The perfect substitutes for the J201 are:
BFW13 and 2n4338
But you have to pay attention to the position of the pins, they are not in the same position as in the J201.
Salu2.

Thanks for your help  :tu:
Bye.
Salu2.

Well, what I really want to do is a power amp stage because i want to use different preamp stages with the same power amp, I will use a switch to change from a preamp to another......and I think that with an chipamp I can have more problems that whit an transistor power amp, but if you think (I see that you are more experienced that me with amp construction, this is my first amp construction, but not my first electronic work, I have done many PCB's without any problems at this time) that with an chipamp I will have no problems with the preamp switching........you are welcome to give me your tips  :tu:
I am looking for a clean sound power amp, I will make the distortion or crunch tone with different preamps has a chipamp a cleaner sound that an discrete power amp?
Salu2.

Well, I will work a few days with this schematic, but if it still doesn't work........¿Anyone has other schematic for a power amp made with transistors? I prefer a transistor power amp and if I can I don't want to use a chip amp, my idea is to make a 5-10W power amp, I don't need too much power to play at home.
Salu2.

Hello I've tried to do this guitar amp: http://www.redcircuits.com/Page52.htm
I've separated the preamp stage from the power amp stage and the problem that I have is that the preamp works correctly without any problem but when I connect de power supply to the power amp stage the fuse (1,6A) blows quickly, I've measured with the Ammeter and it gives me a measure of 6A!!!!! I have to say that the transistors are all in the correct position and with a good heatsink (designed for 20W)........who can be the problem?
Anyone has tried to assemble this amp? I'm start to think that the schematic is not correct......
Salu2.

If you want a really Marshall Amp and if you know how to work with a schematic, in Dreamtone you have all the schematics to make your own JCM800 50Watt Amp (Pre and Power Amp with tubes) I know here in Spain two guys who have made it and it's incredible how it sounds........
Salu2.

I will try it and I will try to put anywhere a Gain Pot too, I think that every chip can work with a Gain Pot, the only one Problem is where to put it, but I'll investigate it.
Salu2.

I have a question about this amp, it's possible to add a volume pot and a gain pot? If it's possible.......where can I put it?
Salu2.

Quote from: joecool85 on November 30, 2006, 03:02:10 PMWho cars if it looks good on a scope, unless it sounds good it doesn't matter.

Yes, that's really what I mean in my last post, but I wasn't sure if this could be bad for the preamp, I know which is the sound who I like and if I can Bias the preamp like my ear likes it for me it's better so as if I do it with the scope. Now that I know that there are no risk to bias the preamp like I want.......my problem is resolved.
Salu2.

Well, in my workplace we have scopemeters and I could probe to bias my preamps with this method, it's a great idea.
There's the option to do it by ear.......finally I think that what we all want is that our preamp sounds good for our own ears and everyone has his own taste, so if it isn't critical to made it by ear I think that's the best method.
Thanks all for your help and your ideas :tu:
Salu2 from Spain.

So the best option is to do the bias "with the ear"? Or it is the easy way option? It's better to measure with the Voltmeter till I have in the Jfet the half of the power supply voltage? I mean if it's better for a long life of the preamp or this is not critical?
Salu2.

Hello, at first place sorry if my english is not good but I hope that anyone can understand me well.......
I have seen many schematics of JFET preamps here in the forum and I am new at building preamps, that's cause I do this question. I don´t know what to do to bias correctly a preamp. Anyone can help me?
Thanks.
Salu2.