I've got a two-stage "fetzer valve" jfet preamp setup that I like, but I'm sure a simple op-amp stage would work at least as well. Check out this thread, http://www.ssguitar.com/index.php?topic=1426.0 . J M Fahey's suggestion about the "Rod Elliott project 27" sounds interesting.

Maybe you should check out the Nelson Pass's "Zen" amplifier. www.passdiy.com/pdf/zenamp.pdf. You might can bridge a couple of these for 40 watts.

Like Joe, I just recently used an old ATX power supply housing. I have no idea about the UK, but here in the U.S., radioshack sells a cool little aluminum enclosure. I've used them for a Ruby amp, a couple of preamps, and for my "Proto Box" (has a small solderless breadboard inside and various holes drilled for pots/jacks). I'd be willing to bet similar enclosures are available at any electronics supply store. These ones on the maplin site, http://www.maplin.co.uk/Module.aspx?ModuleNo=1728, look similiar, but if you're ordering enclosures, I guess there are some better ones.

QuoteI once saw in another Forum the question about whether amp makers put rat turds into the amps on purpose, being that he always found them Grin

Crate put roach crap in mine.

QuoteMmmmm, maybe you haven't dissected any consumer/computer electronics lately?

Well, honestly, I haven't too recently. However, I have disected quite a few consumer/computer electronics, and I've yet to run into any shielded power cables. I've seen shielding in other stuff, but not power cables.

Maybe for FCC testing, but the real world, it might not help much unless you shield the power cables in the walls of your house.

QuoteIt's good to find all this information. Today I've been reading the paper of Dimitri Danyuk "On triode Emulation", doing some math and trying to get the same graphics shown on the paper. (here is a link to the paper). I don't understand the last part, when Dimitri differentiates the double logarithm if the normaliced transfer function in order to obtain the exponent.

The paper talks about using a resistance on the Source of the FET as a negative feedback in order to change the transfer function from a power 2 to something very similar to a power 1.5 . Basically, he tries to find the Rs that gets closer to that power 1.5 . He finds that the best match is Rs= 0.83*Vp/Idss . Well, I run some plots in matlab and I get that the best match in order to minimize the difference is Rs = 0.64* Vp/Idss as show on this figure: ....

This sounds like the theory behind the Fetzer Valve article on runoffgroove.com. I might play with the Fetzer Valve design using your figures for calculating Rs. BTW, JFETs are more like triodes than Enhancement MOSFET's, but not more triode like than depletion mode MOSFETs, which can be pushed into enhancement mode.

Because your power chain does not end on the cable (although that's all that comes with your amp when you buy it).
Much more important is *WHERE* you plug it.
But don't worry, the solution is easy (if a little expensive):
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=110-439&vReviewShow=1&vReviewRand=2818820
*Please* read the reviews and comment..

:lmao:

Hahahahah. After reading the reviews, I think I need to buy a hundred of those. I think I'm in the wrong business.

I think most expensive power cables are made for the sake of being expensive. There are, however, things to consider when choosing speaker cables, audio cables, etc.

Ok, suppose you had a power cable that had some measurable skin effect for high frequency noise. How much impedance will this create for a short power cable. And, you're talking about a high impedance signal to begin with. Plus, once again, in the power supply, you'll have at least one really large capacitor that will easily shunt this hf interference to ground anyway. So I still do not see how this is relevant to power cords for amplifiers.

Perhaps the skin effect is relevant for engineers working for the power company and anyone working on rf applications. But I really think the skin effect is irrelevant when considering power cables for audio amplifiers.

Your strongest signal on your power cord is, of course the low frequency 60 hz power. Anything in the Mhz or Ghz range is inaudible and will probably not amount to a rats ass. Any high frequency noise on the power cable should be shunted to ground by the filter caps in your power supply. If the caps in a power supply will reduce a 60 hz ripple current to acceptable levels, then signals in the Mhz or Ghz range have no chance. If you have a noisy amplifier, it probably has nothing at all to do with your power cable. If you're picking up radio stations with your amp, then you need some high frequency filtering in your preamp, not a fancy power cable. I would think that heavy gauge wires would be less flexible and more likely to break. The quality of having low impedance at dc and low frequencys while having the impedance increase with frequency is called inductance. It would be much easier to put an inductor in series with your power line than resort to using thick gauge wire.CHeck out http://en.wikipedia.org/wiki/Choke_%28electronics%29. There may be issues other than high frequency interference to consider. If you have a really high power amplifier, you may want to have a power cable rated for the required current. I guess there may be something I'm not considering, and I'm sure anyone with more experience than I will point it out if I am wrong, but I really do not see any need for special power cables.

I wouldn't worry too much about the substitution. Just make sure that the cut off voltage and Idss for the bf256 are about the same as the 2n5486. Keep in mind that even JFET's with the same part number will vary quite a bit. For the Dr. Boogey, get some j201's if you're using a 9v supply voltage. For Q5 (gauss markov schematic) you might use a MPF102. If doing the mensur version which uses a much higher supply voltage, use 2n5457's or something like that. You might use transistor sockets to try different FETs. I wish I did. Also, checkout J M Fahey's post above. He's got a pretty good idea. The measured characteristics of an individual JFET are more important than the part number printed on it.

Get a $50 osciloscope. Check out this post on diystompboxes.com: http://www.diystompboxes.com/wpress/?p=96

Cool amp. I've got an old PSU housing that I've got saved up to use as an amp chassis. Is this another ruby?