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Cigar box Apheared 47

post #1 of 58
Thread Starter 

After my (mostly) successful experiment with the CMoy, I am ready (hopefully) to move onto my next amp. I was considering a more expensive/complicated amp like an M^3 or PPA but I think I'd like to keep it simple and make some version of a CMoy or an Apheared 47.

 

I've been reading and searching, and unfortunately I don't understand a lot of what I'm reading. From what I understand the A47 is similar to a CMoy, but it incorporates a buffer. That's good because if I rebuilt my CMoy I would have had to figure out how to put the buffered ground onto the rest of the amp. From what I understand, a buffer regulates the power between the amp and the powersupply. I could be wrong though...

 

So I believe to make it sound better I would also build a power supply that would accept the DC from the wallwart. So I was thinking it would go something like this:

 

Wallwart AC->DC---->Power supply (like a http://tangentsoft.net/elec/tread/)---------->A47 or CMoy

 

Does this make any sense? From my reading I've seen that most of the higher end amps like the M^3 require a power supply, and the quality of it matters. Would a DC to DC power supply make any sense in an amp like this? Does the buffer that is in the Cmoy or A47 include the powersupply?

 

How should I procede?

 

Sorry for all the questions, it is difficult to research when I'm not sure what questions to ask. I can build things reasonably well when I have instructions to follow, and it certainly makes more sense in my head :P

post #2 of 58
Thread Starter 

After more reading and searching, it seems I may be in over my head. I need to use a railsplitter between the TREAD or other powersupply and the amp, and I'll need to figure out how lay it out on a board. I'm going to try it though.

post #3 of 58

using a rail splitter is very simple. i'm going to assume the tle2426 since that's what's usually used on cmoys and such, it's just a small thing with 3 leads. you put +/- go in as inputs, and the last lead puts out a voltage in between the two. just look at the schematic to see which lead is which.

post #4 of 58

If you are using wall power why use a rail splitter at all?

Just do a dual rail power supply. Two TREADS if you will...

Far better than a rail splitter and lots of power for an A47.
 

Quote:
Originally Posted by T.B.N. View Post

After more reading and searching, it seems I may be in over my head. I need to use a railsplitter between the TREAD or other powersupply and the amp, and I'll need to figure out how lay it out on a board. I'm going to try it though.

post #5 of 58
Thread Starter 
Quote:
Originally Posted by Avro_Arrow View Post

If you are using wall power why use a rail splitter at all?

Just do a dual rail power supply. Two TREADS if you will...

Far better than a rail splitter and lots of power for an A47.

 

Would it be better to use a power supply that already has two rails? It would have to be simple because I don't quite know how to translate a schematic to a physical layout on a board.

post #6 of 58

Yes
 

Quote:
Originally Posted by T.B.N. View Post



Quote:
Originally Posted by Avro_Arrow View Post

If you are using wall power why use a rail splitter at all?

Just do a dual rail power supply. Two TREADS if you will...

Far better than a rail splitter and lots of power for an A47.

 

Would it be better to use a power supply that already has two rails? It would have to be simple because I don't quite know how to translate a schematic to a physical layout on a board.

post #7 of 58

Let me put it to you this way...

 

A TLE2426 on it's own can provide, at most, 30 mA of current.

Big rail caps help but this will not be enough for an A47.

 

If you add a buffered ground with BUF634 you can get 500 mA.

This would be about the minimum you would want for an A47.

 

Even a pretty simple and cheap dual rail regulated power supply

can do 1500 mA easy.

post #8 of 58
Thread Starter 
Quote:
Originally Posted by Avro_Arrow View Post

Let me put it to you this way...

 

A TLE2426 on it's own can provide, at most, 30 mA of current.

Big rail caps help but this will not be enough for an A47.

 

If you add a buffered ground with BUF634 you can get 500 mA.

This would be about the minimum you would want for an A47.

 

Even a pretty simple and cheap dual rail regulated power supply

can do 1500 mA easy.

 

I am having trouble converting a schematic into something that would work on a protoboard as I've never done this before. I made a cmoy, but the process is basically laid out for you following the tangent tutorial. I've also made a tube guitar amp, but it was so dead simple and was point to point wiring.

 

 

Would the dual rail regulated power supply you mention be something I could build, then input DC from a wallwart, or would I use a wallwart and put it straight into the A47? From what I read, wall wart power supplies have a lot of noise, which is why a separate power supply is often incorporated into the amp. Would using a wallwart with another power supply be overkill, unless I make a complete one with a transformer and the whole nine yards?

 

Sorry for all the questions, I'm beginning to think I need an electrical engineering degree to do any of this...

 

post #9 of 58

You would need to find a wall wart that has +, - and Ground connections.

Most wall warts have only + and Ground. It's useful in this situation to

think of Ground as being 0 volts.

The heart of most dual rail power supplies is a center tap transformer.

You can also use a dual coil transformer and get the same result.

A simple dual rail supply can be built on a proto board with point to

point wiring. I have one I built this way. It's not pretty, but it works well.

The main thing to watch out for is working with the AC from the wall.

 

Here is the one I built...

 

Power Supply.jpg

post #10 of 58

Here is a schematic for an A47 with a BUF634 rail splitter.

I drew this a while ago but never built it.

 

Apheared 47.bmp

post #11 of 58
Thread Starter 

Thanks for the information! That clears a lot up for me. 

 

Two questions:

 

Does it make sense to build a power supply that only includes the DC section, and let the wall wart do the AC/DC conversion, or would it be better just to make the whole power supply, including the transformer? In your schematic, a dual rail power supply isn't necessary because of the rail splitter, right?

 

Do you have any tips on translating a schematic to a physical layout? I've been trying to draw it on graph paper but I have no idea what I'm doing.

 

Alright I guess that was three questions... 

 

thanks again

post #12 of 58

The ground channel is not necessary with the dual rail power supply.

 

I think that the lack of availability of the kind of wall wart you would need means

that you should consider building the AC section yourself too.

 

Here is a tutorial on the construction of the A47. You can use it as a guide,

don't feel that you have to follow it exactly.

post #13 of 58
Thread Starter 

That link to the guide is very helpful. I've been looking over the board layout compared to the schematic and I can see how one might figure out how to create a layout from a schematic. 

 

I notice that he neglected putting the C5 resistor in, and that the TLE2426 has only 3 pins, when on the schematic it seems to have 4. (which are labeled 1,2,3 and 8 for some reason...)

 

Why is that?

post #14 of 58

There are two versions of the TLE2426.

One is in a package like a small transistor with three pins (TO92).

The other is in a package like an op amp with 8 pins (PDIP-8).

The 8 pin version is better than the 3 pin version even though

they are supposed to be identical.  The extra connection on the

8 pin version is for a noise reduction capacitor.
 

Quote:
Originally Posted by T.B.N. View Post

That link to the guide is very helpful. I've been looking over the board layout compared to the schematic and I can see how one might figure out how to create a layout from a schematic. 

 

I notice that he neglected putting the C5 resistor in, and that the TLE2426 has only 3 pins, when on the schematic it seems to have 4. (which are labeled 1,2,3 and 8 for some reason...)

 

Why is that?

post #15 of 58
Thread Starter 
Quote:
Originally Posted by Avro_Arrow View Post

There are two versions of the TLE2426.

One is in a package like a small transistor with three pins (TO92).

The other is in a package like an op amp with 8 pins (PDIP-8).

The 8 pin version is better than the 3 pin version even though

they are supposed to be identical.  The extra connection on the

8 pin version is for a noise reduction capacitor.
 



I see... and with the 8 pin version, only 4 pins are used then, 1,2,3 and 8, which has the capacitor on it. A quick question about the capacitors: the schematic calls for a 1uF capacitor, one for the power supply and one for the amp section. Can I use the same type of capacitor for both, or are there different requirements? I'm going to use 25V rated caps for the whole thing I think, because the amp will run on ~18V power supply.


Edited by T.B.N. - 12/5/10 at 7:48pm
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