[JohnR]

I'm wondering if anyone could relate their experiences with shielding for a phono preamp. Has anyone built a tube phono pre in a "wood side with Al top" enclosure and then later moved it into an enclosed metal box?

[sts9fan]

As in sheilding the whole box?  When I built my Pearl I used shielded mic cable for all the connections. 

[JohnR]

Hi - yes, I meant the box itself. Unsure as to how much shielding is actually needed in practice for this kind of circuit.

[sts9fan]

Is the power supply in the box?

[JohnR]

Ah, good point. Yes, that's the intent. I suppose I should worry more about that.

[Wayner]

Keep the power supply components on one side, preamp components on the other. Perhaps a steel plate between the 2 for some shielding. Steel, is a better shield then aluminum. Mu-metal is the best, but most expensive. Also insulate the input connectors from the metal.

Wayner 

[Dan Banquer]

Are engineering types and ex manufacturers allowed to comment in this thread?
d.b.

[sts9fan]

No need to ask

[Dan Banquer]

My first question is do you really need the case as a "shield"? If you live in an environment where you are close to transmitting antennas or you have other electronic gear giving off assorted interference then yes you do need a shielded case.

If that's not the issue then there may well be a safety grounding issue.

Can you volunteer any applicable information that might help to answer your question?

d.b.

[Speedskater]

Dan, I think that everyday we see more and more sources of interference. Soon our refrigerators and water heaters will be communicating to the power company or your PC.  An unshielded system will suddenly have interference problems at the worst possible times. Your guest has a new cell-phone or your neighbor gets a wireless system or a new communications tower gets turned on.

[Dan Banquer]

Dan, I think that everyday we see more and more sources of interference. Soon our refrigerators and water heaters will be communicating to the power company or your PC.  An unshielded system will suddenly have interference problems at the worst possible times. Your guest has a new cell-phone or your neighbor gets a wireless system or a new communications tower gets turned on.

I would generally agree if one lives in an urban or suburban area, but out in the country?????

I'll wait for more info on this one.
    d.b.

[Steve]

Hi - yes, I meant the box itself. Unsure as to how much shielding is actually needed in practice for this kind of circuit.

Hi John,

Yes, I have been working on a phono stage (separate line preamplifier) with external power supply and shielded, metal chassis phono section. Frankly I would not go any other way.

Good luck with your project.

Steve

[JohnR]

My first question is do you really need the case as a "shield"? If you live in an environment where you are close to transmitting antennas or you have other electronic gear giving off assorted interference then yes you do need a shielded case.

Hi Dan - thanks for responding. I guess that's the question I'm asking... I haven't built the preamp yet, just thinking ahead to chassis options for the next project after my line stage. I'm in a suburban environment but on the edge of the city; no transmitting towers close by and in fact I'm in a bit of a shadow for regular TV and cellphone transmission. I do have cordless phone and wireless networking in the house.

I'm thinking that perhaps I will go for an enclosed Al chassis (e.g. Transcendent Sound phono), as a reasonable medium between open chassis (e.g. Bottlehead) and Steve's fully-shielded choice. I may put the PSU in a separate chassis.