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?
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?
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
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
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?
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?
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!!!!
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!!!!
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.
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 said:
take the output of one amp and connect it to the speaker and to the inverting input of the 2nd amp. then connect the output of the second amp to the other side of the speaker. theoretically, there should 4 times the output power of a single chip but for the one i did, it is closer more than twice the power.
i built mine without a PCB because the circuit is so simple. and my transformer is 20-0-20V at 2 amps and its working fine.
Thanks! So what is the VA rating of the transformer for both channels? I opted for a shared power supply, with a single transformer with double secondaries. Any problems with this? I mean, everyone here is suggesting to have 2 psu... but like I said hi-fi quality is not my target...
And to have about 50W per channel, what supply I have to look for? I mean what voltage of the transformer, it's ratings, capacitors...
And to have about 50W per channel, what supply I have to look for? I mean what voltage of the transformer, it's ratings, capacitors...
i'm not sure of the thermal resistance of my heatsinks, i got them in a grab bag...but i think that a CPU heat sink will work fine even without the fan unless it is one of those heatsinks that is only a fan. the fan may cause interference with the signal but i'm not sure.
yes u shoulld isolate the chip electrically from the heatsink since the back side of the chip is connected to the negative supply and the box you are mounting it in is grounded.
yes u shoulld isolate the chip electrically from the heatsink since the back side of the chip is connected to the negative supply and the box you are mounting it in is grounded.
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