Hey, I love transistor circuits!  Let's see those schematics!  And welcome to the board!

Wow, I seem like a dork using all those exclamaition marks eh?

Right.  I'm assuming what teamuk was saying is that if you put too much amplification (gain) in one section (poweramp or preamp), it tends to lead to noise and distortion.  But I could be wrong.

Its ok, its great to ask questions like that!

If we increase the gain of the poweramp, we won't need as much gain in the preamp section.  If we can increase the gain enough on the poweramp, we may even be able to get by using something like an LPB1 booster for a preamp.

It's cool RDV, I just remembered you had mentioned building one.  Good idea socketing R3.  I think if I decide to mod mine at all I will socket that as well so I can play with it easier.

Alright, I've been talking to brian, and stock out of the box the lm3886 kit he has is at roughly 33 for gain.  We could easily raise it to 48 by replacing R3 (680 ohm) with a 470 ohm resistor.  He also said it should have no problem with even higher gain and that the only big problem people had was too low of gain (below 10).

Gain = 1+ Rf/R3

Stock Rf is 22.1k and R3 680 ohm

**edit**
I'd like to see someone try it out.  I can eventually, but it will probably be a while before I get a chance to as I've been pretty busy.  RDV, weren't you building a test bed for stuff like this?

Looks like earlier when I had posted stuff saying about 60v for input on the lm3886, I was right, but not for the way the chipamp is setup.  We only need 1vRMS if I'm correct.

Yes, please share.

In talking to brian, we might be able to just increase the gain on the chipamp circuit, then we'd just need a 1:1 buffer/EQ setup in front of it!

Chipamps are designed so that they don't need a preamp, however, that is for when you are running a lineout from a computer, CD player etc.  This means that you need to get guitar signal up to that strength by way of a preamp.

So, here is what we need in a preamp:

- Gets us up to linelevel
- basic EQ (probably 3 band)
- protection, ex-someone pluging in AC power to the input
- input buffer of around 1m

This was for getting them printed from a company.  If someone on here can make them, thats way better.  I for one, don't make my own PCBs.  But yeah, that was basically the $100.

Exactly.  And what the group buy has to do with it is, if we can get 10 people to GB the lm3886 kit from brian for $50 shipped, then he will do the PCB design off the schematic we create, and we won't have to eat any of the prototyping costs, but we will have to still buy the PCBs.  This isn't necessarily how we have to do it.  We could do this all on our own.  However, if we design the PCB, then print 5 as prototypes, thats $100.  Until you get past 50 or so boards it doesn't get cheap.  And you don't want to print 50 boards and find out they have something wrong with them.

The group buy was for a mono lm3886 kit, this includes one amp PCB and components, along with one power board PCB and components for $50 shipped.

http://www.ssguitar.com/index.php?topic=32

Naw, I think I am going to find a gutted cab on eBay and use that.  I'm no carpenter either lol.  I've made solid sub boxes for my car, no leaks or anything, but those are made out of advantec and don't need to be pretty since they are covered in carpet.

I'm thinking about doing a lm1875 combo with 2x8.

Is that what you needed that lm3886 PCB for?

Good idea to make a test bed btw.