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Old 7th May 2018, 02:10 AM   #11
Printer2 is offline Printer2  Canada
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Skip the first stage.

Click the image to open in full size.

something like this for the reverb.
Click the image to open in full size.

and for kicks,

3A DC-DC Boost Step-up Converter Voltage Regulator 5V-35V to 9V 12V 24V 36V 48V | eBay

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TPA3118 PBTL Mono Digital Amplifier Board 1x60W 12V 24V Power Amp | eBay

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Last edited by Printer2; 7th May 2018 at 02:16 AM.
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Old 7th May 2018, 06:47 AM   #12
Gnobuddy is offline Gnobuddy  Canada
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The real thing (Princeton Reverb) needs so much power that the only practical way to run it off-grid for a reasonable amount of time is to take along a gasoline-powered generator. (Cost out a 500 watt-hour lithium battery, you'll see what I mean.)

When real butter is ruled out, maybe fake butter? The Joyo American Sound (FX pedal) does a passable job of making Fendery tones: YouTube

It's also affordable: Amazon.com: Joyo JF-14 American Sound Effects Pedal Amplifier Simulation with Voice Control: Musical Instruments

Add a class D power amp module, a speaker, and a cordless tool battery pack, and you may get close enough to what you want.

I have owned a Joyo American Sound for a few years, and used it a few times. IMO, while it does sound a little "tubey", it doesn't have the touch response of the real thing, nor does it sound as much like an actual Fender amp as that video clip suggests.

You want real tubes, you say? How about one of those Nutube MV50 clean amps? Like this: YouTube

Or this: YouTube

The MV50 series is pretty reasonably priced for a commercial guitar amp (a 50W one at that): Vox MV50 Clean 50-watt Hybrid Tube Head | Sweetwater

I think the MV50 series is designed to run off a 19V laptop brick. So you'd need something like a 20V cordless tool or other external battery, a charger for the battery, and an adapter cable with the same plug tip as the laptop brick to power the MV50 with.

Please be aware that lithium batteries can (and have) burst into high-temperature flames due to manufacturing defects, improper charging, improper discharging, improper storage, improper transportation, etc. I personally knew three men who burned their own vehicles to the ground by charging lithium batteries (for RC planes) inside their cars, which burst into flame while charging, and destroyed each vehicle in a matter of a few minutes.

-Gnobuddy
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Old 7th May 2018, 01:35 PM   #13
Printer2 is offline Printer2  Canada
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Fast charging fools.
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Old 7th May 2018, 06:30 PM   #14
Gnobuddy is offline Gnobuddy  Canada
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I am no battery chemist, but from what I understand, the problem is more complex than that.

For one thing, the usual lipo chemistry is unstable if you overcharge a cell by even a few tens of millivolts. 4.2 volts per cell is okay, but charge to 4.25 or 4.3V, and metallic lithium begins to plate out of the electrolyte onto the electrodes. Lithium is a very volatile metal and bursts into flames on its own if there is any available moisture or oxygen available.

So, for starters, the charger needs to be really precise about maximum charge voltage. It must be designed specifically for the appropriate lithium chemistry, and must be manufactured to sufficient accuracy to be safe.

At least one of the car fires I mentioned earlier occurred because of user error - the owner was using a charger that could be toggled with a push-button switch to charge either lead-acid, nickel-cadmium, or lipo batteries. The only indication of which mode the charger was in, was the colour of the lit LED - either a yellowish green, a reddish yellow, or an yellowish red.

Not surprisingly, this particular charger caused a number of fires, simply by being mis-set to the wrong chemistry while charging a lithium pack. I knew this, and warned the fellow in question about the danger. I told him specifically never, ever to charge packs in his car, but only outside on asphalt or concrete, and to never leave packs unattended while charging (they swell and hiss before bursting into flame, giving you a minute or so warning to stop the incipient fire.) I also told him he should really get a safer, lipo-only, charger.

So what did he do? He set up his charger and lipo packs in the back of his Ford Explorer, started the charge going, didn't double-check the colour of the LED, and walked away to his apartment. His car burned to the ground, and for the next two years, he lied to me about the cause, claiming it was revenge arson (he was a private investigator.) Eventually the truth slipped out by accident. Doh!

The other two guys also made the mistake of charging packs in their cars, unattended. Both paid for it with vehicle fires.

Okay, user error and carelessness, what if we don't make those mistakes? Suppose the user gets a lithium-specific charger that is accurately made, and puts out the proper voltage she should be safe, right?

Unfortunately, no. In a pack of series cells, all the cells won't be of equal capacity (mAh), so one will inevitably finish charging before the others. For example, the charger might charge up to a maximum terminal voltage of 12.6V for 3 series cells, which in an ideal world, splits 3 ways into 4.2 volts per cell. But if one cell is weak, it will reach 4.2V first, while the other two cells are well below 4.2V.

That weak cell will then proceed to overcharge, and when it hits 4.3V or so, it will burst into flames.

This problem has only one solution - there needs to be a protection circuit that monitors the voltage across every individual cell in a series pack, and shuts down the charger if any one cell approaches a dangerous overcharge. But in those early days of lithium for RC, such chargers were rare, and expensive, and many lithium packs did not include any kind of connector to let the charger monitor individual cells.

Even if you had the right charger and the right pack, temperature was a factor. In sunny locations, a battery pack inside a parked car could exceed the maximum safe temperature, making the pack go unstable, and burst into flames (never leave your cellphone on the dashboard of a car parked in the sun!)

Even today, lithium packs continue to burst into flames unexpectedly. The problem has afflicted even reputable manufacturers - Samsung, Sony, and other manufacturers of cellphones and tablets and laptops. (The situation is worse with no-name manufacturers - remember those Christmas "hoverboard" toys that were bursting into flames right and left, and had to be recalled in vast quantities?)

In the music/ audio world, I see companies becoming aware of the dangers of lithium batteries, and taking a new tactic, for example, look at the specs for the Laney Audiohub 4x4 portable, battery-operated small P.A. system: AH4X4 - Laney

Did you notice that the Audiohub 4x4 is designed to run on 3 lithium cells, but comes without them, and also without a lithium charger?

I think that is the manufacturer's way of covering their behinds. They're not legally liable if the lithium pack and/or charger that you bought, burns down your house or car.

At this moment, I am contemplating putting together a battery-powered small P.A. for acoustic guitar and vocals, which I can take to a park to enjoy the beauty of Spring accompanied by music. I'm still pondering the battery issue. Lithium is lightweight and packs massive capacity, but the safety issues are very real, and I no longer have a garage with a concrete floor in which to store the things. Lead acid is toxic, heavy, corrosive, and has abyssmal charge capacity. NiMH is heavy, self-discharges, and is hard to find these days. What to do?

-Gnobuddy
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Old 7th May 2018, 07:03 PM   #15
Printer2 is offline Printer2  Canada
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Ten years ago I babysat a solar car with Li batteries driving from Texas to Canada. Keep them in their limits and they are OK. I had a picture of another team's car that was toast due to a fire.
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Old 7th May 2018, 07:43 PM   #16
Gnobuddy is offline Gnobuddy  Canada
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Quote:
Originally Posted by Printer2 View Post
I had a picture of another team's car that was toast due to a fire.
Exactly. Like dynamite, very safe, until something goes wrong...

(Precautions for dynamite include: turn over the box regularly, don't store in excessive humidity, don't let it get too old, don't store in excessive heat, never drop it,...)

On second thought, lithium batteries are more like "Happy Fun Ball": YouTube

-Gnobuddy
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Old 8th May 2018, 02:31 AM   #17
thoglette is offline thoglette  Australia
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Quote:
Originally Posted by Gnobuddy View Post
Lithium is lightweight and packs massive capacity, but the safety issues are very real, and I no longer have a garage with a concrete floor in which to store the things. Lead acid is toxic, heavy, corrosive, and has abyssmal charge capacity. NiMH is heavy, self-discharges, and is hard to find these days. What to do?
There's more than one Lithium chemistry (in fact there's dozens). In particular, Lithium Iron Phosphate batteries have much better characteristics and are starting to eat into the space between VRLA and low-discharge NiMH (which I have no difficulty finding "down under").
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Old 8th May 2018, 03:46 AM   #18
Printer2 is offline Printer2  Canada
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Back to the proposed amp, BSIAB first stage works.

Click the image to open in full size.

Hope to put a tone stack after it and see what comes out.
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Old 8th May 2018, 03:49 AM   #19
Printer2 is offline Printer2  Canada
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Quote:
Originally Posted by Gnobuddy View Post
Exactly. Like dynamite, very safe, until something goes wrong...

(Precautions for dynamite include: turn over the box regularly, don't store in excessive humidity, don't let it get too old, don't store in excessive heat, never drop it,...)

On second thought, lithium batteries are more like "Happy Fun Ball": YouTube

-Gnobuddy
Lot of phones out there operating.
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Old 8th May 2018, 04:46 AM   #20
Gnobuddy is offline Gnobuddy  Canada
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Quote:
Originally Posted by thoglette View Post
In particular, Lithium Iron Phosphate batteries have much better characteristics
M1 cells made by A123 Systems were my favourite lithium cells for larger packs, because of their relative safety. They were the first high current capability LiFePO4 cells I know of, spun off from research at MIT in the early 2000s. You could discharge a 2.3 Ah cell at 30 - 35 amps continuous current without any drama, no puffing, no significant heating, no catching fire.

M1 cells were heavier than lipo, but cheaper, safer, and tougher, ideal for larger electric RC planes that could cope with the extra weight.

I used to get them out of DeWalt 36 V cordless tool batteries about twelve years ago, I think around 2005 or so. DeWalt was using them for the same reason I was - they were safer than other lithium cells available at the time.

A122 Systems went under after the Fisker electric car company failed. The name still exists, now under Chinese ownership. I haven't been able to find their trademark cells in recent years.

All the cordless tools I could find recently use lithium-ion cells, which seem to be essentially lipo cells rolled up and stuffed into a metal can for a little better protection. Not as safe as LiFePO4, but it seems A123 lost its footing at a crucial time in the growth of the lithium cordless tool industry.

-Gnobuddy
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