How to improve power supply?

Ptss, how do you know it is inadequate? Most likely it is linear power supply followed by voltage regulators. AFAIK nothing changed in design or available regulators since mid 90s. There are few areas that might bring improvement. It might be possible to replace power supply caps with better ones, replace rectifier with one that has soft recovery diodes, add high frequency filtration of input voltage - either external (power conditioner) or internal (metal box modules or power socket with filtration). It is also possible that your pre has fine power supply but something else deficient. Why not to sell it the way it is?

The power transformer. Look into Plitron transformers. This update could be HUGE in clarity and dynamics.

If your power supply does have regulators, replace them with Bellesons, which are much quieter(http://belleson.com/download/Superpower_datasheet.pdf). Replace the rectifiers, or bridge, with with either HEXFREDs or Schottky diodes. Parts Connexion offers small PC boards, for building your own bridge with discrete diodes(if needed). Your filter capacitors could probably use a freshening up. Why not increase the capacitance, and pick up some dynamics? Keep that increase to 20% or less.

Hi K.
I know it's deficient because of the "inordinate" gains I obtain from using a 'combination' of ac power isolation & conditioning devices bought to enhance my listening. I am using -and need to use- an Equitech 2Q balanced transformer, MIT AC2 & AC1 reference power cords, and MIT Z Stabilizers--all to excellent effect. Spectral advertised the DMC 20 separate power supply as very effective - and it is the size of the preamp control unit; however I don't find that it is good in the real world (knowing nothing of lab tests/performance). Perhaps it's excellence is in it's ability to allow me to hear the gains by my power products? But, I expected it to provide quite clear power on it's own. Do I expect too much?

Thanks Ja. As you see above I am using the oversize 2Q Equitech unit to provide balanced power. I appreciate your PLITRON suggestion however EQUITECH products are being used by NASA and Ames Research Centre so the quality must be there. Also, I note BETA Transformer Technology Corporation is providing the same to NASA and Military.

09-17-14: Ptss
Hi K.
I know it's deficient because of the "inordinate" gains I obtain from using a 'combination' of ac power isolation & conditioning devices bought to enhance my listening. I am using -and need to use- an Equitech 2Q balanced transformer, MIT AC2 & AC1 reference power cords, and MIT Z Stabilizers--all to excellent effect.

this is a totally wrong assumption on your part. Even if you improved your in-chassis power supply, you would still need the AC isolation & the Equitech. Almost all the power & pre power supplies are unregulated so they are quite sensitive to the grunge on the AC power coming out of the wall socket.
The AC isolation & the Equitech unit is cleaning up the AC power coming into your electronics & it will still need to be in place after you upgrade your pre & power supplies.

Now, your power supply caps probably need to be replaced as correctly suggested by Rodman99999 simply due to the electrolytic dielectric material drying up over a period of 20 years. You could also gain by using HEXFRED rectifier diodes, I agree with this.
But you will still need the AC isolation & Equitech after all these upgrades.
IMO you could get rid of the AC isolation & Equitech if you had a regulated power supply (like a SMPS used in many class-D amps). A regulated power supply will maintain regulation over a wide range with very little output ripple & will also have good load regulation (i.e. minimal output voltage changes when the load current suddenly changes. Sudden changes in load current are expected as a normal when listening to music which is quick moving signal).

Ptss - Don't get too wrapped on what is being used by NASA, NOAA, NSF, etc. We are talking about audio systems, not GHz telecommunication systems to Mars. The Plitron will dramatically outperform the kiddy toy power transformers in 90% of those used in preamps of the 90s and later.

Thanks Bomb. I don't want to start a disagreement but in my understanding regulation does not provide "clean" power. It provides a degree of stability, ie regulation within given parameters. I may not be up on the latest facts so I will do some research before commenting further. When I complain the PS is inadequate it is based on the statements by the products representatives when I bought the units new-- that the PS made the pre virtually immune to ac powerline disturbances(noise). Oh well, I will look into the info that has come into this thread and probably have more questions. I'm not in the least interested in technical aspects but a degree of self education seems helpful in this hi-fi / well , music listening hobby. Thanks for your input.

Like many other electronic components; regulators generate noise. A number of ways to address that noise have been discussed and tried, by hobbyists and companies. ie: (http://www.edn.com/electronics-blogs/the-practicing-instrumentation-engineer/4422750/Simple-circuits-reduce-regulator-noise-floor) (http://www.diyaudio.com/forums/solid-state/1437-reducing-noise-voltage-regulators.html) (http://www.belleson.com/comparenewclassd.php) (http://www.belleson.com/compareburson.php) (http://www.ti.com/ww/en/analog/tps7a30/index.shtml?DCMP=hpa_pwr_tps7a30&HQS=Other+OT+tps7a30-bt2)

Mu metal the transformer. Magnetic fields are Bad with a capital B.

Hi Rod. My biggest efforts have been to remove noise. Equitech balanced power, MIT, Furutech. All to "great" effect. Love that silence.

YES, Mr P: That silence reveals the truth of the saying, "You don't know what you've got, 'til it's gone!"

Geoff, I don't understand.

Ptss, the magnetic fields, the induced magnetic fields produced by the transformer are bad for the sound and extend all around the transformer. Doesn't it make sense to get rid of these stray magnetic fields for once and for all?

Geoff, I understand and agree with the goal of eliminating stray magnetic fields; but I don't understand 'how' to do it.

How should I "Mu metal the transformer"?

Use toroidal transformers - very small magnetic field outside.

All transformers should be wrapped with one or two,layers of mu metal, a highly permeable alloy. Toroidal transformers are no exception. In addition, if feasible, should be decoupled from the chassis by removing the bolt and by placing a layer of cork beneath the transformer, isolating the sensitive circuit boards from the transformers.

Geoff Kait
Machina Dynamica

Good morning Geoff and a big thank you. Listening to classical gets better for me with every refinement. I will look into Mu metals to find the most appropriate and post it here. Using the cork makes perfect sense. Maybe there's a sandwich with cork that can be more effective. Looking into it. Enjoy the day :-)

Try a couple sheets of Sorbothane, with the cord between. Be certain that the bolt(s), holding the x-former, remain(s) free floating(isolated from the chassis) as well. Good info: (http://www.sorbothane.com/standard_product_guide11.php)

Keep in mind, if using MuMetal sheet; If it has to be bent(to
any great degree), annealing in a hydrogen atmosphere is
recommended, to restore the grain structure/permeability.
MuMetal foil is also available, if you can arrange a way to
surround the transformer with it. The foil doesn't require
annealing, unless severely formed or heliarced. One source:
(http://www.lessemf.com/mag-shld.html)

Thanks Rod, that makes sense. So basically I take it there should be 'isolation' material as a "washer" between the afixing bolt head and transformer surface as well as under the transformer.
I am going to check the torque required to loosen the bolt, which will be more than it needs to be retightened. Thanks for the SORBOTHANE idea. Coincidently I've read a bit about it lately and it sound good to me. If it's good enough for NASA and the Liberty Bell--it's good enough for me!

I've use Sorbothane, in a number of applications. A great product. The bolt can contact the transformer, but needs to be isolated from the chassis(or vice versa). Nyloc nuts and flat washers are good for maintaining the position of your transformer, and keeping the nut on the bolt, without having to tighten them all the way down and transferring vibrations. ie: (http://en.wikipedia.org/wiki/Nyloc_nut)

Thanks Rod.

Rod, finally had time to check Wiki article. Very informative and food for thought. Thanks again.

Happy listening!

I've just come back to this post. Rodman, I'm finally getting around to my gear as I may need to send my pre back to Spectral for some type of switch for changing phase. I'll research your info again and post more soon.

Just read about GIRON from LessEMF.com. Any experiences?/ Comments?