Speaker Impedence vs Amplifier load.

[Thad E Ginathom]

yeah, thats shorting the speaker terminals. kinda like putting a wire into both the terminals of an electrical socket. sparks will fly

... which I can understand

But while we are on the subject (everything you ever wanted to know about impedance but never dared ask):

Why, then, was I told, way back, never to run an amp with no speakers attached? Or was that wrong?

 

[doors666]

... which I can understand

But while we are on the subject (everything you ever wanted to know about impedance but never dared ask):

Why, then, was I told, way back, never to run an amp with no speakers attached? Or was that wrong?

I dont see any harm in that, though I also dont see any use of that.
There is no load on the amplifier terminals, that means that thats an open circuit. If you increase the volume, shouldnt make a difference. Its kinda like saying dont switch on the switch if there's no bulb connected.

 

[captrajesh]

Why, then, was I told, way back, never to run an amp with no speakers attached? Or was that wrong?

I dont see any harm in that, though I also dont see any use of that.

AFAIK, that caution is definitely applicable to Valve amplifiers. Experts can chip in with reasons.

 

[sunder]

Here I have attached the file regarding the Mcintosh's MC2150 stereo amp. In that we can see the back panel for the speaker terminal strip, consisting the screw terminals for the wide range of impedence. Most of the Vintage amps have the speaker output strips with minimum two different impedence i.e. 4 ohms and 8 ohms. But not Bi-wirable.
Thank you.
sunder.

 

[GeorgeO]

Better power supply= good trafo and beefy caps

 

[jaudere]

so if the transformer is not adequate, will changing the cap only help in improving low frequ response of the amp?

 

[Hari Iyer]

so if the transformer is not adequate, will changing the cap only help in improving low frequ response of the amp?

To play low frequency you require more current and if the capacitor value is not high enough they will not be able to hold the charge that is demanded by the low frequency signal. Increasing the value of the filter capacitor in the power supply stage will help to hold the charge in the capacitor longer which can be utilized by the demanding low frequency signal.

 

[sound1]

That's funny, after I put my Class D the bass has improved and how! Probably it's becasue of the power supply???

 

[rishiguru]

Better power supply= good trafo and beefy caps

+1 from me.

I am really enjoying this thread. Very different from general mass market audio conversation.

 

[ravi_d]

try to upgrade the caps on the output stage to higher values, that should make it a lot better. what speakers are u using with the class d. usually the impedence drop is in the 100-300 hz range and thats a critical zone as tons of music lives there.

Can you please explain what kind of caps are used in the Class D Output stage? If you're talking about the caps in the Low Pass Filter after the Switching Transistors can you explain a bit further how upgrading the caps in the Low Pass Filter will improve the Bass performance.
I believe the LPF has no control over the Power Supply or the Amplification part. If I'm wrong I would like to know more about it.

 

[ravi_d]

An amplifier not being able to handle a consistent 2 ohm load is not necessarily a bad design. In fact its just that it is designed with different set of goals like say offering superb performance for 8 ohm and 4 ohm loads.

I was reading a book called 'Audio Power Amplifier Design Hand Book' by Douglas Self and trying to understand the subject with my limited Electronics knowledge (BTW I'm not an expert here).

It is said most amplifiers are designed to handle loads between 8 ohms and 4 ohms with occasional dips to 3 ohms etc. But extending amplifier capability to deal with lower load impedance for anything other than very short periods has serious cost implications for the power supply transformer, heat sinks etc.
It is mentioned an amplifier will not have same performance at 4 ohms as it had at 8 ohms and the performance getting worse at lower impedance values. To improve the lower impedance performance and power delivery the number of output device pairs have to be doubled and sometimes tripled which adds to the cost.

So considering such serious cost implications and the wide availability of speakers with good impedance performance it is deliberately chosen most entry to mid level hi fi amplifiers designed for 4 -8 ohm loads.

 

[doors666]

most of the speaker designers also dont go for speakers that go below 4 ohms nominal, so there is really no need to make amps compatible with 2 ohm loads. You will frequently see 4 ohm loads though. Most of the 2 way or 2.5 way MTM speakers are 4 ohms as usually 2 8 ohm speakers are wired in parallel.

 

[cpt blood]

Hi all.Guyz, if anyone's interested in torroidals please let me know.I have a few for sale.35-0-35 5 Amp and 28-0-28 10 Amps.Very heavy and voltage drop is almost non existant.