Talk:L pad
From Wikipedia, the free encyclopedia
 |
This article is within the scope of the Professional sound production WikiProject, a collaborative effort to improve Wikipedia's coverage of the technology, equipment, companies and professions related to professional sound production. If you would like to participate, you can visit the project page, where you can join the project and see a list of open tasks. |
| Start | This article has been rated as Start-Class on the assessment scale. |
[edit] "Rheostats" or "Potentiometer"
A recent editor changed "An L pad is a special configuration of rheostats" to "...special configuration of potentiometer" (emphasis added). I've reverted this because I disagree with this change on several counts:
- It's still conventional to refer to the two-terminal device as a "rheostat". You'll even see potentiometers referred to as "rheostats" when the wiper is shorted to one end so that the pot operates purely as a variable resistor and not as a voltage (potential) divider.
- The editor made potentiometer singular. Grammar aside...
- There's no configuration of a single potentiometer possible that performs the function of an L-Pad.
Atlant 19:02, 12 February 2007 (UTC)
- Traditionally, the word rheostat was used to refer to a variable resistor in DC applications. Potentiometer was used for AC applications including audio, where the device presented an impedance (resistance plus reactance). Common usage over the years has of course mangled this distinction. I don't have time to track this down and verify it, so help yourself. ... Kenosis 19:59, 12 February 2007 (UTC)
[edit] Switched L pad
There are also switched networks using fixed Rs and typically a rotary switch.
—Preceding unsigned comment added by Tabby (talk • contribs)
- Please feel free to be bold and add this to the article!
[edit] Valves vs. transistors
"This constant-impedance load was important in the days of vacuum tube power amplifiers because such amplifiers often did not work efficiently when terminated into an impedance greatly different than their specified output impedance. Maintaining constant impedance is less important to modern amplifiers using solid state electronics, so L pads are rarely seen today."
Is this really valid? Tabby (talk) 05:28, 3 January 2008 (UTC)
- Umm, yes? Why do you not think so? Seriously, transistor amps have output impedances that are a small fraction of an ohm so they're happy driving any nearly-resistive load across a wide range of impedances. This was definitely not true for vacuum tube amps; for example, they had a nasty habit of roasting the screens on their output tubes if you tried to run them into too-high an impedance. Hence the L-pad; that substituted more and more of a dummy load as it inserted more and more resistance into the speaker path.
