Regulated Power supplies

[khush]

I have a cyrus amp to which I added the optional regulated psx-r power supply, the result was a significant improvement in sound quality. Whether this is just due to the earlier stages of the amp having more stable cleaner rails I don't know.

It is suprising that more designers don't regulate the supply to the input and driver stages of their power amps. The Pass A75 uses additional voltage doubling rectifier circuits on the main windings which seems a neat way to avoid having to provide extra windings or taps on the trannie.

Why more manufacturers don't provide add-on regulated power supplies is suprising. It would seem to make good commercial sense to provide an easy upgrade path to existing customers.
It certainly works for Naim and their line level power supplies, just look at the prices they charge , £725 for a transformer smoothing caps and a couple of TO3 3 terminal regs and they sell them by the bucket load.
Khush

[analog_sa]

The regulation of the i/p and voltage stages supply brings sonic improvements not because of the inherent principle of regulation, but because it minimises the interstage interactions. As such it is an acceptable commercial comromise but for the ultimate multistage amp the best solution is to have independent power supply for each stage. I've found that a lot of simple amps change dramatically if built with 2 or 3 power supplies. The improvement IMO is larger than building them as monoblocks. Same of course, and maybe to a higher extent, is true of valve designs. Being mostly simple stages with no significant PSRR valve amps show real improvements with many power supplies. And no, multiple series pass regulators do not bring the same improvement.
Amazingly, even opamp circuits improve when each stage has independent supply. Years ago i built an opamp RIAA using split correction and 3 stages of amplification each with their own NiCd supply. The rhytmic abilities of this circuit exceeded everything i've built ever since.


peter

[chris ma]

Hello Folks,

Anyone wants to put your 2 cents in my pocket?

Power supply parts list

Transformer - PLITRON 300VA 22-0-22

Positive rail –
Bridge rectifier – MIC KBPC2504, not heat sink mounted, just suspend in air by transformer secondary output wires
PSU capacitors - 3 times BHC Aerovox ALT22A 15,000uF 63V bypassed with
ACROTRONICS KP1.72 100nF polypropylene each
Voltage regulator - LM388K, mounted on 0.5C/W heat sink

Negative rail –
Bridge rectifier – MIC KBPC2504, not heat sink mounted, just suspend in air by transformer secondary output wires
PSU capacitors - 3 times BHC Aerovox ALT22A 15,000uF 63V bypassed with
ACROTRONICS KP1.72 100nF polypropylene each
Voltage regulator - LM388K, mounted on 0.5C/W heat sink

Connects to amprefier PCB with
Quiescent Voltage set at 20V
Quiescent Current set at 4A
Power consumes approx. 200W at idle

After 1 hour power on:
What temperature would one expects the bridge rectifiers get to?
What temperature would one expects with the transformer?
What causes the temperature to rise with the rectifiers and transformer?
What is the life expectancy for such a power supply unit?
Besides mounting bridge rectifiers on heat sink or utilizing fans, any other options to lower the PSU temperature?

Regards,
Chris

[HarryHaller]

http://www.users.zetnet.co.uk/avondale/

NAPRegulator2.jpg towards bottom of page.

http://www.passdiy.com/pdf/zen-ver3.pdf
Zen Variations - Part 3: Active Supply Regulation

[planet10]

Originally posted by HarryHaller
http://www.users.zetnet.co.uk/avondale/

NAPRegulator2.jpg towards bottom of page.

Thank you for that URL. Very interesting stuff.

dave

[HarryHaller]

Forgot one.....

[Ren Hoek]

Hey man, why go to all the trouble to use Schottky diodes and leave the snubbers off?

Ren

[jan.didden]

Hey HH,

Neat setup. Slap on a couple of opamps and you would really have a winner...

Jan Didden


"If you don't know where you're going, any road will take you there" - Anonymous the Younger

[HarryHaller]

The schematic is from:

“A Power Supply Regulator For the Adcom GFA-555,” Kit Ryan, The Audio Amateur4/89

"Slap on a couple of opamps and you would really have a winner..."

If you can find on op amp with +/- 35 volts rails!

[Ren Hoek]

Hey man, Burr-Brown and Apex make them.

Ren