Simple Symetrical Amplifier

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If i could give just one advice, then it would be ... wear sunscr...... Sorry!! .... only do Current feedback where it is possible...

Another mather... When you raise the bandwidth, what about stability into capacitive loads???????

I do not use Zobel or inductor, and maintain low distortion, high bandwidth (500KHz) and in my test protoamp i have a Zout of less than 30mOhm @ 20KHz. And still it is stable into 10uF load.

Sim of the final circuit tells me less than 2mOhm of the final amp at 20KHz.

Before asking how it is done. This does not leave my doorstep, but it can be done....

So the DFin my final circuit is equal to the Hypex NCD400.
 
If i could give just one advice, then it would be ... wear sunscr...... Sorry!! .... only do Current feedback where it is possible...

Yes yes yes :up:

Another mather... When you raise the bandwidth, what about stability into capacitive loads???????

I do not use Zobel or inductor, and maintain low distortion, high bandwidth (500KHz) and in my test protoamp i have a Zout of less than 30mOhm @ 20KHz. And still it is stable into 10uF load.

You mean 10 uF parallel to 8 ohm resistor or 10 uF alone as a load? :rolleyes:

Sim of the final circuit tells me less than 2mOhm of the final amp at 20KHz.

Is this new amp a merge of Mirand and TSSA as you already mentioned lately? :cool:
 
I do not use Zobel or inductor
Serial inductor is not always required against oscillation. But it helps to protect feedback to carry HF, induced in the Loudspeakers wires witch can be worse than the same hf in the input.

The same remark applies at the Preamp output, reason why the cabling i suggested earlier was done the way it is.

I wonder why no audiophile cable guru has never thought to sell shielded loudspeaker's wires, instead of alloy gallium plated ones, isolated by Teflon/bamboo with cryogenic treatment.
 
I wonder why no audiophile cable guru has never thought to sell shielded loudspeaker's wires, instead of alloy gallium plated ones, isolated by Teflon/bamboo with cryogenic treatment.

You could try screened Cat 6 network cable ( CAT 6 STP )

Try it before you laugh - You might be pleasantly surprised - it takes a pretty high spec cable to carry a 1000Mb/s signal.
 
You could try screened Cat 6 network cable ( CAT 6 STP )
Try it before you laugh - You might be pleasantly surprised - it takes a pretty high spec cable to carry a 1000Mb/s signal.
Nb: It can carry such a bandwidth only if source and target impedance is 100 Ohms for a perfect "transmission line".

I will not laugh as i use them between my digital filter and my active speakers (one pair for basses, one pair for treeble, one pair for power on/off command, one pair for volume remote control of the power amps). With balanced 100 Ohms audio lines as required ;-)

Forget about that flat bandwitch for the < 0.1 ohms source of a power amplifier and a > 8 ohm loudspeaker, but who care ?
 
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Serial inductor is not always required against oscillation. But it helps to protect feedback to carry HF, induced in the Loudspeakers wires witch can be worse than the same hf in the input

Cool, I think this is the first time I listen to something like this (those other times I might not listening). So that's why some use zobel at both ends of the inductor?

I wonder why no audiophile cable guru has never thought to sell shielded loudspeaker's wires, instead of alloy gallium plated ones, isolated by Teflon/bamboo with cryogenic treatment.

I think it will become a capacitive load for the amp? Do you mean the negative cable shielding the positive one??? I have been wondering about that many times. But I just didn't want to "re-invent" the mistake.

With CAT5, CAT6, and similar telecom cables, I still use it. Sometimes I have worry with the stranded cables but it has been years and I cannot see issue with oscillation.

But it is hard to find cables for such application that doesn't sound "hard". Indeed the resolution is its hallmark but the hard sound can be fatiguing sometimes. Don't know if this is a "true to the sound" issue. But I like the soft sound of silver wire. Or may be I cannot decide until now :D
 
I think it will become a capacitive load for the amp? Do you mean the negative cable shielding the positive one??? I have been wondering about that many times. But I just didn't want to "re-invent" the mistake.

Using shielded cat 6 as an example, I would try using the inner pairs for loudspeaker send & return - all coloured wires for send, all whites for return.

Connect the screen at one end only for shielding duties. I'm guessing amp end grounded to casing would be best - but I would try both options - the other option being running a case ground to the speaker to earth the far end of the screen - could try earthing the driver chassis as well.

I have used Cat6 or the pairs inside Cat6 for nearly all duties for a few years now - There may be better cables out there but I also know that there are many that are worse. For anyone on a budget it provides incredible value for money.

I recently upgraded a £20 pound interconnect cable to 2 x Cat 6 twisted pairs and the improvement was amazing - cost was more because I elected to use Eichmann plugs but the interconnects effectively become the cost of the plugs you choose. There is no screen on regular CAT 6 so I keep i/p impedance low - 10K or less

I think I'll order some screened Cat6 tmrw for speaker leads and see it I can hear any difference !
 
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Sim of the final circuit tells me less than 2mOhm of the final amp at 20KHz.

Before asking how it is done. This does not leave my doorstep, but it can be done....

So the DFin my final circuit is equal to the Hypex NCD400.

Here's info about output impedance of SSA BIGBT HP before CCS were installed. Real measurement shows that 2 mohm calculated by sim isn't unrealistic at all. :yes:
After CCS modules were added SSA was sold so quickly I didn't have enough time to make another set of mesurements, but I believe that the output impedance in latest iteration would go even lower, very close to sim's 2 mohm. OLG + feedback + smart PCB layout can do that. :yes:
 
That's interesting, You & Sonny seem to highly value a very low o/p Z

I found 0.1 - 0.2R sounds nicest except for big bass speaker or sub which need low Z to drive them.

There's Catch 22 involved in a damping factor of specific amp. Higher DF means by definition the amp puts more effort to "correct" the output signal according to an input signal, that's OK at least in theory. But what if the amp is not fast enough, higher DF number would make a lot more of phase-timing distortions than it should, ruined the sound more than if DF would be lower. By high speed amps like SSA is, high DF means only that the output signal would be really close to the original, speaking of time coherence, so very pleasant to listen to even with high DF. :yes:
 
I think it will become a capacitive load for the amp? Do you mean the negative cable shielding the positive one???
Of course, the amp is supposed to have enough phase margin to stay stable under such a capacitive load. Zobel included.

As a general law, and like for a bridged amp, the shield have to be connected at the ground of the amp and free Loudspeaker side (no current).

About Zout of an amp (damping factor) your best value depend of the speakers themselves.
1- Bass reflex are calculated for a given source impedance (cable included). It matters for low end flat response.
2- But best is the damping factor, best is the pulse response.
3- But on some loudspeakers (medium, tweeters or wide band) too much damping can increase the material resonances if the cone fractionate. By example, my JBL 2" motor, highly damped by itself, sound better with a passive attenuator between itself and the amp.

So, best is the damping factor of the amp, best it is, and you can play with external serial resistances. And, because DIY are Gods, they can tune the FB compensations for perfect flat (and square waves) response with their real world loudspeakers installation, including wires.
 
Esperado, so fine tuning between amp and speakers with optimal serial resistor. Meaning best square waves measured on speaker driver terminals or on axisys microphone's signal?
Unless you use a digital filter or a very good tuned Speakers (regarding group delay) there is no way to look in an understanding way square waves via a mike. But it is the way to tune the group delai of the enclosure (geometrical alignment of speakers)
I prefer to tune the FB compensation, looking at the speaker's outlets of the amp to get no overshoot on square waves with wires and loudspeakers in place, then try different resistances on medium/tweeters speakers (each band separately for a multi band one.
Well, with passive filters, serial resistances of coils or attenuators are often yet too much to can improve anything. Thus it applies mainly on active multy-ways systems or wide band single speakers, and i tune them with ears: too subtle for any measurements.

By high speed amps like SSA is, high DF means only that the output signal would be really close to the original, speaking of time coherence, so very pleasant to listen to even with high DF. :yes:
Exactly.

Whatever the point of view from which we observe an amplifier,, slewrate is definitively the goal.
"Faster" is the amp, more you can add Feed back. Despite the wrong bad reputation of feedback, more feedback more DF, less harmonic distortion.
"Faster" the amp, less IM or TIM. better the sound.
We have a perfect example with the current source we were talking about here. It increase bandwidth SO reduce distortion. Everything is stuck together.

L.C you are one of the rare audio designer with have a *complete* view of audio closed loops. Including the signals generated by the loudspeakers when they move, feeding the feedback returns with high level errors signals.

I'm convinced that, when the CSSA (Complete state-of-the-art symetrical amplifier ) will be tuned in the littlest detail, this forum will have his master piece.
 
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