[OT] Adding volume control to electronic device

gray_wolf > wrote:
>
>Remember the old drive in movie theater speakers with the volume control?=

Those were 70V system. 70V constant power going down the cable, each tap
has a step-down transformer, then an L-pad (not a simple pot but a three
element pad so the transformer always sees an 8 ohm load) and a crappy
speaker. Because they were all parallel loads, if the main cable was shorted
by someone driving away without removing the speaker, it would take all of
them down.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

"gray_wolf" wrote in message ...

<snip>

>Remember the old drive in movie theater speakers with the volume control?

Sure do! I had a um....habit....of driving off without putting them back on
their stand.
At one point I had about 20 of them. Now that's what I call Hi Fidelity ;-)

Poly


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2021-01-13 / 19:52:40 (UTC +0100) / polymod:
>
>
> "gray_wolf"Â* wrote in message ...
>
> <snip>
>
>> Remember the old drive in movie theater speakers with the volume control?
>
> Sure do! I had a um....habit....of driving off without putting them back
> on their stand.
> At one point I had about 20 of them. Now that's what I call Hi Fidelity ;-)

Due to the height of the stand? ;-)

On 14/01/2021 4:52 am, Scott Dorsey wrote:
> gray_wolf > wrote:
>>
>> Remember the old drive in movie theater speakers with the volume control?=
>
> Those were 70V system. 70V constant power going down the cable, each tap
> has a step-down transformer, then an L-pad (not a simple pot but a three
> element pad so the transformer always sees an 8 ohm load) and a crappy
> speaker.
>

Not switched tapped transformers ?

>Because they were all parallel loads, if the main cable was shorted
> by someone driving away without removing the speaker, it would take
> all of them down.

A bit like any singel speaker cable system in that regard !

geoff

On 13/01/2021 5:43 pm, geoff wrote:
> On 14/01/2021 4:52 am, Scott Dorsey wrote:
>> gray_wolfÂ* > wrote:
>>>
>>> Remember the old drive in movie theater speakers with the volume control?=
>>
>> Those were 70V system.Â* 70V constant power going down the cable, each tap
>> has a step-down transformer, then an L-pad (not a simple pot but a three
>> element pad so the transformer always sees an 8 ohm load) and a crappy
>> speaker.
>
> Not switched tapped transformers ?
>
> >Because they were all parallel loads, if the main cable was shorted
> > by someone driving away without removing the speaker, it would take
> > all of them down.
>
> A bit like any singel speaker cable system in that regard !
>
> geoff

I ran the snack bar at the local drive-in when I was a kid. I don't recall any real
speaker loss. I heard that driving off with the window rolled up and speaker inside
would break the glass. I remember the tube power amp ran four 807s

"Phil W" wrote in message ...

2021-01-13 / 19:52:40 (UTC +0100) / polymod:
>
>
> "gray_wolf" wrote in message ...
>
> <snip>
>
>> Remember the old drive in movie theater speakers with the volume control?
>
> Sure do! I had a um....habit....of driving off without putting them back
> on their stand.
> At one point I had about 20 of them. Now that's what I call Hi Fidelity
> ;-)

Due to the height of the stand? ;-)
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

No, the driver :-)

Poly


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On 14/01/2021 2:39 pm, gray_wolf wrote:
> On 13/01/2021 5:43 pm, geoff wrote:
>> On 14/01/2021 4:52 am, Scott Dorsey wrote:
>>> gray_wolfÂ* > wrote:
>>>>
>>>> Remember the old drive in movie theater speakers with the volume
>>>> control?=
>>>
>>> Those were 70V system.Â* 70V constant power going down the cable, each
>>> tap
>>> has a step-down transformer, then an L-pad (not a simple pot but a three
>>> element pad so the transformer always sees an 8 ohm load) and a crappy
>>> speaker.
>>
>> Not switched tapped transformers ?
>>
>> Â*>Because they were all parallel loads, if the main cable was shorted
>> Â*> by someone driving away without removing the speaker, it would take
>> Â*> all of them down.
>>
>> A bit like any singel speaker cable system in that regard !
>>
>> geoff
>
> I ran the snack bar at the local drive-in when I was a kid. I don't
> recall any real
> speaker loss.Â* I heard that driving off with the window rolled up and
> speaker inside
> would break the glass. I remember the tube power amp ran four 807s
>


The cable wasn't shorted then.

geoff

On 14/01/2021 4:52 am, Scott Dorsey wrote:
> gray_wolf > wrote:
>>
>> Remember the old drive in movie theater speakers with the volume control?=
>
> Those were 70V system. 70V constant power going down the cable, each tap
> has a step-down transformer, then an L-pad (not a simple pot but a three
> element pad so the transformer always sees an 8 ohm load)

"3 element pad" - wouldn't that be a T-Pad ?

geoff

On 1/14/2021 10:02 PM, geoff wrote:
> On 14/01/2021 4:52 am, Scott Dorsey wrote:
>> gray_wolfÂ* > wrote:
>>>
>>> Remember the old drive in movie theater speakers with the volume
>>> control?=
>>
>> Those were 70V system.Â* 70V constant power going down the cable, each tap
>> has a step-down transformer, then an L-pad (not a simple pot but a three
>> element pad so the transformer always sees an 8 ohm load)
>
> "3 element pad" - wouldn't that be a T-Pad ?
>

Yes, or a "Pi"-pad.

> "Phil W"Â* wrote in message ...
>
> 2021-01-13 / 19:52:40 (UTC +0100) / polymod:
>>
>> "gray_wolf"Â* wrote in message ...
>>
>> <snip>
>>
>>> Remember the old drive in movie theater speakers with the volume
>>> control?
>>
>> Sure do! I had a um....habit....of driving off without putting them
>> back on their stand.
>> At one point I had about 20 of them.

And 20 broken windows? :-)