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DIY gigging bass amp
DIY gigging bass amp
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Old 21st June 2018, 12:04 PM   #1
deblacksin is offline deblacksin  Israel
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Default DIY gigging bass amp

Hi all! One of my first posts here on the forum, after years of studying so much from threads posted here.

I am a guitarist and i mess with electronics for about 8 years. Mostly i build guitar pedals and tube amps. I want to try building a solid state amp, and thought of building a bass amp for my bassist. I guess a head configurarion with preamp output would be ideal for gigging at places with cabinets/DI.

The preamp will probably be the acoustic 360. But i found out that building an improperly, unprofessional power amp will set thr house on fire and is extremly dangerous, as it messes with Watts 5 to 10 times than a standard guitar tube amp.

Can i just build a preamp and than connect to a power amplifier like this one? 2 Channel 3000 Watts Professional Power Amplifier AMP Stereo GTD-Audio Q3000 700371824723 | eBay Is it an overkill/not compatible? What type of amp should i look for? Can i insert the preamp output to both channels simoltaniusly to achieve a stronger output?
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Old 21st June 2018, 04:53 PM   #2
TBTL is offline TBTL  Germany
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How much would you like to DIY? Assemble an amplifier from modules? If so, I would look at class D amplifiers for weight and cooling reasons. Hypex sells class D amplifier modules and I have heard that some bass player use those. They are a bit pricey, but they are good.

I wouldn't trust a 3000 W (also sold as 2x 150 W) amplifier priced at 109 dollars. Gigging amplifiers must be reliable.
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Old 21st June 2018, 07:49 PM   #3
Enzo is offline Enzo  United States
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Bit ti answer your question, yes, you can build a preamp and connect its output to a commercial power amp.

The 2x150 in the title of that link is a typo, scroll down the page - they intended to write 2x1500 into 2 ohms.

And I have to agree, a $3000 amp for $100 is very suspicious to me.
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Old 22nd June 2018, 08:49 PM   #4
diyMartin is offline diyMartin  Denmark
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This is actually a comment on the last question on inserting the preamp signal in both channels.

First of all though: Bass amps (and speakers for that matter) are absolutely within diy range. I might even say that I have seen more well working diy bass amps/speakers than I've seen sucessful guitars amps/speakers - maybe bass player are more adventurous :-)

Solid state - and indeed class D - amps are well suited for bass (I would hate to try to get my hands on the output transformer capable of 300W at 32 or 41Hz for a valve amp).

But back to my comment: If you send the preamp signal to both channels - BUT IN opposite phase - and if the class D amplifiers are half-bridge (=not brigde tied) then you can get an stronger combined output from the two channels - this technique is called "bridging".

Stop here though: all the real high power (>1000W) class D amps that I've looked at, already are bridged (BTL) internally. In this case sending the preamp signal to both channels will gain you nothing.

I would also question the need for 1500 or 3000W for a bass guitar and the speaker(s) required to survive this would be rather costly (and sound men working the PA system hates when

the bass guitarist is playing louder than the PA :-)

You could - and this is really my idea of the perfect bass guitar system comming through - better use the two channels with an active cross-over and then use one channel to drive a larger speaker (15-18") and the other a smaller 6-8" for mid/treble. This has benefits in improved radiation pattern (making the sound less dependend on the angle you listen to the bass).

Last edited by diyMartin; 22nd June 2018 at 08:52 PM.
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Old 22nd June 2018, 09:19 PM   #5
deblacksin is offline deblacksin  Israel
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would building a preamp box only, and connect this one to existing PI systems would produce the same result? how much the power amp affects the sound, if any?

I build mostly dual 6v6 guitar amps, which are about 18W-20W and they are enough for rehearsal or a gig when the volume is below 9 o'clock..
so to begin with, how powerful should a bass amp be to compare live drums in relatively small and closed places? I know watts don't really translate to dB, but an estimate?

about "how much to DIY", I would of course prefer to build a complete scratch amp. but I got a bit frightened of the many posts saying bass power amps are extremely dangerous, and have to be professionaly designed. If it was a tube amp I'd feel much more comfortable, but I have no real experience with solid state power amps hehe.

and thanks for the approval of the "build a preamp and send its output to a commercial amp input".
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Old 24th June 2018, 01:54 AM   #6
PRR is offline PRR  United States
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Originally Posted by deblacksin View Post
....Can i just build a preamp and than connect to a power amplifier like this one?...
All the classic Grateful Dead "instrument amps" were preamps feeding big Crown or Mac bare power amps. The amp you link is a no-name equivalent of those boxes. It is NOT "3000 Watts", but it seems to be an almost-honest 2*200 Watts in 8 Ohms and some more in 4 Ohms (though it will strain more). Yes, Y-cables can feed several such amps (each with their own loudspeaker); the Dead had like 89 amplifiers on "just" six channels/preamps.

Last edited by PRR; 24th June 2018 at 01:57 AM.
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Old 24th June 2018, 04:19 AM   #7
leadbelly is online now leadbelly  Canada
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As has been said, you can of course use a commercial power amp. In fact, many professional bassists have rigs that look more like a PA rig than a guitar rig.

I just wanted to touch on your comments that a bass power amp is dangerous and is to be avoided. I think that is perhaps going too far. It's true that a bass amp should be designed for hard use, with output devices biased conservatively and generous heatsinking, but if that's what you really want we could help with that.
I'm trying to date a sexy philosopher but she doesn't even know if I exist.
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Old 24th June 2018, 05:35 AM   #8
freddi is offline freddi  United States
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DIY gigging bass amp
about 40 years ago, I plugged a bass into a friend's parametric EQ - that allowed some interesting timbre variation vs simple bass/treble type tone control - it would be nice to have a high input impedance on the parmetric/preamp as to not bog down an un-buffered passive pickups with lots of turns.

These days, there are a lot of class D mono modules available which would make the exercise a lot easier than starting from nearly "scratch" - you would have to ask around as to what's cost effective and reliable over long term

(I do like big old tube amps like Traynor YBA3)
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