maybe just a guitar speaker on top if you have one kicking around.
200Hz is waaaay to low for bass guitar amplification. A 4 string produces roughly between 40 and 300Hz base frequencies, so that's without the higher harmonics that actually give the tone it's character. IMO at least the 5th harmonic needs to be reproduced to give proper instrument definition. Placing an extra horn will leave a wide gap between lows and highs.
Perhaps the driver can produce much higher frequencies and it's just the existing low pass filter that needs some tweaking. If you can up the frquency to e.g. 600Hz, it might work.
Perhaps the driver can produce much higher frequencies and it's just the existing low pass filter that needs some tweaking. If you can up the frquency to e.g. 600Hz, it might work.
1) that schematic has at least one gross error: it does not show any DC connection to pin 6 of IC 203.
Some must exist on the actual PCB but makes me suspect the schematic.
2) That said, and instead of messing with the SW, (you still have to make a Bass preamp, if possible add some speaker to carry the rest of the range, etc.) I would rather get as small cheap , typical "15 W beginner's/practice Bass Amp", which usually have small enclosures and a light 8" or 10" speaker , add a preamp out jack and drive the SW with that signal.
Instant killer amp !!!!!
And it might be usable in a Garage situation.
Remember that although the SW has a 75W amp , the speaker there is very low efficiency, precisely to get that low in such a small enclosure.
But it would perfectly match a regular 15W amp, which would sit on top of it as a "head" .
Good luck.
Some must exist on the actual PCB but makes me suspect the schematic.
2) That said, and instead of messing with the SW, (you still have to make a Bass preamp, if possible add some speaker to carry the rest of the range, etc.) I would rather get as small cheap , typical "15 W beginner's/practice Bass Amp", which usually have small enclosures and a light 8" or 10" speaker , add a preamp out jack and drive the SW with that signal.
Instant killer amp !!!!!
And it might be usable in a Garage situation.
Remember that although the SW has a 75W amp , the speaker there is very low efficiency, precisely to get that low in such a small enclosure.
But it would perfectly match a regular 15W amp, which would sit on top of it as a "head" .
Good luck.
I have been using a preamp to test SW with a bass guitar - gets loud, but my first problem with making a bass amp out of this is the frequency response of the amp (curve posted previously, but post was dropped when moderators moved me to this forum. I HAD wanted to talk to linear OpAmp guys....).Anyway, posted below is amp response (at spkr), jives with SONY specs (28-200Hz). Changed C204 from 0.1 to 0.01uF (per poster tip to LPF on IC202), but didn't work. Assumed RC LPF (lo-pass filter) was C204, R208 & R209. Cutoff freq calc'd out to 175Hz with 0.1uF, hoped to see 1750 Hz with 0.01uF....but didn't. Am I changing the right component? Should I lower the R (208 & 209)? Cant do much until I open up the amp response.... Thanks!
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Well it's the official Sony schematic, but as you spotted it has an obvious error on it
If I get time tomorrow I'll check the PCB layout.
No, it can't work without a DC path - however, the PCB layout clearly shows the connection points for a component between pins 6 and 7 (feedback resistor), which has been inadvertently missed out on the circuit and the layout.
The first part of IC203 isn't a buffer either (it's part of the filter), the second half is the buffer.
Unfortunately the picture you've posted shows the wrong side of IC203
Hi,
Modify the connector wires so out of the input board goes
to in of the control board, don't connect the main board
in and out. It should work fine.
Drive it with a bass multi-effects pedal as preamp.
rgds, sreten.
This is cheap and cheerful : http://www.behringer.com/EN/Products/BDI21.aspx
Modify the connector wires so out of the input board goes
to in of the control board, don't connect the main board
in and out. It should work fine.
Drive it with a bass multi-effects pedal as preamp.
rgds, sreten.
This is cheap and cheerful : http://www.behringer.com/EN/Products/BDI21.aspx
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sreten - I still have the problem of the frequency response of the amp being too tight, not enough mid-range. I was told the low-pass-filter was in IC202, but according to Texas Instruments (see pic), it looks more like a hi-pass..... I want to raise the cutoff freq - the current response is shown below. Thanks
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sreten - I'm leaning towards your suggestion, since I haven't been able to figure out the SONY preamp filter, just bypass the preamp (since it's gonna need more gain from just that anyway to use a bass guitar). I used a Tascam US-100 preamp just to test things, but have a bunch of ECG990 2W chips that I want to use, and can put tone control on, will give that a shot. My plan is to spend $0.00 on this project!
Hi,
Not using a bass preamp is very false economy in the long run.
Not like it is expensive. It has bass, treble and presence controls
and I assume the the drive takes it from clean to very dirty.
Though presence may linked to the drive more than tonal.
It also is a straight XLR D.I. box with ground lift, which is useful.
With a proper bass amplifier, where you wouldn't really
need it, the blend option becomes useful as stomp box.
At the price not much not to like, except that it is simply
very cheap and simply won't sound fabulous. But neither
will the Sony sub in all likelihood. You may be lucky in
that the sub driver has a peak before the treble dies.
rgds, sreten.
Not using a bass preamp is very false economy in the long run.
Not like it is expensive. It has bass, treble and presence controls
and I assume the the drive takes it from clean to very dirty.
Though presence may linked to the drive more than tonal.
It also is a straight XLR D.I. box with ground lift, which is useful.
With a proper bass amplifier, where you wouldn't really
need it, the blend option becomes useful as stomp box.
At the price not much not to like, except that it is simply
very cheap and simply won't sound fabulous. But neither
will the Sony sub in all likelihood. You may be lucky in
that the sub driver has a peak before the treble dies.
rgds, sreten.
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I would be very curious to know how this "bass" preamp is any different than any other stomp box with tone,drive, presence and level controls. Maybe because you plug a bass into it instead of a guitar? And then into an amp with a big speaker? It would be an easy fix to my project, but I'm into this stuff to play and learn. Don't have a gig next Friday to worry about! I'd rather get the schematic for the thing and figure out how it works. But I really do appreciate the suggestion!
I took sreten's suggestion (thank you!), it was easy to connect the input pcb to the control card return (thus bypassing the preamp) - the connectors actually fit (once I verified orientation!), and LAB (that's "low and behold") it took less external preamp signal to make good volume from the speaker! Needed 550mV before, but only 260mV with preamp bypassed....some preamp! I actually removed the external Tascam preamp and went direct from my bass, and got decent output. Still needs preamping, but the amp response is LEVEL from 30hZ to (insert how high you want here) !!! The speaker evens reproduces the mids pretty well (for a practice/garage amp). Enough playing for one day.....
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