Balanced stepped attenuator vs. This

[wkbdgeorge]

Hey everybody,    question:  For tube audio stuff it seems that an attenuator before the xlr output after the transformer is useful in certain applications.  Ive read that a balanced stepped T pad attenuator is the way to go.... or if you can find a daven.  Well,  what is everyones thoughts on this?:

http://hairballaudio.com/shop/product_info.php?cPath=21&products_id=33

Its the attenuator for 1176s.  will that be good, or is that not the way to go?  Thoughts?    -G

 

[shabtek]

what pow'r needs to be burned? don't see where that pad-pot says.
nice, convenient part that will probably be fine
do you need balance? prolly not: overated for most of us

a box with a few of these and/or some stepped attenuators (0, -10, -20, -30...) can get closely there too.
Reference NYD.

 

[wkbdgeorge]

Well..... I do like the idea of balance.  Its never hurt me.  What kind of change in sound would putting this on the output of a transformer be? 

 

[emrr]

no change.  it's still balanced if you connect between hot and cold, and leave ground out of it. 

 

[shabtek]

emrr, does that not throw off cmrr?

I know functionally a t-pad generally does a fine job

 

[emrr]

CMRR; dunno, don't care anymore, since T's wired this way work great in my circumstance.  Certainly better than grounding a side!  Even then, fully unbal gear never gives me problems around here. 

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

http://www.groupdiy.com/index.php?topic=2192&start=0

related to CMRR, and this ap, in reverse; I argued a lot.  Point relating to floating transformer output or input. 

http://www.groupdiy.com/index.php?topic=14888.msg190942#msg190942

 

[PRR]

> does that not throw off cmrr?

"Shouldn't". If your receiver has great CMRR, you can ground one side of the source. When real receivers have imperfect CMRR, balanced or floating sources help. If the output is transformer, then it very-nearly "floats". The leakage is worst at high frequency due to stray capacitance (unless you have underground lines; then wet-insulation may be significant conductance).

It takes a very exceptional set of circumstances to make T-Pad "unbalance" be a problem. Working under a radio transmitter is one.

Anyway.... why would you WANT more than 3dB or 6dB pad after the transformer? Reason: to f*ck-up the signal with a too-too-hot level in the transformer, without smoking your receiver. If your signal is THAT hot and THAT f*cked-up, why are you worrying about noise?

 

[emrr]

If your signal is THAT hot and THAT f*cked-up, why are you worrying about noise?

Succinct