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Old 8th October 2012, 07:57 PM   #3601
tessier is offline tessier  Canada
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Hi Salas

Here is the asc file.

Thanx

Paul
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Old 8th October 2012, 08:13 PM   #3602
Salas is offline Salas  Greece
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OK try with square waves. B1 should do a great 100kHz square wave if we keep the source impedance adequately low (20K pot max). I give you settings for 10kHz SQW.
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Old 8th October 2012, 08:24 PM   #3603
tessier is offline tessier  Canada
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Hi

10khz SQW work perfect.

What are the settings for 200kHz SQW ?

Thanx

Paul
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Old 8th October 2012, 08:59 PM   #3604
Salas is offline Salas  Greece
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I put those for you. See how it craps out with the input cap.
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Old 10th October 2012, 04:49 PM   #3605
AndrewT is online now AndrewT  Scotland
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1nF with 1k gives 1us RC time constant for the Input low pass filter. That has F-3dB ~160kHz.

That amount of filtering is not liked by most listeners. They hear some loss of treble signal.

You can try experimenting with values of 680p, 470p and 330p to see if these are more to your liking.
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Old 11th October 2012, 02:06 AM   #3606
tessier is offline tessier  Canada
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Hi Andrew

F-3dB ~160kHz, it's a quite high frequency, how can anybody could ear some loss of treble signal ?

Thanx

Paul
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Old 11th October 2012, 06:31 AM   #3607
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It's common to aim for an F-3dB point at least 10x higher or lower than the limit of the range you're trying to reproduce (20khz in this instance, so 200khz) to avoid noticeable attenuation or phase distortions within the target range of accuracy (20hz to 20khz).
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Old 11th October 2012, 09:17 AM   #3608
AndrewT is online now AndrewT  Scotland
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Quote:
Originally Posted by tessier View Post
...............F-3dB ~160kHz, it's a quite high frequency, how can anybody could ear some loss of treble signal ?...........
this question is typical from Members who do not follow the relevant Threads containing all the anecdotes of the "sound effect" of the various band limiting filters that are usually fitted to the inputs of Power Amplifiers.

Why do Members so often refuse to read the information that is here?
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Old 11th October 2012, 09:51 AM   #3609
Salas is offline Salas  Greece
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Quote:
Originally Posted by sharpi31 View Post
It's common to aim for an F-3dB point at least 10x higher or lower than the limit of the range you're trying to reproduce (20khz in this instance, so 200khz) to avoid noticeable attenuation or phase distortions within the target range of accuracy (20hz to 20khz).
My function generator puts out its best SQW at 1/20 its nominal -3dB high band ability, rounds slightly at 1/10, and gradually loses performance to obviously rounded the higher I push it. It was the same for my older analog one not only the newer DDS which has to be filtered for ringing at a point, its the same ratio from its rougher but best rise time TTL output. Any 3MHz-5MHz decent generator will do fine for audio, will give 150-250 kHz most excellent SQW.
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Old 11th October 2012, 12:07 PM   #3610
Salas is offline Salas  Greece
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To put some hardware in this spice infested world, here is what a quick B1 symmetrically powered with 220R gate stopper can pass @150kHz with budget 3MHz gen to a budget hacked scope. Well, I aim for AIM TTI gear when better heeled after the next aeon, LOL.
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