First Electronics Project - Parts Approval Please :)

[CorySCline]

Hello all! I am intrigued by this world and have decided to build a VERY small guitar amp as my first project. However, before I partake on this mission, I would like to show you the diagram and parts list and compare to what I am about to order. My biggest concern is the IC. There are SEVERAL options for the TDA7052. That worries me in my selection. Thanks in advance for he help

Parts List:
R1: 22K 1/4W Resistor

C1: 10µF 25V Electrolytic Capacitor
C2: 100nF 63V Polyester or Ceramic Capacitor
C3: 220µF 25V Electrolytic Capacitor

IC1: TDA7052 Audio power amplifier IC

J1,J2: 6.3mm Stereo Jack sockets (switched)

SPKR: 8 Ohm Loudspeaker

B1: 9V PP3 Battery


This is the list I am about to order from mouser.com: (Links included)
R1: Carbon Composition Resistors 1/4W 22K OHM 5%
C1: Aluminum Electrolytic Capacitors - Leaded 25volts 10uF 4X7mm L/S=1.5mm Bulk
C2: Polyester Film Capacitors 0.1uF 400VDC/200VAC 10%
C3: Aluminum Electrolytic Capacitors - Leaded 220uF 25volts 20%
IC1: Audio Amplifiers 1W BTL MONO AMP W/VOL CTRL
J1,J2: Phone Connectors 1/4 STEREO SWITCHED
SPKR: Speakers & Transducers 30 x 16.5mm 2W
Battery Clip: PP3 Battery Holder

This is the closest I could find, however I could have made mistakes. There are a couple of things though, and I may be getting ahead of myself. I would like to incorporate into this circuit the following:
1 LED, when the circuit is connected (When the jack is plugged in)
1 Volume control. I see that the IC supports it. Would it be difficult to wire a knob onto it? If its simple enough to do, which knob should I use? (Mouser links appreciated)
Instead of a 1/4 inch headphone jack, I would like to use a 1/8 inch (I dont own any 1/4 inch headphones). Would that mess anything up?
Also, how would I pick a correct board to lay all this out on? I am unable to find any decent tutorials on picking one and they all seem to have the pads and traces connected in different ways.

Sorry for the beginners level questions, but I believe asking for help is better than trial and error (At least with electricity)

 

[jackorocko]

I am unable to find any decent tutorials on picking one and they all seem to have the pads and traces connected in different ways.

that is the fun part. It is up to you to layout your pieces and wire them up. Once you have all them laying in front of you with a board you will start to see how it all comes together.

 

[CorySCline]

that is the fun part. It is up to you to layout your pieces and wire them up. Once you have all them laying in front of you with a board you will start to see how it all comes together.

Awesome. Thats comforting. I like creative license . Any advice on the rest of the post?

 

[KJ6EAD]

No volume control? What are you planning on plugging in to J2?

 

[CorySCline]

This will be an electric guitar amp. It will have a 2W speaker attatched to it, with J2 being an option for headphones. The original design assumes the volume controls on the guitar itself will be sufficient. I am not under that same impression.

 

[davenn]

This will be an electric guitar amp. It will have a 2W speaker attatched to it, with J2 being an option for headphones. The original design assumes the volume controls on the guitar itself will be sufficient. I am not under that same impression.

it will probably be enough, at least to try the circuit out for a start. give it a go,
as long as the guitar vol control can take the level to zero output there shouldnt be a problem

Dave

 

[CorySCline]

OK, well assuming I stop getting ahead of myself and stick to the design 3 Questions remain:

1) Do I have the correct parts picked out?
2) What do the 5 contacts on the headphone out mean? I can only find 2 or 3 contact jacks.
3) With C2 and C3, since they are connected can I do inline as such: 1 > C2 > C3 > Ground
or do I need to go 1 > C2 > Ground and 1 > C3 > Ground?

 

[CorySCline]

I have attatched a DIY Layout Creator render. Please check the connections against the originally posted diagram. I have removed the output jack alltogether. Have I done everything correctly? Thanks!

 

[(*steve*)]

On first glance, the blue wire seems completely wrong. If you don't place the cut on the board that would connect pins 3 and 6, then you could also eliminate a single black wire. If you used that lead as the ground, you could eliminate more

I would tend to place cuts in the board so that signals don't go further than they need to. Probably not an issue here, but it will often allow you to make the whole circuit smaller and less subject to strange effects caused by capacitance. between tracks.

 

[CorySCline]

I have removed the cut between pins 3 and 6, as suggested. I have also removed the blue wire. After further review, I could not recall why I even put it there lol. Does everything seem to be correct now? New layout uploaded . I guess where my mental block is, I seem to think that electricity must follow the SPECIFIC path laid out in the diagram. Am I incorrect in this assumption? Is it true that it only need reach the required point, by any means necessary?

 

[(*steve*)]

Except in fairly special situations, a line on a circuit diagram only specifies that there is a conductive path between these points. It does not specify any order.

If you look at some printed circuit boards you will see large islands of copper that connect components. On a circuit diagram, this will probably be just a line. Here is an example.

Power supply (and ground) connections are often not shown as joined up, and you are expected to realise that. It's a trap for young players. See here.

 

[JoeyAVR]

HI Cory

The circuit diagram is just that, a diagram to show what is connected to what, it's not a drawing of the actual circuit. When you get to advanced stuff where things are placed can really be important, but for this project, you just need to keep the connections reasonably short and lay them out so YOU can understand what is going on.

The black arrowheads in the drawing of the headphone jack represent switch contacts. the idea is that when you plug in the headphones, the switches open and disconnect the speaker.

C2 and C3 are side by side (in parallel) not end to end (in series) for a reason. They are doing different jobs. even though they are both capacitors. C3 is a big one and stores some electricity that it can give up quickly to power the amp when you hit a loud note. many circuits have such capacitors to help them ignore changes in the power supply. This helps stop the sound petering out at high volume when run from a battery.

C2 is a much smaller capacitor, it allows much faster changes 'glitches' in the supply to travel through it, rather than through the amplifier chip. In theory C3 could do this job, but in practice C3 won't be a 'perfect capacitor' and has some resistance which makes it less good at dealing with these fast signals.

 

[jackorocko]

the reason why your schematic layout won't matter is because some schematic symbols for pin layouts won't match the real life pin layout. So this will force you to make the appropriate connections irregardless of the schematic layout vs your real life layout. Then you add in Steve's point about shorthand grounding practices.