Simple, Solid and Loud (First Amp Build)

[PeteTLT]

Hey Forum!

I'm new to the forum but not to electronics (I'd say novice), I've built a guitar and a few pedals, but recently I've run into a snag.

I'm using a Bass Peavey Amp as my secondary in my Wall-O-Sound set up, but two things suck about it, 1: It's not mine and 2: It's not loud enough sometimes. Though the members in my band think I'm nuts, I'm pretty sure its an issue with the amp, every once in a while, it'll crap-out and go quieter. It isn't an issue when I'm practicing but at shows its annoying. The only thing I can do is boost it on the mixer I'm using but that only boosts the signal, and with a noisy signal its hard to find a balance between noise and usable signal.

All I want is something with a volume knob that I can hook up to a 12" 8ohm speaker. It doesn't even have to be that clean if it can get loud. It has to compliment an Orange Rocker 30w Head on a 1X12 cab.

I need a schematic and... hell, well, Idea's! I'm new to the amp end of this.

Please Help!

[polo16mi]

If you have a few more skills that i think (at least you can solder), maybe you can take a look at this

http://www.generalguitargadgets.com/projects/13-amps/58-lm3886-amp

50W on 8 ohm speaker, easy to do, reliable, tested and cheap.

You will need a preamp, but i guess that you can start using some of your pedals as it.

You will need learn to etch a pcb board (not big deal), our friend google sure can bring you a lot of "how to" , and some guys of here can help you to success.

If you can make a pedal, you can do an amp, for sure.

Hope help you.

[PeteTLT]

You will need a preamp, but i guess that you can start using some of your pedals as it.

Preamp? How so? I'm running it through a mixer, and I can already hear it straight through the board's phone's so am I right in that assuming is something already doing the job?

[polo16mi]

Maybe i misunderstand you.

What you want to do?

Connect your peavey to an amp with volume control an 1x12 speaker?

Please, can you describe your setup? I guess bass guitar----peavey---- mixer.....

[PeteTLT]

I'm trying to making amp that I can hook up to a 1X12 cab.

I'm running my guitar into a pedal board which splits my signal into two (well actually four, 3 going to the peavey and 1 into the orange) then into a mixer then out of the mixer (using the left and right as output 1 and 2). My Primary amp is an Orange and my secondary is a Peavey, but the peavey isn't loud enough so i want to build an amp to replace it.

What I was saying before is that I don't understand much about amps and preamps, but I know that when I plug my headphones directly into the mixer and play I can hear the as guitar clearly as I need, does that mean I already have the preamp you speak of?

[Roly]

Yes, your headphone output should have enough level to drive the LM3886 (or just about anything really) crazy.

A couple of points; to get 50-odd watts in an 8 ohm speaker you are going to need a split supply of at least +/-35 volts DC with a current capacity of 2.5 to 3 amps.  The trap to avoid is using filter capacitors that are too small.  You need to find ones that have a ripple current rating higher than the current you will be drawing (or use several smaller that add up to something greater).  You are also going to need a good heatsink for the IC.  Since these can be a bit expensive you might consider recovering one of the larger CPU coolers with fan from a junked computer.

For a one-off you can avoid etching a PCB by simply getting some plain matrix board and hand wiring the components point-to-point (oh the Mojo!  8| ) using the PCB layout as a guide.

You don't mention the model or power of the amp you are currently using.  Does it have an Fx Out or Pre Out socket on the rear?  If so you could use this as your preamp and your new box as "boots".

I'm running my guitar into a pedal board which splits my signal into two (well actually four, 3 going to the peavey and 1 into the orange) then into a mixer then out of the mixer (using the left and right as output 1 and 2). My Primary amp is an Orange and my secondary is a Peavey,

I have to say I'm a bit sus about this arrangement - it has a fair bit of potential to cause you all sorts of problems such as earth loops and anti-phase problems. You certainly need an amp of your own, but your signal routing may also need some attention.

{and isn't it that really cute General Guitar Gadgets laying claim to something right off the IC datasheet, how sweet  <3) }

[J M Fahey]

Well, what GGG actually claims to is to their PCB design (which *is* protected as a "work of art") and probably also the page HTML, which was also written by them.
Does not look like they are claiming the schematic design itself (which anyway never is covered), of course following the original datasheet suggestion.
AT LEAST they do not follow the FET+trimpot horrors craze  :trouble , but their versions of commercial, well designed effects.
And their PCB designs are reasonable.
A site more honest than many.

[polo16mi]

So.... LM3886 GGG  is #1 candidate for our friend?

[PeteTLT]

I have to say I'm a bit sus about this arrangement - it has a fair bit of potential to cause you all sorts of problems such as earth loops and anti-phase problems. You certainly need an amp of your own, but your signal routing may also need some attention.

The ABY at the beginning of my set up is a Radial Twin City with 180˚ polarity switch, which I can use to set the phase right?

The Radial website says:
"To eliminate hum and buzz from ground loops, the Twin-City is equipped with an isolation transformer on output B. This is augmented with a ground lift switch and 180º polarity reverse switch that ensures both amplifiers play in phase while noise is reduced to an absolute minimum even when using older vintage amps that are generally more prone to noise. As a buffer, the Twin-City lowers the impedance and susceptibility to noise, making it the ideal signal driver for large stages when using long cable runs."

Could this help in the issues with earth-loops as well?

Sorry, I'm still a bit new to this so I don't know if I've already been taking steps in that direction so far or not. I've been fighting with this set up for about 5 months now so I've been trying a lot of different set ups and this one seems to work the best so far.

Also, I wouldn't be using my headphone jack, I was just trying to figure out if the fact I could hear myself without an amp through my mix board, in this case with my headphones, does that mean there's a preamp. I did, however, find my answer to that after I asked it... I never even though to google if a mix board could be use as a preamp, which it can. So, it is a preamp... So!!! I'm leave wondering the same as polo16mi:

So.... LM3886 GGG  is #1 candidate for our friend?

IS IT? I really want to start!

And Thanks for the advice!  :tu:

[Roly]

@JM - it's not their copyright but the fact that they want to limit circulation of what is effectively a free ad for one of their products, the PCB.  It just struck me as 20th century thinking.
Why do you put it on the web?
Because I want people to see it so I can sell boards!
Well then why limit circulation?


@PeteTLT - okay, that ABY calms my concerns.

If you have access to an amp that has a Main In or Fx Return you can try driving that with your mix output and I think there is a very good chance you will find it has sufficient level.

The LM3886 with the GGG board looks reasonable, and you also need to start window shopping for your power supply parts, get the physical measurements of the transformer, filter caps, heatsink, and try making some scale drawings of the mechanical layout, and see if you can fit it in to your intended case.  This process can take several loops when you find e.g. your intended transformer won't fit into your intended case and you have to start over with amended ideas.

[J M Fahey]

@ pete tlt: well, by sheer chance you have the *one* pedal specially made to correct phasing problems, cool  :tu:

@ Roly: @JM - it's not their copyright but the fact that they want to limit circulation of what is effectively a free ad for one of their products, the PCB.  It just struck me as 20th century thinking.
Why do you put it on the web?
Because I want people to see it so I can sell boards!
Well then why limit circulation?

I always try to "read between the lines"
Don't think they want to limit diffusion, quite the opposite as you say.
I guess they want to protect (weak protection, as I said) from guys ripping their drawings and posting them elsewhere as "own work" .
This way, GGG allows you to post it , but as a link to their own site, so when you see the image in somebody else's page, anywhere in the World, you already are inside GGG.
Not too strong a shield, but at least they can write to the other guy and complain.
The other guy can't say "oh!! is that so? don't understand how any mention of you disappeared?

By the way, I invite you to like my own Aussie Amps Page on FB, with tons of schematics and pictures I took *personally*
.
.
.
No, just kidding 

[polo16mi]

....My Primary amp is an Orange and my secondary is a Peavey, but the peavey isn't loud enough so i want to build an amp to replace it......

...I wondering what happens if you plug your guitar straight to your peavey, in your gig setup. It is loud enough?

In the other hand, can be more specific about your peavey model, so we can check its manual (if we found it, of course)? or at least if one of ours guys know it, they can help you better.

Now, no clear enough what you need, maybe betters connection setup solve your problem , or as you says, you need more equipment.

I´m not heavy weigth here, but hope help you.

[phatt]

The best I can make out of this;
Although you have (what looks like) a well designed ABY box
You may have introduced earth loops *After* that point in the signal chain. The mixer may have a grounded circuit common and the next thing is the Peavey Bass Amp which will almost certainly have grounded common.

I'm with *Polo's*advice
You need to give This maze of gear some Names and Model labels if you want better help. 8|

If I where you and get the bass amp problem sorted long before you go chasing ground loops as the Amp may not be delivering full power because of faults.
Cheers ,, Phil.

[Roly]

By the way, I invite you to like my own Aussie Amps Page on FB, with tons of schematics and pictures I took *personally*

Somebody beat you to it, published and sold a book that was largely a direct lift of a major section of the site.  A number of people got a lot more bent out of shape about it than I did.  Meh, somebody who copies you is still behind.   

{What's Farcebook?}

the Amp may not be delivering full power because of faults.

My thoughts also.   

[joecool85]

You could always get the excellent ChipAmp.com LM3886 mono kit.  I've used them with great success and the PSU comes with HUGE 10,000uF caps.  It is $50 for the kit with all the parts you need.  Well worth it in my opinion.