Well...here I go...lol

so, i decided rather then try to make the worlds best mixer for a first project, lmao...that i would look fro something "reasonable" and a little bit "modular".

"Reasonable" means no 120 dollar impedance matching trannys on every channel input, no obscure and hard to scrounge parts, solid state, "old school" readily had, easy on the wallet componentry. Ya know, something "M. Forest Mims" would have used for an "intermediate mixer project" if he wrote a book on such. (but no 741's and 386's...lmao...he loves those things...lmao).

"reasonable", also means i flipepd a coin and picked out a "net project active mixer" that seemed like it wasn't TOO basic and un-useable to a hobbyist, but yah, i know it will likely make you real mixing professionals PUKE if you injected a signal thru it and measured the outpout, lmao.

"modular", meaning i narrowed it down to a couple that all said "can add as many channels as you like, just about" LMAO...thats for me, hee hee. If I'm gonna polish a turd, i want it to be a BIG turd when i am done polising it, lmao. (when i fail, i like to fail big...lol)

just to impress you guys that I'm not the WORST newb that ever rolled in here, I did the obligatory search for "which resistors are best", so i wouldnt have to sound like an idiot, and now i see i should use metal film. I had suspected as much, but...my "burgular amarms" circuits years ago didnt know the diff, lmao.

did the same thing for which caps are best, and it seems i can use any onesi darn well please and SOMEone will come to my defense for it, lmao. Question: "what are 'Oragne Drops' ??? are these those round flattened circular disk-y thiings, that resemble an aspirin painted with gloss paint??? you know, super 70's caps??

I chose this project:

http://www.redcircuits.com//Page53.htm#Input

OK...so here comes my newbie questions you just KNEW were coming, lmao.

I can convert nano to pica and all that, that aint my question...I'm naturally making the prototyoe of my first Input amplifier module. If you would look at the parts list...I would bring your attention to:

R6 4K7 1/4w RESISTOR
R8,R13 220R 1/4w RESISTOR
R11 560R 1/4w RESISTOR
C3,C4,C5 2u2 63v ELECTROLYTIC CAP
C7 4u7 83v ELECTROLYTIC CAP

now...4K, I understand fine... 4.7K, fine

BUT... 4K7 ??? is that 4.7K=4700?? or, 47K ??? I dont recall this format. It SEEMS like hes using the "k" like a decimal point, though i cant figure out why?? (probably a newb question, and I'm gonna hear it, but...)

I assume 220R is 220 Ohm, adn 560R is 560 Ohm (I hope...corect me otherwise...I assume he doesnt have a "Omega" key on his keyboard...me neigher, lmao.)

now...I use "u" for micro...
is 2u2 2.2uf ?? or 22uf?? I'm not used to this format, dang it...

4u7, = 47uf, or 4.7uf, or what???

is this some great britian or europeannotation i never saw in forest mims books?? LMAO It doesnt seem to be a typo, he keeps doing it.

If someone could clear this up, I would be "off and running", as this project does not seem to require any "tuning" procedures out the ying yang, you know, i hate the 12 dollar projects that are kinda cool, but you just need 12 grand of specialized test equipment to build it, lmao. This one, i chose 'cos it seems very straightforward.

I guess i use the best metal resistors i can find, and decent caps too.

the matched npn-pnp pair, tied at the base, and the smooth matched emitt/collect/collect/emitt flow like that, this general configuration reminds me of a class-whatever RF linear amp i remember lookingat back in the day, just here its working at AF instead.

Question: if i try to get decent caps and resistors and components, and watch the leads dont get long, and stuff, can i expect anything at all out of this thing?I was thinking hat even when i am done with the prototype of just this section, i could test it with a microphone to get it up to level to feed my sound card, right, so i can test record in CEP?

Rather than fiddle and fart around with point to point and numerous small leads, or whatnot, I downloaded a free program Express PCB/Expres SCHematic. I re-made the diagrams in the schematic editor, way cool, and i am now half way thru a two layer PCB, lmao. well 2/3rds actually.

Question: do i HAVE to send the pcb output to the company to let them proto my boards, or can i somehow hijack the output and etch my own boards with the solder traces? I turned off the "other layers" and was rewarded with just the copper traces...can i take the graphics output into paint program and "paint-fill" the trace colors and backbround color correctly to DO somethiing for my own etch with this??? If i CAN, I'm gonna make all KINDS a stuff, lmao. Whee! (I'm kinda like a kid in a candy store having free PCB cad software right now, please excuse me, lmao)

yah...basically, whats that funny notation for pasive component values, and can my software me used for my own etching somehow...and if you get a moment, lay the sad truth onb me about how bad this thing will sound, best possible outcome, when i am done...

I assumed it would go better using dual traced etch boards, so theres no leads, and i am getting fairly "dense", "even" packing of the components. If anyone wants the board layer file when i am done, i'll let you know when i am done proofing it.

[quote author="sedstar"]
BUT... 4K7 ??? is that 4.7K=4700?? or, 47K ??? I dont recall this format. It SEEMS like hes using the "k" like a decimal point, though i cant figure out why?? (probably a newb question, and I'm gonna hear it, but...)

I assume 220R is 220 Ohm, adn 560R is 560 Ohm (I hope...corect me otherwise...I assume he doesnt have a "Omega" key on his keyboard...me neigher, lmao.)

now...I use "u" for micro...
is 2u2 2.2uf ?? or 22uf?? I'm not used to this format, dang it...

4u7, = 47uf, or 4.7uf, or what???[/quote]

4k7 = 4.7k
220R = 220 Ohm
2u2 = 2.2uf

It looks like it will pass sound... for something that definitely passes good sound for a cheap price do a search for the Green Pre!

Justin.

> I chose this project:

Interesting.

When I glanced at the input stage, I said "What the...??????" Then I skimmed the general concept. As a 9V battery power mixer, it makes sense.

That input stage has several subtle points. But it is NOT balanced input. Long mike wires in hostile environments will buzz. True, I worked a LOT of unbalanced in genial rooms with happiness. But a specific modern got-cha is that there may be no simple universal way to connect this to Phantom-power mikes (without the dreaded transformer).

And with wall-power and modern low-price chips, you could get about the same performance with many less parts. NE5532 would give two channels with the same noise and THD without the transistors and all those biasing parts. Heck, a NE5532 could give one stink-free balanced input for about two bucks.

If you are making music, it will be thrilling on well-used $2 preamps. If you ain't making music, $2,000 preamps will only excite the 0.1% of the world who get excited about $2,000 preamps.

It is an excellent article in that it shows a complete workable mixer, but I'm not sure this is the thing for a modern home studio.

Best cap? Best resistor? Ya know, many people can't tell. There is no certain damnation in using 0.25W carbon-film everywhere. Everything you've listened to and everything you record goes through dozens of electrolytics between studio and home hi-fi (let's not even think about MP3).

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Collecting unrelated thoughts under a meaningless Subject may scatter the discussion.
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> hes using the "k" like a decimal point, though i cant figure out why??

Write "4.7K" on a blueprint. Make a copy. Copy the copy. Copy that. Now you have "47K". Small dots do NOT copy well, and quickly vanish. (Also old guys like me have dim eyes.....)

Someone invented this whacked idea of putting the unit-letter where the teeny dot goes. Although (like Hz and pFd) this was invented after I learned to read schematics, I do approve of it, and even do it sometimes.

this is the input amp as per the project...

http://24.3.232.229/SEDstar/Electronics/InputAmp.gif

this is the PCB trace I made. Rough draft, but, i dont think i missed any connections or components...

http://24.3.232.229/SEDstar/Electronics/InputAmpSection.jpg

once you hit my PCB up off the server, its a little undersized at first...if you hover the mouse over the lower rite corner, you can full-size it.

if i can make a tiny 9v powered mixer that works fair to middling, if might serve some useful purpose here and there. WHen over at the guitarists house, i can run a line thru it then on to the laptop to record in MultiTrack software. If someone wanted to sing "on a short cord", lmao, or play a electronic keyboard, i could nudge them in. I hear you,the DESING aint there, but what it lacks in quietude, it might make up for with a small footprint and battery power. At least a 9v wont introduce much noise (i dont think...lol)

If i get all three working, i might be able to "bum the circuit" for size and mountlocation to get really small channel strips. If it aint gonna be a world class audio thing anyway, i got to thinking about smaller components, hee hee. this thing would get tiny QUICK with a few SMT's and inoine SIP with small lead spacing.

Now, at that point, I certainly wish i COULD re-design parts of it, as you suggested the balanced approach on the cheap. The improvement, along with reduced footprint, might make it more handy.

the main thing though, is to get myself designing PCB's from schematics and building some stuff. I've seen some scematics fro soe cheap guitar amps, and i think a full channel strip might feed the input of one.

I can follow the circuits around in a basic fashion, picking out some stuff, yet i lack the ability to GROK and re-design. I'd like to add a few more eq knobs to spread out the bands more. I understand basic feedback loops, but dont have enough practical curcuit knowhow to tweak. I can vaguely recall a certain class of RF linear and arrangement that allowed the noise to "buck it self out", but implementing it off the cuff? not yet. I understand some shunts and chokes and filters in and of themselves, but only in a textbook "101" way.

I dunno...made small enough, a drummer might get use out of all those channels and tiny footprint and 9v power, at least live, to make his OWN feed to send to the main board. Drummers with big kits and lots of mics tend to "hog up" whole sections of mixers quick, and they already have enough gear to lug around.

but...as long as i make somethign that actually works for now, I'm ecstatic...if i can actually make it moderately useful, so much the better.

Thanks for the input, guy.

PS - thanks for clearing up the "decimal point madness" for me, too...i was really sweating that, lmao...stuff like that bugs me, hee hee.

2-layer PCB's have the thru-holes plated to get the signal from one layer to the other. You might just make the board single layer and use some jumpers to "jump" over where you need to.