Hello guys, been a while since my last post.
I have been toying around with the idea of building a bass guitar amp for band practice. The idea was to get 150ish watts into a 8 ohm 15".
I stumbled onto this thing: LM3886 3 x 159W Parallel Mono Channel Amplifier Board - eBay (item 270644493655 end time Nov-02-10 21:31:50 PDT)
Which looks promising, allthough I have no idea if these chips will work well for bass guitar.
I think I'm going to build a simple preamp, something like this: http://www.diyaudio.com/forums/attachments/musical-instruments/54423d1133730880-bass-preamp-circuit-anybody-guitar-para-eq.gif
What I'm wondering, will these chips handle the task of being a bass guitar amp?
Will I need more power, or will that 168W thing work?
I have a 8x12V Halogen light transformer, maybe I can use that thing? Never used it, I tried to hook it up once, but I couldn't get a voltage reading from it, I guess it needs a load to fire up... not sure quite how I do that
What kind of power supply do I need? and what VA rating? 168VA? or 612VA?
Will a heat sink suffice for cooling? Or do I need fans?
DocZ
I have been toying around with the idea of building a bass guitar amp for band practice. The idea was to get 150ish watts into a 8 ohm 15".
I stumbled onto this thing: LM3886 3 x 159W Parallel Mono Channel Amplifier Board - eBay (item 270644493655 end time Nov-02-10 21:31:50 PDT)
Which looks promising, allthough I have no idea if these chips will work well for bass guitar.
I think I'm going to build a simple preamp, something like this: http://www.diyaudio.com/forums/attachments/musical-instruments/54423d1133730880-bass-preamp-circuit-anybody-guitar-para-eq.gif
What I'm wondering, will these chips handle the task of being a bass guitar amp?
Will I need more power, or will that 168W thing work?
I have a 8x12V Halogen light transformer, maybe I can use that thing? Never used it, I tried to hook it up once, but I couldn't get a voltage reading from it, I guess it needs a load to fire up... not sure quite how I do that
What kind of power supply do I need? and what VA rating? 168VA? or 612VA?
Will a heat sink suffice for cooling? Or do I need fans?
DocZ
Hello guys, been a while since my last post.
I have been toying around with the idea of building a bass guitar amp for band practice. The idea was to get 150ish watts into a 8 ohm 15".
I stumbled onto this thing: LM3886 3 x 159W Parallel Mono Channel Amplifier Board - eBay (item 270644493655 end time Nov-02-10 21:31:50 PDT)
Which looks promising, allthough I have no idea if these chips will work well for bass guitar.
I think I'm going to build a simple preamp, something like this: http://www.diyaudio.com/forums/attachments/musical-instruments/54423d1133730880-bass-preamp-circuit-anybody-guitar-para-eq.gif
What I'm wondering, will these chips handle the task of being a bass guitar amp?
Will I need more power, or will that 168W thing work?
I have a 8x12V Halogen light transformer, maybe I can use that thing? Never used it, I tried to hook it up once, but I couldn't get a voltage reading from it, I guess it needs a load to fire up... not sure quite how I do that
What kind of power supply do I need? and what VA rating? 168VA? or 612VA?
Will a heat sink suffice for cooling? Or do I need fans?
DocZ
they will easily handle the task of being a practise amp. for stage performances you would need more power, i think (when not playing through pa).
you can use the 8x12V transformer. wire 4 x 2 windings in parallel and use two of them in series for each rail, so you will get 24-0-24 V AC and about 34V DC, which should be fine.
you dont need fans as long as your heat sink is large enough. i would say just try it. if it gets too hot, the lm3886s will shut down. using them without any cooling will surely destroy them.
Thank you for your reply, it will be used as a practice amp in my band practice space, with the band. I used to have a 60W amp, which worked "OK", but I needed to crank that sucker to the max to get it to a descent volume against my drummer and guitarist. Thought 150W would give me more headroom. But maybe I need to get up to 200 - 300w? can I bridge two of those boards perhaps?
I'm sitting here messing with that transformer. How do I "switch it on" ? just to test it...
DocZ
I'm sitting here messing with that transformer. How do I "switch it on" ? just to test it...
DocZ
with +-35V dc and 8ohm load that 3 x lm3886 will give no more than 50W.
The reason for paralleling chip amps is to get more power into lower resistance loads.
To get 100W you need to bridge two lm3886 chips into 8ohm load.
That board will delivery 150W but only into 2.7ohms but then power supply must not be higher than +-28V dc
The reason for paralleling chip amps is to get more power into lower resistance loads.
To get 100W you need to bridge two lm3886 chips into 8ohm load.
That board will delivery 150W but only into 2.7ohms but then power supply must not be higher than +-28V dc
150W will give more headroom, but it will be barely noticeable. You'd need to go all the way up to 600W to get it to sound twice as loud as 60W. 600W is possible with multiple paralleled-bridged chip amps, but not into your 8R unit, you'd need a lower impedance. It would be cheaper to use some kind of soft clipping circuit to get the sound louder. LM3886s do not clip tidily - for this reason, if you don't use a soft clipper/compressor, I would recommend the TDA7293 as a more suitable part. They have the advantage of being able to be paralleled without sharing resistors.
Take a look at 41Hz.com. They have a number of amp kits, the Amp2 will deliver 600W into 8 ohms, bridged. The guys there will help you with advice on the build. You may decide to go with paralleled speakers to give you a 2 ohm load, but if you look at what they have on offer it will open up your options a lot.
Having 600W on hand will mean you have ample power delivered by an unstressed amplifier, much preferable to running at full output.
w
Having 600W on hand will mean you have ample power delivered by an unstressed amplifier, much preferable to running at full output.
w
A lot of distortion, and not pleasant distortion, higher order stuff. These chips simply aren't designed for 2R. You'd have to run with very low rail voltages not to run into thermal protection. Perhaps you'd get 25W - that's just a guess.
look at the 3886 datasheet.
It is never specified for any load of less than 4r0.
A 4ohm speaker is much more demanding than a 4r0 resistor.
A single 3886 can never properly drive a 2ohm speaker. The maximum output current limit of 7A @ Tc=25degC tells you it is incapable of driving those low impedance loads.
You don't have a choice.
Hi Docz
For what it's worth here's my experience with the 3886...
They are very good to excellent for HiFi and Home Theater use when well constructed with reguard to circuit layout and grounding. For high power applications like musical instruments and PA, not so much. The main problem is that when you push them hard, the on-chip protection circuits are much more likely to kick in, which will cause all kinds of NASTEE sounds. Trust me, you would be much happier using a real instrument amp, that's what they are designed for. I played bass guitar for about 25 years, had to give it up for carpal tunnel problems, but never was satisfied with anything but the real thing. My favorite set-up was my Fender Prescision Bass with round wounds, played through my Traynor Valve 50 watt and a 4X10 cab.
Good luck with your quest.
For what it's worth here's my experience with the 3886...
They are very good to excellent for HiFi and Home Theater use when well constructed with reguard to circuit layout and grounding. For high power applications like musical instruments and PA, not so much. The main problem is that when you push them hard, the on-chip protection circuits are much more likely to kick in, which will cause all kinds of NASTEE sounds. Trust me, you would be much happier using a real instrument amp, that's what they are designed for. I played bass guitar for about 25 years, had to give it up for carpal tunnel problems, but never was satisfied with anything but the real thing. My favorite set-up was my Fender Prescision Bass with round wounds, played through my Traynor Valve 50 watt and a 4X10 cab.
Good luck with your quest.
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