Variations in PA Transformer response

"Martin Stall"

** I think you are confusing the terminology.

The 100 volt winding is most likely the primary.

** The 5W tranny should have a 16:1 turns ratio - so 100 volts comes down to 6.3 volts.

The 60W tranny should have a 4.5:1 turns ratio - so 100 volts comes down to 22 volts. .

** You need to say why you think there is a difference.

The maker's specs ? You tested them somehow ?

..... Phil

It looks as though the larger transformer has been wound with fewer turns-per-volt of thicker wire so as to give higher overall efficiency at the expense of L.F. response. The turns ratio of the smaller transformer has probably been adjusted to compensate for the losses on full load.

The amount of steel per watt is the important factor, not the total amount of steel.

--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk

The second transformer takes higher input voltage, due to higher input power with the same nominal input impedance.

--
 - Don Klipstein (don@misty.com)

No, Don. The 100V specification is the line voltage with the amp at maximum output. It's the turns ratio that sets the power at the speaker.

--
You can't fix stupid. You can't even put a band-aid on it, because it's
Teflon coated.

Martin Stall schrieb:

Hello,

if you take two transformers, one for 100 V to 10 V, rated at 5 W and the other also for 100 V to 10 V, but rated for 60 W, both should have the same turns ratio.

But you are looking at something different, the output voltage for both transformers is the same, 100 V. But the input voltage must be different, because the first should deliver 5 W into 8 Ohm, the second

60 W into 8 Ohm. For 60 W, a higher voltage is necessary than for 5 W. It is correct that the turns ratio is lower for the second one.

Lets calculate, P = U^2/R U = sqrt(P*R) U1 = sqrt(5*8) = 6.32 V U2 = sqrt(60*8) = 21.9 V

The second transformer uses thick wires for higher current, therefore the windings have less resistance.

Bye

Michael A. Terrell schrieb:

Hello,

Don was right, because he and Martin defined the 8 Ohm matched side as input and the 100 V side as output of the transformer when the transformer is connected to the amplifier. If the transformer is connected to a speaker, the 100 V side is input and 8 Ohm side is output.

Bye

Sigh. Your vast ignorance is showing. A 100V audio transformer is

10,000 ohms/watts.

That makes:

The primary impedance of the 65 watt transformer 10000/65 or 153.85 ohms.

The primary impedance of the 65 watt transformer 10000/5 or 2000 ohms.

Come back when you've designed and installed a couple hundred constant voltage sound systems and know what the hell you're talking about. The DCR of the windings has nothing to do with the impedances.

Please go away.

--
You can't fix stupid. You can't even put a band-aid on it, because it's
Teflon coated.

Michael A. Terrell schrieb:

Hello,

but you should accept that it is possible to define the 100 V winding as primary as you do, but it is also possible to define it as secondary and the other winding as primary.

If you don't like my postings, don't read it. But if I go away or not is my decision, not yours.

No matter how the hell YOU define it, it is an industry standard system. The turns ratio determines the wattage rating, not some lame ass mumbo jumbo you think should apply.

--
You can't fix stupid. You can't even put a band-aid on it, because it's
Teflon coated.

I would agree with that. Originally designed to minimise voltage drop and power loss down long runs of pa cable and allow rough and ready equalisation of SPL over the intended area.. The transformers usually say 100 volt line on the primary and typically a series of taps on the secondary labeled in watts, at the specified load impedance.

Quite a good system in engineering terms. Low tech and low cost in the days when labour and materials were cheap...

Regards,

Chris

It's still a cheaper way to install sound systems, when compared to distributed amplified speakers. It also allows you to set maximum volume at each speaker throughout the system without wasting a lot of power. I've installed them in schools, churches and factories.

--
You can't fix stupid. You can't even put a band-aid on it, because it's
Teflon coated.

"ChrisQ"

** Commonly, the primary has taps labelled in watts ( 0.5, 1, 2, 5, 10 etc) at both 70 and 100 volts while the secondary has various load impedances like 4, 8 & 16.

Means the same tranny can be used for many different jobs.

Since modern 100 volt line amps range up to 1000W per channel power atings - one can supply several thousand speakers at modest ( ie background music) levels.

... Phil