• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Has anyone built a PS like this?

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Choke input supplies have been in use since at least the 1930s. I guess I don't see anything innovative there other than the lack of proper snubbers. What am I missing?

edit: If you're interested in choke input supplies, go to Radiotron Designer's Handbook where they are covered in great detail. Much of the article you linked to is total bosh, but there are real advantages (and disadvantages) to choke input filters.
 
I have tried it and liked it; but:

1) it produces a much lower voltage

2) It makes my choke buzzzzzz

If you can design around these things, by testing your choke for noise and buying a higher voltage transformer, then its probably a fantastic idea, especially for a single ended amp... A choke input power supply will probably be better in terms of voltage and current regulation.
 
Choke input supplies have been in use since at least the 1930s. I guess I don't see anything innovative there other than the lack of proper snubbers. What am I missing?

You're missing the point of the wonderful innovation of using a choke-input power supply in HIGH-END audio equipment. All of those $12,000+ amplifiers previously had power supplies made up of $3.69 worth of parts. Now that this guy has taken the bold step of using $78.50 worth of parts, the price of the equipment can be jacked up another $6000.00.

John
 
Power Supply

The often overlooked weak link of many amplifiers, both tube and solid state is the power supply. In any amplifier the power supply is a trade off between cost and size vs performance. Even if cost is not a concern size and weight is. When I designed and built the 845SE, I decided early on that if I put everything on one chassis, using the transformers that I wanted, I wouldn't be able to lift the amp. For the details see
http://www.tubelab.com/845_power_supply.htm

One of the advantages of using an external (or seperate) power supply, is that it allows the use of larger transformers and capacitors. In most cases a physically larger transformer (of the same voltage rating) will have a lower internal resistance because it is wound with heavier wire. The use of higher quality capacitors is important because they have a lower equivalent series resistance, ESR. Most often this means a larger capacitor, especially if oil or film caps are used.

The other main advantage of an external power supply is that the main source of hum is removed from the amplifier. Think about this, If there is NO AC in the amplifier (that includes current induced by a ground loop), there can be NO hum.

If you get the picture that the power supply is important, you are right. This is really important in a single ended amplifier, because of its inherently low rejection of power supply noise, PSRR. No power supply is perfect but the ideal power supply will have a zero internal resistance for ALL frequencies from DC to above 50KHz.

Too often a large capacitor is added to the output of the power supply in an attempt to lower the total ESR. This is not a bad idea, but the ESR of a capacitor is often inversely related to size. In my experience it is best to put your best capacitor right at the output transformer. This usually means on the amplifier chassis. On the 845SE the red lead from the output transformers connect directly to a large oil cap.

You will notice that up until now, I haven't even mentioned the circuit. Yes the circuit is important, but the quality of the components is far more important. These circuits don't look much different than those found in most any old vacuum tube electronics book. There are advantages and disadvantages to most any circuit. As pointed out previously, a choke input power supply will have better regulation than a similar sized cap input power supply. A good quality choke with a low DC resistance must be used.

I noticed that in these schematics the outboard power supply is often connected through the existing power supply filter. If the existing components are of inferior quality then their characteristics are added to the characteristics of the external power supply. If you are connecting up an external power supply to an existing amplifier, I would connect it at the red lead of the output transformer, bypassing the existing filter. If you are building a new amplifier from scratch, pick the power supply design, then choose the best components that you are willing to buy, then figure out if you can fit the power supply and the amplifier on the same chassis.

I usually breadboard an amplifier design using an external bench type power supply, then I design a power supply for the amp. See http://www.tubelab.com/PowerSupplies.htm for details.
 
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