Pooge 5.51 positive regulator

[audiodoc]

I plan on building the Pooge 5.51 voltage regulator noise reduction circuit.My question is :What adjustment(s) need to be made to possibly use a 7805 5 vdc regulator?Is the 1k trim pot allowing for voltage output adjustment?

Mike

http://www.diyaudio.com/forums/showthread.php?s=&threadid=5336&highlight=jung+regulatorurl

 

[jan.didden]

Pooge 5.51

You get the lowest output voltage when you short R862. In that case, Vo will be the ref voltage of the 329, 6.9V I think it is, +Vbe of the transistor, say 7.5V. If you want to go lower to Vo=5V, you need to replace the ref with something 4.3v or lower.

Jan Didden

 

[ALW]

Quick mod

Add a cap across R861, with an impedance that's low relative to it's value.

It reduces noise significantly at higher frequencies, and lowers output impedance an order of magnitude.

In this form it's a VERY good sounding regulator.

You could try a TL431 as a reference, set to it's min o/p (2.5V), or just a zener of suitable value.

Andy.

 

[audiodoc]

pooge 5.51

What value of cap across R861 do you recommend? I take it that the voltage in should be ~4.3 vdc or so to get 5 vdc out? For 15 vdc,would I come off the V out leg of a 317 into this circuit for the replacement on my circuit board or does this circuit replace a 317?

Mike

 

[ALW]

Cap value

What value of cap across R861 do you recommend?

Depends upon the value of R861 a bit, but basically the impedance of the capacitor wants to be low relative to the value of R861.

Xc=1 / (2*pi*f*C) should tell you all

A.

 

[jan.didden]

Re: Quick mod

Add a cap across R861, with an impedance that's low relative to it's value.

It reduces noise significantly at higher frequencies, and lowers output impedance an order of magnitude.

In this form it's a VERY good sounding regulator.

You could try a TL431 as a reference, set to it's min o/p (2.5V), or just a zener of suitable value.

Andy.

Hi Andy, seems I beat you to this thread by about 15 mins...?
Your advice is right on the dot, as usual.

BTW, how's the supplies coming along?

Jan Didden

 

[ALW]

Jan

Are you back from hols?

I've been busy building for actual orders, and doing specific implementation documentation, so I'll get onto this weekend.

How's your AP BTW- I never got a reply from the UK distributor

Andy.

 

[audiodoc]

impedance of cap

In your equation:Xc=1 / (2*pi*f*C) f=the frequency to filter,C=capacitance value or 3.0 x 10(8) m/sec?

Mike

 

[GRollins]

Capacitance in Farads, hence microFarads will be 1e-6.

Grey

 

[audiodoc]

Xc=1 / (2*pi*f*C)

For the calculation to find the cap needed - what frequency is chosen for the upgraded Pooge circuit from ALW? You kind of leave me with missing info.Higher frequency from what to what?

Mike

 

[jan.didden]

Pooge etc

I don't think you can give a hard freq value. Basically, the feedback divider (the two resistors that divide down the output voltage to the base of the comparator transistor) also divide down the error voltage with the same ratio. That decreases the accuracy of the loop with the same ratio. Now, for DC, that is not critical. I mean, you probably don't worry about an output voltage of 15.2 or 14.88 instead of 15. But the ac errors (noise, ripple) you really want to be zero. So when you put a cap over the top resistor, the AC feedback ratio can be made 1, that is, ALL ac errors are fully fed back to the base of the comparator transistor. But of course that only happens when the cap impedance is zero, which for a practical cap cannot be realised.
At the same time, realise that the performance of these circuits deteriorates with rising frequency. At low freq, it is probably good enough to do without the effect of the cap, but above 1 kHz or so, the cap can start making a contribution.
Taking into account these factors, I use rule of thumb to make the cap such a value that it starts to work at 1kHz, so at 1kHz Xc should be the value of the upper resistor. But there is not much stopping you taking a (much) larger cap.
Hope this helps,

Jan Didden

 

[audiodoc]

pooge 5.51

One Last questionoes this noise reducing circuit substitute for a 317 or do I come off of the output leg of the 31 into the Pooge 5.51 for the desired effect?

Mike

 

[jan.didden]

Pooge

Mike,

I am not sure I understand you. The Pooge 5.1 is a complete regulator, not just a noise reduction thing. You can of course use a 317 as a preregulator to further improve the performance; that is discussed in other threads.

Jan Didden

 

[audiodoc]

pooge regulator

Thanks for everyones help and being patient with me.I know very basic electronics(eye doctor)and like to tweak.Let me know if I can make any more inprovements.

audioeyedoc

 

[jan.didden]

Re: pooge regulator

Thanks for everyones help and being patient with me.I know very basic electronics(eye doctor)and like to tweak.Let me know if I can make any more inprovements.

audioeyedoc

Ah! You must be the one with the clear view!

 

[audiodoc]

clear view

We specialize in Lasik - laser eye surgery.I see the circuit boards very clearly now-except I'm beginning to need reading glasses.

Mike

 

[audiodoc]

pooge 5.51

Is r862 in the pooge 5.51 circuit a 1k/.5 watt trim pot to adjust resistance or just 2-1K/.5 watt resistors in parallel?Stuck again.

Mike

 

[audiodoc]

pooge 5.51

In the Pooge circuit 5.51 - what value of LED is used?Is this a voltage drain?

 

[ALW]

R862 can be a pot, but for stability it's best to use two resitors in parallel, adjusting just one for the desired output voltage.

The LED provides bias for the current source, any standard LED will be fine here, with a nominal 2V drop.

Andy.

 

[audiodoc]

pooge 5.51

I have now built the Pooge 5.51 and ALW's revised 5.51.My problem now is that the LED is suppose to stay on and after 5 sec.it goes off.Any suggestions on what the problem may be?
Mike