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Old 21st January 2013, 04:33 AM   #1571
kad is offline kad  Canada
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Well I must confess by the deep level of technical info in 157 pages worth of reply to date? Plus the redirections?

The first few pages were fantastic discovery.

May I then ask you to perhaps help answer this question:

Which latest version of a specific product would you recommend to a neophyte like me? For instance a kit including PCB and perhaps parts to achieve this Low-distortion Audio-range Oscillator objective?

My apologies, for not being more specific at this moment? Since I'm somewhat confused?


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Old 21st January 2013, 04:58 AM   #1572
richiem is offline richiem  United States
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You'll get some replies here -- How low is low for you? The EMU-0204 USB sound modules have pretty decent DAC boards that generate low-distortion output from software like ARTA. Or the QuantAsylum QA400 may be just the ticket.

These days, computer control is pretty good, and performance, while not state of the art, will be good enough for most tasks.
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Old 21st January 2013, 05:38 AM   #1573
1audio is offline 1audio  United States
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I still think Victor's oscillators are the best deal. Contact him here: viccc at ml dot lv. Anything else will be a lot of work and probably not as good.

A QA400 will do a fine job of analyzing and is a real value for the price. However its limited to 1V in and not much more out. I'm working on an interface to make it more useful but got sidetracked by real work.
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Old 21st January 2013, 05:56 AM   #1574
mkc is offline mkc  Denmark
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Hi Demian,

I'm waiting to receive my QA-400. I was thinking of opening a QA-400 thread to share add-ons, tools and experiences, like your front end suggestions.

Mogens
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Old 21st January 2013, 06:29 AM   #1575
richiem is offline richiem  United States
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Let us know here if you do open that QA400 thread.
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Old 21st January 2013, 07:49 AM   #1576
mkc is offline mkc  Denmark
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Hi Dick,

Sure. It was also my intention to include link to your twin-t filter. I have a 1 KHz and 10KHz version of Victors oscillator and have been looking at making a version of your twin-t with fixed frequencies.

Mogens
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Old 21st January 2013, 08:46 AM   #1577
RNMarsh is offline RNMarsh  United States
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Default It isnt as bad as it looks --

Quote:
Originally Posted by kad View Post
Well I must confess by the deep level of technical info in 157 pages worth of reply to date? Plus the redirections?

The first few pages were fantastic discovery.

May I then ask you to perhaps help answer this question:

Which latest version of a specific product would you recommend to a neophyte like me? For instance a kit including PCB and perhaps parts to achieve this Low-distortion Audio-range Oscillator objective?

My apologies, for not being more specific at this moment? Since I'm somewhat confused?
It really isnt as bad as it looks -- just change the IC's and a few caps and trimmers and you are done with the mods. Then just use its' own analyzer to tune the thd with the trimmers for a null. That's about it. The nice thing about the 339A is that it has a wide range of frequencies and it can be used as an rms voltmeter with db scales. The analyzer will accept a wide range of voltages on its input. It will give you a fast indication of the thd+n with a minimum of fuss and cost less than any other options.

We here got carried away with the oscillator and have been curious as to how low can we make it can go... far lower than the THD meter/analyzer part... but an indication well under .001 (-100dB) should show that you have a pretty good amp/preamp circuit.

The other options mentioned are also fine and may be of acedemic interest for you. They are not hard to use but require more knowledge in use and interpretation/meaning of the results, especially FFT -Thx RNMarsh

[BTW -- the 339A oscillator I have now has 2nd and 3rd at the residual of the ShibaSoku THD analyzer (-135).]

Last edited by RNMarsh; 21st January 2013 at 08:57 AM.
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Old 21st January 2013, 09:20 PM   #1578
richiem is offline richiem  United States
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As a matter of general interest, I simmed a passive Twin-T filter to see what the attenuations of harmonics are. Here are the results for the 2nd thru 5th to the nearest 0.1dB:
2nd: 9.1dB
3rd: 5.1dB
4th: 3.3dB
5th: 2.3dB
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Last edited by richiem; 21st January 2013 at 09:24 PM.
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Old 22nd January 2013, 04:19 AM   #1579
RNMarsh is offline RNMarsh  United States
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The oscillator is running! The freq scale switch' shaft set screw was loose and the switch wafers were not full turning where they needed to be... kinda half way in between positions. So, back on our heads! -RNM
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Old 23rd January 2013, 09:59 PM   #1580
RNMarsh is offline RNMarsh  United States
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Default refresh -

Refresh Notes on the thd of the 339A oscillator: Attached is the H2 and H3. Note this is on the lowest scale -- .0003%.... about .00002% and .00001% -- nulled/trimmed at 1KHz.[without external notch on H2 or H3]

Thx-RNMarsh

H2 339A 1KHz.jpg

H3 339A 1KHz.jpg

Last edited by RNMarsh; 23rd January 2013 at 10:08 PM.
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