Low-distortion Audio-range Oscillator

[HpW]

@vicnic please name in in more detailed manner about your reference brand.

As any pointer(s) and exact brand name and size... Melf or else & Company, brand name, size, may source and year of purchase O😉

Thank you...

Hp

 

[vicnic]

I have an old stock of Soviet precision metal film resistors S2-29V that I use as a reference. Compared them to Dale's 5 ppm resistors and there was no difference in the measurement area. Statistics and various practices indicate that they are most likely linear, as far as I can currently measure.
But in general, each sample of any resistor and capacitor should be tested individually before it is used in critical locations.

 

[HpW]

IMHO those, as Demian wrote: Vishay doesn't even publish linearity info on the Bulk Metal resistors. https://foilresistors.com/docs/63140/var.pdf

In the old days there was the Alpha Core as also none inductive as in a black plastic block.

As mentioned:

At that, negligible capacitance/inductance of foil resistors (when compared to wirewound resistors) significantly reduces
probability of self-excitation or "ringing" of amplification circuit.This is why Bulk Metal® foil resistors are such a good
choice for low-noise applications...

In the old days there was the Alpha Core as also none inductive as in a black plastic block.

MELF resistor from Token Electronics as none inductive as RFM series

 

[vicnic]

The better resistor is two resistors in series instead of one. 🙂

Yes, in many cases.
Also, by connecting four identical resistors in a series-parallel circuit instead of one and comparing the results, we can understand whether the resistor is linear or not.
One resistor ARG05FTC1502:
https://content33-foto.inbox.lv/albums/e/elterra/ResitorLinearityMeasurements/1R.jpg
Four ARG05FTC1502:
https://content33-foto.inbox.lv/albums/e/elterra/ResitorLinearityMeasurements/4R.jpg

 

[ginetto61]

my $130 Juli@ does that good with much narrower noise skirt

here's one RMAA test: RightMark Audio Analyzer test : Juli@ loop

hi excuse me Which model precisely ? thank you very much

 

[Frede]

I am about to build the 1kHz oscillator designed by Victor.
I intent to design with leaded parts (no smd).
My question:
I have difficuties finding the BAS70, I would like to know a replacement (leaded) for BAS70 please.

 

[vicnic]

As a replacement for BAS70 you can use two single through hole diodes:
https://eu.mouser.com/ProductDetail/Vishay-Semiconductors/BAT83S-TR?qs=WLTup5mM6hhDIDIvrvxhEg==
or
https://eu.mouser.com/ProductDetail/Vishay-Semiconductors/SD101A-TR?qs=IenFidxwq1RH4/rg/e4u3A==

 

[Frede]

@vicnic thank you very much.
One more question,
in my system where I intend to use the 1kHz oscillator the supply voltage is +/-12V.
What influence will that have on the performance?

 

[vicnic]

-V supply is the reference voltage for AGC. You will get 1.25 times lower output voltage. You can change the R7 value for to get output voltage back.

 

[Frede]

This is my version of Victors 1kHz oscillator.
I must explain, my design is with leaded parts, because I cannot design with surface parts because of my eyes.
I plan to use the 1kHz oscillator in an existing design (see photo’s)
This is a 1 kHz ref. signal source with a 60dB attenuator (1dB step) and a dual output driver (very low output impedance). All is controlled by Arduino.

The 1kHz oscillator works great.
I have some difficulties getting the oscillator to start, but I received fast and good help from Vicnic.

The specification of my 1kHz version is not at level of the original Vicnic design, but I will later optimize according to Victors recommendations.

For you information ......... a couple of photo's of the system, my layout of the oscillator and the very first test results.

 

[Bob Cordell]

VERY nice design!

What audio interface (sound card) did you use with Audio Tester?

Also, a nice Arduino project.

Cheers,
Bob

 

[Frede]

Hello Bob,
Thank you very much for your kind words.
I am using my own soundcard interface (Arduino controlled) and Creative USB0204 soundcard - interface to AudioTester (TrueRTA and REW)
Frede

 

[anatech]

Hi Frede,
Wow, really nice design! I'm impressed.

This would be an amazing project for many members, or kit given your hard work. My hat is off to you! Excellent!

 

[Pizzigri]

Absolutely!!!
Frede, unless you want to make a commercial product, I'd be really interested in making one following your project!

 

[Frede]

Hi Pizzigri,
I will absolutly not make a commercial project for any of my projects.
If anyone is interested I will be happy to share.

I have been using the setup of:
My own Soundcard interface - USB 0204 - Audio Tester - TrueRTA for more than 10 years (perhaps 20 years now)
Testing classic audio products like amplifiers - gramophones - FM receivers ect. in my small company Classic Audio.
I have now sold Classic Audio.

I have really a number of project for audio testing allready made with good documentation.
But I am not going to make any commercial project for any of the designs.

 

[Pizzigri]

Ohhh I was sending you a PM, and I didn't see you replied here! Thank you, Frede!

 

[jackinnj]

@Frede Bravo!

 

[RickRay]

That is one very well designed, versatile tool. I really like the what you decided to display. I would definitely be interested in building one.

 

[RickRay]

Special shout out and thank you to @vicnic for helping @Frede!

 

[jackinnj]

If you get two of Victor's oscillators, you can do IMD tests.