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Old 13th April 2013, 06:35 AM   #38041
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Quote:
Originally Posted by sonidos View Post
SE -
and telecomm relays...
ie: paid way too much for relays for no reason other than they were the most expensive ones in the catalogue, and therefore "the best".
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Old 13th April 2013, 06:37 AM   #38042
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I know the feeling... flipping through the Mouser catalogue, and see those $300 relays, and think, "hell yeah, make a preamp using THOSE".

freaking high school, right there.
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Old 13th April 2013, 06:37 AM   #38043
qusp is offline qusp  Australia
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and a bad passive design would have AC in the BOX John? I have not seen such a device ... are you expecting a significant piezoelectric effect from such an expensive switch? if not what other effect might a small amount of vibration cause in a large passive control? and how exactly does selected areas of damping material on some of the flat surfaces alone, prevent this effect?

you must have different meanings for the words clean and direct over there in the USA? how else would you wire up a control of this type? apart from, more directly...

as discussed, the fact they are not bundled means there is more likelyhood of ground loops because it makes a more effective aerial and coax/foil will do nothing to avoid EMI

Quote:
Originally Posted by John Curl
IF I can get a constructive word in to this discussion: Let's see what is GOOD about this passive design.
First: No AC in the Box
Second: Thick walls with added damping.
Third, Clean, direct design with first class volume control and pretty good looking switch.
Four:Wires are separated and not bundled.
If I had not worked on the Blowtorch project, I would have prefered a passive preamp much like this one.

Last edited by qusp; 13th April 2013 at 06:39 AM.
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Old 13th April 2013, 06:40 AM   #38044
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Admit it, the volume control in that passive is a PEC with fancy case over it...
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Old 13th April 2013, 08:33 AM   #38045
S.A.G. is offline S.A.G.  Italy
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A passive attenuator done right:

Weiss :: High End : ATT202 PASSIVE ATTENUATOR

No AC in the box, just 12VDC. No DC as well if you can live without the remote. Single input.

Cheers

Giorgio
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Old 13th April 2013, 08:40 AM   #38046
PMA is offline PMA  Europe
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Another "toy":
Attached Images
File Type: jpg passive2.JPG (153.5 KB, 142 views)
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Old 13th April 2013, 08:40 AM   #38047
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The wiring on John's example is unnecessarily long. Put a GSM phone near it when it's searching for a tower and let me know what you hear. Most amps have the token "RF filter" with some lame 0.01 uF cap but really have never tested it.

Last edited by chris719; 13th April 2013 at 08:43 AM.
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Old 13th April 2013, 09:45 AM   #38048
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Quote:
Originally Posted by S.A.G. View Post
done right
Not enough wires.

http://www.stereoknight.com/photo/si...ide%20wire.jpg
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BOXES for crying out loud
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Old 13th April 2013, 10:37 AM   #38049
PMA is offline PMA  Europe
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Yes, they must be long and unshielded.
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Old 13th April 2013, 11:53 AM   #38050
SY is offline SY  United States
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Quote:
Originally Posted by S.A.G. View Post
A passive attenuator done right
Looks nice. I'm afraid to ask the price...

But let's not lose the forest for the trees- all the units we're talking about here are unity gain, which is correct for modern sources. Line stages with gain are an accretion from the '60s. Steve's circuit has some gain from the input transformer because of some oddball headphones' requirements, but for line-stage-only use, one could certainly use a 1:1 input transformer.
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