Low-distortion Audio-range Oscillator

[davada]

Originally Posted by dirkwright

Bob's oscillator is NOT easy to build unless you know where to get the rotary switches. I do NOT want to buy an old Heath oscillator just to gut it for Bob's oscillator. Bob's circuit is not easy to modify for pc mounted relays.

You are one of the highly skilled designers here that could easily offer a ready to go PCB and BOM that anyone could buy, but you don't. You refuse to take a leadership role here and force people like me to try to learn and understand all of the details of oscillators when I don't want to learn that.

It's not that we don't want to sell you boards. It just that our designs are still in the making. I'm not really speaking for everyone else.

We can't really take Bob's design and make boards for it and sell them.
Although if you look around the forum you will find that some have offered boards for there interpretations of Bob's oscillator. Maybe they still have some boards kicking around.

This is a DIY forum. A place to exchange knowledge, ideas and engage in technical discussion. It's really about doing it for yourself.

If you want help, you have been offered plenty. If you want boards you'll just have to wait until someone offers them.
You seem to reject everything offered to you so why would we trust you would buy our design if it were offered.

What we put up here is up for grabs by anyone. The next thing we know is someone slapping a patent on or taking credit for something novel we've done.
It has happened.

[1audio]

Originally Posted by dirkwright

I don't think you understand. I don't want to design my own oscillator. I don't want to do research into all of the different kinds of AGC circuits, and the pros and cons of each one. I just want a nice oscillator for my own use that is better than the Kenwood that I have now. Victor's oscillators are a pain in the @ss to deal with. I can't put them in a box unless I get a custom faceplate made. The board doesn't fit into a standard kind of box, I just about ruined one of them trying to remove some components, and he requires a stupid 35 volts to operate it. I wasted my money buying his oscillators in spite of the fact that they are very good performers.

I know Victors modules are a bit unconventional but mounting them really is intended to be a few round holes (rca jacks, level control and mounting screw (ground). I have made several suggestions for the 35V issue and at least one guy has successfully mounted a module is a cookie tin (good excuse to buy some) and is running it off of 4 9V batteries.

I think you are looking more for a kit like a Velleman where most of engineering is done and its kitted and just waiting to go into a chassis. This may happen here but it could take a while.

I'm here for the intellectual exercise. I see the interesting and big challenge is an ultra low distortion oscillator that doesn't need exotic stuff to calibrate or optimize. Samuel's targets are quite reasonable except I would ratchet up the flatness spec. Its really nice to just know that the error is essentially zero.

I think the targets can be met and without adjustments if the AGC element can be made to be really transparent. The State Variable has the best chance because the distortion from the AGC is low pass filtered twice. I think the Intersil sample and hold is a good option even at $8.00 since its still current production and available. The opto AGC can work but its time constants are long and it has a high voltage co-efficient making for distortion proportional to signal.

Tuning is a big challenge. It requires either a lot of parts or precision variable parts (pricing a dual gang precision pot can be shocking). Switches and relays are also expensive. This is why reclaiming a chassis with suitable components can be very attractive. The Heathkit would not be my first choice but its not bad. A board that could drop in and work in one would be pretty slick.

Failing that option a lot of decisions about what is needed are required. Continuous tuning is a big issue to address. A set of cardinal frequencies could make a lot of sense. Match those to a twin t filter with some signal conditioning and it could be very useful front end to a soundcard + fft.

[davada]

Hi Demian,

I sent you a PM with my email address. If the files are huge I not sure provider will accept them. If this is the case then we can use my gmail account.

Thanks again,

[klewis]

Originally Posted by dirkwright

Bob's oscillator is NOT easy to build unless you know where to get the rotary switches. I do NOT want to buy an old Heath oscillator just to gut it for Bob's oscillator. Bob's circuit is not easy to modify for pc mounted relays.

You are one of the highly skilled designers here that could easily offer a ready to go PCB and BOM that anyone could buy, but you don't. You refuse to take a leadership role here and force people like me to try to learn and understand all of the details of oscillators when I don't want to learn that.

Dirk, where do you get off speaking to Dick like this? He is suposed to supply you with what you need because you are to lazy to learn or unable to learn about this topic? Dick has shared considerable knowledge here and on his website.

Go buy a used device if you can't or won't do the work yourself, but, don't blame Dick, or anyone else.

Ken

[spind]

+1

[Samuel Groner]

There have been plenty of group buys on good designs on this forum, why not for an oscillator?

Because you continue to tremendously underestimate the difficulty of such a project. Anyone with basic experience and knowledge can put together a few transistors and call it The Subjectively Ultimate Power Amp. However getting reliable distortion figures at or even below the -120 dB level is an entirely different world--the notch filter is far less forgiving than the hum ear. I've spent now several years researching the design of high-performance oscillators and invested money for which you could by an entire pile of working HP 8903Bs (and I'm not doing this for profit!). Still I don't have a design at hand which I can offer as fully tested and well documented project. I'll share it once I'm there, but your attitude makes me feel like my efforts are not appreciated and I shouldn't.

Samuel

[richiem]

@Samuel Groner -- My build of Bob Cordell's oscillator runs around 0.6ppm THD at 1kHz at 6.3VRMS output, when tweaked for best overall operation across all ranges. I was able to optimize at 1kHz with a bit less than 0.3ppm THD. That's pretty good, but not ground-breaking. It would be interesting to try out some of the SG-505's tweaks on the build; but now I'm using different amps in it, not 5534s.

I would love to look at an SG-505 -- When they were affordable, i was doing other things -- now I'd like to have one but don't want to spend the ridiculous amount of money they bring, even in poor condition.

[Samuel Groner]

The Fluke 510A is a really interesting solution as well. it captures the peak voltage without a quad signal for triggering.

Just for the records the link:

http://assets.fluke.com/manuals/510A_AD_imeng0000.pdf

Also very interesting is the Fluke 5200A:

http://assets.fluke.com/manuals/5200A___imeng0300.pdf

Samuel

[KSTR]

Originally Posted by richiem

I would love to look at an SG-505 -- When they were affordable, i was doing other things -- now I'd like to have one but don't want to spend the ridiculous amount of money they bring, even in poor condition.

That's true. One has to be patient and wait until a good offer pops up. I was lucky to shoot mine in a TM503 rack together with an AM503+probe and a 1U TM500 prototyping/DIY kit (very rare) for less than EUR 500, supposedly from the estate of someone deceased and all in excellent condition. Not exactly cheap but well worth in the end. Applies to TM500 stuff in general, no way I could easily design and build a better (let alone cheaper) diff-amp than the AM502, for example...

[dirkwright]

Originally Posted by Samuel Groner

Because you continue to tremendously underestimate the difficulty of such a project. Anyone with basic experience and knowledge can put together a few transistors and call it The Subjectively Ultimate Power Amp. However getting reliable distortion figures at or even below the -120 dB level is an entirely different world--the notch filter is far less forgiving than the hum ear. I've spent now several years researching the design of high-performance oscillators and invested money for which you could by an entire pile of working HP 8903Bs (and I'm not doing this for profit!). Still I don't have a design at hand which I can offer as fully tested and well documented project. I'll share it once I'm there, but your attitude makes me feel like my efforts are not appreciated and I shouldn't.

Samuel

Considering that this is the first time you have shared this on this thread, then your offense is misplaced. If and when you offer some kind of kit for sale, I'll be one of the first to buy it. I had no idea you were considering this, so thank you for your efforts.