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Old 11th September 2008, 06:07 PM   #1
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Default Preamplifier wave forms

this is a circuit i ve been building designed from rod

this is the wave form in the output on frequency 28.500 hz square wave

question :
A) you may notice that square wave gets rounded from this frequency point (28500 hz) and then gets almost triancle at 100 khz
is this normal ?????

B) the circuit is designed arround NE5532 but strangelly TL082 seem to behave the same regarding frequency response what will determine that 5532 is better than TL082???? is there any other way to mesure this ???? or simply take it as a fact that 5532 is better than TL 082 ???

C) finally is there any other better way that will make 5532 perform perfect square wave till 100 khz ?????

thank you
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Old 11th September 2008, 06:08 PM   #2
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Default here is the circuit

here is the circuit that belongs to ESP pages

forgot to mention that it also remains linear until 60khz ....then it start to drop ....
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Old 11th September 2008, 06:29 PM   #3
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A square wave consists of a lot of sinewaves, starting with the main frequency and then all odd harmonics. Like, if you have a 1kHz square wave, that is built from sine waves at 1kHz, 3kHz, 5kHz, 7kHz etc. Now, if you put that in an amp that at some point has a decreasing freq response, the higher frequency components get more attenuated. That causes the sharp edges of the square wave (which depend on the higher freq parts) to disappear and the wave gets rounded.

Since ALL feedback amplifiers at some point start to show falling freq response, it happens with all of them. But, for audio, this is pretty much moot because your amp is flat to 10's of kHz. What you see in your 28kHz square wave (which of course has nothing to do with an audio signal anyway) is probably because of falling freq response above 100kHz or so.

Makes sense?

Jan Didden
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Old 11th September 2008, 06:33 PM   #4
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the 5532 does better than that
maybe a problem with your implementation or the measurement?
Project 02 uses uncommon high resistance values.
Rod Elliott has a forum on his own. Maybe he would answer performance issues with his circuits?
regards
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Old 11th September 2008, 06:34 PM   #5
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Default janeman

yes it makes sense and more or lees is understandable .... but then what ???? i forget this circuit and built my shelf a doz preamp or other that will perform perfectly till 100 khz as stated ????

is all this a procedure that will guarantee better sound quality for the regarding stage ????

is this the correct procedure to see if you really have a good preamp in your hands ????
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Old 11th September 2008, 06:37 PM   #6
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Default thanks

Quote:
Originally posted by Juergen Knoop
the 5532 does better than that
maybe a problem with your implementation or the measurement?
Project 02 uses uncommon high resistance values.
Rod Elliott has a forum on his own. Maybe he would answer performance issues with his circuits?
regards

i will try to see about simular circuits with ne 5532 and get back to you ....i may be post in esp forums also

thank you very much
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Old 11th September 2008, 06:40 PM   #7
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Default Re: janeman

Quote:
Originally posted by sakis
yes it makes sense and more or lees is understandable .... but then what ???? i forget this circuit and built my shelf a doz preamp or other that will perform perfectly till 100 khz as stated ????


is all this a procedure that will guarantee better sound quality for the regarding stage ????



is this the correct procedure to see if you really have a good preamp in your hands ????
nope

nope

nope
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Old 11th September 2008, 06:51 PM   #8
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Default you were very correct

Quote:
Originally posted by Juergen Knoop
the 5532 does better than that
maybe a problem with your implementation or the measurement?
Project 02 uses uncommon high resistance values.
Rod Elliott has a forum on his own. Maybe he would answer performance issues with his circuits?
regards
i forgot that i was making these tests with the original cable of my signal generator that is 50ohms cable .....

i replaced the cable and see what i get now @ 28.500 hertz
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Old 11th September 2008, 06:54 PM   #9
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Default tschrama

Quote:
Originally posted by tschrama


nope

nope

nope
.......i would love to here your approach ...except nope nope nope

thanks
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Old 11th September 2008, 06:58 PM   #10
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hm, whats your signal generator?
regards
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