$7 Harbor Freight wireless headphones modded for Tesoro Vaquero

[Ism]

Hi all, I hope this is a useful mod and maybe someone with better electronic savvy than me will improve on the changes I've made.

I saw a wireless headphone advertised at Harbor Freight for $6.99, so I bought one. The headphones operate in the FM bandwidth. The headset has a small telescoping antenna, the transmitter has no antenna. At the short distance from the detector the antenna on the headset doesn't have to be extended.
The board inside had to be small enough to adapt for use with the detector. disassembling the case revealed a 4"x 7/8" circuit board. I filled the battery compartments of the headphones and the transmitter, connected my Tesoro Vaquero to the audio input, powered everything up and got a terribly distorted signal in the headphones. By the process of elimination, I plugged the transmitter into my computer. The sound quality wasn't bad so I knew it was the detector. I tried my Minelab Sovereign, it was worse. So I went to work modificating.

The Tesoro puts out a 5v p-p square wave signal with the threshold at max. I figured the square-wave wasn't the type of signal that the input could digest. I found that by removing the capacitor near the audio input (see pic) the sound quality improved greatly. The input level was still too high and distorted, so I reduced it by adding an 82 Ohm resistor across the common and "conditioned" input (essentially a fixed volume control). That reduced the audio to the proper level and quality. I tried it on my Sovereign but it sounds almost as bad as before the improvements.... I'm not sure why.

I got a 3"x 2" plastic job box from Radio Shack that cost little over $3 with tax. I was able to remove the transmitter's RCA jacks and shorten the board to 2-13/16" long. A perfect fit to slide between the slots that are molded to the inside of the box. I started cutting holes in the box. for the on-off switch, audio input jack, LED, and the battery compartment. I cut the plastic around the battery compartment to the size and shape shown and bonded it in the cutout that I made in the box cover. This is as far as I got tonight, I will attach it to my detector tomorrow. I haven't field tested the setup but it sounds pretty good from the bench and there doesn't appear to be any delay of any kind.
I was in a hurry to get this project done (my excuse for the poor workmanship).

The transmitter component changes worked for my Tesoro Vaquero. I cant verify how the mod will work on other detectors but its a place to start.

 

[jabbo]

Looks like a nice project for those who have the electronics skill. Let us know how it worked out for your detectors.

 

[Ism]

A couple negatives about the headphones.

1. I usually detect using ear buds so my experience with the long term usage of a headset is lacking. The earpads are a bit stiff. I worked the pads with my thumbs and it softened them somewhat but they appear replacable, better earpads may be available.
2. I'm not sure if they are considered heavy in the realm of wireless headsets but the antenna could be removed to drop a couple ounces. (I don't think weight is an issue)
3. There is some slight microphoning I'm not sure if this is inherent in the headset or due to my removal of the capacitor. It isn't an issue, just an observation.

I am adding a couple photo's that I coudn't include in the original post.

 

[Ism]

I added a 1/4 stereo headphone plug to the body of the project box. It needed to be mounted on the outside for clearance from the shaft. I didn't hardwire the plug because I tack glued the PC board in the box to keep it from moving. I didn't want to disect my creation just for that. The upgrade will have afterthought improvments including adjustment for input sensitivity.

 

[poohbear2170]

I like your idea i think i will try it on my E-Trac

 

[Ism]

PoohBear, I couldn't get this unit to work with my Sovereign (the audio is garbled). So I don't know if it will work with the E-trac.
I wish I had a solution to the incompatibility issue. Someone that is tech savvy may be able to solve the problem. I'm just a hack with enough knowledge to be dangerous so it will take me time to figure out a solution...grin

Since assembling the unit microphoning issue mentioned in the above post has disapeared.

 

[poohbear2170]

Okay thanks for letting me know !

 

[nova74]

How many hours have you put on your machine since mod was done? What has battery life been like? This I think is a good mod as most if not all hunters know the frustration of getting cords caught.

 

[GoGoGopher]

Also, does it pick up FM radio stations at all...The last FM wireless I tried did....

Thanks,

 

[Loosecanon]

I just built one of these to use with my Lone Star. It works very well, the resistor value ended up different so the problem is too much audio into the transmitter. I am going to build an adjustable attenuator that way it should be able to be used with any model.

 

[Ism]

GoGo, the headphones pick up FM if it doesn't connect to the transmitter right. I haven't used them since I made them. They have a background hiss that comes and goes.
I thought it was a neat project but my electronics mod could have been engineered better. My Tesoro Vaquero didn't have enough audio so I Iowered the input resistance of the transmitter and it helped.
Then there was a distorted signal until I removed the capacitor. I made it work for my Minelab by making an inline volume control but there was that background hiss and the struggle getting it to link reliably.

I am using a different wireless headset that cost $100. They have a slight delay but using a moderate sweep it goes unnoticed. Unlike ANY bluetooth set which has a very noticable delay.

I like to expiriment and if I find things others might like to try, I share it. They are only $7 and work very nicely for that price. But for serious detecting, they should go in the round file.

 

[micro065]

Hi, I got this to work fine on my E-trac with no distortion. All I did was not remove anything on the PCB, and used a 330 Ohm resistor instead of the 82 Ohm. I found this by accident, because all I had on hand was an 330 Ohm resistor. Also I did not use an in-line volume control. On mine everything on the PCB is very different from the one in the pictures in this thread. I hope this helps.