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Choke power supplys in Comp Symmetry BJT power amps

69.71.1.177

Posted on August 19, 2011 at 08:00:32
Granted I'm not a school trained EE. But it seems to me that just a bridge rectifier and two big caps 10,000 ufd, 100v computer grades and maybe a snubber .1 ufd is not enough CLEANING. Some fierce charging current is going on that makes a rather dirty noise floor. Why aren't chokes and solid state regulation (ripple filters) applied to BJT complemetary symmetry power amplifiers? Some say it eats up the damping factor like gang busters. Appears to me that each stage of an amp needs it's own bipolar power supply ripple filter, the input and driver stage more so than the output stage. Anyone used solid state regulation in the C-S BJT amp? Ray

 

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RE: Choke power supplys in Comp Symmetry BJT power amps, posted on August 19, 2011 at 16:25:32
djk
Manufacturer

Posts: 5667
Joined: June 17, 2000
A pair of big air-gapped chokes suitable for a SS amplifier will cost more than the power transformer. Other than that, it's a good idea.

Regulating the low-current voltage-gain stages will give 95%+ of the benefit of a fully regulated supply, and at a fraction of the price.

An Electrocompaniet Ampliwire would be an example of this.

Some of the Nelson Pass DIY designs used small air-core chokes (2mH~3mH) in a Pi fiter to reduce HF noise. Some of his commercial designs use a CRC with an inrush current limiter (around 1Ω cold) as the R.
Not 2 Big 2 Jail

 

RE: Choke power supplys in Comp Symmetry BJT power amps, posted on August 19, 2011 at 17:07:01
Charles Hansen
Manufacturer

Posts: 6035
Joined: August 1, 2001
DJK is right. Ayre used choke-input power supplies in our original five products, of which two were power amps. The cost of the power supply (which is a significant fraction of the entire product is doubled. Plus high-powered chokes create a high-powered mechanical buzz that customers hate.

There are other ways to skin that cat that don't have the drawbacks of chokes. Please also note that there is a BIG difference between a true choke-input power supply and a power supply with a choke. The latter is more of a gimmick, created largely to give the marketing department something to spin.

 

RE: Choke power supplys in Comp Symmetry BJT power amps, posted on August 22, 2011 at 02:43:43
kurt s
Audiophile

Posts: 1137
Location: California
Joined: October 12, 2009
"Please also note that there is a BIG difference between a true choke-input power supply and a power supply with a choke. The latter is more of a gimmick, created largely to give the marketing department something to spin."


This is truer for a lower impedance high capacitance PS for SS and OTL amps. For high impedance amps, OPT style tube amps, the CLC filtered L component is much more useful: smaller lower current chokes, a higher order and more complete filter for 100-120 Hz as especially SET amps have poor PSRR. Less important always with balanced design.

 

Kurt: Do youhave schematic examples of a properly designed choke input PS( +-100v) for a SS amp?nt, posted on August 23, 2011 at 09:06:21
nt

 

RE: Kurt: Do youhave schematic examples of a properly designed choke input PS( +-100v) for a SS amp?nt, posted on August 24, 2011 at 01:12:42
kurt s
Audiophile

Posts: 1137
Location: California
Joined: October 12, 2009
No, but it's the same principles applied. The critical inductance, the voltage expected with margin, the regulation improved, etc. The complete formula never changes, but the values entered will. Then there's practical matters. For a complete analysis, simulators can show a lot in the different cases.

For one case, use typical tube PS LC values. For a given sized current draw and capacitance in the PS, change the values expected for a SS amp, too. Try different values and see the simulated results. Do not forget to put in the correct R values in the L's.

 

Cello used a choke in their Performance Amplifier, posted on August 28, 2011 at 08:30:45
stellavox
Audiophile

Posts: 216
Joined: June 23, 2004
Single unit with two windings - Does this make any sense?

Was as big as the power transformer itself.

No idea of the millihenry? value. Contacted the manufacturer with the part number but they wanted $1000 to search their files!

Charles

 

RE: Cello used a choke in their Performance Amplifier, posted on September 1, 2011 at 07:20:41
e.goewie@hetnet.nl
Audiophile

Posts: 49
Joined: September 7, 2002
Hello,
I am planning to order the latest virtue amp called the threee as soon as it is available. In the past i did have an hiraga solid state amp with did use 200mh 2.5A 1ohm chokes in the power supply. I wanna try to make a single rail power supply for the three. I did ask some questions on the virtue site but no answers so far.
If i remember correctly the best supply would use 4*12 volts battery to get 55 volts or a 48 volts switching power supply.
I have a transformer that has a secondary winding rated 39 volts at 9 A. Hammond does have some high current chokes but i don't know if they have enough inductance to make a true choke input power supply. I think the current drawn by the amp will not be stable like an hiraga amp. So maybe first a cap after the rectifier. Anyone likes to share some ideas? Greetings, Edward P.s i do have some 400 millihenry 2 A 4.2 ohm chokes but i think their resistance is to high. Hammond has an 150mh 3A and 1 ohm.

 

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