simple'is preamplifier power supply.

[snip]

Hello there.

So I've been thinking about building a pre amplifier in a Hifi-2000 chassis I have laying around for driving a power amplifier (BJT based symasym clone thingy) that I am also building, this will be for use when I eventually get a bigger place and can set my speakers up.

I want it to have two inputs, one with a phono stage for my turntable and one for my DAC. I am thinking of employing the 'Le Paciffic' single ended phono stage, the Pass B1 buffer and the Lightsp^H^H buffer that must not be referred to by that name.

So something like phono-stage -> three pole switch -> B1 -> attenuator.

This is the schematic for the phono stage, as you can see it uses much the same topology as the B1.


I will only use the MM part as I do not have an MC cartridge.

Now the B1 is specified at 18V supply, but I can't see why it could not be run on 24V, alternatively I could always use three regulators, one giving 24V for the phono stage, one giving 18V for the B1 and one giving 5V for the attenuator. The 5V will just be a 7805 fed via a resistor from the incoming DC feed (External DC supply at something like 26-30V, by means of a transformer and CRC filter)

So how to build the power supply?

I want to keep this rather simple so was thinking of using an LM317 followed by a simple noise shunt kind of like Fig. 1 one this page: http://www.wenzel.com/documents/finesse.html

As I said either using two of them at different voltages or running both the B1 and the phono stage at 24V.

I'm looking for suggestions as to how I might better implement this, without making the circuit overly complicated as it will be implemented on strip board.

I'm open to buying a commercial regulator if it is not too expensive, obviously this would only make sense if the performance was significantly better than the LM317 with the noise shunt idea.

I guess perhaps using a diode in series with a resistor to feed the 7805 might be considered good practice to prevent that regulator polluting the main feed rail?

//Jan

[Marco]

Hi Jan,

I suspect that your link below (via "blogger.com") works only for you, as all I'm getting is a white box with a red cross in it.......

You need to upload your pictures to either Photobucket or Imageshack for them to be viewed on this site

Cheers!

Marco.

[leo]

Some nice little projects for beginners on here including regulated psu's with drawings etc http://www.decdun.me.uk/gainclonepre.html

[leo]

BTW The Wenzel circuit is dead easy to knock up and try

Heres another circuit which is quite effective when added on the out of a LM317 http://www.diyaudio.com/forums/group...ple-eater.html

[Mike]

You could use more than 5V for the ,err, 'LDR based attenuator'.

It would be quite happy using the same 18V supply as the B1 as long as the 7805 regulator has sufficient heatsinking.

[snip]

Hi Jan,

I suspect that your link below (via "blogger.com") works only for you, as all I'm getting is a white box with a red cross in it.......

Marco.

Dooh, ok try this.

http://www.snip.dk/dump/2SK170schema.jpg

That was the first image of the circuit I found, it looks a bit odd but it is easy to make out the diagram, that is the MM part only, the MC stage is before it, but I am not interested in that part.

//Jan

[snip]

BTW The Wenzel circuit is dead easy to knock up and try

Heres another circuit which is quite effective when added on the out of a LM317 http://www.diyaudio.com/forums/group...ple-eater.html

Yes it is a simple circuit indeed. No problem for me to construct at all.

That JLH board looks nice, I'm tempted to get hold of a few of those.

//J

[snip]

You could use more than 5V for the ,err, 'LDR based attenuator'.

It would be quite happy using the same 18V supply as the B1 as long as the 7805 regulator has sufficient heatsinking.

Ah. I thought those LDR thingy's were for low voltage only?

If the attenuator could run off 24V, as in not having a 7805 to regulate the voltage it would be neat, then I could run the whole box from a single regulator and just run everything at 24V

I'd really rather not have the input leg of a regulator IC connected to the rail that feeds the phono stage for instance, maybe I am being paranoid here but I think that would lead to noise.

//J

[Marco]

Dooh, ok try this.

http://www.snip.dk/dump/2SK170schema.jpg

That works fine - cheers

Marco.

[Mike]

Ah. I thought those LDR thingy's were for low voltage only?

If the attenuator could run off 24V, as in not having a 7805 to regulate the voltage it would be neat, then I could run the whole box from a single regulator and just run everything at 24V

I'd really rather not have the input leg of a regulator IC connected to the rail that feeds the phono stage for instance, maybe I am being paranoid here but I think that would lead to noise.

//J

Hi Jan,

I'm just going from the schematic shown here:http://diyaudioprojects.com/Solid/DI...ve-Attenuator/

As you can see, the attenuator has it's own supply section running from 8-20V input to give the 5V needed. I would feed it from the same 18V that the B1 requires. At least that's what I'm doing with mine.

Cheers...