Official Luthiers Forum!

Audio signal generators that are useful for plate tuning cost a fortune. (some are more than $50K!) While looking around for something cheaper I ran across a Windows program this should work. Put your old PC in the shop and add an amplifier to the audio out and you should be ready to go.

Go to SigJenny
to get what appears to be a free signal generator. I played with it a bit last night and it should work for plate tuning. It has a sweep feature that should make it useful for spectrum analysis using A Carruth's "stinger" to excite the top.

Cool find Mike

Great find. I grabbed the speaker test program "NWin" as well having a means to evaluate the results could be important. A guitar top is just a speaker with a complex frequency response.

http://www.surfhousesurfcam.com

Mike, you might have found the key to a low cost standard test system we could all use as discussed in a previous thread.

You will, of course, need an amp to go along with that. 12W is about right.

The problem with hard wired signal generators is that you either get a piece of test equipment that does a world of stuff you don't need (gigHz square waves) or you get something that's custom made for plate tuning, and it costs a lot because it's a specialty item. I used to make the things, and the actual parts count was pathetically small compared to a video game, but we had to charge a bunch for them because they were essentially hand made.

I'd like to put in a plug for Don Bradley. He took over the business from me when my Dad, who was the real electronics guy, died. The new digital units Don puts out are wonderful. They are plenty powerful, the wave form is perfect, the resolution is awesome, and they cover the whole range from under 1 Hz to 20,000.

I've had some problems getting SigJenny to run on my computer. Sweepgen runs fine. I usually use my old version of 'Coolwave' to generate sweep signals. The 1W or so that my sound card puts out is fine for most testing, but won't generate glitter patterns.

A friend and I stayed at Don's house when I was taking Harry Fleishman's class last year. Don took us out to his shop one afternoon and showed us his signal generator stuff. Pretty neat to see it firsthand as he vibrated some violin plates.

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Jonathan Kendall, Siloam Springs AR

Alan...Can you post Don's contact info since LMI is no longer listing his signal generator (for those who dont have a signal generator and are in the market)?

For those that are hunting for a signal generator...I will also put in a plug for Don's stuff...top notch equipment and just what is needed and works right out of the box.

For those that are looking on eBay for used equipment...it is possible to get a unit that works but understand that most of the ones listed are often in a frequency range that is meant for radar and television, not what is needed to generate glitter patterns. Alan can speak much better to this than me but what is critical is a range that goes low enough...it also has to be able to display easily the frequencies that it is putting out...surplus gear is only a good deal if it is useful for the purpose it is intended...

I should have posted this yesterday, but I had some things to do...

Bradley Engineering
P.O. Box 141
Forestville CA 95436
(707) 887-9746
sonomadb@sonic.net

I hope that's the right e-mail....