Daven T attenuator/BA6A questions.

[Paultec]

A 3 pole switch is not a 3 deck switch.

The deck of a switch can have multiple poles or just one.

The number of decks is like have multiple switches on one switch, a bit like having dual/triple pots.

Hope that helps.

Paul

 

[DaveP]

Letterbeacon,

Unless you are trying to totally recreate a Daven, this arrangement, with a simple Lorlin 2x6 way rotary switch does the job on my BA-6A.
http://www.groupdiy.com/index.php?topic=44312.0

The Pads are further down the page.  The resistors were 2.5 ~7W wire wound Vishay from RS.

They can handle the full 10W if they have to and present a very close 600 ohm load.

best
DaveP

 

[letterbeacon]

A 3 pole switch is not a 3 deck switch.

Thank you, I thought as much, but because I couldn't find any 3 pole 6 position rotary switches anywhere I was starting to think that maybe 3 deck and 3 pole were the same thing.

Letterbeacon,

Unless you are trying to totally recreate a Daven, this arrangement, with a simple Lorlin 2x6 way rotary switch does the job on my BA-6A.
http://www.groupdiy.com/index.php?topic=44312.0

The Pads are further down the page.  The resistors were 2.5 ~7W wire wound Vishay from RS.

They can handle the full 10W if they have to and present a very close 600 ohm load.

best
DaveP

Thanks Dave, I was actually looking at your schematics this afternoon.  I'm still trying to get my head round all the different types of attenuators -what sort of attenuator is your output pad?

Would it be suitable to use as an output attenuator on a mic pre?

Thank you.

 

[DaveP]

Hi Letterbeacon,

It is a balanced U pad and is simple to calculate as it's just a voltage divider dropping 6dB/position.

It can be used on the output or input of any balanced amp.

This site is useful:-

http://www.uneeda-audio.com/pads/

This type can also be used as an input pad too.  You will notice that for 6db drops the resistance between the poles keeps halving.  Say you wanted 2 x 25k for the BA-6A input, the total adds to 50k, therefore, for a 6dB drop the 2nd position will have to add up to ~25k, the 3rd to 12.5 or 13k, the 4th to 6.2k and so on.  You don't have to use 6dB drops but they are ideal for getting you in the right ballpark.  The exact values are not critical as long as they are the same on each section to maintain balance.  Use 1% metal film types and measure matching pairs if possible.

best
DaveP

 

[letterbeacon]

Thanks Dave, I think I'm slowly getting there now!

The reason I couldn't immediately identify which type of attenuator pad you used is because I couldn't work out on your schematic which resistors are the equivalent of R2 in the uneeda schematic.

So the difference between a U attenuator and a bridged T attenuator (which I've seen recommended elsewhere) is that you use a U attenuator when you don't need to change the impedance.

Thanks for your patience!