Gainclone for guitar

[Giaime]

Hello there! I'm an electric guitarist and I make up my mind to build myself a stereo Gainclone to power up a 4x12 cabinet, with the signal from my preamp. I'm not experienced in gaincloning, but I saw that with these power opamp you can get to 50W for channel, with minimal components. Would you more experienced suggest me what to look for? Keeping in mind that...

1) I don't need ultra hi-fi quality, it's for guitar, I just want it reliable.
2) 50W per channel or near, with the possibility to drive both 4ohm and 8ohm. This is important, because I haven't bought the cab, usually they're 4ohm for each channel, but I can change my mind and buy a 2x12 that has 8ohm per channel.
3) So I thought about the LM3886, but here in Italy I couldn't find them. Can someone suggest me a similar TDA sort of thing, because I can find them easier?
4) Can I use CPU ventilated heatsinks for the chips? I don't care for a few fan noise, because it's meant to be used on stage.
5) Since I don't need super hi-fi quality, what is the minimum rating for the transformer that I can use? I've thought to spend few money without a dual power supply....

Can someone help me?

[Giaime]

Bump.

I've seen that recently many guys are in the process of building a chip instrument amplifier. Maybe shall we create a permanent discussion?

[hitsware]

http://www.st.com/stonline/products/selector/203.htm

>because I can find them easier

[Giaime]

Thanks for the link! I think that the TDA2052 would do the trick, but the RMS power is a bit too low...

Suggestions are welcome!

[Nasse]

Well all I can tell I plugged my small modelling effects gadget to my lm3886 amp and it sounded very good

Maybe these chips are so clean, it is just better to leave the distortion stuff to be done in the preamp

I´m sure you can find 3886 in Italy, or buy it from some mail order component shop

www.generalguitargadgets.com

There is nice looking pcb pattern and power amp schem for 3886, I don´t have tested it but anyway.

Another edit: TDA7294 is about similar power specs as 3886

[Giaime]

Yeah I will plug my PodXT in to it. I just need a clean power amp.

The pcb on that site seems good, I would use two of them.
But what circuit should I use for that 18v bipolar supply? Transformer ratings, ecc...

And the heatsinks?

Someone knows of some distributor in Italy where I can find the lm3886?

[jsteigs]

i just finished a bridged lm3875 for my guitar. so, its 100W, single channel and beautiful sounding...i still have to make the preamp though. but why do you need stereo for guitar? all guitar amps and cabs are mono. also, a 4x12 cab is a bit of an overkill for a 50W chip amp.

[Giaime]

Thanks jsteigs! Post schematics! This forum is all about them....

a) I need stereo 'cause my preamp is stereo. If I would like mono I would keep my cold-souning Fender.
b) why a 4x12 is overkill for 50W? For example the Marshall 4x12 is a cab with 25W Celestions, so each channel is 50W maximum. I've seen 18W tube heads moving the air of 2 4x12 cabs...

Post Schematics!!!!

[jsteigs]

i just used the schematic from decibel dungeon, built it twice (each one about 50W), and put it in a bridge configuration resulting in an amp about 100W.

http://www.decdun.fsnet.co.uk/gainclone.html

what you could do instead of bridging then together is to have one amp powering one channel and another amp powering the other channel since you want stereo.

i agree that fenders dont give a very nice sound...i prefer marshall

usually you see 100W tube amps powering the 4x12 cabs and tube amps are generally louder per watt than chip amps. but u could still power a 4x12 with smaller amps.

[Giaime]

Thanks! I would build the 2X50W, but for personal knowledge, how do you bridge them? I'm not an expert...

I would try the generalguitargadgets PCB, but someone can suggest me a good power supply? And what about transformer ratings, ecc...?