5 volt Guitar Effects via USB connection?

[Philippe]

is this concept feasible?  for those of you who attend tech trade shows, there's almost always a promotional giveaway that includes a portable cell-phone charger. these devices charge/recharge via your computer's USB port (or an AC adaptor) & provide a remote back-up when you are not near a wall plug or re-charging station.

on a USB connector: pin #1 = power & pin #4 = ground.

curious...are there any guitar effects/designs that can optimally operate on 5 DC volts/1000 mA?

this would make for a very compact (almost pocket-sized) effect with miniature pots (or slide-switches) + a 3pdt toggle switch covering the bases.  as replacement cellphone batteries are somewhat expensive/overpriced for what they are, these re-chargeable 'freebies' could supply the power at a minimal expense.

the question is...are there any low-voltage designs and/or a template for cutting USB openings in an enclosure?

[GibsonGM]

Great idea, Philippe!   I don't know of any current (or past) designs that run on 5v, primarily because higher voltage = more amplification possibilities, of course.   9V is the standard, because you're able to get +4.5V and -4.5V, which seems to play well with amplifiers and stuff.

Have you looked at using a 5V supply to run a CHARGE PUMP, and being able to raise that up to more 'standard' voltages?  I think that has a lot of merit, because you are right - there are MANY sources of 5V and USB around now.  I'm not sure how viable a charge pump would be (I don't use them personally), but well worth looking into!!

[Gus]

Some older effects ran on less than 9VDC
One could design a FF like circuit or treble boost or ... to run at 5VDC

[GibsonGM]

Some older effects ran on less than 9VDC
One could design a FF like circuit or treble boost or ... to run at 5VDC

Sure could, but how would the output levels be?   I suppose no worse than guitar >> amp, LOL...you must get a BIT of boost.  Would depend how much signal you eat with caps and whatnot.   

Something to try, and a good idea. Easy to see what'll happen, turn the knob down from 9V to 5V   

[Transmogrifox]

You could always make a little spider box that can be USB powered.  I built a little 4V-9V input to 9V output SMPS boost converter that seems to work fine with dummy loads.  I have not yet tried power FX with it to see how it does for noise, ground loops, all that.

The most robust design would use an isolation transformer as part of the SMPS so you have isolated ground between USB source and audio ground.  You never know what noisy beast converter they might have in the 5V converter.

[Gus]

I just ran a sim of a 5VDC like FF one knob fuzz

two 2N2222's or 2N2222a's
10K collector resistor for Q1 Q1 C to +5VDC
two 1K collector resistors for Q2 in series with a .01uf cap in parallel with the top one Q2 collector to +5VDC. Total resistance value 2K with a low pass filter out
150K Q2 e to Q1 b resistor
1k emitter to ground resistor for Q2 bypassed with a 47uf
.22uf, or .47uf or 1uf etc for input cap TRY a .22uf first
1uf film from the center node of the 1K and 1K Q2 collector resistors to a 100K volume control
sim shows about 3.2VDC at Q2 C and about 1.5VDC at Q1 C

I would add power filtering between the supply and fuzz

[Kipper4]

I would add power filtering between the supply and fuzz.

I might just stick the oscope on an usb socket and see what it sees.

Great idea in principle the only downfall is if it becomes mainstream is that some people will expect anything attached to usb to automatically do AD conversion.
I think it is a great idea. There's some low voltage stuff here

http://www.muzique.com/lab/lowvolt.htm

[PRR]

Many of the old-time op-amps need about 7V to wake-up.

Yes, there are many 5V opamps today.

[idy]

FZ-1 famous 3V fuzz.

[duck_arse]

cmos inverter based circuits, maybe they'd like 5V.

[R.G.]

Battery charging is what's known in the power supply biz as an "easy load". Batteries will take any charge that's shoved into them and as long as it's not so much current as to damage the battery or force the battery to a voltage that damages its electrochemistry, they're fine. There are fine points of how much, how fast, waveform, etc. for best battery life, but still - they're easy. In fact, many old school battery chargers considered the battery being charged to be the "filter cap".

Digital loads are much easier than analog ones. Digital logic has been designed to ignore the power supply voltage and ground as much as possible. How much is possible depends on the logic family, but still, as much as possible.

USB chargers are intended to power digital loads in most cases, or to charge batteries. They may be beautifully quiet. The operant term there is "may be".  Given the enormous range of complaints about everything in audio, there will be some unfortunately unsuitable USB chargers, just on noise issues. It's probably the lowest cost ones that will have skimped on filtering, and those are probably what you get as giveaways.

So, out of general conservatism - i.e., there ain't no such thing as a free lunch - if you assume a free USB charger is noisy until proven otherwise, you're only going to get pleasant surprises, not unpleasant ones. Count on filtering them until proven otherwise.

And, as already noted, count on having to read the datasheets for ICs you use on 5V. The TL072 and many other opamps can only swing to within 1.5 to 2V of either the plus or minus power supply. They may work on 5V, but you'll only get 1-2V of swing peak to peak out of them. Other opamps may need 7V, as Paul mentions. Still others will swing rail to rail in both inputs and outputs. Other ICs will work fine on 0-5V. It's in the datasheets.

USB chargers are good for double-and-regulate schemes to wipe off some of the noise. Also (probably) for triple-and regulate to get to 9V. You might even see if you can get *two* free ones, and somehow cobble a stacking Y cable to get 10V to regulate to 9V or whatever. You'll want to look for whether the charger is safety certified when you do this - or actually when you use anything that plugs into the wall.

At some point, you have to ask what the cost of a "free" power supply is, though. There is a ceiling on the amount of effort I'd want to put into working with a free USB supply, as commercial wall warts with proven quiet 9V outputs are about US$20. That's a long way from free, but it's easy to spend $20 in power supply add-ons and filtering without realizing it. It's another variant of why they call economics "the dismal science".

[Gus]

I searched for power bank schematics and ICs.  A lot can be going on in the circuits. 

I did not post why I would filter. R.G. did a good job explaining.

Are the inexpensive banks FCC part 15 accepted, UL, CE, etc. ?

[Philippe]

Are the inexpensive banks FCC part 15 accepted, UL, CE, etc. ?

the ones that I have are CE, FCC & RoHS approved (as stated on the enclosed instruction sheet). RG's concept of a dual-bank power supply would easily attain a 9v minimum although it would add to the bulk.

I was initially envisioning an effect (in a smaller than conventional enclosure) that could attach via velcro to a guitar strap & easily be turned on/off with a flick of a toggle switch.  your idea of a treble booster would fit the bill (if assembled on a terminal strip & the voltage requirements properly met). the sizing of any PC/perfboard becomes critical in this instance & a voltage 'pump' would only add to the dimensional requirements...thus something like a mini-delay would be totally out of the question/picture.

the banks that I have are 3/4"x 3/4" x 3-5/8" & could easily attach to the exterior of the enclosure.