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regulator booster

I cant remember exactly. Im new to all this pcb lark.

I wondered - with the popularity of 'TeddyRegs' - if many would be that interested in this little 'RegBooster' PCB project anyway?
 
Im sorting out a Farnell order on these as I want to try them on the 4 x 7805 regs that supply the DAC's in myCD player. I already have some 3.3uF Oscons and 10uF/25v Tants. Will these caps be OK, I was planning to use the Oscons in place of the film caps?

For the 10k resistor what power rating will be ok? Do I need film types or not?

One more question:

Teddy writes....

Ooops. I forgot to mention, a ground wire has to be connected from the circuit ground to the main PCB ground. I used a short wire connected to the ground leg of one of the main PCB tantalum (the Vout tantalum of the original regulator circuit).
Click to expand...

Cant the ground connection be taken to the GND pin location on main
pcb. The idea is to make this a 'drop-in' mod thus avoiding the extra wire connection.
 
mikesnowdon said:
Im sorting out a Farnell order on these as I want to try them on the 4 x 7805 regs that supply the DAC's in myCD player. I already have some 3.3uF Oscons and 10uF/25v Tants. Will these caps be OK, I was planning to use the Oscons in place of the film caps?

For the 10k resistor what power rating will be ok? Do I need film types or not?

One more question:

Teddy writes....



Cant the ground connection be taken to the GND pin location on main
pcb. The idea is to make this a 'drop-in' mod thus avoiding the extra wire connection.
Click to expand...

You can do this with your 7805 because it's got a GND pin. However, the 317 family of adjustable regulators are floating devices and don't have a ground pin, yet still need to reference ground; that's why you need to add an extra wire when using the booster circuit on an adjustable reg (317/337/1086 etc) as opposed to a fix reg (7805/7905 etc).

Hope that helps,
Carl
 
Silly me :) I get it now.

So are 0.25w resistors fine or do I need higher rated parts? Also, any need for metal film resistors or is it not important here?
 
Cool thanks.

I was just sketching up to see how they would fit together. If I build these P2P I could get them really small. The 3.3uF oscons are tiny,about the same size as the BC547C and the 10uf Tants are minuscule.
 
Got parts on the way to build these up. Im a bit concerned about the 1ohm output impedance caused by the VBE. I'll be using these on wolfson WM8740 DAC chips. Dunno if the benefit of reduced noise is going to be outweighed by the increase in supply impedance.

If it is a problem how could I reduce the output impedance of the VBE?

(Slightly off topic but relevant: Im going to use some 330uF Nichicon KZ's for the post reg decoupling. These are on the DVDD and AVDD supplies and will be direct - but better - replacements for the stock 330uF caps. Are these ok?)
 
Are you building these using the initial idea of the VBE.... BEFORE the reg? If so, then do you think the VBE will affect the final output impedance?

seriously - I'm asking - i would have thought not significantly but I don't know for sure.
 
Yes. If its high impedance going into the reg then it will be high coming out, as far as I understand. Im not certain though.

EDIT: If you read the posts about halfway down the first page there is indication that the output impedance could be as much as 1ohm. I will be using this circuit on 7805 regs so I have no idea if that makes a difference on not?
 
The impedance that circuit sees is almost solely set by the last regulator, the one it is connected to.

There is a very small contribution from upstream regulators, reduced by the rejection factor of the last regulator. Using a 7805, you get about 1000:1 rejection, so the VBE upstream contributes only a milliohm at the output.
 
Oh, well thats good then. I'm using the VBE before the 7805 reg with a 330uF KZ Muse on the reg output. I'm going to build these up on stripboard similar to how Teddy has.

I was wondering if a simple R/C on the reg output was a good idea?
 
I'm using SuperTeddyRegs for the TeddyDAC (coming soon...) which is based on WM8741 and they improved the performance of the WM8741 in a way that I had a hard time to believe.

Not only that it improved the sound but for the first time I measured a difference in the frequency response as a result of a regulator. I measured the frequency response at high frequencies on the Wolfson evaluation board with and without SuperTeddyRegs, and there was about 2db difference at 18-20KHz. I was very strange to me but I'm certain about the measurements.

The effect was noticeable only on one filter in which there was a drop in high frequencies that disappeared when I used the SuperTeddyRegs.

Bottom line: don't worry about output impedance, in my opinion you'll get better results by using the VBE after the 317.

Teddy
 
Cool.

So if I use the VBE after the reg how do I make sure I'm getting the correct supply voltage? The DAC/clock circuits in my CDP run on 5v logic. So I need to make sure the DAC's get exactly 5v right?
 
Additional thoughts:

I know I could use a LM317 but Im put off by the added complexity and space between regs is very tight. I could build off board regs and wire them in, but if I did that I might as well just use STR's. The thing that appeals to me about the 'reg-booster' is its simplicity, its nice and easy. I read in the first post that the dropout of the VBE is about 1v, so I could take my chances with a 7806 reg and hope its close enough to 5v after the VBE.

?????
 
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