Question for electronics engineers

Larry Jamieson · Post by **Larry Jamieson** » 6 Oct 2004 5:47 am

A local church has a sound system with as speaker from the sanctuary sound system in the foyer. They would like to put a volume control on the speaker in the foyer. What kind of a pot should be used, and how will it affect the amplifier to have this speaker turned off on occasion? Thanks for your input. My electrical knowledge of this type is limited to replacing pots in guitars...
Larry Jamieson, Walton, NY

Jim Smith · Post by **Jim Smith** » 6 Oct 2004 5:55 am

I'm not an electrical engineer, but a rheostat can be used for that purpose. Radio Shack used to sell them, but I'm not sure if they still do.

John Daugherty · Post by **John Daugherty** » 6 Oct 2004 6:31 am

Larry, you will need an "L-pad". They are sometimes called speaker volume controls. They keep a constant impedance load on the amp output. Get one with a wattage rating to handle the power supplied to the speaker (probably around 20 watts). They are priced from about $20-$50.....JD

Ray Minich · Post by **Ray Minich** » 6 Oct 2004 6:37 am

Deleted, redundant. John's entry says it all & his hit as I was typing mine

[This message was edited by Ray Minich on 06 October 2004 at 07:38 AM.][This message was edited by Ray Minich on 06 October 2004 at 07:39 AM.]

John Daugherty · Post by **John Daugherty** » 6 Oct 2004 6:47 am

Is this a great site or not? Fellow steelers standing in line, waiting to help. Way to go Ray. Maybe you can help me someday......JD

Blake Hawkins · Post by **Blake Hawkins** » 6 Oct 2004 6:49 am

Larry,
What you need is an "L Pad" this is a specially designed attenuator which maintains a constant load on the amplifier as the volume is decreased.
A simple rheostat will not do that.
There is also the question of the amount of power to the speaker. An ordinary guitar volume control is only rated at 1/4 watt.
It will burn out quickly.
The "L Pads" come in 15, 50 and 100 watt ratings. Also in mono or stereo.
A source for "L Pads" is "Parts Express"
1-800-338-0531. www.partsexpress.com
The part number for a 15 watt, mono,8 ohm
pad is: 260-248. Price $2.35. (that may have increased since my catalog was printed.)

Radio Shack used to sell some low quality controls, but I couldn't find them in my RS Catalog.

There is another option depending on the design of your sound system. On the back of the speaker there may be a small transformer with taps labeled in watts. If your speaker is attached to a 5 watt tap, moving the wire to a 2 watt or 1 watt tap would lower the volume. You could install a switch to select the desired tap and thus control the volume.

Blake

Blake Hawkins · Post by **Blake Hawkins** » 6 Oct 2004 6:50 am

OOPs, I too was typing at the same time.

Sorry.

Blake

Larry Jamieson · Post by **Larry Jamieson** » 6 Oct 2004 9:09 am

Thanks you so much, to one and all for the quick response and the information I needed. This is a great Forum, people helping each other and sharing what they know. Thanks again, and be blessed!
Larry Jamieson

Ken Fox · Post by **Ken Fox** » 6 Oct 2004 9:46 am

If it is fact a 70 volt or 25 volt transformer, an Atlas AT-10 attenuator will work well. It is a single gang device that has an auto transformer to properly change the impedance for volume control. Rauland-Borg, Dukane, Bogen and Lowell Industries have the same device as well as L-pad for a straight 8 ohm application. Watch the L-pad, it must be able to handle thae wattage, or a fire can occur.

Will Holtz · Post by **Will Holtz** » 6 Oct 2004 10:24 am

When picking out an l-pad be sure to get one with a "log" or "audio" taper, not a linear taper. Otherwise the sensitivity of the knob will not be what you expect.

Jennings Ward · Post by **Jennings Ward** » 6 Oct 2004 11:24 am

Ditto: I could not have said it better rhan U'all.......jennings.....Play steel for the beautiful angelic sound of it.......

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