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Impedance matching anyone

Hello Tim,

I have not seen a screen grid connection to a tap of the output transformer in any of them. Probably I didn't get to see the Rolls Royce class of tube amps in those days.

It is likely that they did that. Although I believe Hammond had the electronics module designed by an outside contract firm.

I remember my teenage days when it was customary to pack speakers with bales of damping materials. Then you needed hundreds of watts to drive them but luckily there was that old cheap work horse, the 2N3055. I did prefer tubes in those days. More oompf. The meanest tube amp delivered around 700-800 watts, mostly depending of how much the mains circuit breaker could stomach. One strong twang on the electric guitar and the lights went out.

The real freaks built Klipsch horns. But that required access to precision wood working tools which none of us had.

Regards, Joerg

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Joerg
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Tim, Keep in mind, though, that later tube amplifiers used an "ultra linear" configuration, where the screens were connected to taps on the output transformer. This made a pentode look more like a triode.

Now add in 20 DB of negative feedback to the input of the phase inverter, plus the local negative feedback to the screens. Unless I am getting confused, a damping factor of 20 with a 16 Ohm speaker implies an output impedance of 0.8 Ohms.

Tam

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Tam/WB2TT

snip

That argument's in a different set of posts...

------------------------------------------- Tim Wescott Wescott Design Services

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Tim Wescott

Hello Roger,

That's a test we used to do after we built speakers in my teenage days. Shorted and open made hardly a difference. However, it was customary to pack speakers with tons of acoustic damping material. Didn't know much about speakers back then but the gurus of those days said that if the test shows little difference then the damping and tightness is "ok".

I don't know about how "hifi" these were but Led Zeppelin or the Stones sounded really good with the volume on 10 (usually until the laws came...). These weren't just plain hobby speakers, it was the good stuff from JBL and similar sources and we meticulously followed their instructions.

Regards, Joerg

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Joerg

It is possible to build Klipsch horns without any great degree of woodworking precision. I use a homemade pair for the LF end of a battery-portable P.A. setup and they are perfectly serviceable (they just look a bit rough).

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~ Adrian Tuddenham ~
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Adrian Tuddenham

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