Member
Joined 2003
I'm in the early stages of building a new speaker and can choose a crossover network topology that leans toward a capacitive load...a network presenting a more inductive load is also possible. Which is better for amp performance? A few words of "why" would be appreciated (I'm not a SS amp guy).
Thanks,
Paul
Thanks,
Paul
Hi Paul,
The less reactance, the better for any amplifier. This is especially true of tube amplifiers. The solid state kind are usually less affected by phase angle, but odd things can happen.
Capacitive loads are about the worst for a solid state amp. You effectively reduce the high frequency feedback voltage when things get out of whack. Not good for stability sometimes. Inductive loads won't hurt stability, but the excess dissipation in the output stage is not welcome.
-Chris
The less reactance, the better for any amplifier. This is especially true of tube amplifiers. The solid state kind are usually less affected by phase angle, but odd things can happen.
Capacitive loads are about the worst for a solid state amp. You effectively reduce the high frequency feedback voltage when things get out of whack. Not good for stability sometimes. Inductive loads won't hurt stability, but the excess dissipation in the output stage is not welcome.
-Chris
Member
Joined 2003
Hi Paul W.
When an amp drive a reactive load some precaution can be made.
With capacitive load you should check the stability of the amp.Connect an audio generator and a scope and check the overshoot and ringing on the signal.If instability is produced you should change(or add) a Zobel network.
When a large inductive load is driven you must to protect the output transistors with two diode connected from the negative supply and speaker output and from speaker output and positive supply.
Obviously the betterfor all the amp(tube or solid state) is resistive load.You can also compensate with a RC network the inductive loads
The suggestions of Anatech and Darkfenriz are also excellent.
Cheers
Vittorio
When an amp drive a reactive load some precaution can be made.
With capacitive load you should check the stability of the amp.Connect an audio generator and a scope and check the overshoot and ringing on the signal.If instability is produced you should change(or add) a Zobel network.
When a large inductive load is driven you must to protect the output transistors with two diode connected from the negative supply and speaker output and from speaker output and positive supply.
Obviously the betterfor all the amp(tube or solid state) is resistive load.You can also compensate with a RC network the inductive loads
The suggestions of Anatech and Darkfenriz are also excellent.
Cheers
Vittorio
Hi Vittorio,
Paul is designing a speaker. We have to worry about what it does. 😉
Paul W,
Slightly inductive is excellent. It should be an easy load for most amps then with minimal phase shifts. Good choice!
-Chris
Paul is designing a speaker. We have to worry about what it does. 😉
Paul W,
Slightly inductive is excellent. It should be an easy load for most amps then with minimal phase shifts. Good choice!
-Chris
Hi Chris
my worry is that Paul not plans a crossover that cause problems on its amplifier(or worse than it breaks off) .
Slightly inductive is a good choice.A RC network in order to compensate this little inductive load is also possible.
Cheers
Vittorio
my worry is that Paul not plans a crossover that cause problems on its amplifier(or worse than it breaks off) .
Slightly inductive is a good choice.A RC network in order to compensate this little inductive load is also possible.
Cheers
Vittorio
Hi Vittorio,
Well, let's see what he does. That is always a concern.
I had a guy blow up an Adcom GFA-555II twice. He made his own sub crossover. I asked him to bring it in after hearing the crossover was really hot. The first element was a 220 uF bipolar cap across the input.
-Chris
Well, let's see what he does. That is always a concern.
I had a guy blow up an Adcom GFA-555II twice. He made his own sub crossover. I asked him to bring it in after hearing the crossover was really hot. The first element was a 220 uF bipolar cap across the input.
-Chris
A capacitive load adds a phase lag to the feedback voltage.
According to D. Self, lowering the impedance of a speaker using some RC or RLC networks to make it resistive is not a good idea : the amplifier will have to deliver more current which means more distorsion. A good amplifer does not suffer from instability with usual loads.
According to D. Self, lowering the impedance of a speaker using some RC or RLC networks to make it resistive is not a good idea : the amplifier will have to deliver more current which means more distorsion. A good amplifer does not suffer from instability with usual loads.
Hi forr
this is not always true.
For different reasons some amplifiers with a large amount of NFB or some tube amp do not like reactive loads.
When compare the distortion on a tube amp that drive a inductive load with the same load compensated with a RC network we can see that the distortion decrease.Test this in order to believe....If we speak about sound we can discuss to the infinite 😀
Cheers
Vittorio
this is not always true.
For different reasons some amplifiers with a large amount of NFB or some tube amp do not like reactive loads.
When compare the distortion on a tube amp that drive a inductive load with the same load compensated with a RC network we can see that the distortion decrease.Test this in order to believe....If we speak about sound we can discuss to the infinite 😀
Cheers
Vittorio
Member
Joined 2003
No concern about destroying amps. Even the capacitive version isn't as reactive as many ESLs...and it is the more reactive of the two.
Given other constraints, the XO will be as resistive as practical. The inductive/capacitive question is just an opportunity for me to select the best overall compatibility between speaker and amp.
Paul
Given other constraints, the XO will be as resistive as practical. The inductive/capacitive question is just an opportunity for me to select the best overall compatibility between speaker and amp.
Paul
Is there a model I could use as a worst case scenario for capacitive testing and another one for inductive testing? I think a 220mfd cap across the output may be a bit much for capacitive.
Hi d3imlay,
220uF is not a reasonable load for any amplifier.
A 45 ° phase angle on your load would be a stressful test for an amp. Resistive loads are the most common, I've heard of people adding 0.22 uF across and 8 ohm dummy load as well.
Really, you just have to check your designs into a standard load and provide safety margins. The 0.22 uF cap is more for testing stability.
-Chris
220uF is not a reasonable load for any amplifier.
A 45 ° phase angle on your load would be a stressful test for an amp. Resistive loads are the most common, I've heard of people adding 0.22 uF across and 8 ohm dummy load as well.
Really, you just have to check your designs into a standard load and provide safety margins. The 0.22 uF cap is more for testing stability.
-Chris
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