Resotune II

[Recording Engineer]

Well if the bidding works by just posting here, I’m in for $250.

 

[boji]

This clear quality is a novel measurement

As is its descriptor. 'Clearing heads' sounds more like meditation than tuning.
I feel lucky to have one and to know the dude who dreamed it up.

In an alternative future I imagined a version for luthiers, used to select tonewood.

 

[Tubetec]

Strikes a bum note with me , a genuine novel concept and well engineered product that does exactly what it says it does gets nowhere without greasing the wheels of the advertising train with dollar .

 

[JohnRoberts]

Strikes a bum note with me , a genuine novel concept and well engineered product that does exactly what it says it does gets nowhere without greasing the wheels of the advertising train with dollar .

No regrets that is just how the world works. I always planned to partner with a large company but failed to execute to that plan, mea culpa (my fault).

====
I am encouraged by the new found support. I may be able to squeak out a couple more units before I run out of the next critical component (faceplate escutcheons).

I don't feel great about auctioning these off to the highest bidder, but that is the free market way to allocate scarce resources, so I need to stick to my economic philosophy.

More later but it looks like several people will be disappointed.

Thanks again for the interest and positive feedback.

JR 

[update- I was able to get three more boards operational (using sample dome switches) so this will be the final units (again). I had to order supplies (more batteries) so will know the total number available after final assembly and test later this week.  /update]

 

[Pip]

I guess I have to counter $250.00 is bid.

Thank you

 

[JohnRoberts]

I just ran out of another $0.20 part....  I really hate paying $5 to ship $3 worth of components but that too is life in the EOL lane.

Both parts I ran out of are on order and should arrive by the end of the week.

Unless something else bites me I should be able to build and ship 4 units (I think).

I'll give you guys an opportunity to reduce your bids while I have more than 4 homes for these 4 units.

JR 

 

[Recording Engineer]

I'll give you guys an opportunity to reduce your bids while I have more than 4 homes for these 4 units.

I’m not sure what that means. I guess I reduce my bid to the most anyone else pays, up to $250? Does that work?

 

[bluesman714]

John:

    Would you consider, at some point, to sell a bom and plans to the diy community?

 

[JohnRoberts]

John:

    Would you consider, at some point, to sell a bom and plans to the diy community?

;D ;D ;D  Methinks you underestimate the complexity and design effort involved. There are over 5000 lines of software code running inside the microprocessor.

I will be glad to post the schematic, I will consider sharing the source code, but do not expect me to support that poorly documented machine language. I am not sure I can even follow everything I coded up ten years ago, let alone explain it.

IMO the cleverest software I implemented in this version is the fast "find note". To perform a sweep over multiple octaves, waiting for the sundry resonances to settle at each note takes a lot of time. I figured out a way to scan 3 different octave spaced notes simultaneously. By synchronously sampling the returning signals based on the expected wavelengths I was able to make rough level measurements of the three octave notes simultaneously. This cuts the sweep time to 1/3rd. Hint it relies upon the octave spacing to mathematically isolate one octave content content at a time based on how I mix and match the samples.

If I were designing this today using a blank sheet of paper I would use FFT and shotgun a spread of sine waves to quickly identify important resonances. I actually had this working on my bench using a DSP processor with built in 16b DAC. I think I made 8 different sine waves simultaneously, they had to be reduced to 1/8 full scale level to prevent saturation when arithmetically combined. The plan would be to read 8 spaced notes, and based on the results of the first pass generate clusters of notes around the lower two resonances, to zero in.. This should identify the important resonances in a small fraction of the time that even the 3x sweep speed of RESOTUNE II takes. This first step worked but I stopped pursuing this DSP approach, years ago. (I was also going to use a nice graphical display with touch overlay control.)

Fine tuning a specific resonance using FFT would likely involve a spray of three notes, one at target, one above and one below. The relative levels of the three returns would give real time tuning advice faster than the current RESOTUNE II sweeps above and below.

The Clear function would be performed the same way, generate tone at lug resonance (first overtone) and measure the relative phase shift of the sine wave returning. 

I may share the RESOTUNE II schematic later today, there are some IMO clever circuits I'd enjoy bragging about. 

========

EOL Status  I have the absolutely positively "last" four RESOTUNE IIs ever built up and tested. I am now waiting for batteries and some minor hardware (already on order and due by early next week).

Between now and then I will assess how many people want these, looks like at least three forum members here have made bids and at least two customers who contacted me through my website. So at least one will not get a tuner.  :'(

JR

 

[emrr]

Thanks John!

 

[JohnRoberts]

thanx... I just cut up dowels for the last time ever...  ;D

For today's TMI here is the RESOTUNE II schematic...

There is a lot going on so I will point out some of the highlights.

#1  4x AA batteries... The Resotune I ran off a 9V battery and had lousy battery life so I worked on that. While checking out this last batch of processor board I loaded random bench batteries into it and it worked but gave me a low battery warning... (blinking LED). One of the rechargeable batteries was literally 0V and the unit still worked with only 3 good batteries.

#2 reverse voltage protection. The mosfet in the top left corner just cuts off open circuit if negative voltage is applied. When on the on resistance is quite low for negligible drop.

#3 Using 4 batteries created a new problem... 4 brand new hot batteries exceed the max working voltage of the class D audio chip. So I designed a crude discrete voltage regulator using another mosfet and a couple transistors. This only prevents too much voltage from reaching the class D amp chip (bottom middle of schemo), when battery sags into the safe range this pre regulator turns hard on. A second 3.3 V LDO regulator provides clean voltage to the micro... It is not hard to get > 3.3v from 4x AA cells.

#3+ You will notice some weird discrete device configurations around the PS and the turn on/off switch. The power down function is performed the typical way for micros, shorting the on/off pin on the micro to ground tells it to turn off, and the micro tells the pre regulator to turn off, for zero battery drain when off. The turn on is more complicated with a trapeze act. The same on/off button turns on the pre-regulator long enough for the micro to boot up and tell the PS to turn on. Not trivial.  There is a low battery flag coming from the LDO that tells the micro to start blinking (while it still works even with only 3 batteries).

#4 next in the top middle of the schematic is my high side switches to multiplex my 16 line LED driver to control three banks of 12 LEDs; 12 green for Lug note, 12 red for drum (fundamental) note, and 12 sundry other indicators. I update the driver with SPI.

#5 the class D amplifier gets it's sine wave input from low pass filtered a PWM output from the micro. I have ferrite beads in series with the class D amp output and caps to ground before feeding the speakers. The loudspeakers would pretty much ignore the HF noise but I wanted to be a good RF citizen.  8)

#6 Not shown on the schematic I drive two 8 ohm speakers in series, this thing makes more than adequate level while sipping current from the batteries. RESOTUNE I used a class A/B audio buffer for horrible efficiency. 

That was easy.... not.  8)

JR

 

[bluebird]

Pretty awesome John, but wheres the toobz?  ;D

 

[corgan4321]

If anyone passes on one of these final units, I'm a taker!

 

[JohnRoberts]

If anyone passes on one of these final units, I'm a taker!

Thank you all, I have now allocated all of the final units. If any of these sales do not complete, I will reopen bidding.

JR

 

[Winston OBoogie]

Its a shame that what seems like a very useful tool was under appreciated by the folks that could really use it.

Besides proving that the idea and tech worked, I sincerely hope you made a few spondoolies along the way.

Respect. 

 

[JohnRoberts]

Its a shame that what seems like a very useful tool was under appreciated by the folks that could really use it.

Besides proving that the idea and tech worked, I sincerely hope you made a few spondoolies along the way.

Respect.

I left my footprints in the sands of time... This drum tuner is just one of several marks I left behind.

no regrets, but I am getting old and tired.

JR

PS: One thing I almost regret is the outlet tester I designed that actually works. Mine identified RPBG like the cheap 3 lamp testers do not. But again I abandoned it after sharing with the world how it works. http://www.johnhroberts.com/OD1.htm

 

[emrr]

Maybe the tuner and the outlet tester as a 2-pack, in vending machines.  Maybe that would do it.  ;D

 

[JohnRoberts]

Maybe the tuner and the outlet tester as a 2-pack, in vending machines.  Maybe that would do it.  ;D

;D

Sadly the magic price point for the outlet tester is <$10...  I can not imagine living long enough to recover the tooling cost and agency approval fees. I have already made UL several hundreds of dollars richer just buying the UL spec that covers these cheap testers that don't work. I can imagines easily paying several tens of $k to prosecute a UL file for my improved tester all the way to UL approval.

===
Likewise the magic price point/ package configuration for a drum tuner is a <$20 smart phone app... but my novel approach does not work without the more involved configuration (two speakers yadda yadda).

I am resigned to the fact that I will not earn back my initial tooling investment (I still have hundreds of pounds of aluminum extrusion from the first generation RESOTUNE I need to sell for scrap), and my many hours of unpaid research and development. I literally never took a salary for 15 years. Over the years I have paid taxes on paper profits (sales-inventory cost and - advertising).  Time to stick a fork in this under appreciated charity effort. I proved that the technology works.

I will still keep the lights on to support 3 year warranty.

====

The light at the end of the tunnel is getting closer, I shipped out two of the last four units this morning. I am still waiting on parts to finish the final two. The two customers I allocated these last units to have not responded yet, so if they do not pay up, I will reallocate these last two units. But they still have a few more days to respond.

JR

[update- the batteries I ordered arrived today and #3 of 4 allocated came across with the funds so number three is shipped.

I still need a minor hardware part (rubber feet) to finish building #4. Coincidentally about 6 months ago a customer contacted me about where he could purchase replacement feet... I just sent him a set for free. Ironic that I am now short exactly one set of feet,,, no good deed goes unpunished. 

#4 hasn't responded with the money yet, but he has a few more days before I can even ship.  /update]

[update 2-  #4 has checked in and his unit will ship next week after I get the missing parts. 

NoMo tuners fo sale.    [/update2]

[update 3]  final parts arrived this morning... Tuner #4 is built, tested and ready to go. It is sitting on my shipping bench ready to go out monday morning. Won't need that shipping bench any more either. /update 3]

 

[JohnRoberts]

Now I am just running out the clock on my 3 year warranty. My last official tuner sales were in 2020, so less than a year of warranty liability left to go.

So far exactly zero warranty claims, I consider that a robust reliable design.

Yesterday my phone rang and some drummer asked me if I had an old RESOTUNE laying around that he could buy... Sorry no.

After the 3 year warranty clock runs out, I can clean the rest of these old JIC parts out of my house.

JR

 

[emrr]

I wish someone would license this from you John. But not me!