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Old 26th August 2012, 08:38 AM   #541
owdeo is offline owdeo  Australia
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Prove it - please answer my question re ESR with some figures then!
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Old 26th August 2012, 08:52 AM   #542
owdeo is offline owdeo  Australia
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Originally Posted by jcx View Post
any idea how old the AP System 2 is??

have you really worked though all the menu items on a 2010 model?

you can get 2.5 Msample, 1 MHz signal bandwith audio analyzers today from AP

care to hypothesize what exactly they miss - in enough detail that you could write a measurement script?
In short, no and no . I am a hobbyist... and I don't claim any expertise in this area, just enough knowledge to be dangerous perhaps
The point is though, unless you can be sure how each measurement correlates with perception/hearing you can run everthing in the menu, show some graphs and figures, and you still won't know whether you have a better sounding amplifier.
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Old 26th August 2012, 09:07 AM   #543
owdeo is offline owdeo  Australia
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Originally Posted by Fast Eddie D View Post
Walt Jung has demonstrated how to measure some of these "unmeasureable" artefacts. I linked to some of it earlier in this thread.

I am not too quick to agree with Mr. Self's comments either. I can hear too.

I would like to know why you think it's "strangling" the music too. I wholeheartedly support your quest to improve this circuit. I haven't built it. But I've used some of the concepts employed in it. And these circuits worked very precisely too.

I am working on improving my "state of the art" too.

I will take a second look, and see if I see any room for improvement.
Glad to hear we have some common ground then - I didn't get that impression from your initial post

It does work very precisely in every way as designed and the variable tone controls are brilliant. If only it didn't mildly stangle my music as well I'd be a convert Perhaps it is because I used polypropylene decoupling caps instead of the specified polyester as suggested earlier, but somehow I doubt it.

Thanks for the WJ articles link. I've read some of his later ones on opamps before but had never noticed the earlier ones and they look very interesting - some more reading for me to do now.
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Old 26th August 2012, 10:26 AM   #544
AndrewT is offline AndrewT  Scotland
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Originally Posted by AndrewT View Post
You have modified the design and complained about the sound quality, all on the basis "I didn't think it was" or "it shouldn't do any harm" !
Quote:
Prove it - please answer my question re ESR with some figures then!
the evidence is in what you said, you confirmed you did not adopt the recommended decoupling.
You have only just recently told us you modified the design.
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Old 26th August 2012, 02:44 PM   #545
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"Strangling" is such a subjective term. What I think of as "strangling" is really dynamic compression. However, this is a trait of loudspeakers typically. A properly designed line level circuit should not do this in any way.

Another subtle phenomenon that's hard to put your finger on is a noise floor of complex harmonics. Since some harmonics are musically related to fundamental tones, it doesn't really stand out like IM distortion does. But even at 60 or 80 dB down, many people are aware of it, even if they can't consciously hear it. Such is the nature of psycoacoustics. It can "veil" the sound. In a power amp it can go from a subtle "veil" to what I call "mud" as you drive it harder. (we've all heard "mud" at one time or another. ) But this shouldn't be a major issue with a line level circuit.

Lazy or inadequate power supply bypassing can introduce IM distortion in power amplifiers. Going the extra mile with the power supply design can make a huge difference in an otherwise ordinary circuit. But this shouldn't be an issue with line level circuits.

Have you looked at a square wave? I sometimes tweak feedforward compensation to "clean up" a square wave. But it's easy to get in trouble with feedforward compensation. I try to use as little as possible or skip it altogether if I can. On fast, wideband SS amplifiers it can get cumbersome. It can put a lot of "snap" back into tube amps without getting in too much trouble though.

Last edited by Fast Eddie D; 26th August 2012 at 02:48 PM.
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Old 26th August 2012, 03:01 PM   #546
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Originally Posted by AndrewT View Post
the evidence is in what you said, you confirmed you did not adopt the recommended decoupling.
You have only just recently told us you modified the design.
So he messed with the decoupling? Decoupling for line level circuitry is not trivial.

My recommendation is to verify that the circuit works as intended first before tweaking.
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Old 26th August 2012, 03:38 PM   #547
redjr is offline redjr  United States
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Originally Posted by owdeo View Post
...by building the predecessor to this preamp design...

I'm posting here because I think the preamp I've built is subjectively "mildy strangling" the music....
I have followed this thread closely and read every post. I appreciate your comments and some of the counter-points that have been made. Just to be clear, the pre-amp you built was the original, roughly 1996 design of D.S. pre-amp? I vaguely remember reading that you mentioned it earlier in the thread, but wanted to be sure.

I have no knowledge of, or listening experience with the original D.S. pre-amp, so I cannot make any 'sonic' comparisons between the two. But despite the similarities in design, it seems to me we should not rush-to-judgement or even anticipate what the 'sonic signature' will sound like, however subtle it may or may not be in the new design - some ~15 years later. Isn't it fair to suggest that there may be enough subtle changes to either component values, placement, or even the whole topology of the design - that includes upward to 25 op amps - that the cumulative impact of those changes may help to improve the sound over the original design?

I'm in the process of completing this new pre-amp, but have not fired it up yet. I'm being lazy and waiting for Elektor to either offer and publish a custom enclosure, or make a decision to roll my own. But this thread might help to motivate me to finish it sooner.
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Old 26th August 2012, 04:06 PM   #548
Bare is offline Bare  Canada
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All that circuitry? just to replace (poorly imo) a Stepped attenuator and a very few short wires.
Fill yer boots :-)
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Old 26th August 2012, 04:32 PM   #549
redjr is offline redjr  United States
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Originally Posted by redjr View Post
... that the cumulative impact of those changes may help to improve the sound (or not) over the original design?
One more thought.... I strongly believe in the science and math of electronics. And for the most part believe that generally speaking, better specs produce better sound. We also know that lousy specs on certain measurements will surely yield a crappy sound - whether it's a pre-amp, amp, speakers, source device, etc.
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Old 27th August 2012, 12:15 AM   #550
AJT is offline AJT  Philippines
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Originally Posted by Fast Eddie D View Post
So he messed with the decoupling? Decoupling for line level circuitry is not trivial.

My recommendation is to verify that the circuit works as intended first before tweaking.
how true....i get call from some guy asking me to modify an equipment or how to improve the sound of the gear.......asked where the gear was, and the guy said he is still to purchase the gear.....so i told him, listen to it first and give it some time....

owdeo seems to be asking for something i think no one here can give....we can only point to clues, the rest is up to him....
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