[Ruffy]

First off. I wont be owning any cans past 32ohms anytime soon. I'm a super n00b when it comes to electronics. I can solder just fine but when we get to theory and understanding what a circuit does and tracing paths. I'm horrid.
Secondly, I've chosen to use dual 2227PA Op amps. I'll prob get the OPA2132PA later on down the road if I ever start rolling amps (*glares at wallet*)

I'll be using this layout for my PCB perfboard http://www5.head-fi.org/forums/showthread.php?t=31941
I'm also using this place as a reference
http://feistworks.com/ben/a47/

My questions are :
Where do I put the LED? Do I really put it on the power in line? Meaning it would go Power Source+ -> On/Off Switch -> LED+Resistor -> Board? Wouldn't this be harmfull in any way? Or is it done how I set it in the Layout Picture?

Where exactly do I connect the Pot to? The Protoboard pic in the first link doesnt have it. and the second links diagram is different. So looks like i'll be tracing paths to figure out whats what right? I've done it on the diagram below but Im unsure if its right.

When changing gain, I change the 4.7kb Resistors right? Both? As I understand it i can also swap the 10kers

What Ammount of power/voltage should I be putting into this thing Any idea? I have like 20 walwarts. Best ranges seem 13, 16, 18, 30(big monster but it might be VAC so i have to check it). The schematic on the second page says 18vdc

Does the Current matter at all on the wallwarts? Does the device only pull what it needs regardless of how many mA the plug is capable of? Told you I was a noob

If i up or lower the voltage, do I need to change the 10k resistor for the led? Little flag just went up in my head so I thought id ask

I know that the wallwarts I have will most likely put noise into the amp and I'll get a better one or build a proper thing for it later.

Picture of my board layout as I understand it . Letme know if anything looks off please.

Parts List Below

Code:

[left] Capacitors 2 565-1610-NDCAP 470UF 50V ELECT KY RAD $1.04 2 495-1086-NDCAP .47UF 50V METAL POLY $0.64 2 495-1087-NDCAP 1.0UF 50V METAL POLY $0.82 *In case I ever want to tweak the bass* Resistors 1 P2U4103-NDPOT 10K OHM 12MM HORZ MET BUSHIN$2.66 5 2.49KXBK-NDRES 2.49K OHM 1/4W 1% METAL FILM $0.54 *Gain to 5* 5 4.75KXBK-NDRES 4.75K OHM 1/4W 1% METAL FILM $0.54 *Gain to 3* 5 47.5XBK-NDRES 47.5 OHM 1/4W 1% METAL FILM $0.54 5 100KXBKRES 100K OHM 1/4W 1% METAL FILM $0.54 ICs\Transistors 2 1N5822DICT-NDDIODE SCHOTTKY 40V 3A DO-201AD $1.36 1 BUF634T-NDIC 250MA HS BUFFER TO-220-5 $8.10 1 296-1994-NDIC 1/2 RAIL VIRTUAL GND TO-92 $1.30 2 OPA2227PA-NDIC DUAL PRECISION OPAMP 8-DIP $7.92 1 HLMP1790-NDLED SS GRN DIFF LO CURR PCB 3MM $0.34 Misc 2 CP-3535-NDCONN AUDIO JACK 3.5MM STEREO $2.08 [b]Subtotal$28.42[/b] [b]Estimated shipping : $3.85[/b][/left]

I appreciate any input. I'd like to order the parts tonight and I'm just going over things as much as possible before I commit myself to this.

 

[MisterX]

Quote:

Where do I put the resistor?

Wherever you want to.

Quote:

Where exactly do I connect the Pot to?

In left
In right
and ground

Quote:

When changing gain, I change the 4.7kb Resistors right? Both?

Quote:

First off. I wont be owning any cans past 32ohms anytime soon.

You answered your own question before you even asked it.
(you don't need to change the gain)

Quote:

What Ammount of power/voltage should I be putting into this thing

What does the opamp's datasheet tell you?

(http://www-s.ti.com/sc/ds/opa2227.pdf)
Quote:

Does the device only pull what it needs regardless of how many mA the plug is capable of?

Yup, but if the device needs more current then the power supply can provide what happens?

Quote:

If i up or lower the voltage, do I need to change the 10k resistor for the led?

10k is kinda high for that LED but the question is moot because you should resolve the power supply voltage before you try to figure out what the Rled value should be
Make sense?

 

[Ruffy]

first question was meant to ask *where should I put led

*

 

[MisterX]

Even if you change the question the answer is still the same.
Connect/put the LED wherever you want to.
As long as you connect it between the V+ and V- rails and have a resistor in there somehwere it's gonna be ok.

One of the best things about building an amp on perfboard is you can move the parts around to suit your needs.
If you don't like where the buffer is.... move it.
Nobody is gonna yell at you.

As long as you connect it the same way it's gonna work just fine.

 

[Ruffy]

Quote:

Originally Posted by MisterX Even if you change the question the answer is still the same. Connect/put the LED wherever you want to. As long as you connect it between the V+ and V- rails and have a resistor in there somehwere it's gonna be ok. One of the best things about building an amp on perfboard is you can move the parts around to suit your needs. If you don't like where the buffer is.... move it. Nobody is gonna yell at you. As long as you connect it the same way it's gonna work just fine.

The whole "connecting it" however I want is what scares me since im liable to end up having it explode.

 

[Pars]

Quote:

Originally Posted by MisterX As long as you connect it between the V+ and V- rails and have a resistor in there somehwere it's gonna be ok.

Good advice... however, they might want to make sure they put it after the power switch, so its only on when the amp is on (or exploding...)

 

[Ruffy]

Quote:

Originally Posted by Pars Good advice... however, they might want to make sure they put it after the power switch, so its only on when the amp is on (or exploding...)

so dont do it as I had on the Diagram? (Looks at protoboard) Seems fine to me.... Cept the whole running the LED and the entire circuit in parallel kindof seems odd. I really need to find my old electronics books and get to reading.

 

[Pars]

Quote:

Originally Posted by Ruffy so dont do it as I had on the Diagram? (Looks at protoboard) Seems fine to me.... Cept the whole running the LED and the entire circuit in parallel kindof seems odd. I really need to find my old electronics books and get to reading.

No, its fine on the diagram. Your switch will be between the batteries or other power supply and the board. If you wire the LED in before the switch, it will be on all the time. Put the RLED in series with the LED, in between the V+ and V- and you'll be fine. The resistor is required to keep the LED from drawing too much current and burning out.

MisterX's diagram of the pot wiring is correct for the typical Panasonic pot used (from Digikey).

 

[Ruffy]

well the parts are ordered

Hopefully It arrives while I'm at home as Im going to have a busy next few eeks

Wonder how long digikey takes to ship
I selected US Priority as shipping.

 

[The Monkey]

Quote:

Originally Posted by Ruffy well the parts are ordered Hopefully It arrives while I'm at home as Im going to have a busy next few eeks Wonder how long digikey takes to ship I selected US Priority as shipping.

They're pretty good with shipping, probably 2-3 days. My experience has been 2 days.

 

[Ruffy]

Quote:

Originally Posted by The Monkey They're pretty good with shipping, probably 2-3 days. My experience has been 2 days.

well they shipped it yesterday

So digikey truly does rule

With this I might actually get it friday-saturday which would be cool.

 

[Ruffy]

Ok digikey truly rules
Cheapest shipping USPS priority pretty much assures 2-3 delivery all over the US. Ordered 9/7/2005, Arrived 9/9/2005

So looks like Im building my amp tommorrow.

Bought a 5-40watt soldering station($25) By Elenco. Seems all my current soldering irons are 30watt and above(No wonder some of my previous projects failed miserably)

I was going to buy a Sub 20 watt iron but all they had at Frys were 12watt pencil for 30 something bucks. Eventually I'll buy a Hakko or similar.

Still undecided on whether or not I'll paint my enclosure(Bone color right now)

 

[Ruffy]

well this sucks, It seems I Forgot a set of 10k resistors(I guess I looked at my list, saw the 10k pot and thought all was well)
On top of that the caps I ordered are small box types

So looks like i Have to goto radioshack and buy some caps + 10 resistors.

Id order from digikey again but that damn 5 dollar charge hurts when you only need 2 dollars worth of items

 

[looser101]

Box type caps will work fine as long as they physically fit.

I can send you a couple of matched 10k resistors if you like. But I am in Canada and you are probably in the U.S., which means it will probably take a week to get there. PM me if you are interested and can wait.

-R-

 

[Ruffy]

Quote:

Originally Posted by looser101 Box type caps will work fine as long as they physically fit. I can send you a couple of matched 10k resistors if you like. But I am in Canada and you are probably in the U.S., which means it will probably take a week to get there. PM me if you are interested and can wait. -R-

they are box the problem is they're tiiinyy that kindof changes my breadboard as id have to do some more jumping to get the leads to go where they're supposed to.

the 10k resistors would be great but shipping from canada would take too long. I'll just buy some generic crap from ratshack for now, or I'll check fry's and see if they have anything