[Braver]

it's finally here

got almost everything, except for a case (saw a great looking alu one in the Conrad catalog, ordering that one, maybe make one out of wood later) and battery holder (got a cheap clip now) and in/output jacks..ordered 2 jack, but they aparantly weren't headphone jacks

thinking of ordering one of the Neutrik jacks that looks like those on the high-end Headroom gear (but silver colored) and a pair of RCA input jacks.

tried to solder a resistor few minutes ago...didn't went by the book (apparantly didn't wet the tip properly), but it looked tight and shiny, so I guess with a few more tries I'll be ready to go

BTW, the iron, my aluminum volume knob and especially my multimetern (tiny!) look soo cool

hehehe.

now for the questions

1. the LED. how do I connect it properly? it's got one long leg and a slightly shorter one. forgot which goes where tho

2. grounding stuff. basically, the leads all go to one of the big strips on the PCB right? or do the left and right channel go to seperate grounds?

3. what does the ground do exactly? my memory is very vague about this

want to know what I'm doing here!

4. the the top part of the iron got all copper colored and purple at the "root" is this okay?

(can you tell I'm a newbie here

)

any other tips are ofcourse welcome

 

[aeberbach]

1. Here's a page with information on diodes:

http://www.newcastle.edu.au/departme...by/sensors.htm

(A bilby is a native Australian animal. Newcastle is about an hour north of Sydney. The IR LEDs shown are connected the same as normal ones.)

Don't forget a current-limiting resistor. If you connect a diode directly across a battery it will be very bright for a very short time and then will burn out and be bright no more.

2. Everything that is ground gets connected together. Try to connect everything roughly at one point, don't make a ground "loop" which can cause noise. The main thing to be careful of is that the case gets grounded at only one point, usually the volume pot. Of course you need to have multiple points on the PCB.

3. Your amplifier amplifies a signal. The signal is relative to ground. If ground is 0 volts, the signal goes above and below that level.

4. As long as the tip is shiny and evenly covered with solder it is OK. The color of the rest of the tip will usually go through strange colors when it is new.

 

[Braver]

very helpfull reply aeberbach!

so the long leg of the LED connects to the resistor. and if do it wrong, it will just not shine if I turn the power on right?

about grounding the case, how do I do that exactly? just solder a wire to the inside of the case and to the strip where I ground everything else?

 

[aeberbach]

Right, unless you have some insane voltage beyond its rating the LED acts as a diode (and in fact is a diode) and will not conduct.
An easy way to ground the case is to use a solder tab (looks like a washer with a bit sticking out) on the main shaft of the volume control, it gets bolted down when you attach the shaft to the front panel. Solder a wire from the tab to the ground on the PCB and you're in business. What you should avoid is grounding the RCA inputs, usually on the other side of the case. Different makes use various methods of isolation, the WBT ones (expensive!) use a complete insulating sleeve.

 

[wab]

[edit]aeberbach beat me to it and he makes more sense

[/edit]

BTW is there really a need to ground the case since it's already connected to ground via the jacks/pots etc?

 

[Braver]

ah, so I should have some isolation between the RCA inputs and the case.

hey wab, what kind of headphone jacks are you using?

 

[wab]

For my portable amp (in a simson bandenplakset case

) i used some cheapo 3,5mm jacks (which I got at the local electronics/parts shop) but for my soon to build super-home-cmoy I will try to get some nice gold-plated 6,3mm ones.

BTW. Those Neutriks conrad sells look nice but are very big and require some major hole-drilling.

 

[Braver]

yeah, thats what I thought as well. they also have some board mounted ones, but I don't like that. the 1.5mm alu frontplate will be much sturdier. and I want them centered (in hight) on the frontplate.

damn I need to find a local electronics shop

how bad is the corrosion with the regular non-protected copper PCB's? want to get it good before putting a lot of money in stuff I'll have to unsolder within a year. or could I use a protection spray or something after I soldered everything in place?

and yet another question, which row of pins on the pot is for the left and which row is for the right signal (haven't got them here with me, maybe I can find it on the pot)? or doesn't it matter? (saw L and R indications on the pics of the pot of the Grado RA-1, so figured itmight matter).

 

[aeberbach]

I think the case should only be grounded at one point, and for me that's the volume control knob. Everything else that sticks through the case is either non-conductive, or insulated. Otherwise you have a loop. The inputs are shielded by cable that is connected to the ground on the volume control pot, that is connected to the case. It may not matter in some cases but being careful about these things just gives you less to trace when you hear a hum.

 

[Braver]

hey I found a spray that could put a thin film of acrylhars (that dutch

, no dictionary here) over the PCB. could I use this to protect the electronics from corrosion after I put the entire thing together?