No global negative feedback

I repeat, read before you post, my amplifier is not SET, it is PP... :rolleyes:

You are so unconfortable with cheap equipment, or is it with those that have inexpensive equipment... :confused:
 
Measurements of Linn Unidisk SC in Stereophile:

"The volume control operated in steps that varied from 0.5dB to 1dB, with the average over the range "40" to "90" equal to 0.8dB. One complicating factor was that with digital sources, the maximum setting of "100" resulted in significant overload; the maximum usable setting (which I defined as 1% THD+noise) was "96" for CD but "90" for SACD, DVD-A, and external data, which will interfere with A/B comparisons between CD and hi-rez media. The output level at these settings was 2.85V, or 3.1dB higher than both the CD standard and the specification. The analog inputs overloaded at the same output level, and offered a maximum gain of 13.15dB. These inputs offered an impedance of 5.8k ohms, which is higher than the 300 ohms specified but will give a bass-shy sound with typical capacitor-coupled, tubed source components. The Unidisk's analog inputs offered a wide measured bandwidth, ââ'¬â€œ3dB at 129kHz, meaning that these are not digitized."
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Analog inputs are not digitized, can the volume be digital ?
 
murray johnson said:
Some of those amps look interesting. Have you listened to any of them? Are prices shown on the site, I can't tell!
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i did, murray. they vary in sound - some i liked, some i didn't. i will focus on them more very soon when my new speakers arrive.

everything is built to order and there is a flexibility in meeting your demands. that is also one of the reasons why they don't sound consistent - i mean 2 similar amps do, but there are so many variables re what caps, resistors or valves fit into your budget.

the prices are always discussed upon the requested specs but they are not expensive. they do cost more than chinese but certainly less than europeans.

however, my favourite manufacturer from this part of the world is:
http://www.taticaudio.com/
there is an english section of his website.

he is cheaper and (for my taste) more focused on the real issues of the SETs - i think he recently build a custom order SET with ITs for someone from norway, based on a russian military version of 2A3 (6B4G or something like that). he is fanatically dedicated to the SETs, he bulds his own transformers and at the end charges really very moderately for what you get. most of the amps shown there are between 600 and 900E, the preamps are under 400E. we tried to estimate what is his margin - it's not more than 150-200E per amp.

another great guy:

http://www.solajaaudio.com

pardon me for hijacking the thread, i'm off.
 
As alluded earlier, negative feedback has been found to be an inexact solution to amplifier distortion. This is due to propagation delays (the very small but measureable amount of time it takes for a signal to move from the input of an amplifier to the output) which are a normal phenomenon of amplifiers. In order for negative feedback to work according to the math, it must be applied to counter the input signal in real time. Propagation delay in the amplifier circuit prevents this; the negative feedback will always be lagging the original input signal. This lag results in ringing effects and enhancement of odd-ordered harmonics that the human ear/brain system is particularly sensitive to: in General Electric's tests conducted in the 1960s, amounts of only hundredths of a percent were found to be audible and irritating to the human ear. In other words, a disparity exists between the mathematical proof for negative feedback and its actual application, and is example of the engineering phenomena to which Golten and Verwer refer. Despite this, negative feedback is commonly accepted in the audio world, causing the reigning design, test and measurement paradigm to have a built-in weakness.
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http://www.atma-sphere.com/papers/paradigm_paper2.html
 
Lovely article. Do you notice how none of these manufacturers bother to warn you about increased noise and reduced bandwidth?

Another thought is your speakers. Do you have an impedence curve for them or have you tried a zoebel across the coils yet?
 
I dont need you to explain impedance to me, was asking about the Zoebel thing...

Isnt it a Zoebel Network on my amplifier, a resistor and a capacitor in parallel with the outputs... :confused:
 
The Zoebel network is not really there to simulate the normal load, but rather to insure a proper load at freqs above 20-30 khz, to improve HF stability.

Loudspeakers can sometimes represent a very high impedance at out-of-band higher frequencies.

You would often have a zoebel in your speaker's crossover. You don't have a crossover. Do you have an impedence curve?
 
No impedance curve, no crossover, no Zoebel Network, I am poor... :(

But I have supertweeters with crossover, in parallel with the speakers, and a Zoebel thing in the amplifier's output... ;)
 
melorib said:
No impedance curve, no crossover, no Zoebel Network, I am poor... :(
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I can't help you then.

But I have supertweeters with crossover, in parallel with the speakers, and a Zoebel thing in the amplifier's output... ;)
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Of absolutely no importance whatsoever in this case from what I can see, although it's nice to see you haven't ripped that little lot out too.
 
Sure doesn't sound like it to me Antonio. I don't know why a waste my time trying to help you - you just see it a some ego challenge.

If you don't know the impedence curve of your drive unit, and it's crossoverless and a nominal 4 ohm load, I'm amazed any idiot would advise you to rip out circuitry from your amp bu then perhaps I shouldn't be surprised by the insanity of certain elements of the hobby that you seem to embrace.
 
No point in continuing this discussion. It's fairly clear you dont understand the basic effects of a zero NFB amplifier's interaction with a reactive load, nor if truth be told, any of the reasons behind building that particular circuit in the first place.

You feel qualified to rip apart a piece of electronics because you've read an article in Stereophool and subscribe to TweaksRus. You've "lifted a veil" whilst rolling off the treble and making the background noise intrusive, yet when you are told why this happens you behave like a child denied one last ride on the rollercoaster.

It's like trying to help a five year old with his homework - only somewhat less rewarding. Ian, I follow your lead.
 
You ignore or disdain the opinions of several very qualified persons, some members of this forum, not talking about me, when you ran out of arguments you make false statements trying to make a point, for instance:

You've "lifted a veil" whilst rolling off the treble and making the background noise intrusive
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The "veil" was lifted when I removed GNFB, the rest happened days later, when I removed the input CAP, wich has nothing to do with GNFB...

Then you behave like a child denied one last ride on the rollercoaster and follow the lead of your akin.

I could do like most, and not bother answering the troll posts, but then whoever visits the forum will think that we are all morons, because usually you have the last word...
 
Sim, comprei umas Tudusan em Janeiro.
Now I've moved tye stereo to a bigger room (3,30m celing, hard thick walls, very reflective) and they no longer sound as good as they did before, possibly because they shoot upwards...
 


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