[till]

As one might imagine, space requirements are an issue. Are there any reasonably priced stepped attenuators on the market with a height of about 25 mm or less? I have come across a model that has a height of only only 9.8 mm, width is 30 mm (part number 327-686 at http://rswww.com / http://www.rs-components.de , direct links won't work, sorry). It is a modular system. 12 steps per module is the maximum. The axis has a diameter of only 4 mm, so an adaptor would be needed for using a standard knob. Having no experience whatsoever with stepped attenuators, I am guessing that one would need two 1x12 modules for stereo.
Can this thing be used as a stepped attenuator at all? Are there better solutions?


EDIT: Part no. 327-692 seems to be for the single 12-step modules.

 

[Edwood]

That's very cute.

They're both listed as one pole 12 way, or two pole 6 way.

Wouldn't be a lot of volume levels.

-Ed

 

[till]

Quote:

Originally Posted by Edwood That's very cute.

Yes, indeed

Quote:

Originally Posted by Edwood They're both listed as one pole 12 way, or two pole 6 way. Wouldn't be a lot of volume levels.

At that size, there have to be drawbacks... OTOH, I never listen at loud or even medium levels. 12 steps ought to be enough to cover my volume range. Of course, I wouldn't mind to have 24 or 36 steps or whatever and go until 0 dB attenuation, an amp that will produce a signal which is less loud than its input might seem goofy to sane people

 

[Edwood]

That is really going to limit how many different impedance headphones you'll be able to use, though.

Even 24 steps is barely enough for some headphone ranges.

-Ed

 

[kevin gilmore]

If you put in two of them, one could be coarse, the other fine, between
the two you could get 36 steps which would certainly be enough.

 

[morgan jones]

If you set the 12-position switch to 1dB steps, it would be 0 to -11dB. Adding a 12dB attenuator controlled by a toggle switch would extend your range to 0 to -23dB in 1dB steps. If you didn't mind using two rotary switches, you could set one to ten steps (each 1dB) to provide 0 to -9dB, and the second switch could have six steps (each 10dB) to give 0 to -50dB, giving you a total of 0 to -60dB in 1dB steps. This is how attenuators were done in the days of analogue music lines.

 

[till]

Thanks for the input! I'll go for dual attenuators or a single one and a toggle switch, depends on what enclosure I decide on and what preliminary tests tell me about the range I need to cover for different headphones. What the heck, if I need two attenuators and they won't fit into the case, I'll just build an amp for low-impedance cans and another one for high-impendance cans (once I own one of the latter ones)

 

[morsel]

The description at RS says it is break before make, which means you will get nasty pops when you rotate it.

 

[till]

Quote:

Originally Posted by morsel The description at RS says it is break before make, which means you will get nasty pops when you rotate it.

I found a thread on curing the pops with break before make attenuators, I'll try the proposed shunt resistor as a remedy when the project is ready for lift-off (in summer, hopefully). A tiny make before break attentuator would be preferred, but I didn't find anything yet.

EDIT: the cure is intended for rotary switches, not for attenuators as I first thought. As is my (novice) technical understanding, a very large resistor to ground won't weaken the signal significantly. Please correct me if I'm wrong.

 

[MonkeyMan]

I'd guess that if we could come up with a set of desired specifications, perhaps we could get a decent per-unit-cost from DACT, Gold Point, etc.

Obviously, this could be a relatively costly venture, but I think that is we could find someone willing and able to manufacturer such a beast, the portable amp market would buy them up like crazy.

That said, perhaps we should consult with the ultimate (IMHO) guru of ultra high-end tiny portables, none other than the widely known and respected Dr, Jan Meier.

I will e-mail him a link to this discussion. Can you say Meier PC v3.0?!

Let's entertain for the moment a target price point of $500 USD:

#1 add an insanely terrific "make-before-break" stepped attenuator (Roderstein resistors, but of course)

#2 eliminate the DIP switch bank, and hard-wire the output bias to Class A operation

#3 get rid of the "power on" LED

#3a in place of the "power on" LED, install an on/off toggle switch (but mount it so the orientation is front-to-back instead of side-to-side)

#4 upgrade the electrolytic capacitors to Black Gates

#5 upgrade the wiring from the battery terminals to the board to Cardas internal "hook-up" wire

#6 get rid of the crossfeed toggle switch and instead give us a rotary selector labeled poitions 1, 2, & 3, to give use more cross feed choices (like the cross feed choices on the HA-1 mike)

#7 design all of this to fit into the existing PCII chassis dimensions

#8 offer as an optional accessory item a top-of-the-line "medical-grade" Elpac PS that comes factory terminated with the proper plug and voltage requirements

#9 whatever else anyone thinks would be "cool"

I absolutely LOVE my PCII, but wonder how much farther the design could be taken, given a significantly higher price-point.

 

[till]

My addition to #9: an aluminum case. I'm not really fond of plastic enclosures. And with the Bulgin battery compartments (among others), aluminum really is a better option IMHO.
Maybe you should start a new thread on this, if Jan is interested in thinking about and discussing such a project. I most certainly hope so