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Old 30th June 2007, 11:35 AM   #1981
Hartono is offline Hartono  Indonesia
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Hi Juergenk,

Distortion can be below noise floor , but it can be significant compared to the output signal minus noise.

Hartono
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Old 30th June 2007, 11:45 AM   #1982
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Hi,
yes, it could be below noise and maybe it's relevant, but as it is never shown in data sheets etc.
So I'm curious, if this claim could be proofed.
regards
Jürgen
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Old 30th June 2007, 12:01 PM   #1983
Hartono is offline Hartono  Indonesia
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Hi Jürgen,

proofing with testing is harder to do, but just for the sake of clarity, the analogy is if we compare very slightly(tiny....) underbiased class B with class A ,let's assume both design have similar noise floor, but what happen under there is different.


Cheers,
Hartono
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Old 30th June 2007, 12:16 PM   #1984
sandyK is offline sandyK  Australia
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Default DX Amp

Hartono
At the risk of beingf off topic, I do believe that what you are saying is correct. Proving it conclusively, is a different matter.

Carlos
Perhaps you could see if you can find a way to further refine the crossover area of DX, without copying Hugh's circuitry ?
Graham Maynard will probably have some good ideas to share with you?
SandyK
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Old 30th June 2007, 12:57 PM   #1985
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maybe we could turn this into:
"What happens in the DX-Amp below noise?"
that would still be on topic
I don't think your're right Hartono. When the ouput current gets smaller, the pushpull stage operates more and more in class a, reducing crossover artefacts.
regards
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Old 30th June 2007, 01:03 PM   #1986
Hartono is offline Hartono  Indonesia
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Hi Juergenk

"the pushpull stage operates more and more in class a, reducing crossover artefacts."

my example is for underbiased class B anyway we agree on the same thing, I also agree about the class A you mentioned.

"What happens in the DX-Amp below noise?"

I'm sure Carlos is pretty smart about his DX amp. I was refering to IC amp before. anyway..........we agree on the same thing :-) which is .....good.......

Hartono
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Old 30th June 2007, 01:49 PM   #1987
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This discussion depends upon how anyone TESTS an amplifier, because loudspeaker current is NOT resistively linear with voltage.
You can have near immeasurable THD across a resistor, but poor reproduction via a LS.
You can have 1% distortion across a resistor, but most satisfactory LS reproduction.

Biasing can affect the response speed of a class-AB output stage within the closed NFB loop. The NFB can reduce errors but not remove them.

I cannot advise Carlos on bias circuitry. This is a compromise that is fundamental to all class-AB amplifier circuitry, so I wonder what might be achieved (or degraded) by doing so.

There is always a compromise between efficiency, bandwidth and reproduction.

PROOF ???
Move your loudspeaker into another room. Listen to your amplifier output via headphones. Listen to the increased loudspeaker induced distortion as you switch the amplifier loading between resistor and remote loudspeaker !!!

Cheers ........... Graham.
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Old 30th June 2007, 02:13 PM   #1988
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Default Bellow the noise floor is also a little bellow my interests.


I am searching for sonic modifications, sound stage deepness (perception and the origin of that into an amplifier...or...what translates into deepness...the reasons, the stages, the causes).

The amplifier sounds fine into the comparisons i have made....yeah!...loose here or there...but also show superiority in something.

I think it distorts too much early..... i can perceive something already strange when power goes up ..... i am trying bigger clean power...but i am perceiving that behavior, the same performance in many others too.

It is possible that i am dreaming too much....as amplifiers normally do not play with the same quality when reproduce class A (1 watt)
compared with 35 watts rms, for instance.

But some subtle (sútil) details.... well...sorry folks.... i left this to those guys loves to observe instruments..... i have used them as tools, and they are not more than tools to me...when working, into Power RF transmitters alignment i use to watch the spectrum analiser to reduce those harmonics intensities...but after that i prefer to watch the image.... not to waste energy into harmonics is the focus in my work.

Also i use to apply the same idea to sound..... i prefer to listen to the music, and instruments are used only when hardly needed...to debug defects...not those subtle things.

I do not want to make my amplifier so good as Aksa...also i am not able to do, and i think that a try to offer something so good as Aksa, and for free..is something absurd to my character... i am not able to behave this way.. He is a friend, was my teacher in many moments, a brother..someone to trust.

I do not want to create any problems to him..... and i love that i could not make Dx amplifier so good as Aksa.... this shows me Hugh Dean value.

If i had discovered, something able to beat Aksa... the unit would be keept in secret, to produce a business, to offer Hugh or to my own pleasure.... a very selfish pleasure, because publishing here would be negative to Hugh sells...well.... in the reality, not one is able, anymore, to disturb Hugh sells and credibility..... his customers are not in the forum, and they are not affected by our ideas...but..for precaution i would never try this.

Mine is a non comercial..not a business unit...It is a diy offered, and suggested for free. why to offer a free option better than my dear friend's product, the one teached me a lot of things.... negative!

It is fine...it is OK the way it is...people can tweak and try to modify, under their own decision and risks.

I am Hugh Dean's friend, not an enemy.... offering something better, a non comercial, non business unit...for free..when he ask money for his products...what will I be doing?

regards,

Carlos

.................................................. .................................................. ...........

Vinyl

It is all rigth...i have readed your post...

thank you,

Carlos
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Old 30th June 2007, 02:39 PM   #1989
microp is offline microp  Latvia
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Default Lets go....

HI, Carlos!

I have read almost all posts about dx amp and symasym4/5.... I want to build it (dx)

Could you, please, send me eagle files? I am using mill machine for pcb's.

I have already built one amp, but there is a problem with midrange... bass is great and treble beautiful ... but at mid it is something like raining. As I am a beginner in electronics I better create something that is tested

Need pro advice!

Thanks!!!

I will use 25-0-25 power supply...
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Old 30th June 2007, 02:51 PM   #1990
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Default Microp..... i have a defect... i use to talk true, sometimes this is understood as


rude.... that i am rude.

Well.... i am already too much old to control myself in such way.

Meeting (virtual) made with all Dx group.... including constructors, decided not to stimulate, not to make easy, not to help too much modifications.

Why that?

We had observed other threads...something i was dreaming as a very good thing turn a nightmare to my point of view..... other amplifier with
many options...was Symassym....now a days Michael has not control of his creation, there are modifications that do not cooperate with sonic quality and he could not avoid.....he gave eagle files...he made this easy.

I read people complaining...was just one...but one is enougth to teach us.... someone modified the amplifier...resulted not good, and Michael was blamed..when the amplifier made is not Symassym anymore.

Not giving Eagle files... at least the boards will not be exactly the same.... will be another amplifier...another option...people will not have the chance to Blame me or my group of friends.

Many folks asked this into direct mail.... you made different.

Eagle files will not be open.

By the way Microp.... if you are able to construct Symassym, if you decided to use all those parts...well.... better to forget Dx amplifier as Symassym has better dinamics and better voices, also better bass... loose for treble only...so... if you have doubts..... Symassym is a better option....Dx is simple and cheap...not needing those things....Symassym can be considered one step up!

regards,

Carlos
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