Low-distortion Audio-range Oscillator - Page 72 - diyAudio
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Old 14th October 2012, 05:57 PM   #711
KSTR is offline KSTR  Germany
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Quote:
Originally Posted by 1audio View Post
Ultra low distortion audio oszillator the never ending search for a pure sine is one effort with unbelievable breadboarding. If someone has a layout that worked I would be interested.
That one IS crazy, even the great Jim Williams would have been impressed I guess.

A double-sided single PCB for this will be tricky, but I could imagine a "hybrid" approach using a main board and vertical sub-PCBs, and the occasional shield and p2p wiring. Although I'm tempted to try I foresee a lot of effort going down the river until this plane will really fly...

For the time being, Victor's plug&play builds shall do for me.
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Old 14th October 2012, 06:17 PM   #712
davada is online now davada  Canada
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Quote:
Originally Posted by KSTR View Post
That one IS crazy, even the great Jim Williams would have been impressed I guess.

A double-sided single PCB for this will be tricky, but I could imagine a "hybrid" approach using a main board and vertical sub-PCBs, and the occasional shield and p2p wiring. Although I'm tempted to try I foresee a lot of effort going down the river until this plane will really fly...

For the time being, Victor's plug&play builds shall do for me.
I've done a couple of double sided boards with ground planes recently.
One turned out great and the other was a flop. I have to fine tune the process.
What mades it work was a 1/16 inch acrylic sheet placed between the the upper and lower
transparencies. A piece of scrap 1/16 FR4 at the top to have something to tape to, all on sheet of glass. Replace the acrylic sheet with the board when everything is lined up.

This is off topic so I'll leave it at that.
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Old 14th October 2012, 07:14 PM   #713
euro21 is offline euro21  Hungary
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Victors's 1KHz board spectrum.

Battery powered (4*9V), shield only small aluminum enclosure (cost ten bucks, installation about 3/4 hour handwork :-) ), M-audio Transit USB ADC, Visual analyser run on laptop.
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Old 14th October 2012, 07:54 PM   #714
1audio is offline 1audio  United States
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Looks like the limits of the Transit. You will need a notch filter to see more. Clearly this is very cost effective.
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Old 14th October 2012, 08:36 PM   #715
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Definitely limited by your sound card at this point, but the response looks impressive (the card, not the oscillator) in comparison to my M-Audio ProFire 610.

The only way to really see what Victor's oscillator can do is to notch it.

I have had some difficulty getting ideal driving capability out of Victor's oscillator after some testing this weekend. Tried driving my balanced input preamp, followed by a notch filter, to see how my preamp measures up. Fought for a long time with noise, grounding, and the annoying reality that Victor's oscillator really wants circuit common to be referenced to earth/shield.

I have Pete Millet's soundcard interface, which helped a bit to at least get me some decent measurements (happy to say the preamp measures really well), but the interface adds a bunch of 60Hz and its harmonics to the spectrum, as well as adding quite a bit (-116dB) of 2nd distortion to Victor's output. So there was no reliable way of measuring 2nd harmonic at this point, but at least the 2nd is fairly benign.

I will look into a Jensen output transformer to better balance out the oscillator output. In my experience a good transformer having to only run at 1 kHz will beat the soundcard interface.
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Old 14th October 2012, 09:50 PM   #716
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Quote:
Originally Posted by davada View Post
Even an amatuer like myself can see that the layout of this board is very poor. I am interested in working on this in spite of my lack of experience.

Based on the schematic, it looks like the output is balanced. Is that correct?

I think I will start by building the super gain block first and see how that goes.

Last edited by dirkwright; 14th October 2012 at 09:55 PM.
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Old 14th October 2012, 10:28 PM   #717
klewis is offline klewis  United States
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Quote:
Originally Posted by 1audio View Post
I thought someone had built this and posted info on it. Some of the LT app stuff has proven really hard for me to duplicate and this was so off the wall I did not try. I would like to see the layout they used to make it work.

Ultra low distortion audio oszillator the never ending search for a pure sine is one effort with unbelievable breadboarding. If someone has a layout that worked I would be interested.
Using the advanced search function, put in username "frex" in topic "oscillator"
Frex has built it and sells the boards. I'm about half way through building it.
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Old 14th October 2012, 10:36 PM   #718
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Quote:
Originally Posted by klewis View Post
Using the advanced search function, put in username "frex" in topic "oscillator"
Frex has built it and sells the boards. I'm about half way through building it.
It would be useful for folks to read Bernie Oliver's article in the HP Journal on how bridged T oscillators really work.
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Old 14th October 2012, 11:22 PM   #719
davada is online now davada  Canada
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Originally Posted by scott wurcer View Post
It would be useful for folks to read Bernie Oliver's article in the HP Journal on how bridged T oscillators really work.
Do you mean this one?

The Effect of u-Circuit Non-Linearity
on the Amplitude Stability of RC Oscillators

http://www.hpl.hp.com/hpjournal/pdfs...Fs/1960-04.pdf
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Old 15th October 2012, 12:08 AM   #720
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Quote:
Originally Posted by klewis View Post
Using the advanced search function, put in username "frex" in topic "oscillator"
Frex has built it and sells the boards. I'm about half way through building it.
It's a very nice looking board:
[3rd round] AN67 Ultra-low THD 10kHz sine oscillator PCB Group buy. - Discussion Page 10 - diyAudio

He did a great job. It's designed to fit into a specific chassis. It's certainly the highest performance Wein bridge in the known world.

My idea is to have a set of fixed frequency oscillators all in one box with a selector switch to power up and connect the one to be used. Each oscillator could be optimized for it's particular frequency, though I don't know how to do that. I want all oscillators to be on separate boards, each board having a mounting hole in each corner of the board to maximize flexibility in installing it in a chassis. This one could certainly be the basis for the 10kHz oscillator I would use. I'm thinking of: 1kHz, 10kHz, and a twin tone oscillator of some kind for IM testing.

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