How necessary are they really? How much of a problem is it if speaker Z rises at hf? I'm asking myself if I can get away with omitting them on small amplifiers. I omitted one on the little class A amp without any problem.
NT
Some amps will tend to oscillate when connected to a cable+crossover+speaker load.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
They're probably only needed if you have a cross-over network and are concerned with the load impedance to the amplifier making it go unstable.
I might also use a Zobel network, located at the amplifier, if I had very long wiring runs to the speaker. ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
I don't know much about speakers, I've made some air core B field coils, and stuck Zobel networks on them. I don't recall much testing without the Zobel in place. (old design) So I could be making things worse... They work fine.
George H. (For me a Zobel is the parallel combo of a series R+L and R+C, such that with ideal components it looks resistive at all frequencies. (RC=L/R)
But diverts power from the real load at the "crossover" frequency. ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
The Phase Linear 400 Series Two has no coil. Just a cap and resistor to ground right at the output terminals.
Thank you to all... its as I expected, but lacked confidence. Ie a 1 way speaker not on a long wire = no real problem without an RC or RL. Odd then that manufacturers of chips aimed directly at 1 way small speaker on short leads advise including an RC.
NT
** So did all the Phase Linear power maps.
And they would *oscillate like mad* under the right capacitive load conditions.
Meant that only figure-8 cable could be used for the speakers - unless you added a small L after the output.
25 turns of wire would on a thick pen did the trick..... Phil
** You lack a brain as well. ** Bollocks. ** Single chip IC amps need an RC zobel or they will oscillate into an open circuit and/or most single speakers. If the maker specs it in the data sheet it IS needed.
.... Phil
If you google Zobel + loudspeaker, you get the standard audio-world nonsense. There's no acoustic problem if the speaker Z rises with frequency; the amp is a voltage source, after all, and the speaker doesn't know if the amp has an RC inside.
The problem is that a lot of amps will oscillate, loaded or not, and an RC on the output helps. The oscillation is usually supersonic, so the tau of the RC can be pretty short.
-- John Larkin Highland Technology, Inc picosecond timing laser drivers and controllers jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
And they would *oscillate like mad* under the right capacitive load conditi ons. "
Which cranks up aother few questions. I have seen these things with the coi l, and/or the cap and resistor both outside and indise trhe feedback loop a nd/or the protection relay or fuses. What gives ? Seems like the best way i s the coil to the resistor and cap and it is all probably outside the feedb ack netwwork but insie the protection relay.
Doesn't that seem logical ? Really. Why do it any other way ?
Also, just WHAT conditions ? I got a 400/2 and I am curious. what kind of l oad like electrostatics ? Or maybe systems with peizo tweeters ? I know tho se did wreak havoc on one little amp or something I had but it wasn't reall y high fidelity. (yes, there is high fidelity without audiophoolery, the pr oblem comes when people got too much money)
u added a small L after the output. "
WTF is figure 8 cable ?
Seems like alot less turns would do it, probably in most cases. But then ho w do people detect that ? If it is oscillating at 1 MHz nobody can hear tha t. Do the lights dim ? Is there like a hum in the speakers from the filters draining ? And if left untouched, do these tings just either blow the amp or tweeters and leave everyone in a mystery ?
Just some thoughts here.
** It's the speaker CABALE that is the potential hazard. ** Twin lead.
** But I have tried it and YOU have not.
But then how do people detect that ? If it is oscillating at 1 MHz nobody can hear that. Do the lights dim ? Is there like a hum in the speakers from the filters draining ?
** The output transistors quickly overheat, fail and the fuses blow.There may be a little hum to warn you or the internal zobel resistors will send out smoke signals.
... Phil
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