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Battery-Powered Princeton Reverb
Battery-Powered Princeton Reverb
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Old 6th May 2018, 05:50 AM   #1
dotneck335 is offline dotneck335  United States
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Default Battery-Powered Princeton Reverb

What I really want for my lap steel guitar is the sound of a Fender Princeton Reverb that is battery-powered. Has anyone done this? How can you power 12AX7s and 6V6s from batteries?
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Old 6th May 2018, 06:50 AM   #2
JMFahey is offline JMFahey  Argentina
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From a practical point of view, no.
125W constant power drain for 12/15W power output makes batteries useless.
Either you can carry them and last little or you need a truck.

Get a killer emulator, your choice, even a SansAmp Classic will sound good in the Blackface setting, feed it into a battery powered Class D (or even Class AB) power amp and call it a day.
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Old 6th May 2018, 07:39 AM   #3
dotneck335 is offline dotneck335  United States
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SansAmp Classic: Production suspended until further notice.(TECH 21 - SANSAMP CLASSIC, Analog Amp Modeling, Guitar Pedal, Tonality, Harmonics and Dynamics)
Any others?
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Old 6th May 2018, 03:21 PM   #4
dlvoots is offline dlvoots  United States
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As JMFahey pointed out, it is not practical. There are ways to do what you want to do, but you have to decide how crazy you want to get in order to do them, and whether it's worth it to you or not.

One option is the same as electronics afficiandos had to work with in the 1920's and 1930's -- two or three sets of batteries. They had to use an "A" battery to bias the power tubes, a "B" battery for high voltage, and a "C" battery to power the filaments. You could convert your Princeton IF you could find suitable batteries. They probably won't be rechargeable and probably very expensive. You [*could*] do it, but I think that JMFahey's observation wins.

BTW, that's were the term B+ comes from -- the "B" Battery!

Another option is to lug around a couple of 12 volt high capacity deep cycle RV batteries. Wire them in parallel and connect them to a 400watt inverter to get your mains voltage. It would work great for maybe 45 minutes to an hour, depending on battery capacity. The down side is that good deep cycle batteries run a couple hundred bucks each, and you'd have to recharge them after you're done playing. Again, I'm suspecting that JMFahey's observation wins again

The third option has potential for battery use -- a class "D" power amp and any amp emulator circuit that you hook up in front of it. A solid state amp may need 50-60 volts from the mains supply, but the amp emulator circuit probably runs on less than a third of the voltage, which would be easily within a battery solution. The challenge would be to find a suitable amp emulator board to work with, probably from a "basket case" amp on eBay.

You might combine bits and pieces from each solution above -- a small "emulator amp" or pedal, a class "D" power amp, an inverter, and an RV deep cycle batter. They are all relatively poor returns on investment, but hey -- If they get the job done, they get the job done.

Dave
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Old 6th May 2018, 03:32 PM   #5
Printer2 is offline Printer2  Canada
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How much power do you want, how will you be using it? Lap steel is usually clean, a Frontman 15 does a good Fender clean but is not a lot of power. On the battery side of things that is good. How much power you want out of the amp and the length of time you want to run it determines the size of your battery. You need to nail that down first.

dlvoots snuck in a post before me. I would take the simplest preamp circuit that would do the job and go PWM on the back end.

Last edited by Printer2; 6th May 2018 at 03:36 PM.
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Old 6th May 2018, 04:12 PM   #6
Thomasha is offline Thomasha
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A real battery powered tube amp would be nice. But low wattage probably.

I'm planing to build something like this using 6ak6's or 6g6's. Both have heaters that only require 150 mA at 6.3v. It would only require a lot of 3.7v cells. I think 6 hours of runtime would be already enough. Who plays longer than that anyway...
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Old 6th May 2018, 05:36 PM   #7
dlvoots is offline dlvoots  United States
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Quote:
Originally Posted by Printer2 View Post
dlvoots snuck in a post before me. I would take the simplest preamp circuit that would do the job and go PWM on the back end.
HAH! Sorry 'bout that.

Dave
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Old 7th May 2018, 12:18 AM   #8
dotneck335 is offline dotneck335  United States
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Quote:
Originally Posted by Printer2 View Post
How much power do you want, how will you be using it? How much power you want out of the amp and the length of time you want to run it determines the size of your battery. You need to nail that down first.
Well, I play country, blues, and rock; I'd like, let's say, 100 db SPL @ 1 meter with 10 db of headroom for ~ 4 hours. A decent lightweight neo 10" speaker would probably do, and if it were nominally sensitive, I'd need about 12-15 watts of power----~ the same as a Princeton. Reverb necessary, any other effects a bonus, but not as critical as getting that Blackface sound. I'd welcome suggestions of something I could build.

Last edited by dotneck335; 7th May 2018 at 12:20 AM.
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Old 7th May 2018, 01:42 AM   #9
JMFahey is offline JMFahey  Argentina
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If so inclined, you can build your own sansamp equivalent, driving an EBay sourced 12V "car type" amplifier, driving same as Princeton does: a real Jensen RI (opr its cheaper cousin, a MOD one) 10" but 4 ohm to better match the car type amp.
Personally I settled on 12V 7AH gel/alarm batteries as giving the most bang for the buck, but you can go Hi Tech of course.

This project is complex because of the elaborate switching and the zillion combinations, but you can hardwire just *one* setup and simplify it immensely.


tonepad -- FX projects
Which would be the plainest Fenderish type, simplest speaker simulation and microphone, etc.
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Old 7th May 2018, 01:50 AM   #10
thoglette is offline thoglette  Australia
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Quote:
Originally Posted by dotneck335 View Post
I'd welcome suggestions of something I could build.
Ok, following up on the work of Tubelab, Gnobuddy, Dogstar (Fred Bachbaur), JMF and a host of others, the most likely solution is to use a small amp emulator (that is, a really small amp driving a speaker or speaker like-load) and do everything else (including going from 1W to 20W) in silicon.

There's a number of two-12A*7 amp designs out there which would cut your consumption considerably. You're still going to be spending a bit of money or weight on batteries (Lithium or Lead, pick your poison )

Theoretically a design based on small signal kinkless Tetrodes would sound more like a pair of NOS 6V6, especially ones with not enough emission (read Tubelab George's comments on this).

Or you can get into the various "pencil" tubes which chew even less heater power (the Russian "rod" tubes pull less than an LED)

On the other hand, 4 hrs at 125W is 0.5kWHr. Which is about 5kg (10lbs) of current tech Lithium Iron Phosphate batteries. If you throw out the power tranny and choke you might even be in front :-) The only downside is the loss of sag-induced IMD (from the 100Hz or 120Hz ripple on B+ and screen)

Of course, if weight and cost are no object, you could just lug a 1/2kWHr UPS around with you and be done with it.

Last edited by thoglette; 7th May 2018 at 02:12 AM. Reason: Battery Tech
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