How to make simple battery PS for phono preamp?

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Hi. I've searched google and the forums and for some reason I can't find a simple guide for a complete newbie on how to do this. I have a phono preamp with a wallwart (12V/120mA) and I want to create (or buy) an external battery pack. Any links or videos would greatly help. I am normally successful with google searches, but I must be using the wrong terms.

THANKS,
Robert Jason
 
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If you want to go battery then you need to gather a bit of information first.

1) What voltage does the preamp run on ? You really need to measure it because if the wall wart is a simple unregulated type the output could be nearer 16 volts or more, so you need to be sure.

2) How much current does the preamp draw. Without knowing that you can't hope to select a suitable battery size and capacity.

3) Do you want the battery to be rechargeable and if so do you want it to be rechargeable in situ ?
 
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100ma is quite a lot for battery use (and I still think its worth you measuring the actual current drawn because 100ma sounds a lot for an RIAA preamp)

What model is the preamp ?

So 8D cells (Alkaline) have a capacity of what ? 10 Ah ? so that gives a run time of 10000/100 which is 100 hours as a ball park figure. Rechargeables in that size would only run for around a third of that time.

VRLA batteries (sealed lead acid gell batteries) are another option.
 
My multimeter testing it with a music load playing through show the draw ranging from 40mA to 60mA with the volume at midway (realistic level) and 50mA to 70mA draw when the volume is cranked. It's a TCC Electronics TC-750LC. Here's a photo someone else in these forums took of the model, mine looks exactly the same inside.

http://www.diyaudio.com/forums/atta...0lc-preamp-more-gain-tcc-tc-759lc_pcb-top.jpg

I've considered just biting the bullet and buying a higher end preamp like a Rega Fono Mini, but I believe this one will perform well enough for the price.

Thanks again, Robert
 
Rechargeables in that size would only run for around a third of that time.

No. You can get 10Ah NiMh in D cells. You'd need 10. Low-self-discharge would be best, but you're looking at ~$100. You'd have to be careful with them though, because they can produce a ferocious amount of current, enough to start a car. Probably 2500mAh AA cells would be a reasonable compromise and you could get these for ~$40. They'll probably run ~12.5V fully charged.

Alternately, you could try 6 of these Lithium rechargeables @ ~22 dollars, they run 12.6V fully charged and 11.1 before switching off (they're protected against overdischarge).

Buy UltraFire Protected 18650 3.7V 2400mAh Lithium Batteries (2-Pack Grey)

You can get a cheap charger from the same place, delivery is typically 10~14 days though.

These voltages are probably OK with your 12V device.
 
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I think I found the that thread from the model number and it has the circuit too,
http://www.diyaudio.com/forums/analogue-source/227280-mod-tc-750lc-preamp-more-gain.html

No voltage regulator which for a phono preamp seems slightly odd but never mind. Unless they are relying on the specified wall wart to deliver ripple free voltage.

Why do you want to go battery ? Is it because of any hum or noise ?

Looking at the circuit (if its correct... no reason to doubt it) and the current consumption is going to be low. I'd estimate around 3ma per channel without actually calculating it all out plus whatever the LED runs at. So 10ma quiescent sounds right. That increases the battery life by a factor of 10 over the figures I gave earlier based on 100ma.

CC mentions low self discharge batteries (for rechargeables) and in my limited experience of NiMh cells I have found the high capacity ones are often the worst losing charge in a relatively short time. Thanks for the info re 10Ah cells... I've never used D cells (rechargeables) and wasn't sure what was available. I remember when 2.2Ah was the norm with 4Ah for the high cap types :D
 
Mooly, I think you and counter culture are both guilty of a mistake in the amp-hour rating of the batteries. If 8 or 10 are placed in series to attain the 12V operating voltage, the current capacity doesn't add, only the voltage. The Ah remains about the same as for an individual cell. Ah adds for parallel cells, while the voltage remains the same as for an individual cell. I think you both know that already.
Unless the discussion is really about 10Ah NiMH D cells.

edit: Well shut my mouth. Here's just such a thing right here. Didn't know they were available any bigger than about half that.
 
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My goal is to provide a higher quality power because I've been reading that PSU's are where cheaper products skimp. Theoretically, by taking a fairly inexpensive (but well designed) preamp I can turn it into something much better very simply. To be honest, the preamp sounds fine as is. I'm just tinkering.

So, am I understand this correctly? As long as I'm in the ball-park of 12V, the rest is a matter of size and how long it will last. I could also order a Pyramid 13.8V/2.5A regulated PS on amazon for about $22 open box. The AA rechargeables idea sounds very convenient.
 
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My goal is to provide a higher quality power because I've been reading that PSU's are where cheaper products skimp. Theoretically, by taking a fairly inexpensive (but well designed) preamp I can turn it into something much better very simply. To be honest, the preamp sounds fine as is. I'm just tinkering.

So, am I understand this correctly? As long as I'm in the ball-park of 12V, the rest is a matter of size and how long it will last. I could also order a Pyramid 13.8V/2.5A regulated PS on amazon for about $22 open box. The AA rechargeables idea sounds very convenient.

The absolute voltage isn't critical, lets say around 16 volts as an upper limit. I've said 16 in case any of the capacitors in yours are actually 16 volt devices (the ones in the picture looked to be 25v)

If you just want to try it and see if it sounds different then try one (or two in series) 9 volt zinc carbon PP3 type batteries. Although two would give a nominal 18 volts that will fall to 16v or less under load using PP3's

Now what I would be thinking of doing :) is taking a DC feed from your main amp or preamp to power this so that you do away with batteries and wall warts.
 
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