Hello All,
I am still in the process of making my first GC for an active system.
I have worked out that the amps for the tweeters only need to be app 20 watts rms.
I will be driving the system from my XA333ES SACD player which has a 2 v rms output which I will need to pad down.
From my initial calculations I have found I only need a gain of 9 to get full output with a 1 volt input.
Am I better to reduce the input voltage to 0.5 volts max and have a gain value of app 17.
Any help would be appreciated.
Regards
Blair
😕
I am still in the process of making my first GC for an active system.
I have worked out that the amps for the tweeters only need to be app 20 watts rms.
I will be driving the system from my XA333ES SACD player which has a 2 v rms output which I will need to pad down.
From my initial calculations I have found I only need a gain of 9 to get full output with a 1 volt input.
Am I better to reduce the input voltage to 0.5 volts max and have a gain value of app 17.
Any help would be appreciated.
Regards
Blair
😕
For use in an active speaker system where, presumably you will want the amps close to the drivers, I would recommend using the non-inverted design.
The alternative is to put a buffer before the inverted power amps.
I would just buld the amps with equal gain and then if you need to adjust the tweeter levels, put in some sort of volume control after.
The alternative is to put a buffer before the inverted power amps.
I would just buld the amps with equal gain and then if you need to adjust the tweeter levels, put in some sort of volume control after.
Hello Nuuk,
please excuse my ignorance if I ask why the topology of the non inverting amp is prefered to the inverted design for an active system.
Can you please explain.
Regards
Blair
please excuse my ignorance if I ask why the topology of the non inverting amp is prefered to the inverted design for an active system.
Can you please explain.
Regards
Blair
It is because with the inverted design, the feedback loop includes the items which preceed the amp, like the interconnects and the volume control.
As one of the big advantages of active systems is to have the amps as close to the drivers as possible, this would mean using long interconnects which could effect the performance of the IGC.
Of course, this may not be the case if you put the active crossovers immediately before the IGCs as they would act as a buffer, isolating the ICG circuit from the cables. But it needs somebody more experienced than I am to confirm this.
Konnichiwa,
We have been there before and I must note again that while this view is readily promoted by a fairly high profile poster it is nevertheless absolutely and utterly wrong. The FEEDBACK loop is from the output to the inverting input, REGARDLESS if the Amplifier is inverting, noninverting or pseudo balanced Input.
You are talking about the input loop and that again is the same in all essentials for inverting and noninverting mode but differs for pseudo balanced. What MAY need to be addressed is the circuit stability with open input for the inverting design.
Sayonara
Nuuk said:
We have been there before and I must note again that while this view is readily promoted by a fairly high profile poster it is nevertheless absolutely and utterly wrong. The FEEDBACK loop is from the output to the inverting input, REGARDLESS if the Amplifier is inverting, noninverting or pseudo balanced Input.
You are talking about the input loop and that again is the same in all essentials for inverting and noninverting mode but differs for pseudo balanced. What MAY need to be addressed is the circuit stability with open input for the inverting design.
Sayonara
one of the big advantages of active systems is to have the amps as close to the drive
its an advantage - but not big......there are several much bigger advantages in an active setup.......😉
its an advantage - but not big......there are several much bigger advantages in an active setup.......😉
If you are into very high-end (read: expensive) speaker cables, the advantage may be worth several 1000 dollars...😉
Jan Didden
Jan Didden
janneman said:
I might arrange 5 different pairs of speaker cables connected to a rotary selector. Then, it could give a better opportunity for the amp gain control and, in addtion, another opportunity for an A/B/C/D/E test of the speaker cables. I hope this will help.
Oops, sorry for that mistake. I have no electronics training and that is why I asked for some confirmation.
So what is the answer to the question? Would the inverted GC design work in an active system without causing problems with instability?
And what would be the best arrangement? Crossovers in preamp or immediately before IGCs?
PS I'm going out to get run over by a steam-roller so that I don't have such a high profile 😉
Nuuk said:
Why not? IGC has higher stability than NOINVGC. IMHO.
Because of that, you can place input chinch very close to output terminal. (additional weak NFB, maybe)
Second.
Regards
Konnichiwa,
Well, as said, the notion of all the stuff on the inverting pin being the feedback path has been promoted previously (not by you), but is is wrong. I suspect you read it before and simply accepted it.
Yup, will work fine. It MAY be prudent to raise the feedback resistor to 330k and to make sure to connect a 22k Resistor across the input. The resulting Amp will be unconditionally stable, even with no input conenction, though the input impedance drops from 10k to 6.8K.
Due to their very nature the IGC circuit can be adapted to operate as inverting (Rauch type) active filter. So if you want, simply place the filters for each band around the LM3875. The input impedance will now of course be all over the place, so the input to the various networks should ideally be buffered.
If the Filter Circuits are only supposed to be 1st order this is even easier. So I would always have the filters at or around the IGC. Unless I use a commercial external crossover, like the Behringer Digital DCX2496, in which case BTW I would recommend to use pseudo balanced inputs for the Gainclones.
I was not refering to your Profile (though truth be told you do contribute a lot).
Sayonara
Nuuk said:
Well, as said, the notion of all the stuff on the inverting pin being the feedback path has been promoted previously (not by you), but is is wrong. I suspect you read it before and simply accepted it.
Nuuk said:
Yup, will work fine. It MAY be prudent to raise the feedback resistor to 330k and to make sure to connect a 22k Resistor across the input. The resulting Amp will be unconditionally stable, even with no input conenction, though the input impedance drops from 10k to 6.8K.
Nuuk said:
Due to their very nature the IGC circuit can be adapted to operate as inverting (Rauch type) active filter. So if you want, simply place the filters for each band around the LM3875. The input impedance will now of course be all over the place, so the input to the various networks should ideally be buffered.
If the Filter Circuits are only supposed to be 1st order this is even easier. So I would always have the filters at or around the IGC. Unless I use a commercial external crossover, like the Behringer Digital DCX2496, in which case BTW I would recommend to use pseudo balanced inputs for the Gainclones.
Nuuk said:
I was not refering to your Profile (though truth be told you do contribute a lot).
Sayonara
Thanks for the clarification T. It just goes to show, you can't leave us to our own devices and it's a good thing that you monitor these forums on a regular basis 😉
I doubt that I will be using the GCs in an active system as I still prefer the simplicity of using something like the Goodmans 201s but who knows where the holy grail will take any of us next!
I doubt that I will be using the GCs in an active system as I still prefer the simplicity of using something like the Goodmans 201s but who knows where the holy grail will take any of us next!
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