Is this a dumb idea? Trying to create a mobile setup.

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hillerheilman
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Is this a dumb idea? Trying to create a mobile setup.

Post by hillerheilman » Fri Feb 12, 2021 2:41 pm

Hey forum, I’ve been toying with an idea and I could use your input. As some of you may remember, I’m a manual wheelchair user. I’m trying to create a mobile rolling setup for jamming and maybe some busking. I’m becoming more and more dissatisfied using bias and other modeling stuff for everything and I want to get an actual amp setup instead.

Initially I wanted to just mount a battery powered combo amp underneath my seat. I decided against that though, because my legs would be blocking the speaker and therefore I figured it wouldn’t sound as good.

Then I had the idea to get a couple of small battery powered amps like a micro cube or a pignose, hang them via a strap off the push handles of my chair with one on either side, and use an AB/Y pedal to run them simultaneously. I found, though, that I wasn’t really in love with the tones from some of the small battery powered offerings.

So then I had the idea to take that concept a bit further. What if instead of battery powered amps I hung or otherwise attached an 8 or 10 inch cab on either side, and then a head underneath my seat? I was thinking I might be able to run it off one of those portable camping batteries, which I could also mount underneath me pretty easily. That way I could essentially use whatever amp I wanted and just plug it in the wall at home, or take it with me and power it with the battery otherwise.

Would this work, or is it a dumb idea? I know that in theory it should work, and I know especially tube amps use quite a bit of power, but I don’t think I’d need to power it off the battery for more than 3-4 hours max at a time. I guess really what I’m wondering is if there would be some issues in terms of noise with having the battery and amp so close or something like that I’m not thinking of. I’d appreciate your input, forum.

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Re: Is this a dumb idea? Trying to create a mobile setup.

Post by marqueemoon » Fri Feb 12, 2021 3:25 pm

The ZT Lunchbox Junior will run on 12V DC.

No extension cab option with the Junior though, and the bigger Lunchbox doesn’t have a battery power option.

For the head/cab idea The Temple Audio Ampmod will run on 9-24V and is stereo. That could be fun. You’d just need some kind of preamp to use with it.

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Re: Is this a dumb idea? Trying to create a mobile setup.

Post by hillerheilman » Fri Feb 12, 2021 4:01 pm

marqueemoon wrote:
Fri Feb 12, 2021 3:25 pm
The ZT Lunchbox Junior will run on 12V DC.

No extension cab option with the Junior though, and the bigger Lunchbox doesn’t have a battery power option.

For the head/cab idea The Temple Audio Ampmod will run on 9-24V and is stereo. That could be fun. You’d just need some kind of preamp to use with it.
So the issue with using any amp and the mobile battery would be an ac vs dc thing then?

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Re: Is this a dumb idea? Trying to create a mobile setup.

Post by øøøøøøø » Fri Feb 12, 2021 4:09 pm

You're talking about using a mobile battery power supply that outputs 120V, correct?

I don't see any reason (other than weight, potentially) why that wouldn't work!

One thing you could try would be to find Neodymium-magnet speakers, which would help save on weight a bit relative to size. You could also use some sort of lightweight solid wood for the cabinets (pine would be cheap and easy), which would also save on weight compared to MDF/HDF particle board

I don't know that there are many 8" guitar speakers out there with the Neo magnets, but I know Jensen makes a 10 called the Tornado 10 (they also have a 12" version).

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Re: Is this a dumb idea? Trying to create a mobile setup.

Post by hillerheilman » Fri Feb 12, 2021 6:37 pm

øøøøøøø wrote:
Fri Feb 12, 2021 4:09 pm
You're talking about using a mobile battery power supply that outputs 120V, correct?

I don't see any reason (other than weight, potentially) why that wouldn't work!

One thing you could try would be to find Neodymium-magnet speakers, which would help save on weight a bit relative to size. You could also use some sort of lightweight solid wood for the cabinets (pine would be cheap and easy), which would also save on weight compared to MDF/HDF particle board

I don't know that there are many 8" guitar speakers out there with the Neo magnets, but I know Jensen makes a 10 called the Tornado 10 (they also have a 12" version).
So something like this would work for a power supply?

https://www.lowes.com/pd/Westinghouse-i ... 1002425260

I’m only thinking maybe a two or three hours of use per charge.

I think that maybe I’d be wise to go with 10 inch speakers just for availability. I’ll be researching for sure.

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Re: Is this a dumb idea? Trying to create a mobile setup.

Post by mbene085 » Fri Feb 12, 2021 7:07 pm

What about those Hotone amps that have been discussed here lately?

They're tiny, weightless, and I'd be shocked if they drew much current as a simple solid-state design with a 5W class AB power amp. Connect that to a pine open-back cab with a neodymium speaker and you'd have yourself a super low-weight portable rig that sounds good, too. Your camping battery would probably represent most of the weight at that point.

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Re: Is this a dumb idea? Trying to create a mobile setup.

Post by øøøøøøø » Fri Feb 12, 2021 7:18 pm

The supply from the Lowe's link does advertise that it has "two 120V household outlets" in addition to its low voltage (5V and 12V) options. Assuming this is correct and these actually do output nominally 120V (even 100V would be fine), then yes, this should work.

It claims 155 Watt-hours, which... let's do some math!

A Fender Princeton Reverb (just as a random example) calls for a 1A fuse, which means it draws less than 1A of current under normal operating conditions. This is probably a fairly typical case (some amps will draw more than 1A, some less).

It will draw more current when you're playing loudly than when the amp is at its quiescent (idle) state, so 1A should be a good conservative estimate.

120V * 1A is easy math: 120W. 155 Wh/120W = 1.3 hours.

So as a rough back-of-envelope guess, this power supply would probably get you somewhere around an hour and a half of play time. Very possibly more if conditions were favorable, conceivably less if your amp was very power-hungry... but this is probably a decent baseline guess.

Your best bet may be to go for an amp that consumes relatively low power and make it up with speaker efficiency (i.e. two speakers will produce more SPL from a lower-powered amp).

Solid-state amps are generally more efficient than tube amps in terms of watts-out per watts-in. Tube amps draw a lot of current just to keep the filaments warm, and that energy is obviously lost as heat (not amplified sound). So that's another factor to balance... you may be able to do better than the above rough estimate if you opt for a solid-state amp.

If you comb through the manual/literature/documents for any amp you're considering, you may be able to find a specification for the current draw in Amperes. If so, the math is easy:

Current (in Amperes, or A) times line voltage (120V, in this case) = power in Watts. Divide the number of Watt-hours supplied by your power supply by the amplifier's power consumption in Watts, and you'll get a decent idea of how long you can expect to run.

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Re: Is this a dumb idea? Trying to create a mobile setup.

Post by øøøøøøø » Fri Feb 12, 2021 7:27 pm

mbene085 wrote:
Fri Feb 12, 2021 7:07 pm
What about those Hotone amps that have been discussed here lately?

They're tiny, weightless, and I'd be shocked if they drew much current as a simple solid-state design with a 5W class AB power amp. Connect that to a pine open-back cab with a neodymium speaker and you'd have yourself a super low-weight portable rig that sounds good, too. Your camping battery would probably represent most of the weight at that point.
Let's see! The power requirements listed on their site are very unclear... they don't make a lot of sense to me. It says:
The Nano Legacy amps works with 18V with a maximum output current of 900mA (at 18V 4Ohm).
Hmm... output current? What? 18V? What? Does that mean output from the 18V wall wart supply? And what's the 4 Ohm... are we not talking about supply current but rather speaker current? There's something I'm not getting here... anyway

Let's just gloss over the uncertainty and take the numbers 18V and 0.9A. That calculates to 16.2W, which is probably believable for a 5W solid-state amp. Assuming some inefficiencies in the 18V supply itself (as it steps down from 120V and rectifies to DC), let's just round up to 20W.

That gets us almost 8 hours of play time, assuming I've made the correct set of assumptions. Probably very workable!

5W is not a lot of power from an amp, but driving a pair of 10" speakers in actual cabinets it might be surprisingly loud.

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Re: Is this a dumb idea? Trying to create a mobile setup.

Post by Scout » Fri Feb 12, 2021 7:39 pm

The Nano amps work off an 18v power supply, I think it may be the direction for what
you're trying to accomplish. I bought one on the cheap and coupled it with a Bell and
Howell extension A/V speaker and it's relatively loud and compact.

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Re: Is this a dumb idea? Trying to create a mobile setup.

Post by hillerheilman » Sat Feb 13, 2021 5:46 am

øøøøøøø wrote:
Fri Feb 12, 2021 7:18 pm
The supply from the Lowe's link does advertise that it has "two 120V household outlets" in addition to its low voltage (5V and 12V) options. Assuming this is correct and these actually do output nominally 120V (even 100V would be fine), then yes, this should work.

It claims 155 Watt-hours, which... let's do some math!

A Fender Princeton Reverb (just as a random example) calls for a 1A fuse, which means it draws less than 1A of current under normal operating conditions. This is probably a fairly typical case (some amps will draw more than 1A, some less).

It will draw more current when you're playing loudly than when the amp is at its quiescent (idle) state, so 1A should be a good conservative estimate.

120V * 1A is easy math: 120W. 155 Wh/120W = 1.3 hours.

So as a rough back-of-envelope guess, this power supply would probably get you somewhere around an hour and a half of play time. Very possibly more if conditions were favorable, conceivably less if your amp was very power-hungry... but this is probably a decent baseline guess.

Your best bet may be to go for an amp that consumes relatively low power and make it up with speaker efficiency (i.e. two speakers will produce more SPL from a lower-powered amp).

Solid-state amps are generally more efficient than tube amps in terms of watts-out per watts-in. Tube amps draw a lot of current just to keep the filaments warm, and that energy is obviously lost as heat (not amplified sound). So that's another factor to balance... you may be able to do better than the above rough estimate if you opt for a solid-state amp.

If you comb through the manual/literature/documents for any amp you're considering, you may be able to find a specification for the current draw in Amperes. If so, the math is easy:

Current (in Amperes, or A) times line voltage (120V, in this case) = power in Watts. Divide the number of Watt-hours supplied by your power supply by the amplifier's power consumption in Watts, and you'll get a decent idea of how long you can expect to run.
That all makes perfect sense. I think solid state would be the obvious choice for efficiency. But do you think that a tube amp would be fine underneath my seat? I don’t think it’d be hitting or bumping anything, but it could probably experience some vibration if it’s attached to the frame.

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Re: Is this a dumb idea? Trying to create a mobile setup.

Post by øøøøøøø » Sat Feb 13, 2021 12:52 pm

i think you're right that solid-state is probably the way to go for efficiency, but I imagine a good tube amp could be fine under your seat, depending how it's constructed.

Tubes get hot, and heat can sometimes contribute to destabilizing things and make them more prone to failure under vibration. Many less-expensive tube amps borrow some of their construction techniques from low-voltage and lower-temperature applications, and aren't quite as bulletproof as the tube amps of old, so it is something to keep in mind.

If you're worried about vibration from traveling in your chair, you could always "shockmount" the amp on a small piece of sorbothane or even neoprene mat, and then strap it down with something.

Depending on whether you have a dedicated "busking chair" into which you could install your rig semi-permanently, long zip ties could potentially be a great way to secure the amp head below your seat.

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Re: Is this a dumb idea? Trying to create a mobile setup.

Post by hillerheilman » Sat Feb 13, 2021 2:41 pm

øøøøøøø wrote:
Sat Feb 13, 2021 12:52 pm
i think you're right that solid-state is probably the way to go for efficiency, but I imagine a good tube amp could be fine under your seat, depending how it's constructed.

Tubes get hot, and heat can sometimes contribute to destabilizing things and make them more prone to failure under vibration. Many less-expensive tube amps borrow some of their construction techniques from low-voltage and lower-temperature applications, and aren't quite as bulletproof as the tube amps of old, so it is something to keep in mind.

If you're worried about vibration from traveling in your chair, you could always "shockmount" the amp on a small piece of sorbothane or even neoprene mat, and then strap it down with something.

Depending on whether you have a dedicated "busking chair" into which you could install your rig semi-permanently, long zip ties could potentially be a great way to secure the amp head below your seat.
Zip ties were pretty much my idea for mounting. I was thinking about having a couple d rings on either side of the head and just zip tying it to the frame. I’m still trying to work out if there’s better options.

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Re: Is this a dumb idea? Trying to create a mobile setup.

Post by hillerheilman » Sat Feb 13, 2021 2:42 pm

øøøøøøø wrote:
Sat Feb 13, 2021 12:52 pm
i think you're right that solid-state is probably the way to go for efficiency, but I imagine a good tube amp could be fine under your seat, depending how it's constructed.

Tubes get hot, and heat can sometimes contribute to destabilizing things and make them more prone to failure under vibration. Many less-expensive tube amps borrow some of their construction techniques from low-voltage and lower-temperature applications, and aren't quite as bulletproof as the tube amps of old, so it is something to keep in mind.

If you're worried about vibration from traveling in your chair, you could always "shockmount" the amp on a small piece of sorbothane or even neoprene mat, and then strap it down with something.

Depending on whether you have a dedicated "busking chair" into which you could install your rig semi-permanently, long zip ties could potentially be a great way to secure the amp head below your seat.
Zip ties were pretty much my idea for mounting. I was thinking about having a couple d rings on either side of the head and just zip tying it to the frame. Or perhaps a loop of strong Velcro. I’m still trying to work out if there’s better options.

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Re: Is this a dumb idea? Trying to create a mobile setup.

Post by øøøøøøø » Sat Feb 13, 2021 2:45 pm

Zip ties are very often a suitably elegant solution!

I am racking up a pair of old Auditronics channel strips today, and noticed that the inductors in the EQs are mechanically secured to the PCB with zip ties

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Re: Is this a dumb idea? Trying to create a mobile setup.

Post by 46346 » Mon Feb 15, 2021 3:07 am

one potential problem with many of the less expensive portable AC power supplies, is that while coming from an internal DC battery source, the inverted 60Hz AC is synthesized somewhat crudely, and not as a true sine wave. this causes a classic buzz/hum for audio amplification, it can be pretty annoying.

i've avoided this in two ways:

1) did some research and spent a little more on a stand-alone inverter that was spec'd as 'clean AC sine wave power' or some such. i run that off of
a deep-cycle 12v boat battery. i can play full range 120v AC loud amps for hours and hours. it's a heavy rig, but i need clean and loud!

2) use a good DC powered amp or two, that have their own built in batteries and chargers. you can use the cheaper AC power supplies/inverters from the hardware store to charge the DC amp's battery.

of course if there's a DC powered amp that you really like, you could skip the inverter and just get a fat DC battery rated to match it.

it's also quite possible that some of the recent, less expensive supplies are now synthesizing cleaner 60Hz AC. but be prepared to have to return them if you're getting buzzes. i've tried some that touted 'clean power' but still aren't good enough for audio.

cheers and good luck!
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