Biglump Posted January 14, 2015 Share Posted January 14, 2015 I was wondering (and searching) if anyone has converted a defunct practice amp to 12 volt operation successfully. I was given a Rocktek amp with a duff power supply. A dead PC donated its PSU to get it going again. But I am just wondering about converting it to 12 volt operation by striping out the PSU and wiring 12 volts direct. (though an appropriate fused connector, of course) I'll be hoping to run a passive Bass through it for lunchtime practice sessions at work, so it doesn't need to be loud. I know I really should just get on and try it, but as I have to wait for the weekend to do anything, I thought I would check to see if its been done already. Many thanks. Quote Link to comment Share on other sites More sharing options...
LukeFRC Posted January 14, 2015 Share Posted January 14, 2015 ? so the power supply has gone... and I guess it steps the power down to 12v does it? but that's blown... and been replaced with another one... and you want to take that out and use a 3rd one? or use batteries? Quote Link to comment Share on other sites More sharing options...
icastle Posted January 14, 2015 Share Posted January 14, 2015 Unless you intend using a 12v battery as a supply, I'd be more inclined to repair the original PSU than have to carry two boxes around. Quote Link to comment Share on other sites More sharing options...
Biglump Posted January 16, 2015 Author Share Posted January 16, 2015 Ah, yes, sorry I didn't provide the full explanation. Work is a small lorry, often in the middle of nowhere, that can provide me with either 12, 24v DC or 110 volts AC. The 12 volt supply is really weedy. I've never tested the 24v supply. I have a short scale acoustic bass in there at present, but was thinking of trying to make use of one of my electric 34 inch scale bases. Buying 34 inch acoustic especially could be cruel as it is a tough and un (instrument) friendly environment. Hence wondering if anyone had ever grafted 12 v straight to the LV side of the equipment. I half suspect that as the Rowland micro bass uses 6 x 1.5 volts that I may be needing 9 volts. But the Artec Cubix G2R taks 10 x1.5 v so maybe 15 or 7.5 volts. I guess the question is, what voltage is the low side, please? Quote Link to comment Share on other sites More sharing options...
Phil Starr Posted January 16, 2015 Share Posted January 16, 2015 OK, without any details about the amp it's difficult to be specific. The amps power is limited by the voltage swing, you'll only get 5watts out of a 12 volt amplifier unless it is operating in bridge mode in which case you'll get 20W into 4ohms. Nominal 12V car batteries give 14V so you might get a smidgin more. What this means is that if your practice amp was a 15W amp it might not be as loud once you start using a 12V supply. Most transistor amps will work over a wide range of voltages so they'll work OK, if the voltage is too low then the transistors aren't biased properly and you'll get distortion/no noise, too high and you'll burn out the transistors. If the old supply was working you'd be able to measure the voltage and decide if 24V would be a better match. As it stands it might work or it might burn out the amp. If the practice amp is 20W into 4 ohms it might be running on a 25V supply so 24V off a battery might work well. I guess this is just for reasonably quiet personal practice away from home. 5W might be enough, if you don't mind losing something you got for free you could take a risk with 24V but by the time you smell burning you'll probably be too late. Quote Link to comment Share on other sites More sharing options...
Dad3353 Posted January 16, 2015 Share Posted January 16, 2015 (edited) [quote name='Biglump' timestamp='1421395614' post='2660655']...Artec Cubix G2R taks 10 x1.5 v... [/quote] This amp has a DC input socket,where the outboard psu plugs in, but this can equally be fed from a car battery (nominally 12v, but actually 14v or so...). No modifications would be required, just be sure to respect the polarity, and use cable able to handle the current (2A,at least, which would give the 25w claimed by the makers...). The Roland Micro-cube requires 9v, so a car battery would not be suitable (strong likelihood of 'magic smoke'...). Edited January 16, 2015 by Dad3353 Quote Link to comment Share on other sites More sharing options...
tauzero Posted January 17, 2015 Share Posted January 17, 2015 [quote name='Biglump' timestamp='1421275782' post='2659423'] I was wondering (and searching) if anyone has converted a defunct practice amp to 12 volt operation successfully. I was given a Rocktek amp with a duff power supply. A dead PC donated its PSU to get it going again. But I am just wondering about converting it to 12 volt operation by striping out the PSU and wiring 12 volts direct. (though an appropriate fused connector, of course) [/quote] So you've used the 12V off the PC PSU and that's doing the job? You'd probably be OK running it off the nominally 12V supply, though as Dad says it's actually more like 15V. If you feel you may worry unduly, there's 12V regulators you can get (off That Ebay for example). Assuming there's an 8 ohm speaker in it, the maximum current that it will need to cope with is 12/8 = 1.5A (roughly, the speaker will never be taken up to the maximum 12V but then again the circuit won't be 100% efficient). Quote Link to comment Share on other sites More sharing options...
Biglump Posted May 10, 2015 Author Share Posted May 10, 2015 Well, just to update, this never got built. But thanks for the info. Quote Link to comment Share on other sites More sharing options...
.gif.9ad672bb8b84505709f76b39c8c256ec.gif)
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.