Radio Shack wall-wart and SI T-amp

Garaphin · 10th April 2006, 05:46 AM

Hi all-

Just got my first t-amp recently, and am enjoying it and reading about all the mods I'll be looking to make to it in future...

I ran it on AAs for the first week or so, but the sound started cutting out today during loud moments or when I would turn up the volume so it was definately time to switch to a different power supply.

I got impulsive and ran to Radio Shack, instead of ordering directly from Sonic Impact, where I picked up their 12V 1500mA adaptor (273-1779). I had read enough online to know that this was indeed the values I needed for the amp, however once I got home I read here that this specific power supply actually outputs 15v instead of the listed 12v. I pulled out the old multimeter and indeed, this thing spits out ~14.8v.

Does this pose a serious problem to the life-span or sound quality of the t-amp? So far it's running fine and sounds normal, although I am noticing the top of the plastic case is a litte warm which is something I didn't notice before when running on batteries.

I'm not ready to jump this to a SLA battery, but would like to feel comfortable with my wall wart.

Any thoughts?

Thanks.

geaugafletcher · 10th April 2006, 04:38 PM

I have the same wall-wart powering my sonic impact, and it's been fine for over a month now. I called the RS tech line about the ~15v, they said it's completely normal - the voltage drops to ~12 with a load.

I assume the amp is enough of a load even when idling.

amt · 10th April 2006, 04:39 PM

The T-amp will operate well with up to 14VDC, BUT if yours has been recently purchased, I would not suggest using that high a voltage. The T-amps went through a "de-rating" and the solder heatsinking was eliminated. So the heat you detect is the chip glowing and radiating the heat into the plastic case. If you dont put a heatsink on it, I wouldnt use more than 12V. Did you check the wallwart while powering the amp? With no load, the wart will read higher than when powering the amp(provided it is unregulated). Check it with the amp operating with no signal and then with. That will give you a realistic voltage.

I heatsink all my T-amps. I would suggest doing the same, and operating it moderately if you dont.

amt

Garaphin · 10th April 2006, 06:01 PM

Thanks for the input thus far.

I'm not sure how to test the voltage with the amp connected as a load... I imagine it would require some clips or plugs that I don't have right now. I guess I can rest easy knowing that it's not running at the full 15v.

As for heatsinking, because I have it in the original case still, I'm thinking that I don't have much headroom in their for a sink. I have some very small BGA ramsinks from my computer that may work I guess... anybody know exactly what I can fit in there? Height specifically.

cpemma · 10th April 2006, 10:18 PM

Quote:

Originally posted by geaugafletcher
I have the same wall-wart powering my sonic impact, and it's been fine for over a month now. I called the RS tech line about the ~15v, they said it's completely normal - the voltage drops to ~12 with a load.

I assume the amp is enough of a load even when idling.

I wouldn't count on that; the adaptor does seem to be unregulated so the high off-load voltage is normal for a small transformer. As the RS Tech said, it should be near 12V with a 1500mA load. But the T-Amp only draws about 75mA when idling IIRC, so to be safe see what the voltage is with a 150R or 180R resistor as load. It may scare you.

amt · 10th April 2006, 10:23 PM

If your wallwart can be taken apart, you can check at the cord connection. If not, strip a tiny bit of cable sheilding away from the cord with an exacto and get a reading there.

As to a heatsink, flood on some solder, through the vent holes and onto the slug and then attach a small piece of copper or aluminum. Make sure to tin the heatsink piece first, and keep it hot or you dont have to re-heat the whole thing mess.Copper is far better since it retains the heat longer. Below is a t-amp I added a scrap of copper to. Ugly but works well.

amt

cpemma · 10th April 2006, 11:42 PM

Quote:

Originally posted by amt
If not, strip a tiny bit of cable sheilding away from the cord with an exacto and get a reading there.

A couple of sharp pins hooked to your meter will do the trick (almost) without leaving a trace...

Garaphin · 11th April 2006, 07:41 AM

Ok, hey all. Because of the design of the Radio Shack adaptor and their interchangable plugs, I was able to just barely attach the plug to the cord giving me enough room to get my probes in there. With the amp running, the multimeter is still showing ~14.3v. I'm assuming that was a proper way to take the reading.

I may be making a mountain out of a molehill here, as it's clear other people have used the Radio Shack one without any problems thus far. But I think that I may feel more comfortable returning it, getting my money back, and purchasing the AC adaptor from Sonic Impact directly via the web.

http://www.si-technologies.com/front...sp?productID=3

Does anybody own that particular adaptor? If so, any chance you could check the voltage on that? I'd hate to go through the return process and wait to get the new one if the results are just the same as the Radio Shack model.

cpemma · 11th April 2006, 01:06 PM

There are plenty of regulated 12V adaptors out there, both linear and SMPS, and I'll bet far cheaper than that RS model. Here's one in the US, [url=http://www.rapidelectronics.co.uk/rkmain.asp?PAGEID=80010&CTL_CAT_CODE=30355&STK_PRO D_CODE=M71065&XPAGENO=1]another[/url[ in the UK.

Another way is to insert a couple of 3A diodes (1N5401) in the outlet cord, which will drop 1.4-1.8V depending on load. But a regulated supply is a much better option.

cpemma · 11th April 2006, 01:22 PM

Quote:

Originally posted by cpemma
Here's one in the US, another in the UK.

Damn the short edit time...

10th April 2006, 05:46 AM	#1
Garaphin diyAudio Member Join Date: Apr 2006 Location: Seattle, WA	Radio Shack wall-wart and SI T-amp Hi all- Just got my first t-amp recently, and am enjoying it and reading about all the mods I'll be looking to make to it in future... I ran it on AAs for the first week or so, but the sound started cutting out today during loud moments or when I would turn up the volume so it was definately time to switch to a different power supply. I got impulsive and ran to Radio Shack, instead of ordering directly from Sonic Impact, where I picked up their 12V 1500mA adaptor (273-1779). I had read enough online to know that this was indeed the values I needed for the amp, however once I got home I read here that this specific power supply actually outputs 15v instead of the listed 12v. I pulled out the old multimeter and indeed, this thing spits out ~14.8v. Does this pose a serious problem to the life-span or sound quality of the t-amp? So far it's running fine and sounds normal, although I am noticing the top of the plastic case is a litte warm which is something I didn't notice before when running on batteries. I'm not ready to jump this to a SLA battery, but would like to feel comfortable with my wall wart. Any thoughts? Thanks.

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10th April 2006, 04:38 PM	#2
geaugafletcher diyAudio Member Join Date: Feb 2006 Location: Oklahoma	I have the same wall-wart powering my sonic impact, and it's been fine for over a month now. I called the RS tech line about the ~15v, they said it's completely normal - the voltage drops to ~12 with a load. I assume the amp is enough of a load even when idling.

10th April 2006, 04:39 PM	#3
amt diyAudio Member Join Date: Feb 2003 Location: oregon	The T-amp will operate well with up to 14VDC, BUT if yours has been recently purchased, I would not suggest using that high a voltage. The T-amps went through a "de-rating" and the solder heatsinking was eliminated. So the heat you detect is the chip glowing and radiating the heat into the plastic case. If you dont put a heatsink on it, I wouldnt use more than 12V. Did you check the wallwart while powering the amp? With no load, the wart will read higher than when powering the amp(provided it is unregulated). Check it with the amp operating with no signal and then with. That will give you a realistic voltage. I heatsink all my T-amps. I would suggest doing the same, and operating it moderately if you dont. amt

10th April 2006, 06:01 PM	#4
Garaphin diyAudio Member Join Date: Apr 2006 Location: Seattle, WA	Thanks for the input thus far. I'm not sure how to test the voltage with the amp connected as a load... I imagine it would require some clips or plugs that I don't have right now. I guess I can rest easy knowing that it's not running at the full 15v. As for heatsinking, because I have it in the original case still, I'm thinking that I don't have much headroom in their for a sink. I have some very small BGA ramsinks from my computer that may work I guess... anybody know exactly what I can fit in there? Height specifically.

11th April 2006, 07:41 AM	#8
Garaphin diyAudio Member Join Date: Apr 2006 Location: Seattle, WA	Ok, hey all. Because of the design of the Radio Shack adaptor and their interchangable plugs, I was able to just barely attach the plug to the cord giving me enough room to get my probes in there. With the amp running, the multimeter is still showing ~14.3v. I'm assuming that was a proper way to take the reading. I may be making a mountain out of a molehill here, as it's clear other people have used the Radio Shack one without any problems thus far. But I think that I may feel more comfortable returning it, getting my money back, and purchasing the AC adaptor from Sonic Impact directly via the web. http://www.si-technologies.com/front...sp?productID=3 Does anybody own that particular adaptor? If so, any chance you could check the voltage on that? I'd hate to go through the return process and wait to get the new one if the results are just the same as the Radio Shack model.

11th April 2006, 01:06 PM	#9
cpemma diyAudio Member Join Date: Jul 2003 Location: S Yorkshire OK	There are plenty of regulated 12V adaptors out there, both linear and SMPS, and I'll bet far cheaper than that RS model. Here's one in the US, [url=http://www.rapidelectronics.co.uk/rkmain.asp?PAGEID=80010&CTL_CAT_CODE=30355&STK_PRO D_CODE=M71065&XPAGENO=1]another[/url[ in the UK. Another way is to insert a couple of 3A diodes (1N5401) in the outlet cord, which will drop 1.4-1.8V depending on load. But a regulated supply is a much better option.

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