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Another several thoughts... (and if you don't believe in tweaking, I suggest you don't read this post!)

Jolida,

Provide or point us to more details on and post some pictures of your linear supplies & how they fit into your cMP case... That will help a lot in understanding what happened when you located your linears inside of the case.

But before I go into a few ideas, let me amplify something Dave suggested... If you want to learn a lot about practical power supply design, read up on what John Swenson has written. In addition to the thread Dave referenced, I suggest the following one on DIYHIFI.ORG: http://www.diyhifi.org/forums/viewtopic.php?f=15&t=1957 and also doing a search for posts by John on low-Z power supplies, mostly in the Tube DIY forum a few years back.

To reduce noise induced in your linear supplies, I can think of several things to try:

1. Use 'transformer-ringing snubbers' as John mentioned in the computer PS article Dave cited or the one I listed above from DIYHIFI.ORG.

2. If you aren't using good soft-recovery diodes (like MSR860's), change to them.

And of course, John Swenson's supply is a great solution. BTW, I believe it is his raw DC supply section (transformer -> snubber -> small cap -> choke -> larger cap) that does the supply noise reduction trick. I suspect that any good regulator will work well after this portion.



Then, I can think of a number of other causes for the sound differnces you hear with your linears inside of your cMP case:

1. How your wires are configured and dressed. For the least amount of radiated field, all wires should be twisted or braided with their opposite... Positive against related ground wire, the three wires coming out of a center-tapped transformer braided, etc. Also, route the wires so they are suspended in free-air as far away from other wires, surfaces, and components as possible. If they must come near other wires, try to cross them at 90-degrees. If they have to touch a surface, use a small block of wood to hold them away from the metal. And take your AC inputs to the transformers out of the case as quickly as possible and especially minimize what they touch and come near.

2. If you haven't sexed your transformers (or don't even know what that is), let me know & I'll post references. But if you haven't and if your transformer's cores are electrically connected to the case of the cMP, circulation currents from your transformer's cores may be polluting your grounds.

3. If your cMP case is steel, then it is a good idea to leave the linear supplies outside... And eventually move all of your cMP out of the case. Magnetic steel cases and hardware (non-magnetic is a little better) tends to add a thinness & harshness to the sound.

4. How you have your linear's parts, especially the transformers mounted, will impact the sound. See the pictures of a couple of my supplies... Note that I've removed the steel cap around the laminations and mount the transformers to a wooden (in this case, bamboo) base using brass hardware & nylon standoffs. The brass screws/bolts go all the way through the wood base & are fastened with brass acorn nuts which act as small 'tiptoes' to better control vibration from the transformers. When I have some noticable vibration on a transformer I use compliant footers (typically from Herbie's Audio Products) to isolate them and their bases from the case.














5. Vibration damping of the case, bases, transformers, and supply components like the diodes, capacitors, and heatsinks will make a difference. I use a combination of Dynamat Xtreme (very good for resonant surfaces, but tends to emphasize & muddy bass a bit) and EAR SD40AL (more neutral than Dynamat).

While I do agree that the radiated field from your transformers can cause a problem too, IMHO these factors will generally make a larger difference in the SQ.

All of this does not detract from Dave's post or the information imparted there. But these are all pretty simple things you can easily do and try.

As for how to run wires from your supply into your P4 or Juli@, of course shortest is the best. You are better to have the regulator as close to the power consumer as you can manage. And if you do need to run wires, use a good conductor and insulation and twist/braid them as suggested above. 12-16 inches is not too bad.


Greg in Mississippi

P.S. Also read John Swenson's comments in these threads to better understand some of the complexities of the mechanisms that impact the sound quality of our cMPs and also help explain why things that seem like they shouldn't make a difference in SQ do:

http://www.audioasylum.com/cgi/t.mpl?f=pcaudio&m=90268

http://www.audioasylum.com/cgi/t.mpl?f=pcaudio&m=87759

http://www.audioasylum.com/cgi/t.mpl?f=pcaudio&m=89544


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