Opamp power supply, super regulator alternatives?

[imperfectcircle]

Ok let me start of by saying hat im pretty much a newbie to diy audio, ive built a bunch of kits that consisted of stuffing a pcb and connecting wires...etc. But I haven't really ever designed my own circuits. I recently heard a pre-amp a diy audio friend of mine built it was a basic opa627+buf634 circuit but he used a very high end power supply using a few chokes(CLCLC) and Jung super regs...etc. I was amazed at how good this thing sounded I never imagined such a simple circuit could sound so good, im thinking it has alot to do with the high end overbuilt power supply? So anyways, I just built my own version of the preamp using Opa132+buf634 and an alps "blue" pot. Ive been powering it from a pair of 12v 8ah SLA batteries I scavenged and wired up in series to give a basic +/_ 12v supply. I guess I could stick with batteries and come up with a better way for splitting the rails, but id really like to built a regular power supply for it. Id like to do something like my friend did but a bit less complex and less expensive. So any ideas on what the "best" power supply design for a simple pre-amp like this? DO I want to go with a CLC or CRC before the regulators? I rarely see chokes in SS designs except maybe Musical Fidelity and Ayre. Whats the advantage of a choke(clc) over a resistor(crc)?? WHat kind/size choke or resistor would I wanna use, is there a simple formula to figure this out? What kind of regulators do I wanna use? Id like better performance then a basic 78xx or LM3xx but the Jung regulator is to complex for me. I found these two ideas for regulators which look pretty simple and are supposed to perform better then standard 78xx types.

Neil Mcbride Naim mods

Super "Raygulator"

Wow i have so many questions! I almost don't really know where to start. I haven't really built a "high end" power supply before . Ive just built very simple ones that consisted of a transformer, rectifier, large cap, 78xx/79xx, small cap and thats it. The thing that really got me interested in higher quality power supplies was hearing my friend's pre-amp with its super overbuilt preamp. Most of my questions probably seem dumb to most of the people around here, but im a newbie ad trying to learn so go easy on me If you guys could maybe draw up some simple schematics of your ideas for a high performance opamp power supply that would be really cool, but id just settle for some info and maybe some ideas on what books or websites I can check out to learn more about this stuff. Thanks alot
frank

[analog_sa]

Hi Frank

You may call yourself a newbie but your questions don't really confirm your newbie status

Batteries do some things incredibly well and no matter how much you overdesign a regulator it won't match your batteries in some respects.

First of all download PSU Designer II. It will really help you understand what caps, chokes and transformers do in a PS.

I have found Jung type regulators to sound better than any other type. And that goes against my prejudices: opamps + complexity.

There is an incredible number of circuit topologies you can choose: series or shunt; feedback or open loop. IC or discrete.

These will all sound different and unless you really want to build them all, the easiest solution is to clone whatever your friend got. Down to component types.

There have been several group buys for Jung type regulator pcbs here. Stuffing them with parts is easy and leads to almost guaranteed results. Why don't you do it?

[martin clark]

DO I want to go with a CLC or CRC before the regulators?

Depending on what you are planning for a raw supply - yes, you might want to:

http://www.acoustica.org.uk/t/3pin_reg_notes2.html

This is for basic 3-pin regs, but the principle holds for any active, feedback-based regulator.

[imperfectcircle]

thanks guys, as for the reason I dont want to do the Jung regulator is because its way beyond my understanding of circuits and im in the learning stage right now and would really like to understand the circuit im building. So id like to stick with something a bit simpler for now, I am going to build the pre-amp with sort of a modular design so i can swap in different power supplies. I can always try a Jung regulator later on when i have a better understanding of some of this stuff. Im building this pre-amp more for the learning experience then anything else really, but i would like to get good sound too As for being a newbie, I have some basic understanding of circuits and what different components do, but no where near the understanding of some of the experts on this forum I will download that program and give it a try thanks for the tip!

Frank

[serengetiplains]

Hey analog, maybe complex psu (which includes, as in my case, power conditioning) + simple signal circuitry is best? That's my experience.

Where might one pick up a Jung circuit board?

[analog_sa]

Got mine from Coffin. Don't know if he still makes them.

[FastEddy]

1) a caution about substituting LM317 (in http://www.neilmcbride.co.uk/preamp.html ) for a 78xx ... they have different pin connections, but you already knew this.



2) Concerning differences between op-amps ... basically there is very little as long as the basic specs match up = slew rates, unity gain response, etc. etc. Examples:

http://focus.ti.com/lit/ds/symlink/opa627.pdf ...
http://www.analog.com/UploadedFiles/...eets/AD825.pdf ...
http://focus.ti.com/lit/ds/symlink/opa132.pdf ...

The devil is in the details. In the above comparing the AD825 (page 7 & 8) to your OPA132 (page 6 & 7), one real difference (the AD825 appears to be better) is caused by the manufacturers' Device Under Test circuit used. The '825 gets a better looking 'scope picture (uSeconds settling time of sq. wave) than the '132. This is basically 'cause Analog Devices uses a DIY technique of putting plastic (polystyrene) snubbing caps close coupled to the op-amp supply pins. Carefully examine the circuit as tested on AD825 page 8 and note the double caps on each V+, V- pin.

3) to be continued when the guffaws die down ...

[imperfectcircle]

" a caution about substituting LM317 (in http://www.neilmcbride.co.uk/preamp.html ) for a 78xx ... they have different pin connections, but you already knew this"

Thanks, your right I knew about the different pin outs of different regulators, maybe im not as much as a newbie as i thought I think even the 78xx and 79xx are different. And as for the different opamps, I don't spend to much time worrying about the specs Ive found that the specs don't really tell the whole story of how good an opamp will sound. I tried many different ones in my cd player and I like the opa132 for its price/performance ratio.


"Hey analog, maybe complex psu (which includes, as in my case, power conditioning) + simple signal circuitry is best? That's my experience."

Im starting to think this is right, especially after hearing my buddies preamp which was just a simple opa627+buf634, gain is set at 3. I probably wont need that much gain since my source is an Emu1212m and it has quite a bit of output voltage. Im wondering now if I even need a gain stage and a buffer stage, a simple buffer and pot maybe all I need and would keep the signal path even simpler. Also is there any sort of formula for figuring out the size of the choke and cap to use in a CLC type of supply? Ive downloaded power supply designer 2 but haven't had much time to to mess around with it and it looks to be made more for high voltage tube power supplies rather then low voltage SS?? .

Thanks
Frank

[analog_sa]

There is nothing simple about a 627/634 pre. Have you considered the number of active devices along the signal path?

By "simple signal circuitry" serengetiplains means something like a single active device, not two dozens

PSUD does not have any particular prefence for tubes. As far as formulas go, you'll find them in any electronics text. What simple formulas won't show is the behaviour of the ps with pulse signals, similar to music. PSUD is quite good at that.

[peranders]

Originally posted by analog_sa
There is nothing simple about a 627/634 pre. Have you considered the number of active devices along the signal path?

It's rather simple. Compare my headphone amp using OPA627, AD8610, OPA134 (or whatever) + BUF634. My power supply consists of LM317/337.