How come chokes arent common with SS psu?

[imperfectcircle]

Is there any reason besides maybe cost that chokes dont seem to be very common in power supplies for SS audio equipment but in good tube amps and preamps you always find a CLC type power supply. IM a newbie when it comes to this stuff, I have built quite a few kits, but its only recently that ive started trying to learn about how circuits work and im even taking a basic electronics course as an elective at college this semester. Im really trying to learn about different power supplies and how they effect the sound. I built a very simple CMOY type headphone amplifier to experiment with so I could learn more about opamps and power supplies. So I am sorry if this is a dumb newbie question Im just trying to learn as much as i can about power supplies, mainly to power opamps in a preamp as my next project is going to be either a simple Opa627+Buf634.

[cliffforrest]

It is all about supply current.

Oversimplifying:

Tubes need to run at high voltage. For a given output power and effeciency the supply current will be a lot lower than for an equivalent SS amp which can run at a much lower supply votage.

The amount of iron rquired for a choke is a function of the current running through it below its saturation point.

Chokes for SS supplies would be huge, heavy and expensive.

[imperfectcircle]

What about for lower powered power supplies to power an opamp , id like to come up with a very good clean power supply for the opa627+buf634 preamp id like to build. I saw a common mode choke used between two caps before the regulators to power the opa627 on this DAC
USB1543 DAC

and was thinking about something similar to power my pre-amp. What do you think?? Is there a better idea? Ive seen so many differant ideas for powering opamps its hard to chose which direction to go. I also like this idea of pre-regulating
Naim preamp mods

Ay other ideas I should be looking at??
thanks
Frank

[Pit Hinder]

'Circle,
a very simple reason, and you guessed it. Money. Money and design. It's inside, the customer can't see it, so why bother? If you can get, let alone afford, a decent choke - go for it!
Pit

[poynton]

Originally posted by imperfectcircle
....................I also like this idea of pre-regulating
....................

Hi.

This is an excellent idea.
Search the CD63/73 mods thread for raygulator for results.

Here is the pdf of +/-12v raygulators

http://www.diyaudio.com/forums/attac...amp=1168083193


Andy

[Panelhead]

Several solid state preamps use chokes in the power supply. A small value choke on the output of a 3 pin reg allows for large electrolytics to feed the circuits. And will provide the hf filtering that 3 pin regs lack.
Some large class A solid state amps also use chokes to filter noise. A C-L-C filter works very well if the resonant frequencies are taken into account.
The reason that you do not see more in solid state amps is that C-L-C filter work very poorly in class AB circuits. The choke is high impedance, plus it resists change in current. Exactly the opposite of what is needed for a class AB amp.
Since most amps run AB, chokes are not seen much. Ayre used them in the early days. I personally use them in my line level power supplies. And class A amplifiers.
A regulated supply works much better for class AB. But unregulated supplies also work very good if designed properly.

George

[imperfectcircle]

Originally posted by poynton


Hi.

This is an excellent idea.
Search the CD63/73 mods thread for raygulator for results.

Here is the pdf of +/-12v raygulators

http://www.diyaudio.com/forums/attac...amp=1168083193


Andy

What do you think of the dual regulator in the link I posted compared to this "super raygulator"??

Originally posted by Panelhead
Several solid state preamps use chokes in the power supply. A small value choke on the output of a 3 pin reg allows for large electrolytics to feed the circuits. And will provide the hf filtering that 3 pin regs lack.
Some large class A solid state amps also use chokes to filter noise. A C-L-C filter works very well if the resonant frequencies are taken into account.
The reason that you do not see more in solid state amps is that C-L-C filter work very poorly in class AB circuits. The choke is high impedance, plus it resists change in current. Exactly the opposite of what is needed for a class AB amp.
Since most amps run AB, chokes are not seen much. Ayre used them in the early days. I personally use them in my line level power supplies. And class A amplifiers.
A regulated supply works much better for class AB. But unregulated supplies also work very good if designed properly.

George

I was thinking more along the lines of putting the choke before the regulator, I never really thought about a choke following the reg, can you give me a bit more info on this technique. What kind/size choke and caps would I wanna use after the regs, on a +-12-15v power supply powering some opamps?

Thanks guys for helping out a newbie, this is what i really like about this forum there are lots of people with experience for newbies like me to turn to for advice and info It is greatly appreciated.

[Panelhead]

Use a 1 mH, 1 amp choke after the reg. Use a 100 ufd cap on the output of the reg. Load the choke with as big a cap as you desire. The choke will buffer the reg and prevent ringing.
Just putting a large cap on the output of a 3 pin reg can create problems with stability. The little passive does make the resulting supply higher impedance, which can be an issue.
In one of my linestages, there is a 1 mH choke per rail, the caps at the end are 55,000 ufd. This is extreme, 2200 - 4700 ufd is more common. The idea is to provide passive noise rejection to make up for the dropping noise rejection of the active devices.
When using these large caps, always use small value caps close to the circuit. This provides the local decoupling needed for a fast circuit. To prevent ringing here, I use a resistor less than 1 ohm in series with the cap to damp ringing.
If putting an amp together, I like to add 22 ufd Panny FM caps right at the output devices. These are fast enough to decouple, have enough impedance to prevent ringing, and can supply some current if required. To my ears they always improve the overall sonics.
Good luck in building!

George

[imperfectcircle]

I just wanna make sure I got this correct, after the reg you use a small cap like you usually would(10-100uf) then the inductor and then a bulk electrolytic cap?