Greetings,

I'm glad that I found this group! I'm attempting to re-purpose an old Airline radio enclosure into a desktop guitar amp. The amp board that I purchased (link below) had a power terminal that I have successfully connected and tested with a 9V battery clip. It both powers the 3.5 in internal speaker that I mounted and a 1x12 Celestion speaker cab (via speaker out).

However, I'd prefer to connect a more permanent power supply. Any suggestions? I'm not even sure what to look for? Ideally, I'd like to mount a female connection on the outside that can connect to a male end of a standard power supply (similar to guitar pedal power supply).

https://www.ebay.com/itm/352985278323

Thank you for any help!

 

Welcome to AAC!

I would go with standard 3.5mm barrel plugs and jacks.






You can pick up 12VDC wall adapters at local second hand shops. If the plug on the adapter does not match your jack, simply cut off the plug and replace it with one that fits the jack.

 

Pay close attention to the Power-Supply-Polarity.

Hooking it up backwards will result in instant Blue-Smoke.
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This is what You actually want ..........
It's a roughly ~5-Watt Class-A Tube-Amp, completely assembled, or in Kit-form.

The next part is ...........
A ~3.5-inch Speaker is going to sound like complete garbage.
You will be disappointed.
I would suggest cramming 2 of the largest Speakers that will physically fit into the Cabinet,
at least ~6", and preferably 2 8" Speakers.
These Speakers should be the absolute cheesiest, cheapest, throw-away Speakers that You can find.
Like these .............
https://www.parts-express.com/J.A.L.-Electronics-JAL803-8-Mid-Woofer-4-Ohm-299-4202?quantity=1
.

 

This is what You actually want ..........
It's a roughly ~5-Watt Class-A Tube-Amp, completely assembled, or in Kit-form.

The next part is ...........
A ~3.5-inch Speaker is going to sound like complete garbage.
You will be disappointed.
I would suggest cramming 2 of the largest Speakers that will physically fit into the Cabinet,
at least ~6", and preferably 2 8" Speakers.
These Speakers should be the absolute cheesiest, cheapest, throw-away Speakers that You can find.
Like these .............
https://www.parts-express.com/J.A.L.-Electronics-JAL803-8-Mid-Woofer-4-Ohm-299-4202?quantity=1
.

Thanks for the reply. The 3.5" speaker is just for mounting inside of that small Airline radio enclosure. It's the largest that would fit behind the original speaker grill. And, you're right, it doesn't sound great, but seems suitable for quiet practice in my office or bedroom. The speaker cab has 1 12" Celestion.

Yes, I'm a fan of that YouTube channel. Admittedly, I went to cheap route with the amp board and would have prefered tubes.

 

The pictures are confusing me in that it looks like the power from the black box is arriving at the blue terminal strip on the back of the amplifier, and the speaker is connected by means of a 1/4 inch lug into a jack on the edge of the circuit board facing the cabinet rear..
Where did a "5 watt tube amplifier" fit into this picture??
A 12 volt desktop power supply like for an old computer monitor would be an excellent permanent power supply for an amplifier like that, it it requires 12 volts.

 

The pictures are confusing me in that it looks like the power from the black box is arriving at the blue terminal strip on the back of the amplifier, and the speaker is connected by means of a 1/4 inch lug into a jack on the edge of the circuit board facing the cabinet rear..
Where did a "5 watt tube amplifier" fit into this picture??
A 12 volt desktop power supply like for an old computer monitor would be an excellent permanent power supply for an amplifier like that, it it requires 12 volts.

No 5 watt tube amplifier here. I think that user, LowQCab, was suggesting that I get one? My original question was asking for help connecting a more permanent power supply. That black box holds a 9v battery which is connected to blue terminal switch on the amp. It does the trick, but I'd prefer a plug in option.

Yes, that amp has a 1/4" out that is currently connected to the 3.5" internal mounted speaker. I've also connected a 1 x12 speaker cab to that 1/4" out. The amp can drive both.

How would I connect a 12v computer power supply to that blue terminal?

I'm a total noob. Any help is appreciated.

 

No 5 watt tube amplifier here. I think that user, LowQCab, was suggesting that I get one? My original question was asking for help connecting a more permanent power supply. That black box holds a 9v battery which is connected to blue terminal switch on the amp. It does the trick, but I'd prefer a plug in option.

Yes, that amp has a 1/4" out that is currently connected to the 3.5" internal mounted speaker. I've also connected a 1 x12 speaker cab to that 1/4" out. The amp can drive both.

How would I connect a 12v computer power supply to that blue terminal?

I'm a total noob. Any help is appreciated.

 

I didn't know, at the time, that You were talking about a clean, Acoustic-Guitar-Sound.

Knowing that now, I would recommend a high-quality Graphical-EQ with at least ~10-Bands,
and a high quality, ~100-Watt Home-Stereo-Receiver,
with matching High-Fidelity-Speakers, as a Home-Practice-Rig.
( Gig-use requires abuse-proof, Professional-Level-Equipment only )

Your current Speaker selection negates any and all
Fidelity or Distortion considerations of your Pre-Amp or Pick-up style.
None of that matters with your current ( loosely defined ) "Speakers".

If You expect High-Fidelity Sound-Reproduction, High-Fidelity-Speakers are mandatory.
Speakers are a major source of Distortion,
and must be designed for the expected Location and Audience-Size.

If you'd like suggested DIY Speaker designs,
I can supply those for any intended purpose,
including DIY Professional-Level, High-Fidelity Speakers.
( don't forget to include audience-size expectations )
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Meanwhile, back at the question that was asked, allow me to expand on Mr. Chips' post #2.

While the 12 V output from an ATX-type computer power supply will work, it is waaaay overkill. Any 12 Vdc, 1 A wall wart will work. If you want a permanent connection, cut off the barrel connector, separate and strip the wires, and connect them to the screw terminals on the amp board.

If you want to be able to remove the supply, use connectors such as the ones in post #2 to mate with the wall-wart output plug, solder wires to the mating connector pins, connect these wires to the screw terminals on the amp board, and mount the connector on the rear panel.

If you want to put a complete power supply inside the cabinet, and run a standard line cord to an AC outlet, that also is possible with a little bit more effort.

ak

 

Certainly a "desktop"power supply rated at 12 volts is more than required, but certainly if it is the correct voltage it will be very satisfactory.
I examined the amplifier listing shown in the link and did not see any hint of the specified supply voltage.

The only real challenge would be in the connection, assuring to get the polarity correct. As for wanting to use the original barrel power connector, OK, I guess. I have always fond those connectors to be a real pain, as there are over a dozen different sizes and many of them are the backward polarity, with the center being negative..
So to use a 12 volt or even a ten volt desktop supply, which will be a size similar to that 9 volt battery pack, can work very well.

 

I examined the amplifier listing shown in the link and did not see any hint of the specified supply voltage.

On the manufacturer's site it says 9 V is OK, but 12 V is better. The board uses one LM386, so anything up to 15 V will work. (Depending on what your definition of "work" is.)

ak

 

On the manufacturer's site it says 9 V is OK, but 12 V is better. The board uses one LM386, so anything up to 15 V will work. (Depending on what your definition of "work" is.)

ak

Thank you. So, I could cut/strip the wires on a 12V 1A power supply and simply screw the wires into the blue screw terminal on the amp?

 

So, I could cut/strip the wires on a 12V 1A power supply and simply screw the wires into the blue screw terminal on the amp?

Yes.

BUT, as everyone has said, make sure you have the polarity correct When you have a supply, post a photo of its label. Also, not if one of the wires in the output lead has a solid or dashed white stripe on it, or one side of the cable has one or more small ridges running the length. Usually, there is some indication of which wire is + and which is -. Usually, the marked wire is the negative, but don't trust that.

Usually there is a graphic on the supply showing whether the inside or outside of the barrel connector is +. When you cut off the connector, leave 1 " attached. Split the wires and use a meter to determine which wire is + based on the label.

ak

 

If the TS has a meter then it is also simple to measure the voltage. I have come across a few supplies that had an output much greater than the tag stated. 30 volts instead of 23 volts.
also unregulated and unfiltered supplies that would produce large amounts of hum.

 

The datasheet for the LM386 amplifier IC used in the ebay amplifier kit shows that increasing the supply voltage from 9V to 12V simply increases its heating and you will not notice the tiny increased max output power.
Its output power is the same 0.6W from a cheap clock radio.

 

Thanks again for everyone's help! Would something like this work to replace the 9v battery?

uxcell DC Power 3.5mm x 1.35mm 30cm Length Barrel Female Plug Connector Pigtail 5pcs https://a.co/d/cizrOEL

uxcell 2pcs DC Power 4.0mm x 1.7mm 3A 22AWG 30cm Female Plug Connector Pigtail https://a.co/d/8nijhdh

 

The specifications for the power supply were not obvious, But if the voltage is right and the current is adequate then it should work well.. I suggest verifying that the polarity is correct prior to applying power to the amplifier. With two connectors from different sources there could be a reversal someplace.

 

The specifications for the power supply were not obvious, But if the voltage is right and the current is adequate then it should work well.. I suggest verifying that the polarity is correct prior to applying power to the amplifier. With two connectors from different sources there could be a reversal someplace.

Here's the description of the board:

This is the Guitar Amplifier Kit. This is a fun and easy kit to build. It uses an LM386 Audio Amplifier IC to amplify an Electric Guitar input and will drive a set of Headphones or it can directly drive a speaker. It has a Volume and Tone control for a nice sound. The output power of the LM386 is a minimum of 350mW.

The circuit has been designed for a very small foot-print. The PCB is double-sided, plated thru-holes, 1.20" long x 2.20" wide made of .062" FR-4 epoxy glass

It can run off a 9v battery, but does better with 12vdc. It has a 1/4" Phono Jack (female) to fit a Guitar cable (male) and a 2-pin screw Terminal for the power input and a 1/4 inch phono jack for the speaker output.

 

Getting the power connection polarity right is the most important thing.