Agreed, and most of them safely. But not all - remember the complete recall of the Samsung Galaxy Note 7 in 2016 due to lipo pack fires? ( Exploding smartphones: Why some catch fire and are you at risk? - CNN )
Or the several Boeing Dreamliner fires caused by the lithium power backup subsystem? ( consumerreports.org, hp-recalls-50-000-laptops-over-li-ion-battery-fires-/ (can't insert actual link) )
Or the roughly 50,000 HP laptop computers recalled due to lithium pack fires? ( HP Recalls 50,000 Lithium-Ion Laptop Batteries Over Fire Risk - Consumer Reports )
Or the half-a-million hoverboards that were recalled because they tended to burst into flames? ( Half A Million 'Hoverboards' Recalled Over Risk Of Fire, Explosions : The Two-Way : NPR )
My point is simply that even the professionals - trained engineers working for big companies with tight quality control checks - get in serious trouble with lithium battery packs every now and then. The risks are much higher with casual DIY use. And when things do go wrong with a lithium pack, the resulting high temperature flames and toxic smoke tend to do a lot of ancillary damage.
Because of this, I think it is entirely appropriate to make it very clear that these cells are wonderful things, but also can be very dangerous. There are a lot of rules to be followed to keep them safe (not everyone is good at following a strict regimen of rules), and even when all the rules are followed, these packs are never entirely safe.
I sorely miss those 36V (and later 18V) DeWalt packs of M1 LiFePO4 cells. That's about as close as I've come to having my Lithium cake and eating it, too.
-Gnobuddy
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Can't say much more but I've seen a lot of proposals recently utilising "Winston Battery" (and similar brand) LiFePO4 cells. For back-up and solar powered stuff rather than tools.
There's also one or two people (e.g. Fusion) now selling "drop in replacements" for 12V VRLA batteries (claiming 50% more capacity and half the weight )
So far, I haven't used either in anger so YMMV.
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Some scary stories here...
There are a lot of DIY projects surfacing using 18650 Li-Ion cells, even in battery packs for higher voltages. I always thought that they came with a safety circuit/measure (at least the original panasonics that are kind of expensive).
As long as it doesn't look like a cheap pack of aluminium foil I always thought there were some safety measures. Do you know something about it?
I'm starting a subminiature amp using those, where I only need one or two (1.25v direct heated tubes, like the 5672) for the heaters. I get a 50v B+ with a SMPS.
There are a lot of DIY projects surfacing using 18650 Li-Ion cells, even in battery packs for higher voltages. I always thought that they came with a safety circuit/measure (at least the original panasonics that are kind of expensive).
As long as it doesn't look like a cheap pack of aluminium foil I always thought there were some safety measures. Do you know something about it?
I'm starting a subminiature amp using those, where I only need one or two (1.25v direct heated tubes, like the 5672) for the heaters. I get a 50v B+ with a SMPS.
Just amazing that the amp module barely gets warm when cranked. Just have it on 12V for now. I need to get my electronic bench cleaned up so I can mess around with the preamp section. I went with the Mu-amp as fets are all over the place in terms of bias and thought it would be one less thing for someone to worry about when building the preamp. I would like to see what the amp chip can do on 19-24V, the caps on board are rated as 25V. If we can get a circuit to keep it out of clipping it should be an interesting device.
Beat the snot out of a 8" with the chip amp on 12V. Used two stages of Mu-amps. The first one stays clean to maximum gain, into the second and you have a lot of crunch. Not that that was what I was after but I just had to do it. Hopefully I can get a tone stack between them tomorrow, I have to decide what I want to do with it. I have a sealed speaker with a crude preamp and a bridged car amp in it (must be 25 years old or more, had room in it for a burglar alarm gel cell). The speaker, another 8" sounds fine clean. Actually after a few years trying to get a good clean sound out of tubes I tried it again and was surprised how good it was. It just didn't sound all that great overdriven. So maybe the preamp to go into that or maybe make a sealed cabinet with the PWM amp and 20-30W. I have a Yamaha 8" that is rated for 30W or maybe a 10" Warehouse Guitar Speaker Veteran. I really wanted to do my tube amp but this power amp is cool. Or maybe a tube preamp and PWM amp with the laptop brick and the HV booster. I almost feel like a kid in the candy stor. Oh yeah, the reason I started this was for a portable BF amp. With all the 'Li' talk I forgot.
Speaking of forgetting, I almost forgot I found this.
Speaking of forgetting, I almost forgot I found this.
I surely appreciate your cautions! What battery currently available would you recommend to use for a portable guitar amp setup? Would those alarm-system batteries be good?
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Printer2, clearly I have annoyed you, and that was never my intention. I apologize. I'm sorry, I never meant to derail your thread or upset you.
I have a Squire Standard Stratocaster that has extremely low-output pickups (guess they saved on copper wire costs). With this particular guitar, my Joyo American Sound pedal (solid-state, some say a Sansamp copy) sounds more "tubey" than my actual Fender Princeton Reverb!
I am actually after the same thing as you right now - portable BF clean for guitar, along with a mic input for vocals. After a very wet April, we are just beginning to have a few sunny days here and there in the Lower Mainland (area around Vancouver for those not in Canada). The parks are full of wild flowers, there is lovely spring-green vegetation everywhere. I think a jam at a park would be a wonderful experience - but there is no AC power in the parks, and we have several members who don't sing loudly enough to be heard over their acoustic guitars. So we need a portable small P.A. for vocals, and I prefer using an electric guitar, so if I'm building a P.A., I'm going to add a guitar input. BF clean would be perfect...
-Gnobuddy
Hi-Fi clean, or guitar-amp clean? Any "tubeyness" your can hear? I've never tried the mu-amp topology myself.
I have a Squire Standard Stratocaster that has extremely low-output pickups (guess they saved on copper wire costs). With this particular guitar, my Joyo American Sound pedal (solid-state, some say a Sansamp copy) sounds more "tubey" than my actual Fender Princeton Reverb!
I am in exactly the same state of mind since I built the amp for my friend with that $15 class-D power amp board. It used to be a lot of work to make a discrete 30 watt class AB amp, and it took a big PCB, big TO3 transistors, a big heat-sink, and a big power supply. Now you can get two honest 30 watt RMS channels with a prefab $15 class-D board, a 4-ohm speaker, and a thrift-store laptop brick. Amazing!
Once again, sorry for derailing your thread.
I am actually after the same thing as you right now - portable BF clean for guitar, along with a mic input for vocals. After a very wet April, we are just beginning to have a few sunny days here and there in the Lower Mainland (area around Vancouver for those not in Canada). The parks are full of wild flowers, there is lovely spring-green vegetation everywhere. I think a jam at a park would be a wonderful experience - but there is no AC power in the parks, and we have several members who don't sing loudly enough to be heard over their acoustic guitars. So we need a portable small P.A. for vocals, and I prefer using an electric guitar, so if I'm building a P.A., I'm going to add a guitar input. BF clean would be perfect...
Did you decide not to go the KMG route (perhaps for low voltage reasons?) Please let us know how the FET Twin sounds if you build it.
-Gnobuddy
I am just finishing a portable mini-PA-system,
waiting actually for the LiIOn battery pack.
It will consist of
1 Pedelec Accu 36V/10Ah
2 TPA3255 mono PBTL-boards (2x100W/4ohms)
1 small Behringer mixer modified for battery power, delivered by
1 dc-dc-converter 36V-> +-12V
The hole arrangement is housed in a makita makpac, size2 box. Today I did a first soundcheck in our rehearsal room feeding it with a lab power supply - seems to work great with much power available.
Nah, just because I think you are pretty competent doesn't mean I am not going to call you out on something I don't agree with. We tend to go off topic often and in the end share knowledge we wouldn't otherwise.
I never put anything else in other than guitar and fed it into an 8" so I can't comment on hifi. But the original application note, might be wrong but I think National Semiconductor, had the Mu-amp as a instrument amp of sorts. Not a balanced instrument amp but it wasn't meant to be for audio. I had no EQ or tone shaping going on, there is a whole mess of pedals that use the circuit, each with their own tweaks. I just wanted to get a reasonable amount of gain without having to adjust the circuit for the variability of Fets.
Sometimes I think tubes are overrated.
I just gave that schematic as food for thought for the thread. It isn't a bad starting point. No I haven't gone off on another direction, well sort of I have. I was just working in the direction the OP might find useful. It is just another 'what if', given the parameters how would I go about it. The Class-D module for the amp is a no brainer for a battery powered amp. I am even thinking of using one to drive a spring reverb. The problem I have is I have a high impedance tank, an 8 ohm one would be just ducky. I might use a small line transformer to step up the drive. I think I have some 25V ones.
I have a PAM8610 amp board, not the most hifi of chips but at a cost under $2 shipped from China it should do for the reverb. Then as recovery the same Mu-amp. In a way this is a quick and dirty build, I won't be doing any tweaking. I am debating on building this into a Champ 600 sized cabinet or a Tweed Narrow Panel sized cab. I can squeeze it all in the 600 cab and the 8" in it has a decent amount of bass. Altogether a nice little practice amp.
One of the reasons I am doing it is I haven't seen much in the way of SS projects of this type. A lot of noisy crickets and pedals but not a whole amp given the technology available. The laptop bricks are great, the Class-D module is small,cheap and performs with no clumsy heatsink. The Mu-amp, as long as you wire it right you can drop a wide variety of Fets in it. I had the Class-D amp and two stages of the Mu-amp on the brick with no supply decoupling and no squeals, no motor boating, It was almost too easy.
Just had a little more to add. When you guys were looking at the LND150 I said I wanted to see if I could transpose some of the qualities of the circuit into a low voltage version. I doubt I will for this iteration but I plan to see if it can be don without too much grief. Again, for others to get into electronics, high voltage is not an issue with me.
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I'd never heard of a Makita Makpac before - thanks for the tip! That looks like a good option when you need or want a professional looking, rugged, enclosure.
You're using 8 ohm speakers? 36 V power and an 8 ohm speaker should put out an honest 65 watts RMS per channel or so (assuming 4 volts lost to saturation and power supply droop.) Twice that for two channels, say 130 W total.
No wonder there is plenty of power available! Wasn't Leo Fender's monstrously loud, monstrously heavy Twin rated at 80 watts? You have at least 130 watts...
I have one of these: Yeeco 2X100W Dual Channel Digital Stereo Power Amp Module DC 24V Class D Audio Amplifier Board for 4Ω 6Ω 8Ω Subwoofer Sound System Speaker Car Vehicle Home Theater: Amazon.ca: Tools & Home Improvement
But I found 32V rated electrolytic capacitors on the power rails, so the specifications are a little optimistic.
-Gnobuddy
I think the "all tube guitar amps are better than all solid-state guitar amps" mindset is flawed. But I do think there are a lot of really unpleasant sounding SS amps out there. No wonder some people have taken to hating them en masse.
The heatsink thing still amazes me. I used to use massive finned aluminum heatsinks something like 5" x 8" x 2" for a 30 - 40 W class AB amp with a pair of big fat complementary TO3 output transistors. Meantime, the finned heatsink on the "100W + 100W" (not really!) class D module I have is about the size of a matchbox.
Would be great if it works for a nice clean / crunch channel. If anyone wants more-than-Fendery distortion, I think that oddball 2BJTE circuit is worth trying for a Marshally lead channel. ( 2BJTE - 2 BJT triode emulator )
-Gnobuddy
I think perhaps I am headed in a slightly different direction now. I went scrounging through my guitar stuff, and found a coupla pedals that I forgot I had----a " '59 Fender Bassman" and a" '63 Fender Reverb". They both run off of 9 volts, and draw only about 75mA together. But they're unity-gain structured around 75mV, so I'll need another booster to get to a ~1 volt line level. I can easily wire-wrap up an OPA2134 to do that. For the power, I'm debating whether to buy a used car amplifier or get one of those eBay Class 'D' amps. I'm only needing ~10-12 watts to drive a Jensen (maybe Weber) 10" 8Ω speaker that is ~ 95db sensitive. Which would draw less current? Which would be less expensive? I am assuming that either will pass on the tone that I'll get from the two Boss pedals pretty well. Hmmmm....
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I still look at it doesn't seem real.
Wampler Plexidrive
YouTube
YouTube
Catalinbread Dirty Little Secret YouTube
Catalinbread: Formula №5 YouTube
A site for hours of fun. http://revolutiondeux.blogspot.ca/2012/02/wampler-pinnacle-distortion-limited.html
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I just threw in some 2N5485's. I have some J201's, well at least that is what China says they are.So where are you getting your J201s from?
This bad boy is supposed to make 600 watts at 10% THD on 53 volts, and well into the 500W range at 1%. I believe those numbers. I have personally run it at about 150 WPC on 52 volts until it rattled the drivers loose in my DIY speakers. The heat sink is larger than a 6V6GT, but smaller than a 6L6GC. It was slightly warm after that abuse test. I just got a $50 Chinese bass guitar to go with my $60 Chinese electric guitar. I'm thinking DIY preamp into this bad boy for some serious thunder.
It seems that these are still being offered direct from TI for about $80.
TI Class D EVM Board 50% Promotion
Absorbed Glass Mat gel cell batteries are good and will last 3 to 5 years. The only drawback is weight. I got some "Tenergy" branded LiFePo4 cells from Ebay. 5 in series make about 21 volts which I am using to power a portable PC. I may try the same thing for a portable guitar amp.
Attachments
This battery looks interesting:
LiFePO4 battery 12V 5AH Built-In BMS Solar Ham Radio portable Elecraft KX3 QRP | eBay
A bit pricey, but it is really light!
LiFePO4 battery 12V 5AH Built-In BMS Solar Ham Radio portable Elecraft KX3 QRP | eBay
A bit pricey, but it is really light!
The "really light" part is what makes lithium so attractive. They are pretty amazing batteries when they're behaving properly.
There are a couple of unanswered questions in my mind about the battery pack you linked to. The ad copy says "Charge Requirements Are 14.5 Volts To 22 Volts DC @ 1 To 2 Amps."
IMO that voltage specification is questionable. Even though LiFePO4 is more stable than most lithium battery chemistries, overcharging is dangerous and should never be allowed to occur. The LiFePO4 cells I know about are fully charged at 3.6V per cell, which means this nominally 12-volt pack (4 cells in series) should never be charged beyond 14.4 volts absolute maximum - charging to 22 volts would be quite dangerous.
(Once off the charger, the cell voltage drops to about 3.3 volts per cell, 13.2 volts for a 4S (series) pack.)
Having a built in balance circuit means this pack will stay balanced if slow-charged. However, usually the balance circuit will not limit maximum voltage from the charger - at least, I have never seen a balancer that did that job, it usually falls to the battery charger. If so, the charger must never put out more than 14.4 volts.
I notice the ad copy for this battery pack does say "14.5 Volt Charge Cutoff", so it is possible that this particular balancer also incorporates a big MOSFET in series with the pack, which is turned off to prevent overcharge if you apply more than 14.5V to the pack by accident or carelessness. If so, then it's okay for the charger to put out more than 14.4V, though I personally wouldn't want to risk my safety on whatever is built into the battery pack, so I'd use a charger that won't put out more than 14.4V at all.
I suggest getting some clear answers from the cell vendor, or better, manufacturer, before risking charging this pack - make 100% sure it is okay to connect a charging circuit that provides more than 14.4V, before taking the risk of actually doing so.
Also, keep in mind that at 2 amps, it will take 2.5 hours for a 5 Ah pack to charge. (The old A123 Systems M1 2.2Ah cells could be charged in 15 minutes flat at 10 amps charge current!)
One last thing: is this 13-volt pack going to provide enough power for your requirements? Assuming 3V lost to saturation and ohmic losses in the output stage, you will typically get only about 6 watts RMS into an 8 ohm load before clipping (most of these class-D amps use a bridge-mode output stage.)
These chip amps are invariably stereo, so if you have two separate 8 ohm speakers, you will get maybe 12 watts RMS from both channels running simultaneously. If you happen to have two 4 ohm speakers, you can expect around 25 watts RMS total from both channels.
I suspect that the lowest of those numbers (6 watts RMS into one 8 ohm load) may not be enough power for you, particularly because you have to keep these class D amps from clipping, or they sound utterly horrible.
If, on the other hand, you will be using two 4 ohm speakers, you may be okay, depending on your speaker sensitivity and the volume you would like to have.
If these power levels are too low for you, you really need a battery pack that puts out more voltage than 13.2V. (Note, for example, that Voltwide is using a 24V pack.)
-Gnobuddy
There are a couple of unanswered questions in my mind about the battery pack you linked to. The ad copy says "Charge Requirements Are 14.5 Volts To 22 Volts DC @ 1 To 2 Amps."
IMO that voltage specification is questionable. Even though LiFePO4 is more stable than most lithium battery chemistries, overcharging is dangerous and should never be allowed to occur. The LiFePO4 cells I know about are fully charged at 3.6V per cell, which means this nominally 12-volt pack (4 cells in series) should never be charged beyond 14.4 volts absolute maximum - charging to 22 volts would be quite dangerous.
(Once off the charger, the cell voltage drops to about 3.3 volts per cell, 13.2 volts for a 4S (series) pack.)
Having a built in balance circuit means this pack will stay balanced if slow-charged. However, usually the balance circuit will not limit maximum voltage from the charger - at least, I have never seen a balancer that did that job, it usually falls to the battery charger. If so, the charger must never put out more than 14.4 volts.
I notice the ad copy for this battery pack does say "14.5 Volt Charge Cutoff", so it is possible that this particular balancer also incorporates a big MOSFET in series with the pack, which is turned off to prevent overcharge if you apply more than 14.5V to the pack by accident or carelessness. If so, then it's okay for the charger to put out more than 14.4V, though I personally wouldn't want to risk my safety on whatever is built into the battery pack, so I'd use a charger that won't put out more than 14.4V at all.
I suggest getting some clear answers from the cell vendor, or better, manufacturer, before risking charging this pack - make 100% sure it is okay to connect a charging circuit that provides more than 14.4V, before taking the risk of actually doing so.
Also, keep in mind that at 2 amps, it will take 2.5 hours for a 5 Ah pack to charge. (The old A123 Systems M1 2.2Ah cells could be charged in 15 minutes flat at 10 amps charge current!)
One last thing: is this 13-volt pack going to provide enough power for your requirements? Assuming 3V lost to saturation and ohmic losses in the output stage, you will typically get only about 6 watts RMS into an 8 ohm load before clipping (most of these class-D amps use a bridge-mode output stage.)
These chip amps are invariably stereo, so if you have two separate 8 ohm speakers, you will get maybe 12 watts RMS from both channels running simultaneously. If you happen to have two 4 ohm speakers, you can expect around 25 watts RMS total from both channels.
I suspect that the lowest of those numbers (6 watts RMS into one 8 ohm load) may not be enough power for you, particularly because you have to keep these class D amps from clipping, or they sound utterly horrible.
If, on the other hand, you will be using two 4 ohm speakers, you may be okay, depending on your speaker sensitivity and the volume you would like to have.
If these power levels are too low for you, you really need a battery pack that puts out more voltage than 13.2V. (Note, for example, that Voltwide is using a 24V pack.)
-Gnobuddy
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