where/how to modify a power supply

Nope, not a BIY thread, just a question I thought Id ask that I havent seen asked on a forum before. (a question of 2 parts)

1)
Firstly, lets look at NAIM. They are famous for paying great attention to power supplies. Then, perhaps Border Patrol - who even modify power supplies in other peoples amps.

WHY modify the power supply in particular? Why choose this aspect of a CDP/amp to modify in particular?

2) (the bgger question)
Ok, so youve said WHY to modify it, but where and how to modify it. I mean - are there any common threads to the way that Naim do it and border patrol, and others who pay special attention to it? What makes the different power supplies in a Michell TT special? Whats in a QC to get me excited? Anyone tried power supply modifications of their own - what did you change to what effect?

Looking forward to you gents learned responses.


Cheers
Chris

 

chris,
as i only really am familiar with the way that naim do it i'll have a go at answereing from that perspective....

1) why modify a psu in the first place?
well amps are just taps they let a variable amount of power through to the loadspeakers controlled by a much smaller level of power. if either power level is compromised by poor noise rejection or regulation then the sound isn;t going to be as true to the origional as it could be.
as every piece of audio equipment (outside of the silly money stuff) is built to a cost there and there is usually a better (but more expensive) way of doing something this leads to one solution being upgradeable psu's.
Also i would imagine that allowing seperate power inputs for certain stages is a relatively easy way of allowing an upgrade.

as far as i know (and my knowledge is very limited here) a psu has the following major bits in it
1) a transformer - this can be impoved by increasing it's transient ability allowing better handling of dynamic swings. or pulling less feeds off of it.
2) smoothing capacitors. some think bigger is better however other belive that for a 'faster' sound you need a few smaller caps.
3) bridge rectifier - afaik turns ac into dc. component quality would be important i think (i belive it's 4 diodes) there is also something called a schottky bridge which is meant to be good but all i know is the name not what it is.
4) regulation - not really sure what this does but it sure is important and causes much wrangling where biy psu's are discussed.

any help?
cheers


julian

 

Simple answer here, clean, untainted power will benefit all the componants it feeds, they will have less 'Noise' to pass on down the chain, therefore cleaner and less grainy sound, with better dynamic transients, faster and more open sound.
There are power suppiles, and they are power suppiles, anyone can built one, building a good one that works is a different matter, why not try Andy Weeks on PFM (nice bloke, knows a fair bit about psu's) he could give you a few pointers, without expense, remember that quality regulators are paramount in supply circuit, maybe a potted Tranny or 2 as well. W.M

 

I've had a Q-Power upgrade done to my cdp, which i believe is some type of voltage regulation - is this along the lines of what you are discussing? It was done by the previous owner, so i have no idea what improvements, if any, it has generated. I've also been too busy to pop the lid off and take a look as yet.


Just found a link to the product:

http://www.audiocominternational.com/store/qpower.asp

 

Dino, they are high quality regs, just one small part of the psu chain and at £210 for a set some of our ferturnity may 'wince' a little, however they do have a benefical effect and quite markly so on a lot of equipment.but this is just regulation, they are very accurate regs, however you still need 'clean juice' coming into them as well IMHO.

 

Its intresting that you mention Naim, as I was under the misapprehension that Avondale did/do a lot of PSU mods on these units, and very good they sound afterwards too.

I think most commercial units are built down to a price, and most will benefit from simple upgrades to PSU and else where.

For instance I've a couple of sony units that have made huge strides post diode replacement using 11DQ10 schottcky types. The changes are in the same region of gains as an Op amp change. The mj520 minidisc was a dog out the box, but with a vast number of upgrades to components its now hard to tell source and recording.

Clean mains and clean Dc and plenty of it, is normally the key to good performance. Well one of them.

 

With reference to the Border Patrol PSU.

This is a PSU for Valve kit. There are 2 main requirements to a valve PSU.
1. Low Impedance
2. Low voltage ripple

The BP PSU provides this by using a choke of gigantic proportions. This item alone costs in the region of £150 (check out Sowter for transformer/choke prices). BP also use what is considered by many to be the best sounding valve voltage rectifier in the form of the GZ37. both rare and expensive.

Valve PSU do not need high value smoothing capacitors so can get away with the much better sounding polypropylene ones from LCR for example.

I have to say it is quite simple to design a very good valve PSU. However to design and make a truely excellent one is very hard and expensive and the only place I have seen a fully valve regulated and rectified PSU is in DIY applications.

Lee

 

Hi Chris,

Power supplies are very important to most pieces of hifi. They have to convert incoming 230v AC voltage to the lower (solid state & valve) or higher (valve) DC voltages. This is usually done with the aid of a transfomer which steps up or down the voltage. A rectifier which converts AC voltage to DC Voltage & a fliter (capacitor / inductor network) to give a smooth DC voltage.

The power supply has to supply the required current & voltage demands of the various parts of the circuit. These are different for different parts of the circuit in question. If a circuit tries draws more current, the power supply needs to be able to supply this without interfrence or dipping of voltage & with low ripple.

To get better performance in the power supply, the cost goes up. Better quality transformers, rectifiers, capacitors, inductors etc, cost money & also space. Also circuit bulid and layout help performance.

A lot of amps etc have shared power supplies. A better single supply will improve thing. Also a better step is for each part of the circuit to have it's own supply. By doing this will put the cost up but should improve the performance. Quality of the power is the key.

In power amps, the output stages will draw more current than the input stages. By giving each part of the circuit should improve things. Pre amps need low noise power supplies as well as ones that can handle the current demands.

Turntables need good power supplies to help turn smoothly, without chucking interference in the turntable system.

Cd players are just as demanding.

It is worth upgrading the supplies as the benefits are great as others have mentioned but he cost can go up.

Look at Naim equipment, power supply improvements are part the range. People like Avondale also show that power supplies can improve equipment.

There are many ways to implement all this and it may not be cheap.

For example, the Border patrol use a large power supply that is a choke input design. (Most supplies are capacitor input supplies). You don't see this as often these days as inductors are more expensive & these supplies are harder/ more expensive to build. But they can offer very good regulation & low noise. This one supply then takes over from the on board supply. The improvemets you hear are tightening of bass lines & greater stability of sound. The music flows and is easier to follow.

My Border patrol amp has three of these controlling the output valve, the input valves & one to supply the negative bias for the output stages.

Power supplies can be serious business.

SCIDB

 

Dean, how true you are sir

 

What great responses!
thankyou.

Anyone played with changing power supplies on Michell turntables? ... could I have a vested interest....errr...ummm maybe

Chris

 

so what does a regulator do? i understand the purpose of the other bits in a psu, but not that one. can anyone enlighten me?
cheers

julian

 

as the name implys it regulates the voltage,feed in a fluctuating voltage and in theory you should get a steady voltage out.it may also help in smoothing out the ripple as well