OT: volume control

An "L" pad or if you are a real finiky a "T" pad of the same value as the impedance of the speakers. ...lew...

Ebay has all kinds of audio equipment fairly cheap.

On Mon, 07 Mar 2005 23:59:02 GMT, the inscrutable Lew Hartswick spake:

Is a "t pad" the transformer-type?

========================================================== I drank WHAT? +

Nope -- an L-pad has two variable resistors (rheostats with special taper) controlled by a single shaft. One is in series with the line from the amplifier, and increases in value to reduce the volume. The other goes from the other side of that first one to ground, to shunt signal away from the speaker. That one decreases in resistance as the volume is decreased. The two tapers are adjusted so (among other things) the amplifier sees a constant impedance as the device is adjusted, as long as it is connected to a speaker of the proper impedance. However, the speaker sees a changing impedance, which probably doesn't make much difference with cheap speakers, but certainly does with quality speakers.

A T-pad has three variable resistors on a common shaft. Two are as described above. The third is connected between the joining point of the first two and the speaker, and behaves the same as the first resistor. This assures that the speaker also sees constant impedance looking back towards the amplifier.

All of these can only be used to *reduce* the volume. If the volume at the amplifier is not high enough, you still have to walk back to the amplifier, and turn up its volume, thus making the sound in all of the rooms in the house louder at once.

It is better to feed the low-level signal from the input side of your amplifier to another one in each room. Ideally, do it with a 600 ohm balanced feed per channel. This way, you can boost the signal to whatever volume you need in the room, by using your amplifier to both boost and control the volume.

Enjoy, DoN.

On 8 Mar 2005 01:13:41 -0500, the inscrutable snipped-for-privacy@d-and-d.com (DoN. Nichols) spake:

Gotcha. I set the level in the living room, hit the B speaker switch, and have a pair of toggles in the shop to mute the sound if the phone rings. Some day I really should get volume controls.

And that's how you can spend $50k to outfit your home with an automated sound system.

Thanks, Don.

========================================================== I drank WHAT? +

No. A "T" pad is a 3 element rehostat configured to provide a constant resistance looking at it from either direction. Two in the series direction with one in the shunt direction between the two. As the series ones reduce in resistance the shunt one increases. The signal thus is varied from no attn. (when the series ones are at zero) to infinite (when the shunt one is at zero). Havent use one in close to 50 yrs. ...lew...

Nope! A light dimmer is not a rheostat and cannot be used as a volume control. Consider this: If you connect several speakers, do it in such a way (series - parallel, etc) that the total speaker load matches the output impedance of your amplifier, usu. 8 ohms. Obtain 8 ohm "L" pads (constant impedance attenuators) and connect one at each speaker location.

Could you explain this more. What are L" pads (constant

radio shack? Can car audio speakers be used? also how can more than 4 speakers be used if the amp only has 4 outputs. Do you connect the extra speakers in parallel? Will the power to each speaker be devided in 2? If I only want 1 speaker in the kitchen how do I get mono to it but keep stereo to the other paired speakers. Thanks for your help.

On Tue, 08 Mar 2005 21:56:50 GMT, "habbi" vaguely proposed a theory ......and in reply I say!:

remove ns from my header address to reply via email

Radio shack

Yes. But they are often 4 Ohms, so watch out for matching to the amp.

You should probably start with serial, unless your amp can handle two of the speakers you use in parallel.

Say your amp can handle 8 ohms.

You would get two 8 ohm speakers and connect them in series. This underloads the amp, as you now have 16 ohms. But then to add more speakers, you can add a second series of 2 speakers in parallel right across the first two. This brings you back to 8 ohms again.

As I describe it above, you actually always divide by 4. The first two are only going to draw half the current. So they will share half the power between them. 1/4 each.

When you add the second series pair, you again load the amp to full power, but across four speakers. 1/4 each.

If you _do_ use 4 ohm speakers, then your first serial pair would get half each, as they add up to 8 ohms and you use full amp power. However, if you want to add more 4 Ohm speakers, you have to add them in series, every time, unitl adding some setup in parallel will not give you less impedance than your amp can handle.

If you amp can handle 4 Ohms, then you can parallel 2 8 Ohm speakers first time around. They will get half each of the full power. But then you would have to series connect any other speakers, singly or in parallel pairs, until you could again parallel another set without going under 4 Ohms.

With an amp.

I have T's and L's - The L's are new in a box and at least 50 years old. The T's are likely 70 or so being used with triode output tubes. Pentodes didn't have the power at that time.... :-)

Martin

And I thought I was a pack rat. I have some transistors from the 50s and

Check the prices on ebay. I rooted around to find some CK722s I knew were buried somewhere after seeing them sell for up to $35 each. I remember buying them surplus for 5 or

Ned Simmons