The questions about Hi-fi audio for home use.

[Haze13]

Just fineshed reading a topic about JC-2... Looks good!

[twest820]

Originally Posted by Haze13

Just need to know how to do it

Just do a web search on tube emulation circuits---you'll find lots as well as output trafo emulation and other things; some discussion here in DIYA, rather more in guitar forums. The Fetzer Valve has a fairly nice write up that works as a simple intro for SET emulation---FETs behave like push/pull triodes or pentodes by more or less by default so I tend to see power stage emulation as being more about output trafo emulation. In hi-fi most output trafo behavior that's exploited for guitars is generally undesirable (hence preferences tend to run to output iron that would consume your entire budget), though reducing the amp's control over the drivers by padding its output resistance or limiting feedback seems to be subjectively beneficial for some listeners and speakers as it can mitigate cone breakup artifacts.

There's also an section in the introduction and a chapter on tube emulation in Teemu Kyattala's book (though be cautious of some of Teemu's assertions---for example, he and Rod Elliott make contradictory assertions about Siziklai stability). And if you have access to both hollow and solid state guitar amps try working through the various combinations like hollow state preamp + solid state power and solid state preamp + hollow state power to get a sense of the tradeoffs.

[Haze13]

For cleans there are some good SS guitar amps, but for dirty sound - it's always the tubes...

I always forget that in Hi-Fi stere there is 2 monoblocks! Aleph 3 looks so wonderful, but when I was doing math to know how mutch it will cost, I forgot about it.

Don't think that for home use I need more then 20 watts in 8 ohms, right?

I heard that some say that music style is important too when choosing an amp... I love heavy music... Some times Blues and Classical, but heavy metal is my favorite style.

[Ian Finch]

Better get some heavy speakers and a heavy (as in > 20watt) amplifier, then. If you want to hear bass at good SPL, you need more like 100 watts, even with moderately efficient speakers (>89 dB/watt @1 meter).

20watts is fine for just listening to music but if you want to experience even a little of the live performance levels, you need heavy power.

[twest820]

Originally Posted by Haze13

For cleans there are some good SS guitar amps, but for dirty sound - it's always the tubes...

That's a matter of personal preference for one's distorted guitar tone; you'll find plenty of people (present company included) who prefer solid dirt (and, more often than not, metal dirt is solid rather than hollow). The purpose of a hi-fi amp, however, is to play back recorded material with minimal distortion. Exactly what constitutes minimal is also a matter of personal preference but one's typically looking at THD comfortably under 1%, often an order of magnitude cleaner than the a typical clean guitar channel and quite a ways from the 30-70+% THD of a dirt channel. So one generally ends up at some pains to make the tubes, well, not so tubey. That's kind of an interesting exercise and it tends to generate interesting uses of silicon in regulation and tube stage buffering. But it's usually simpler, easier, faster, and cheaper to accomplish the same thing in solid state.

Originally Posted by Haze13

Don't think that for home use I need more then 20 watts in 8 ohms, right?

Refer to this thread.

[Haze13]

More power it's an expensive thing... For example I can use one aluminum enclosure for 20 watt stereo amp (20 watt per channel). 30 watts Class A operation it's two saparate monoblocks with it's own power supply for each channel (like Aleph 3). 110$ for one transformer, 90 for enlcosure...
just two monoblocks are going to cost me like 600-800$. After an 1k$ tube guitar project + 600$ for a cabinet, this stereo amp will be a like a punch for my wallet.
Now I use Logitech LS21 (4 watt 4ohm subwoofer, 2x1.5 watt 4ohm) and it's loud enough for me. If I can get a little bit more power, with bigger speakers and better quiality of the sound - I'll be more than happy. (and my neighbours). Like with the studio monitors, 5" monitors for close range, and 8" for people who seats like 4-5 meters from the speakers (8" speaker have more power than 5" of cource). There is of course more to it, but that's a "short" story.

[techbiker]

Go pro then. You can purchase a very cost effective crown, peavey amp with 400 watts. Then build a lower wattage one as well.

[indianajo]

I'm using surplus variable frequency motor drives for heat sinks. Chock full of useless blown up SCR blocks, but great fans and current sensor transformers, too. Surely there is a surplus market in RU. Or a factory mechanic in a food plant who would check the dumpster for a beer or two.

[CBS240]

I cannot see why anyone would want a power amp for home Hi-Fi audio purposes that has any kind of coloration. If coloration is to be part of the audio program it should come from the recording. Guitar amps are part of the instrument and thus it is desired to have certain coloration as to be determained by the musician and record mastering. An amplifier for home stereo use should output a signal that is exactly like the input, only larger and with lower impedance to drive a speaker. Perfection is imposible but you can get really close and that should be the goal. So amplifier circuits that add harmonics, be it even harmonics as is typical of triode transfer and tube emulation circuits, are undesirable for reproduction of recorded material. This is my opinion and thus I investigate different types of linearization techniques so as the non-perfect transfer of the amplifying components do not become a product of the output signal. It is possible to build such amplifiers from both solid state and hollow state but it us usually more than just a few amplifying components, rather it is many that work together to achieve the goal of linearity. There is more than one type of distortion and they taint the output in different ways. The circuit must be designed to minimize all types of distortion or the amp will have some measure of specific coloration.

[Ian Finch]

Talking of high power amps that are now redundant and cheap in the US is fine but by the time you ship those monsters to Russia, for example, the sums don't look so good. You could build several medium power amps for that cost.

Apart from the transformer, the build cost for a 100W, or rather 80W amp, is little different. The schematic may even be identical so think about the sums there, unless you are talking about a chip-amp like LM1875 which can indeed be very cheap. If you are determined that 20W is sufficient for all music you like to play then consider these chip amps - they will build up to something far better sounding and simpler than most discrete DIY amplifiers. Otherwise, there are larger ones like LM3886, just as good and cheap.