Low-distortion Audio-range Oscillator

[davada]

Originally Posted by dirkwright

So, is this thread going to lead to a definitive "super oscillator" schematic, or is everyone just punting ideas around?

Yes we will come up with a super oscillator.

Eventually.

[dirkwright]

Originally Posted by davada

Yes we will come up with a super oscillator.

Eventually.

Thanks.

Do you expect a group buy on some boards then? I'm just trying to get an idea on where this thread is leading. The goal, in other words.

[davada]

Originally Posted by dirkwright

Thanks.

Do you expect a group buy on some boards then? I'm just trying to get an idea on where this thread is leading. The goal, in other words.

Well I suppose if one of us makes a break through boards may become available.
You have to clear what you're looking for.

Are you looking for inexpensive medium performance full range or expensive high performance full range? What about a price target?

[dirkwright]

Originally Posted by davada

Well I suppose if one of us makes a break through boards may become available.
You have to clear what you're looking for.

Are you looking for inexpensive medium performance full range or expensive high performance full range? What about a price target?

I like this one:
http://www.users.on.net/~glenk/thd/generator.pdf
which appears to be a variation of Bob Cordell's SVF oscillator.

but I'm willing to build an HP 239A clone (bridge T) also.

So, I guess the former comes under the expensive high performance full range and the latter is less expensive less performance, maybe? Why not both? Why not start with the former and make improvements to it (which I don't have any idea what those would look like)?

[davada]

Originally Posted by dirkwright

I like this one:
http://www.users.on.net/~glenk/thd/generator.pdf
which appears to be a variation of Bob Cordell's SVF oscillator.

but I'm willing to build an HP 239A clone (bridge T) also.

So, I guess the former comes under the expensive high performance full range and the latter is less expensive less performance, maybe? Why not both? Why not start with the former and make improvements to it (which I don't have any idea what those would look like)?

Okay then put an SVO on a separate board from the AGC and multiplier.
This way you have an option for future modifications.

[panson_hk]

Originally Posted by dirkwright

So, is this thread going to lead to a definitive "super oscillator" schematic, or is everyone just punting ideas around?

Any definition/requirement for a "super oscillator"?

[jcx]

how about a "super multiplier" - one which gvies low harmonics of its diference product frequency output

then quite ordinary oscillators or DACs can feed it frequeny pairs

[1audio]

I have attached the Boonton 1121 AGC circuit. This circuit has fast settling and works without any time constant changes from 10 Hz to 140 KHz controlling a SVF oscillator.

Point c is the sine output, point b is the cosine output and point a is the dc voltage back to the AGC element (an analog multiplier in this case). The absolute flatness is in the .01 dB range across its full range. I don't know the settling time but its fast enough to use for swept measurements. An informal test from 500 Hz to 20 Hz showed no obvious change in level.

It may seem complex but all the other solutions are similarly complex and I would guess the cost of an extra wafer on a switch for range caps would not be much less expensive.

The HA2625 opamp is uncompensated and they used the compensation connection to limit the output swing to work with TTL. You would need a separate 5v supply for this circuit.

[1audio]

Originally Posted by jcx

how about a "super multiplier" - one which gvies low harmonics of its diference product frequency output

then quite ordinary oscillators or DACs can feed it frequeny pairs

Do you mean a good double balanced mixer, or a beat frequency oscillator? Beat Frequency Oscillator 700a Equipment General Radio

[jcx]

I ws thinking Gilbert Cell multipliers might be better suited to audio - but not certain of practical limits - obviously Spice perfectly matched Q models will give over optimistic results

and what are we practically aiming for -120, -140 dB for < 20? kHz harmonics + IMD, Spurs?? from 24/192 aduio DACs generating input sines in 50-100 kHz range