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DIY amp directions

Started by Lauren, August 25, 2014, 07:10:38 PM

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galaxiex

Quote from: Lauren on September 22, 2014, 07:42:38 PM
I am!  Sorry I've been MIA.  Life got busy suddenly with a sudden burst of motivation to do some work on our house.  :)  Would love to have this completed by Oct. 14 (anniversary), so I'll be working on this again soon! Have you started soldering?

ummm, no.... I've been busy too, working on some other stuff.

Congrats on your anniversary!  :)
If it ain't broke I'll fix it until it is.

Roly

Oh good, glad you're still with us, I was beginning to worry.

Lovely Spring day here today.  Mowed lawn.  Gave the truck a wash - once ever five years without fail whether it needs it or not.  Down to Melbourne later to hand-hold SWMBO while she has a minor op.

Went past the local parts supplier last week and grabbed a couple of LM386's ... er ... (just in case?)  I mean, I need yet another guitar amp like I need a hole in the head, but all the bits have strangely gathered on the bench awaiting my return, so I guess I may as well join in the fun, eh?
If you say theory and practice don't agree you haven't applied enough theory.

Lauren

OK.  So, I placed all of my components into the CORRECT side of the circuit board  :loco and would like you to look it over to make sure C2 and C5 are in the right places.  I am still missing Q1 and C3, but I did get the pot I ordered in the mail. (That sounds wrong.  LOL).  If it's all in the right places, do I have to test something to make sure they work, or do I have to wait until I get the missing components?  I bought a multimeter and wire strippers, but I am waiting for galaxiex to post pics of the next steps so I know what to do with the wires.   ;)

Seriously, those pictures are SO helpful.   <3)  What I started to do to create a system that really works for me (and I think will help in the future) is to record things in a notebook with the "coordinates" of where things go.  So, for example, "C1: 6B-6D" will help me put things together again without looking at pictures.

Hope I'm on the right track!  I will mark the spaces like galaxiex did once I get the stamp of approval that it's all in the right place.  Thanks!!

Lauren

Sorry it's a little dark...I can't find my camera and have to use my iPhone. :/

Roly

{Still off base, truck conked outside my sons place  :'( (thankfully - he's a mechanic).  Treated to the sight of SWMBO with a micro TV camera up her nose, almost took a pic, and we didn't get live action vids  8| , prognosis good.  Mad Spring rains so I'm better off the roads anyway.}


Looking good.  With your big caps we try to place them so the leads are formed in a small bend then straight down to the hole so they are firmly held.

The main supply by-pass cap, C2 100uF, has to connect across the two long supply rails that run across the board.  Horizontally it doesn't matter exactly which holes the leads go through, only that the + and - lead go through the correct rows to connect to their respective rails.

The same is true for the output caps C5, get it to lay down nicely, its +ve end is fairly fixed but the other end can go to the nearest copper doublet.

How to form component leads (formal, reality often ain't so neat)



{If you want to dig into electronics, NEETS US Navy Electricity and Electronics Training Series, is the on-line go to.}


Quote from: LaurenI did get the pot I ordered in the mail. (That sounds wrong.  LOL).

I thought it was legal over there now.   :lmao:

No, you can't do any live testing until all the components are in place and connected.  Before that you have your final build cold checking to do, starting at some known point, input, IC pin, etc, then tracing where its connections actually go - everywhere they should, and nowhere they shouldn't.  I've certainly picked up my own bloopers, like mis-counting pins on a big IC, at this checking stage.

Then we do the "smoke test".

{camera tip; film or digital, pour in the (diffuse) light  :dbtu: }
If you say theory and practice don't agree you haven't applied enough theory.

Lauren

Can someone tell me if the second item in this pic is one of my missing components?  Thanks!

Lauren

At some point, I would love to understand how you decide what goes where on the board and why.  Just throwing that out there because it's on my mind...right now, my brain is too full with trying to figure out how to build this without trying to understand the whys of it, too.  But it's something I wonder as I stare at the schematics.  :) 

Roly: Is it possible to do a schematic of the underside of the board, or is that a silly request? Galaxiex:  When you take your pics, can you take one of the underside?  I don't know why, but I feel it might help me.   :)

galaxiex

#97
Quote from: Lauren on September 29, 2014, 06:01:11 PM
Can someone tell me if the second item in this pic is one of my missing components?  Thanks!

If you mean the NTE 489 JFET P-channel... then no. You want an N-channel JFET

The 3rd item is what you want, The NTE 457 JFET-N-CH.

:) Please try to refer to electronics parts by their numbers.  :)

With electronics there are soooo many different parts that are all very similar in appearance yet for all that they look the same... many/most will NOT interchange.

Sure I can take a pic of the underside/copper side of the board.
Won't be until tomorrow night tho...
If it ain't broke I'll fix it until it is.

Roly

Quote from: LaurenCan someone tell me if the second item in this pic is one of my missing components?  Thanks!

Your FET is in a little D-shaped cylinder of hard plastic with three wires coming out the end (bottom).
{ps well caught  galaxiex, missed that.  P-Channel or N-Channel?  Yes mam, we got both kinds of music, Country and Western.  Positive channel and negative channel FETs are mirror-images of each other polarity-wise, and, unlike C&W, are not interchangeable.}

Caution: catalogues normally only photograph one of each "kind", so in some cases the actual device may be (somewhat) different, so consider pix as "looks like (sortamaybe)".


Quote from: LaurenI would love to understand how you decide what goes where on the board and why.

"Sketching is essential to creativity" - The Universal Traveler

You plonk down a large rectangle in the middle of the paper and call it the IC.  It's the key component, has more connections, and requires the power supply.

So you sketch in a conceptual power supply, and here reality starts to intrude.  You happen to have a PCB that already has a pair of rails intended to distribute power to a row of IC's.  Why re-invent the wheel and just go with the flow?  Well yeah.  So you shift the IC to the middle of the now defined target PCB (galaxiex) or you consider that but decide to lob it on one side so it's (hopefully) simpler to follow/build (Roly).

I've got copperless matrix, one-pad-per-hole dab board, "Vero" stripboard, and some more committed PCBs like yours with DIP IC's more in mind, but the board you bought condensed the PCB part to a given constraint, it's what I now had to work around, not my first choice but at least now very well defined.

What you have to hand in your junkbox/supplies store strongly influences what you do, which way you go, both at home and in industry.

When you turn on your iron the whole world awaits, and you have to start making choices about which bit you will explore, and there is too much flamin' choice.  There are just so many different ways you can get results, with so many different components, controls, and dress hardware such as knobs, switches, and sockets.


So now you have selected your IC and PCB, placed the IC in the middle of the PCB, now you work around its pins joining up the dots, a resistor here to go there, a capacitors there to go over there ... no that won't work, she's got axial, not radial ... um {sucks end of mouse - not as satisfying as Ye Olde Pencil.}

And so start the recursive loops of design, or circuit layout in this case.

It's a bit like a SuDuKu or crossword; you try stuff until you hit a constraint, such as the edge of the board, and either some detail has to change or the whole lot has to be moved over a bit, back off and take a different run at it.  The capacitors they sent are the right value but much bigger than I had allowed for, so I'm going to have to shuffle some components over to make room for them.

It would be interesting to have a time lapse of me doing that layout to see how parts moved around before coming to rest.

With all stages of design there is a lot of looping back and reworking previous work due to striking some constraint ranging from "you can't get those any more" to "it won't fit".  It's kinda three steps forward and one sideways.  And occasionally you land on a snake and return all the way to Go.  {"Okay, now that you have spent $100,000 and three months proving you can't put wine in plastic bags like that, would you like to reconsider my idea?"}


This leads indirectly to "you can start building before you have all the parts, but you can't start testing until all the parts are in place".   {and I'm reminded of $100k of trout farm controllers that sat in the corner for months waiting for a few long promised digital panel meters (that never came)}.


Quote from: LaurenIs it possible to do a schematic of the underside of the board, or is that a silly request?

Yes.  No.

If you don't have any sort of graphics package may I warmly suggest (freeware) Irfanview?

Pull up the layout, flip L-R, save as layout reversed. (attach)

This is called the "copper side" view and is actually the industry standard view of a PCB, not X-ray from the component side as these DIYLayout Creator pictorial renders are.

The professional and the amateur literally view the PCB from opposite sides.


Historical
PCB are made in graphics layers called "artworks", copper side, component side copper (for double-sided boards), component side printed "component overlay", drilling map, and more depending on complexity.

Traditionally this was done on large sheets of inch-by-tenth graph paper twice actual size in black, blue and red pencil.  At this phase, layout by seat of the pants, there was an awful lot of erasing and re-working.

Next a transparent sheet was taped over the layout and the black and blue used to guide the placement of self-stick symbols and crepe tapes for tracks.  Then the red side.  The the overlay.  and finally off to photography to be reduced and made a solid negative.

This is then photo-impressed on photo-sensitised plain copper laminate PCB, etched with hot ferric-chloride, washed, drilled, cropped, and bingo, I find where I have made mistakes.  Again.  So at least part of the whole cycle repeats until it works or I get fired.

Today we got 'puters.  (and boy did I dream of them back in those days)

DIY Layout Creator is specifically for small projects on stripboard (but adaptable, as in your case).  And free.


"Why is that component connected there?"  is a different question, but this little IC makes a good platform for some basic concepts, however it does mean we have to have a look inside at the internal circuit to understand the role of the external components in its operation.


If you say theory and practice don't agree you haven't applied enough theory.

Lauren

I just got majorly confused...please clarify.  I bought the .047uF Caps.  They look like the ones galaxiex used in his build (2 caps with large green tops).  I also bought another package of 0.047uF caps that look completely different.  They are much smaller and have an orange top.   The only difference is one is Polyester-Film and the other is Ceramic-Disc.  According to the specs, either type is fine.  Are these both the same? They look so different.

I still am having trouble getting my hands on the transistor I need and I keep buying the wrong cap...I *think* I am missing the .1uF cap at this point.  I will try to exchange what I bought tomorrow.  I am also confused that the plans list all of the components, but say nothing about a speaker.  What kind of speaker am I looking for? How big/powerful, and will it have some kind of hookup ports attached to it?

Thanks!
Thanks!

joecool85

If they are both .047uf, they are the same (for this project anyway). For certain things you might need a specific type of capacitor along with its proper value.

Speaker wise I would get the largest guitar speaker that will fit the enclosure you are using. Figure out the size and we'll give you tips from there.
Life is what you make it.
Still rockin' the Dean Markley K-20X
thatraymond.com

Roly

Quote from: Laurenone is Polyester-Film and the other is Ceramic-Disc.

A capacitor consists of two conducting plates or electrodes separated by a thin insulating material generically known as a "dielectric".  These caps have the same capacitance value and are generally interchangeable, but they are made with different dielectrics and so have some different properties.

For our situation the poly's would be the slightly better choice, as they are somewhat better in audio circuits (the ceramics can be slightly microphonic), however you could use either and not notice any difference in the sound.  Ceramics tend to be a bit cheaper and poly's tend to be a bit better quality.

Quote from: LaurenI still am having trouble getting my hands on the transistor

You are just going to have to go mail order.  I hear some of the suppliers over there are very quick, the ones here are.

But if you are going back to your local hokum RS anyway then try tackling the problem from a different angle - what small signal n-channel J-FET('s) do they stock?  Write down the part number(s) (e.g. "2Nnnnn", "Jnnn", "MPFnnn" etc) and post and we'll see.  If they don't stock any then give them a dark "that's-totally-hopeless" look and take your leave of this cheese-free cheese shop.

Is there some other electronics place/joint/activity such as a TV repairer in your area, any Ham radio clubs or nearby operators you could front up to and introduce yourself.  None of your parents into electronics?  Hackerspace?  These dudes will know where to get stuff locally, and as you only want a single N-channel J-FET I'll bet somebody will give you a few (coz you've got a great backstory).


First rule of guitar speakers - bigger is better, at least up to 12-inch.

Second rule of guitar speakers (but the First Rule of micro amps such as this) - efficiency is everything.  This is given (or should be) in "dB/W" decibels of racket per watt in (at a range of 1m).  Forget anything below 90dB/W, 100dB/W is good, and any more is icing on the pud, but every dB counts.

Caution: Hi-Fi and car speakers won't cut it by a large margin (in other words RS are very unlikely to have what you need).

Happily efficiency tends to rise with diameter.

How we connect the amp to the speaker depends on what you have decided for "packaging".

If you have decided to go "head and cab", e.g. the amp in a mint tin and the speaker in a tea chest, then both will need connectors and a lead with plugs to match.

If you have decided to go "combo", e.g. the amp and speaker mounted in the same plastic jerrycan, then the speaker will wire directly to the amp via a socket which can be used to automatically disconnect the internal speaker when the amp is plugged in to an external cabinet, and assuming your partner already has an amp and speaker, this is something he will want to try. {and small amps like this can give quite astonishing results when plugged into a large cabinet like a "quad box" with four 12's).  Or for headphones.

{By about the third battery you will be considering adding a socket for a plugpack/wall wart.}
If you say theory and practice don't agree you haven't applied enough theory.

galaxiex

#102
Sorry for the delay posting these pics. Life stuff to deal with....

Anyway... not sure how much this helps, but here they are.
Nothing soldered yet. The socket pins for the IC (LM-386) are barely visible.
Sorry too for the dim pics, best I could do because the camera doesn't like the light reflections from the copper.
Had to use very subdued lighting or it would just wash-out the image.

Edit; note that there are no wires installed that would go to the off-board parts like the volume pot, battery power, jacks etc...
If it ain't broke I'll fix it until it is.

Lauren

Hi Everyone! Just wanted to let you know that I finally ordered the two missing components...they should be here soon, and then I'll be ready to get back on track with this project.  :)

galaxiex

Quote from: Lauren on October 14, 2014, 04:44:23 PM
Hi Everyone! Just wanted to let you know that I finally ordered the two missing components...they should be here soon, and then I'll be ready to get back on track with this project.  :)

Great! Glad you're still with us!  :)
If it ain't broke I'll fix it until it is.