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Author Topic: Running an amp at lower voltage  (Read 1738 times)

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Offline mblindsey

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Running an amp at lower voltage
« on: October 04, 2014, 09:19:52 PM »
I bought one of these for an economical, I won't cry hard if my kid breaks it, remote playback system. 

http://www.amazon.com/gp/product/B00L7D9PJQ/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1

I have it hooked up to some 6x9 speakers, in boxes I've long had, and the iPhone music sounds good enough. The amp says it wants 12-24V.  I was just researching the possibility of two Wally batts in series to get 18V, when I decided to just plug one in and see what happens.  So far, 25 mins of playback and it's fine at 9V.  Will this work for life?  Will something break before some nice forum member has a chance to tell me?  If even possible, is there benefit to wiring two DVD batts in series?  The Internet fails at telling me if this is okay after all the circuitry they have inside.

Thanks!

p.s.  I had a 12v SLA and another like amp for a while.  That batt died and so did the amp.
Mics:  Microtech Gefell m200/M20/nBob Actives>PFA
Pre's: USB Pre2, V3, V3 (optimod), V3 (optimod), MiniME, MiniMP, MP2
Decks: R44 Oade Concert Mod, M10
Playback: Grace m9xx/MiniDAC->Sen HD 650, Fostex TH-X00, HIFIMAN HEXX
Mixing: RME Fireface UFX->Reaper->Yamaha HS8

Offline mblindsey

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Re: Running an amp at lower voltage
« Reply #1 on: October 04, 2014, 10:21:40 PM »
Perfect, sir.  Thank you.  The search I was actually trying to find was safety related to this (wasn't clear typing/this on a mobile device initially):

"If even possible, is there benefit to wiring two DVD batts in series?  The Internet fails at telling me if this is okay after all the circuitry they have inside."

There are a ton of tutorials on wiring Li-on batts in series prior to all the circuitry most have, and I even have a DVD batt cable that runs my gear with the DVD batts in parallel.  But, I can't determine if it's okay to run the DVD batts we all use in series, with that happening post all the protection circuits (and such) they seem to have.  It's noted to not likely work here:

http://taperssection.com/index.php?topic=157704.0

But, I don't understand why.

Thanks again,
Michael


Actually the internet is quite good at it:

http://www.ti.com/lit/ds/symlink/tpa3118d2.pdf

Assuming of course that's all they have in the box, which other than a few passive components is likely.  If you get curious, you could pop open the box.

So the chip amp is happy down to 4.5V, but max output power is reduced.  On page 10, you'll see that max power at 18V (into 8 ohm) is about 18W, vs. 5W for 9V.  So yes, there would be a benefit to running the batteries in series; the amp could get 5.5dB louder (it should be 6dB for a doubling in voltage, so the amp must have some loss relative in input voltage).
Mics:  Microtech Gefell m200/M20/nBob Actives>PFA
Pre's: USB Pre2, V3, V3 (optimod), V3 (optimod), MiniME, MiniMP, MP2
Decks: R44 Oade Concert Mod, M10
Playback: Grace m9xx/MiniDAC->Sen HD 650, Fostex TH-X00, HIFIMAN HEXX
Mixing: RME Fireface UFX->Reaper->Yamaha HS8

 

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