v272 into a 19" rack

[digichild]

i am about to put a v272 in a 19 " rack...with some xtras of course (gain pot,overload led...)
i am wondering if i can leave the mu-metall box off,or do i get a hum from the toroidtrafo?

 

[mig27]

I once saw pictures of the guts of a 19" rack with two V672 preamps, built by marquette audio labs.

They didn't use the original mu-metal housings of the pres.
But they had the PSU section shielded with a layer of bent steel.

An obvious alternative would be an external PSU...

My 2 cents.


Michael

 

[Rossi]

Actually, I don't think it is mu metal. I may be wrong, but I think it's just plain aluminum. You do of course leave the cover on the audio transformers - that's where they do use mu metal.

Toroidal power transfomer in the same 19" housing shouldn't be a problem as long as the V272 isn't in close proximity. That said, I left the aluminum cover on my V272 and just screwed the whole thing to the back plate of the housing. From the inside of course ;-)

It's probably a good idea to look where the power transformers of the units above and below the V272 are, just to make sure they're not directly under or above your V272 audio transformers. Usually power transformers are on the right side (seen from front), but some manufacturers think they must be different in everything...

 

[Rob Flinn]

Actually, I don't think it is mu metal. I may be wrong, but I think it's just plain aluminum

I have had V676a, V672/2, & U373 on my bench recently & I think the cases are just regular steel

 

[Rossi]

My V272 case definetely is not steel.

@ digichild: Did you do the gain pot mod the way I told you I did mine or did you do it differently?

 

[digichild]

[quote author="Rossi"]My V272 case definetely is not steel.

@ digichild: Did you do the gain pot mod the way I told you I did mine or did you do it differently?[/quote]

thanks for your input...at the moment i still collect infos-want to start to build on saturday everything in a one unit 19" box...i ordered a big box of 50 pots from http://www.pollin.de/shop/shop.php to find out which value works the best :grin:

 

[mig27]

FWIW, I just applied the variable gain of my V272's and ended up using 100k pots in the feedback loop. This gives me roughly 0 ... 50 dB gain.

Cheers.


Michael

 

[digichild]

[quote author="mig27"]FWIW, I just applied the variable gain of my V272's and ended up using 100k pots in the feedback loop. This gives me roughly 0 ... 50 dB gain.

Cheers.


Michael[/quote]

thanks for the info,at the moment i am still waiting for the trafo:then i can start to build everything together...

 

[jensenmann]

thanks for that link to pollin. The 19" boxes are cheaper than from Benkler! What material is the frontpanel made of? Is it pulvercoated?
Jens

 

[rafafredd]

There are some old siemens and telefunken stuff that are shielded in Big Mumetal cases.

 

[digichild]

[quote author="jensenmann"]thanks for that link to pollin. The 19" boxes are cheaper than from Benkler! What material is the frontpanel made of? Is it pulvercoated?
Jens[/quote]

yes pollin is good sometimes...what you mean by pulvercoated?
to me the front looks like "normal " grey aluminium...

 

[jensenmann]

pulvercoated heißt pulverbeschichtet. Die schreiben auf der Page daß die Gehäuse pulverbeschichtet sind. Ich wollte wissen wie die Frontplatten sind (Alu natur, eloxiert, oder auch Stahl wie das Gehäuse, ebenso beschichtet). Vielleicht kannst du mir auch sagen wie dick die Frontplatten sind.
Vielen Dank
Jens

 

[digichild]

[quote author="jensenmann"]pulvercoated heißt pulverbeschichtet. Die schreiben auf der Page daß die Gehäuse pulverbeschichtet sind. Ich wollte wissen wie die Frontplatten sind (Alu natur, eloxiert, oder auch Stahl wie das Gehäuse, ebenso beschichtet). Vielleicht kannst du mir auch sagen wie dick die Frontplatten sind.
Vielen Dank
Jens[/quote]

hi jens
dir frontplatten sind dünn,schwarz und taugen somit nix-ich verwende die von schaeffer
gruss digichild

 

[digichild]

[quote author="mig27"]FWIW, I just applied the variable gain of my V272's and ended up using 100k pots in the feedback loop. This gives me roughly 0 ... 50 dB gain.

Cheers.


Michael[/quote]

did you xchange r15 or r16?