Paper Jamz Amp Mod

[Jdansti]

I was in the Goodwill store today looking for speakers and other electronics I could scavenge for parts and ran across a new Paper Jamz Amp for $4. I decided to buy it and see what I could do with it. Before I start the surgery, I was wondering if anyone has any experience with them.

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[Earthscum]

I don't know anything about them at all, but I keep seeing them for cheap. I would also be interested to hear if anyones bent these things yet. I imagine it's SMD, but I don't see that as much of a deterrent, lol.

[artifus]

pull it apart, lick your fingers and start touching. google reed ghazala and nic collins, maybe adding the words circuit and bending. have fun.

*edit* also - reflecto-porn! hello jdansti!

[Jdansti]

*edit* also - reflecto-porn! hello jdansti!

Whoops!  Good thing I was wearing my G-string!

[Jdansti]

Ok-First test: Plug my Strat directly into the Paper Jamz (PJ) amp using a 1/4 to 1/8 plug adapter.  Results: Nada damn thang.

Second test: Run the Strat through the Tillman preamp through my Dynamic Hype OD through my Valvecaster and to the PJ amp.  Crank all of the volumes to max.  Results: Very low volume from the PJ.

Third test:  Run the output of my iPhone into the PJ.  Results:  Not too shabby and decent volume.   Apparently the PJ amp wants a signal more like a line out or headphones output than what the guitar and pedals produce. Sort of like amplified computer speakers.

Fourth test: Run my Strat through a Sony HR-GP5 multi-FX unit and come off of the headphone output to the PJ amp. Results: Now we've got enough volume to hear something.  Doesn't sound bad for a cardboard box.  Based on a website showing a dismantled PJ guitar, the "speaker" appears to be a transducer or driver glued to the cardboard face. This makes the face of the box act like the diaphram of a loud speaker.  I would guess that the output is maybe 1/2 that of a Ruby amp.

Anyway, as-is, It's not practical as a practice amp for a regular guitar.  I might open it up and look at the guts.  I recorded some video. I'll post it after I get a chance to edit it into something worth watching.

[Earthscum]

From what I can see online, the amp is just batteries and speaker, didn't see any kind of circiutry, that I can remember (read through some stuff saturday night).

Apparently the guitar is where it's at. It has some interesting stuff going on, including a 1W amp chip. The micro controller is wirebond blob. There's a couple really good teardowns of the guitar. It uses capacitive sensing.

I wanna go grab one of the drum sets now, lol. I think that would be the most useful to hack into... maybe even make it into a guitar pedal somehow.

I know this idea is gonna get stolen, but I've been working out ways for the last couple years to make flat (1/4"-3/8" thick) pedals. I gave up when I figured out I'll be looking at micro controllers and SMD, that's jumping in with 4 feet first for me, but it would be so kewl, wouldn't it? 

[Jdansti]

Yep - super thin pedals would be cool, but is a long way from the mega-components that we normally use. After all, 99% of the stuff that we build is based on circuits that were hand built in the 60's and 70's.  Certainly, commercial operations use them. Just about anyone with a design and some cash could have a board shop crank out some SMD based boards.   I wonder though how SMD capacitors and other components would sound compared to the conventional ones.

I'm going to open the sucker up and look for the little man behind the curtain. There's got to be a circuit driving the transducer.  I wonder if the transducer could be utilized for something like driving a plate reverb, or attached to a drum head or something.

[Jdansti]

Well I dug into this thing and as I suspected, there's a small amp and the "speaker" is a driver glued to the cardboard front. I removed the guts and played through it and the driver is very tinny. All I had to do to get some volume and depth was to hold the driver against a piece of paper or cardboard.

A look at the PCB revealed a CE0030B amp chip (http://www.hedepower.com/down/CHIPOWER/CE0030B-EN-10.pdf).
Here's a summary of the chip's features:

- Fully differential amplifier
- Improved PSRR at 217Hz(VDD>3.0V) 83dB (Typ.)
- Power output at 5.0V & 1% THD 1W (Typ.)
- Power output at 3.6V & 1% THD 0.5W (Typ.)
- Ultra low shutdown current 0.1μA (Typ.)
- Improved pop & click circuitry eliminates noises during turn-on and turn-off
transitions
- Thermal overload protection circuitry
- No output coupling capacitors, bootstrap capacitors required
- Unity-gain stable
- External gain configuration capability
- Available in space-saving packages: 8-pin MSOP8, SOP8, DIP8 & DICE

Here are some pics:

Inside showing the speaker driver attached to the cardboard:


The back of the battery compartment showing the location of the PCB:


A close up of the speaker driver:


One side of the PCB:


The other side of the PCB:


A close up of the amp chip:


The next thing I'll do is hook it up to a regular 8-ohm speaker and see how it sounds. I'm wondering if the amp might be usable for a practice amp. I would have to boost the input signal enough for the amp to work. If I have to do that, it might make more sense to just build a full practice amp and not use this. Any thoughts?

[Earthscum]

Sweet... so there IS a chip in there! The stuff I had read led me to believe there wasn't any circuitry involved, just extra battery power to drive the transducer. (I was guessing something like phantom power, in a way).

I got some transducers a while ago when they were on sale. Like these: http://www.parts-express.com/pe/showdetl.cfm?Partnumber=297-206 but white plastic, and the ones I got are 4Ohm x 2 10W  (so basically I have 4x4Ohm 5W... I think). I just came across them the other day and though about this again... I should grab some cardboard and make a life-size PaperJamz half-stack, lol.

Cool deal, man... thanks for the teardown!

[Jdansti]

I got some transducers a while ago when they were on sale. Like these: http://www.parts-express.com/pe/showdetl.cfm?Partnumber=297-206 but white plastic, and the ones I got are 4Ohm x 2 10W  (so basically I have 4x4Ohm 5W... I think). I just came across them the other day and though about this again... I should grab some cardboard and make a life-size PaperJamz half-stack, lol.

Cool deal, man... thanks for the teardown!

Your link says, "Turn almost anything into a speaker!"... windows, cabinets, pictures, etc.  I wonder what they would sound like on a 4' x4' piece of cardboard.

I think that Toyota used transducers in the head liner of my FJ Cruiser. I can hear the stereo sound coming from above my head and the headliner vibrates.

Anyway, the CE0030B chip is manufactured in 8 pin dip. I wonder if Paper Jamz is doing something on the input to allow it to accept a hi power input like the output of another amp (iPod and other headphone amps). If I could get a single chip, I'd like to see if it would take a guitar input. Maybe someone more knowledgable than I could look at the data sheet and tell.  Also, a quick search for the chip on the web only yielded wholesalers. Digikey and Mouser don't have them.

[Earthscum]

This, IMO, would be a decent amp for something like that... TDA2822 Datasheet (and I found they can make pretty decent distortions!)

From what others were saying, the transducers I got actually sounded better using cardboard. I wouldn't doubt it if they were originally intended for exactly what you suspect in your Toy, mounting to headliners.

[Jdansti]

Thanks Dave. I saw your schems for the TDA2822 here: http://www.diystompboxes.com/smfforum/index.php?topic=95477.0. I might try the 2822.

[PRR]

Kerect me if I'm wrong.

The Paper Jamz "guitar" has no strings, has songs built-in. It presumably has a musical greeting-card chip with toonz burned in, outputting a teeny fraction of a Watt.

Then for more annoyance you pay $9 for the most-of-a-Watt amplifier.

WowWee indeed.

If you gonna use the amp with a normal (play it yerself) guitar chain, you need at least a gain of 10 just to get up to the level of the Paper Jamz "guitar" chip, from there you can go into the Paper Jamz amplifier. You also need to be able to drive 5K... this is probably where the ValveCaster fails, its output impedance is ~~100 times higher so the actual delivered signal is ~~100 times smaller than usual, and even VC's high gain can't handle that much suckage.

9V batt and TL071 NI booster. Gain setting can be 10K and 500 ohm resistors.

Yes, it is silly to have more Volts on the preamp than the "power" amp. If you know a good low-volt booster with that much gain, do it.

[Jdansti]

Kerect me if I'm wrong.

The Paper Jamz "guitar" has no strings, has songs built-in. It presumably has a musical greeting-card chip with toonz burned in, outputting a teeny fraction of a Watt.

Then for more annoyance you pay $9 for the most-of-a-Watt amplifier.

WowWee indeed.

If you gonna use the amp with a normal (play it yerself) guitar chain, you need at least a gain of 10 just to get up to the level of the Paper Jamz "guitar" chip, from there you can go into the Paper Jamz amplifier. You also need to be able to drive 5K... this is probably where the ValveCaster fails, its output impedance is ~~100 times higher so the actual delivered signal is ~~100 times smaller than usual, and even VC's high gain can't handle that much suckage.

9V batt and TL071 NI booster. Gain setting can be 10K and 500 ohm resistors.

Yes, it is silly to have more Volts on the preamp than the "power" amp. If you know a good low-volt booster with that much gain, do it.

Thanks PRR.  This adventure was pretty much based on curiosity. When I saw the $4 price, I saw the perfect opportunity to take one home and rip its guts out  . Now I know what makes it tick. I appreciate your information on the gain required.

Re: The PJ guitar, I think they have some prerecorded music on them, but based on some YouTube videos I've seen, I think you can also "play" chords (one string chords). It also allows for palm muting and has a whammy slider bar. All in all, it's still a toy, but it's kinda neat how they use the capacitance controls. As a side note, when we have family get togethers, the kids (little and big) like to play Guitar Hero. I took a cheapo pawn shop Kasino guitar and transplanted the guts from a GH guitar into it. I mounted momentary push button switches in the neck and countersunk homemade wooden switch buttons to match the fretboard. The problem is that the switches wear out too fast. I guess that some of the players really mash down pretty hard. It would be great if I could replace the mechanical switches with capacitive switching. I really haven't investigated this yet, but off the top of your head, do you know if capacitive switching is DIY-able?

[Earthscum]

I've been doing a bit of research into capacitive touch... short attention span, and short story shorter, I started looking Saturday night, and it quickly evolved into spending yesterday seeing about getting into PIC or AVR.

Tammy pretty much summed it up: "Are you talking about the touch points controls ? They're capacitive sensing. Right now not very DIY-able as most of the magic is in the microcontroller."
http://www.diystompboxes.com/smfforum/index.php?topic=91786.msg785150#msg785150

Which, in reality, very DIY-able, if you wanna take that trip. Not like I don't have enough projects to keep me busy, but I think I'm gonna pack some bags, lol. PIC looks fun... AVR looks "popular" to me... easy to get into, etc. but has limits for someone who likes to abuse things (a pocket knife is also a can opener, small hammer, prybar... lol).

I did come across something about a year or so ago on EDN, maybe? about using cmos to make touch switches, but I seem to remember some issues with sensitivity, etc, that a micro controller just takes care of naturally (may have been with debouncing?).

ETA: Here's the teardown on the guitar circuit. EDN - Paper Jamz guitar relies on AAA batteries, printed electrodes and connectors

This one is a much better teardown, IMO: http://stryker.hackhut.com/2011/01/31/paper-jamz-review-future-hacks/

[Jdansti]

I've been doing a bit of research into capacitive touch... short attention span, and short story shorter, I started looking Saturday night, and it quickly evolved into spending yesterday seeing about getting into PIC or AVR.

Tammy pretty much summed it up: "Are you talking about the touch points controls ? They're capacitive sensing. Right now not very DIY-able as most of the magic is in the microcontroller."
http://www.diystompboxes.com/smfforum/index.php?topic=91786.msg785150#msg785150

Which, in reality, very DIY-able, if you wanna take that trip. Not like I don't have enough projects to keep me busy, but I think I'm gonna pack some bags, lol. PIC looks fun... AVR looks "popular" to me... easy to get into, etc. but has limits for someone who likes to abuse things (a pocket knife is also a can opener, small hammer, prybar... lol).

I did come across something about a year or so ago on EDN, maybe? about using cmos to make touch switches, but I seem to remember some issues with sensitivity, etc, that a micro controller just takes care of naturally (may have been with debouncing?).

ETA: Here's the teardown on the guitar circuit. EDN - Paper Jamz guitar relies on AAA batteries, printed electrodes and connectors

This one is a much better teardown, IMO: http://stryker.hackhut.com/2011/01/31/paper-jamz-review-future-hacks/

Thanks for the links. I did a little research and every thing I found uses some type of microcontroller to charge and discharge a capacitor at a given rate.  The MCU looks for a change in that rate. The touch pad is connected to the capacitor, the discharge rate changes when your finger touches the pad. The MCU senses this change and performs whatever action you've programmed. You might have seen this in your research on the PIC, but here are a couple of links that describes this in better detail:

Intro to capacitive sensing: http://ww1.microchip.com/downloads/en/AppNotes/01101a.pdf
PIC10F: http://ww1.microchip.com/downloads/en/AppNotes/01202B.pdf

I have to wonder though if there might be a more "analog" way to do capacitive sensing. For example, a circuit that would charge a capacitor which would then be discharged to ground through a transistor to a touch pad that has an air gap with one side connected to ground. This causes the transistor to switch and activate something. This circuit would have to automatically reset itself (recharge the capacitor).  Of course you'd have to have a separate sensor circuit for each thing you want to control. This might be like the CMOS approach you mentioned.  The other thing is that the laws of physics might say that this idea would not work...

After more research I found this:
1.5V Capacitive Switch: http://www.discovercircuits.com/PDF-FILES/mom1v1.pdf
Up to 50 Remote Touch Switches: http://www.discovercircuits.com/PDF-FILES/12vexc1.pdf
MOSFET Finger Controller: http://www.discovercircuits.com/PDF-FILES/fingersw.pdf

Again, you might have already tread this ground, so my apologies if this is the case.     

[PRR]

Cheap/crude capacitive sensing:

Plug cord into (normal) guitar amp, but not into guitar. Clamp far end of cord to hold still without you touching it. Dime the amp. Don't be touching amp or other metal. Bring your finger near the plug-tip. There's a buzz. (Touch the tip there's a BUZZZ!)

Use any crude high-impedance signal detector to sense the small (or large) buzz. CMOS offers high impedance and high gain but is prone to static damage. TL072 is hot and tough. Drive a diode and smoothing cap, diddle gain, you get voltage when finger is "near".

This assumes you are in a room full of wall-power, but are not right next to fusebox or fluorescent lamp. Since the WowWee product is best used far-far outside the house, or the far corner of the basement (for least parential damage) they surely use something trickier. A 50KHz squarewave couples even better than 60Hz buzz and can't be confused for wall-buzz, but does need a signal source and added wiring.

Actual strings on frets can work as contacts. They will take considerable pressure and wear, as you know. You have to wire every fret, which is a lot of small wires to route in the side of the neck. If you want a 6X22 array you must insulate the strings, but for WowWee fingering you can just wire to the metal bridge/nut so all 6 strings work the same. You probably scan the frets and "take" the hot fret closest to the body, to emulate the speaking-length part of normal string fretting. Electrically it is possible to detect all the contacted frets and do something else, but on a low-action cheaply-fretted guitar you are liable to have more contacts than you expect.

A "good" preamp for the PaperJamz amp (to use with normal e-guitar) is probably a lot more cost/trouble than the amp is worth. An LPB or two, possibly with output mods, may be the least-investment trick.

[Jdansti]

A "good" preamp for the PaperJamz amp (to use with normal e-guitar) is probably a lot more cost/trouble than the amp is worth. An LPB or two, possibly with output mods, may be the least-investment trick.

Thanks - I agree!

[Jdansti]

The saga continues. 

I found a purpose for the little CE0030B PaperJamz amp (kinda sounds like Steve Martin in "The Jerk" when he finds his "Special Purpose").

I'm building a Noisy Cricket practice amp and I plan to install the PaperJamz amp as an MP3 amp in the same enclosure and with separate speakers. I'll be able to plug my MP3/iPhone in and play along with the music. The PaperJamz and Noisy Cricket will be independent circuits including their output speakers. Not bad for $4. 

I had to make a little 5V regulator circuit for the PaperJamz power supply. The little board on the left is the 5V regulator and the one on the right is the PaperJamz amp:




I piggybacked the regulator on top of the input jack with a dab of hot glue:



I tested the final circuit by playing my iPhone through it. It sounded pretty good through the $5 set of speakers I got at Good Will.

[petey twofinger]

they have these for 99 cents at my goodwill , so i  couldnt resist picking one up . thinking it may also work well to amplify a chip synth , like a nic collins deal / 555 opto theramin or something like that . advantage is its size .

off topic i have been finding belkin apc units for att uverse , they have battery back ups they install for the phone system , i have gotten 3 so far , they usually have a GOOD 12 volt sla cell inside ,  you can test / charge the cell with the unit , it also works well as a power supply .

these are perfect for larger " mini amps" in my opinion , anyway . and for 5 - 10 bucks a pop ,  not too shabby of a deal .

got a pete the repeat talking parrot for 99 cents too , hmm . i wonder if this could be easily hacked into a device that would play actual ( albeit down sampled ) guitar notes , use it in place of the quick and dirty test osc .  either that or some sort of looper , but .... can o worms ...