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Old 11th March 2013, 05:43 PM   #2831
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another thing to consider is the variation from device to device.
the spec sheet usually gives a performance minimum.
the devices can vary considerably, so long as they meet spec.
that will include noise, distortion, gain, bandwidth, etc.
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Old 15th March 2013, 05:18 PM   #2832
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meanwhile -- Has anyone built the SW-OPA yet? data, results, issues?
?

-RNM
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Old 15th March 2013, 06:06 PM   #2833
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No one except SW probably. Simulation serves all the play they want. I'm waiting on boards and parts. Ray
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Old 15th March 2013, 07:20 PM   #2834
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Originally Posted by grhughes View Post
No one except SW probably. Simulation serves all the play they want. I'm waiting on boards and parts. Ray
So am I... especially reports on completed ones from those who wanted us to use smd's on thier pcb.

meanwhile, what else can we talk about that's ? Is there a symbol for twiddling your thumbs?

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Old 15th March 2013, 07:28 PM   #2835
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Default Low feedback sounds better because --->

Well then, let me throw this out there --->

One of the reasons for going low gnfb -in my mind- wa to get a constant amount of fb at all frequencies. back in the day, I didnt have such good test equipment for measuring distortion.

I thought that the way sound was described sort of followed the thd curve. --- best at low freqs and progressively worse as the freqs when higher.... that high freq rise at the top end. Still a characteristic of many amps -- pre or power. As we know there are many mechanisms at work.

But limiting this to just the thd and amount of feedback here -- What if -- the harmonic structure did not change with freq ?? What ever the relationship between harmonics at low or mid was the same at the high freqs? Same ratios etc.

Wouldnt that have a sameness to the sound across the audible band? No more, the mids sound this way and the highs sound that way. The character would be the same/similar.

In fact, that is what you get in test performance and in listening results. If the harmonics are high enough to hear or the chain/system has harmonics high enough levels to hear differences. there is no other way to get this kind of favorable result (is there?)... assuming a falling open loop within audio feq band and varying feedback margins/amount of etal.

Thx-RNMarsh

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Old 15th March 2013, 09:14 PM   #2836
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I was struck recently at gazing at the schematic of a piece of test gear; Princeton Applied Research Model 113 preamp. The stamp of the schematic says 1966. Yet, such sophistication did not catch up to audio until the early 80s. A discreet bench test operational amplifier of great sophistication, FET diff amp, ccs on everything, input with all the input protection against overload. It amazed me at how long audiophiles were forced to listen to designs that were of much less sophistication. Audio must be the step child of electronics. It also amazes me at how different topologies sound different. I'm not an EE, just a serious audiophile but it seems to me that design has gone in FADS. What will be the new hare that everyone will chase? Ray
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Old 15th March 2013, 11:48 PM   #2837
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Quote:
Originally Posted by RNMarsh View Post
Wouldnt that have a sameness to the sound across the audible band? No more, the mids sound this way and the highs sound that way. The character would be the same/similar.

In fact, that is what you get in test performance and in listening results. If the harmonics are high enough to hear or the chain/system has harmonics high enough levels to hear differences. there is no other way to get this kind of favorable result (is there?)... assuming a falling open loop within audio feq band and varying feedback margins/amount of etal.

Thx-RNMarsh
The goal is, that there is no "sound" to the system. If the "theories" are correct then that should always be the situation at the moment -- because we can achieve below audible distortion quite easily. People with sensitive hearing know this is a nonsense in real systems ... which IME is all about poor total system engineering, not the competence of an individual component's design ...

Frank
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Old 16th March 2013, 02:23 AM   #2838
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The goal is, that there is no "sound" to the system. If the "theories" are correct then that should always be the situation at the moment -- because we can achieve below audible distortion quite easily. People with sensitive hearing know this is a nonsense in real systems ... which IME is all about poor total system engineering, not the competence of an individual component's design ...

Frank
As things progress... at least at the high-end... everything gets better. However, systems are for one reason or another - not the least of which is cost - often composed of various components of mixed blessings. Some, tube, some IC, some ss discrete, some bipolar, some jFEt, some MOSFET, combos of all and EMI/RFI and grounding and shielding and on and on... that keeps everyone guessing. Source material, acoustics, speakers, mechanical contraptions like the LP and all its variables of noise, and distortions. An infinite number of combinations to configure... not all of which is low enough in s/n, distortions of all kinds etc. Some are better than others. One goal here is to have everyone's complete/entire system be transparent and sound like real live music. Not there yet. Not at either end of the chain. But the potential is greater than ever.

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Old 16th March 2013, 03:21 AM   #2839
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One goal here is to have everyone's complete/entire system be transparent and sound like real live music. Not there yet. Not at either end of the chain. But the potential is greater than ever.

Thx-RNMarsh
Of course, I would beg to differ ... . Digital done right, tweaked sufficiently, ticks the first box, and at least IME speakers can be made to work "good enough" to deliver the live music experience ...

Frank
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Old 16th March 2013, 04:49 AM   #2840
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Quote:
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meanwhile -- Has anyone built the SW-OPA yet? data, results, issues?
?

-RNM
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Originally Posted by grhughes View Post
No one except SW probably. Simulation serves all the play they want. I'm waiting on boards and parts. Ray
as am I, I have many of the parts, need to find time for matching. waiting on an etching bubble/bath as well, I will make my own PCBs. have been distracted with other projects too, ones I really should get finished before taking on anything new.

i've also become distracted with playing with some new parts, EPC eGaNFETs EPC2012 to be exact.
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