universal bridged-t attenuator boards

[plumsolly]

I tacked this on to another thread but thought I'd repost so it might get seen:

I've been thinking about a basic attenuator pcb that could be stuffed for any amount of attenuation in up to twelve steps (or maybe even 24) at whatever input and output impedance you chose and would fit a greyhill or lorlin pcb-mount switch. It would be a bridged-t attenuator. It seems like it would be really handy for a number of applications like after the transformer on a preamp or other piece of gear in order to drive it or even a (way-less-cool-and-useful-than-Igor's) rudimentary monitor controller (obviously this would require a pair or a 2 deck switch wired to two boards) you could also experiment with driving your console's two-buss a bit or whatever else. I'd like to have a rack of 6 or so attenuators that i could put in front of my converters to experiment with driving everything, just patch them in. chime in with your thoughts -Ben

 

[emrr]

I've had that in my head for a long time.  You should do it and get it out of my head.   Simple board that will fit on the back of a lorlin.   Use two as in NewYorkDave's design for more steps via ranging.  

Count desired # of steps and check the switch market.  At some point I suspect higher step counts begin to have similarly priced competition from existing hi-fi kit sources.    Goldpoint, etc. 

Didn't someone have a design here for a logic based programable type, and/or a relay based type?  Having flashbacks....

 

[Ptownkid]

I'd be willing to take this on, get em made, and keep stock.

 

[clintrubber]

I'd be willing to take this on, get em made, and keep stock.

Hi, that'd be nice, but please don't make the mistake that a few others (that will remain nameless) have made here before
of having to much PWTMOOI* ongoing, leading to delays'n'hassle etc  8)

It's of course not up to me, but to see a third person jumping on everything & getting into some hassle wouldn't benefit anyone I guess.

All the best,

  Peter

(*: projects with the money of others involved)

 

[Ptownkid]

I know what you mean, but I wouldn't want any money from anyone up front for something like this. I figured I'd offer to take the chance and stock something like this as most people are scared of getting a run of boards made, and I order lorlins in bulk already.

Cheers

 

[clintrubber]

Hi B,

Perfect, that's a more healthy sequence moneywise !

Cheers,

  Peter


[disclaimer-time]BTW, note I don't want to stab the nameless guys in the back, mighty fine jobs they did/do,
but certain aspects (as unintentional as these were) preferrably not repeated.[\disclaimer-time]

 

[Ptownkid]

Trust me, I know exactly what you mean, and i try and avoid money up front situations as much as possible. Makes things so much easier, truly.

Anyway, back on topic, let's dig up some of the other threads regarding bridged T's and get this discussion/design on track. ;D

 

[clintrubber]

Anyway, back on topic, let's dig up some of the other threads regarding bridged T's and get this discussion/design on track. ;D

Yep, let's attenuate. 

The coarse & fine NYD-design that emrr already mentioned sure looks like a good & economical way to go.
IIRC it also had an additional SPDT-loading switch.

NYD drew various ones, couldn't find his coarse&fine right away, but here's another (in essence half of the one we're looking for):

http://electronicdave.myhosting.net/miscimages/600bridgedt.gif

Bye

 

[Ptownkid]

Ah yes, i remember that one, I'll ask.

 

[clintrubber]

... click-click-click ...

 

[Ptownkid]

haven't heard back yet, haha

 

[NewYorkDave]

I didn't get any message.

I just scanned this thread, is one of these what you're looking for?

http://electronicdave.myhosting.net/miscimages/600ohmatten.gif
http://electronicdave.myhosting.net/miscimages/600bridgedt.gif
http://electronicdave.myhosting.net/miscimages/outputatten.gif

Later!

 

[clintrubber]

Thanks for the links & circuits Dave.


The proposed 'simple' & 'on the back of a Lorlin' would then mean
an unbalanced version of 600ohmatten.gif
by means of two identical boards with each a 2P6T M.B.B.

(It'd be tempting to provide for a balanced version as well, but it'll conflict with
the Lorlin-mounting)

I didn't check the E-XX resistor-ranges, perhaps there are a few
resistor-locations where it'd be good to have the possibility
for series or in parallel ? Might be nice to take that into account then.
I assume Dave checked that already, but there might be a few less
easy values.

Have a good weekend all,

  Peter 

 

[Ptownkid]

Ok, my brain hurts now, which one of those is the one were after?

 

[Ptownkid]

Just noticed the one you referred to clint...

 

[clintrubber]

bump ?  Handy to have these around

 

[Ptownkid]

I'll have a closer look at these soon, been busy trying to find work and keep our house...

The one we'd be best to look at is the one with two lorlins right Clint?

 

[clintrubber]

I'll have a closer look at these soon, been busy trying to find work and keep our house...

The one we'd be best to look at is the one with two lorlins right Clint?

Hi,

Hey, such attenuators nice to have around, but work & house more than nice to have around,
good luck there !

The fine- & coarse- approach NYD took would be most effective I guess, keeps the BOM down
and in addition it would facilitate keeping it at just one PCB-design (identical boards with each a 2P6T M.B.B. for either realizing fine or coarse).

As noted before, we might want to check the resistor-values. In case of certain weird or less easy values it might be good to prepare the PCB: adding a few more holes, enabling series or parallel to arrive at the desired value.
Or in case we want to mount everything flat each resistor-spot could be given an intermediate two interconnected holes, enabling series connection of two vertically mounted resistors.

Anybody other ideas ?

Bye,

  Peter

 

[Biasrocks]

A friendly bump.

Curious, if there's been any progress on this project.

Mark

 

[kazper]

by the time you source the rotary's that can do this in at least 12 steps have the pcb designed and add the resistors etc.. I think it would be best to pay the $40 to one of the two guys here who pimp the bridged T's here.

Just my 2 Cents.