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CMoy questions about layout and components

post #1 of 4
Thread Starter 



So this will be my first DIY project and I hoped to get some feedback from the more experienced guys about my layout and component choices. I followed the tangentsoft schematics and decided to use the TLE2426 for creating the virtual ground.


So here's the layout: http://i.imgur.com/VSNB67f.png?1


I was mainly wondering about the capacitor sizes as is the 1000uF capacitor in the power section too large or are the 470nF capacitors the right size? Because I had the impression that bigger capacitors will boost the bass better. I was also wondering what kind of capacitors should I use, in the layout C1 is a electrolytic capacitor and C2 capacitors are polyester capacitors?

post #2 of 4

That is a nice clean layout, but it could be improved. 


You could probably shrink it down a bunch by doing the following:

Move the TLE2426 closer to the op amp. It can be right above the op amp, really. 

The supply wires for V=/V- should be as short as possible, which is easy since the strip goes right across the top. 

Turn C2 90* (the one currently attached to the right input) so that it points towards the bottom of the board. 

Instead of having so much space for the input & ouput wires move them closer to the middle of the board. 


This lets you cut at least 8 holes off of the board, which will help you fit it in a smaller enclosure. Or maybe let you put more batteries in a similarly sized enclosure. I'd go for more batteries, but to each his own. 


If the physical dimensions of the C2 you buy lets you do it - move C2 to the other side of R2 (closer to the op amp) to save some more width. 


You have enough spare strips that you can put Rled ON the board. This is much stronger and looks nicer than air-wiring it. 



General concerns:

I'm not sure if you will be able to find caps that are the size you accounted for. Maybe. Just be sure to plan for this carefully. 

Bigger caps do (sort of) provide better bass. Since not much music goes *that low*, the op amps have lots of global feedback to make up for problems in the power supply, and the big fat cap is in parallel with the battery the importance of REALLY big cap (higher uF) is kind of reduced in a Cmoy. In any case, 470-1000uF is plenty. 

Since you have a lot of space on the top of the board, you may be able to fit several smaller caps in parallel to get a large total value. 


In the interest of making the amp more "future resistant": 

Have you read Tangent's article on "working with cranky op amps?" Now is a great time to think about designing those things into the amp. They don't cost much and let you choose from a larger pool of op amps later. 


Nobody likes to hear this, ever, but I say it - gain of 5 is too much. Shoot for somewhere between 2.7 and 3.5 depending on where the resistors you are buying line up best per the instructions in Tangent's cranky op amp article. If you get several gain levels to work with the resistors you want to use - go for the lower gain.

post #3 of 4
Thread Starter 

Thank you for the great reply.


I made some changes to the layout following your instructions and here's the current layout: http://i.imgur.com/U9YQYWH.png?1 (this is a layout without taking account the tangentsoft cranky op-amps article)


I also changed the size of the components (more specifically the caps) to correspond better their respected size in real life.


I did give a read to the Working with Cranky Op-Amps article and I will update my layout later on with the suggested updates but for now I would like to know what you think about the smaller version of the layout.



post #4 of 4

That layout looks a lot cleaner. 

Did you leave the "E" strip empty to accommodate the size of the cap? 

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