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Bass amps that run off 9v adaptor
- Thread starter 1dreday
- Start date
Why?
If you plug in the adaptor you can just as easily plug in a regular amp.
If you intend to run it on 9v battery power you are nuts.
If you plug in the adaptor you can just as easily plug in a regular amp.
If you intend to run it on 9v battery power you are nuts.
- Feb 12, 2006
- 61,031
- 5
- 220,918
- Disclosures
- Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
There's not any that I am aware of that represent more than a "few" watts (RMS). Of course there are CLAIMS of higher power but the units are generally not based on RMS metrics.
The problem is due to the current required at 9 volts to generate significant power. Even at 80% efficiency, it takes 12 watts of electrical power to generate 10 watts of audio power, and because 9 volts (without a boost converter) limits the maximum power at 4 ohms to about 3 watts (RMS), it's quite a challenge.
For example, to deliver 20 watts RMS, that would require a power supply capable of (20W x 1.2) = 24 watts which is (24W/9V) = 2.7 amps. I don't think you will find many 9 volt power supplies (wall wart, line lump or battery) capable of this kind of current. The amp's internal voltage needs to be boosted to about 25 volts (rail to rail) to deliver 20 watts RMS.
So, how does car audio do this? The 12 volts is run through a switchmode boost converter which boosts the internal operating voltage to whatever is necessary for the power required. Say you want 100 watts RMS, the internal voltage needed would be about 56 volts (rail to rail).
Now, doing the same calculations, 100 watts x 80% efficiency is about 120 watts at the power supply and when you divide this by the 12V source you can see that it requires 10 amps at 12 volts. This is no problem for a car battery, or an AGM type (gel cell) battery short term. You don't see this on a wall wart in practice.
Of course there are duty cycle advantages to audio so that in practice the supply currents (longer term) are between 1/2 and 1/4 of the continuous power, but the power supply still needs to be capable of the short term demands to operate properly.
The problem is due to the current required at 9 volts to generate significant power. Even at 80% efficiency, it takes 12 watts of electrical power to generate 10 watts of audio power, and because 9 volts (without a boost converter) limits the maximum power at 4 ohms to about 3 watts (RMS), it's quite a challenge.
For example, to deliver 20 watts RMS, that would require a power supply capable of (20W x 1.2) = 24 watts which is (24W/9V) = 2.7 amps. I don't think you will find many 9 volt power supplies (wall wart, line lump or battery) capable of this kind of current. The amp's internal voltage needs to be boosted to about 25 volts (rail to rail) to deliver 20 watts RMS.
So, how does car audio do this? The 12 volts is run through a switchmode boost converter which boosts the internal operating voltage to whatever is necessary for the power required. Say you want 100 watts RMS, the internal voltage needed would be about 56 volts (rail to rail).
Now, doing the same calculations, 100 watts x 80% efficiency is about 120 watts at the power supply and when you divide this by the 12V source you can see that it requires 10 amps at 12 volts. This is no problem for a car battery, or an AGM type (gel cell) battery short term. You don't see this on a wall wart in practice.
Of course there are duty cycle advantages to audio so that in practice the supply currents (longer term) are between 1/2 and 1/4 of the continuous power, but the power supply still needs to be capable of the short term demands to operate properly.
I think the Quilter one ostensibly uses a 9v supply but it's custom for more juice than a pedal train. The 40w of Audio at the business end can get a bit done but you're still needing a wall outlet and a cab = why again is 9v important?
- Feb 12, 2006
- 61,031
- 5
- 220,918
- Disclosures
- Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
The Quilter InterBlock 45 uses a 24v power supply.
When my dad was a kid, he was building tube amps for the local musicians with vibrator power supplies running off a 12V automotive battery. Many of the country halls in his area didn't have AC power yet in the 1950s.
The musicians would carry into the hall a battery removed from one of their cars, and by the end of the evening, they would usually need a boost after the battery was re-installed in the car because the battery would be pretty weak by then. All that effort for maybe 15 or 20W of power.
The musicians would carry into the hall a battery removed from one of their cars, and by the end of the evening, they would usually need a boost after the battery was re-installed in the car because the battery would be pretty weak by then. All that effort for maybe 15 or 20W of power.
OP wants to reinvent the vibrator?
Early tube car radios converted 12 DC to AC using vibrators ... I know, I was there
I'm not sure what the intent is to have an amp running off a 9 volt power source. If for battery power, a 9V battery is one of the worst sources of power, due to its internal resistance. He would be better off looking at gel cells, or lithium cells in series to make at least 24 or 36 volts for a reasonably powered portable amp.
According to my dad there were some tubes developed for automotive use that would work with 12 volts of plate voltage. I've never seen these myself, but I don't think they would have been capable of much plate current.Early tube car radios converted 12 DC to AC using vibrators ... I know, I was there
Pickup a sine wave inverter. They are cheap these days.
No vibrator needed.
Ones based on power tool batteries are readily available and can run a regular lower powered class-d amp
RYOBI 300-Watt Powered Inverter Generator for 40-Volt Battery-RYi300BG - The Home Depot
Buy a weed eater and they throw in a battery. Get a spare.
Other brands make them too.
No vibrator needed.
Ones based on power tool batteries are readily available and can run a regular lower powered class-d amp
RYOBI 300-Watt Powered Inverter Generator for 40-Volt Battery-RYi300BG - The Home Depot
Buy a weed eater and they throw in a battery. Get a spare.
Other brands make them too.
The vibrators were part of the radio revolution in the "Farm Radio" days. Back when there was no power grid.
The trucks and tractors had starter cranks and would charge the batteries during the day.
They pull the batteries in and hook them up to the house radio's for nightly entertainment.
That's where 'standby' first came in. Standby turned off the vibrator for the high voltage, but kept the elements going.
Essentially they were switching power supplies (SMPS) a century ago!
The trucks and tractors had starter cranks and would charge the batteries during the day.
They pull the batteries in and hook them up to the house radio's for nightly entertainment.
That's where 'standby' first came in. Standby turned off the vibrator for the high voltage, but kept the elements going.
Essentially they were switching power supplies (SMPS) a century ago!
It was a little different around our locale. Farm radios were strictly battery powered, A, filament voltage, B for plate voltage, and sometimes a C battery for bias. Auto radios used a vibrator power supply, even though a vibrator supply drew considerable current, but from the perspective of running a radio, the 6 or 12 volt DC charging system was an unlimited source of power, as long as the engine was running.
My grandfather had a 32 volt power system he built, a windmill mounted generator that would charge a bank of lead acid cells, as well as a gasoline driven generator for when there wasn't any wind. He told me he used to heat the tar seals on top of the battery cases to lift out the plates so he could manually de-sulfate the plates, filter the accumulated sediment from the acid, and re-assemble them. These were the good old days.
My grandfather had a 32 volt power system he built, a windmill mounted generator that would charge a bank of lead acid cells, as well as a gasoline driven generator for when there wasn't any wind. He told me he used to heat the tar seals on top of the battery cases to lift out the plates so he could manually de-sulfate the plates, filter the accumulated sediment from the acid, and re-assemble them. These were the good old days.
- Feb 12, 2006
- 61,031
- 5
- 220,918
- Disclosures
- Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
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There were plenty of low voltage preamp tubes, but their production life was cut short with the introduction of the transistor. This is a topic that I have studied for years, a fascinating slice of electronics history:
Low Voltage Tubes.
Correct, this is one of the limiting factors of battery powered amps. It's been improved with the introduction of lithium ion technology, but there's still a size and weight penalty.
only one I know of supposed to be 50w but not even close running battery power but using 8 AA but that takes you to about the same place as a 9v
Last edited:
- Feb 12, 2006
- 61,031
- 5
- 220,918
- Disclosures
- Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
Certainly not without a boost converter and suitable supply current/capacity. With those things, there's no technical challenge to making a 500 watt amp this way except that the size grows accordingly.
