Headphone workover.

[Coota]

Hi, had an interesting conversation with a brother today. Years ago he was a storeman with Telstra in Kalgoorlie, back in the days of the old Bakelite telephone.
Seems the early detectorist around there would give their eye teeth to get their hands on the parts they wanted from the hand piece. They wanted the earpieces to place into headphones, as one told him "Mate, ya don't miss a whisper with those how about two cartons for a couple?"
Anyway, when the old phones became outdated he put in a tender for the relevant parts off the shelve and they have been sitting in his shed ever since!
I will be up that way in a few weeks so will get some cheap headphones and see how they go with the new old parts, shouldn't be hard to fit and I have a feeling it will be worth the effort.
Has anyone ever heard anything similar?

Cheers.

 

[Ridge Runner]

Hi, had an interesting conversation with a brother today. Years ago he was a storeman with Telstra in Kalgoorlie, back in the days of the old Bakelite telephone.
Seems the early detectorist around there would give their eye teeth to get their hands on the parts they wanted from the hand piece. They wanted the earpieces to place into headphones, as one told him "Mate, ya don't miss a whisper with those how about two cartons for a couple?"
Anyway, when the old phones became outdated he put in a tender for the relevant parts off the shelve and they have been sitting in his shed ever since!
I will be up that way in a few weeks so will get some cheap headphones and see how they go with the new old parts, shouldn't be hard to fit and I have a feeling it will be worth the effort.
Has anyone ever heard anything similar?

Cheers.

The thing is with older Phones is they do not colour the sound IE give it a warmer rich Tone Like the Koss Phones Do, and Pairs like the Nugget Busters or Grey Ghosts and the Newer White's Pro Star Don't do that so the Tone is Sharper and you tend to be able to here those faint signals, The Koss Phone are great and don't hurt your ears with the sharper signals But they will cause you to miss faint targets, The Grey Ghost head Phones have a noise Limiter in them so big/close Items don't blow your ears off, and they have volume knobs each side, The Nugget Busters have the Twin Volume Knobs but DO NOT have the Noise Limiter/s Fitted
As for the Whites Pro Stars they look like the GG/NB phones but they are Black and I don't know if they Have the Noise Limiters in or Not.

Hope this Helps.

 

[Coota]

Thanks Ridge Runner, yeah the technology has come a long way since those days. I think I will still try the setup and see how it goes, more out of curiosity than anything else. I could be onto a patch ( fingers crossed) or at least a VERY decent undetected area so if I do find a target with the Koss I'll switch over to the adapted set and see what I hear. Like I said, more out of curiosity about what the fellows with the first gen detectors were on about. Won't cost me bugger all, just a little time. Thanks.

 

[Ridge Runner]

Thanks Ridge Runner, yeah the technology has come a long way since those days. I think I will still try the setup and see how it goes, more out of curiosity than anything else. I could be onto a patch ( fingers crossed) or at least a VERY decent undetected area so if I do find a target with the Koss I'll switch over to the adapted set and see what I hear. Like I said, more out of curiosity about what the fellows with the first gen detectors were on about. Won't cost me bugger all, just a little time. Thanks.

Yeah Keep going with it, Lets face it those little devils are hard enough to find as it is and we need all the help we can get, It's a Great Idea, You know when you hit on a winning pair we expect the forum will get a discount when you market these things,

Seriously though, You will find the sharpness annoying at first but once you have had them on a few hours you will be well aware of what the ground is Telling you, and you will keep wanting to change back and forth, But don't give In because I think you are on to a winner, Good Luck and keep us in the loop,

Happy Testing

 

[N61753]

Sorry about image size.
This is similar to what the old timers were getting from Telstra.
It doesn't use a moving coil type system, it's some other type system which escapes me at the moment.
I've had it in the drawer for at least 45 years, shows you how old I must be.
It is the type of headset they used in crystal radios so it's designed to work with very week signals.
The frequency response will be very poor.

First chance I get I will try it out and let you know how well it works.
And thanks for the post, I would never have thought to try it out.

 

[Ridge Runner]

https://www.prospectingaustralia.com/forum/img/member-images/3834/1411031418_image.jpg

Sorry about image size.
This is similar to what the old timers were getting from Telstra.
It doesn't use a moving coil type system, it's some other type system which escapes me at the moment.
I've had it in the drawer for at least 45 years, shows you how old I must be.
It is the type of headset they used in crystal radios so it's designed to work with very week signals.
The frequency response will be very poor.

First chance I get I will try it out and let you know how well it works.
And thanks for the post, I would never have thought to try it out.

Great, Well if they are made to work on weak signals they might even put the new stuff to shame and that's where we need it most,

You're in good shape for a 21 year old

Thanks for posting the Pictures.

 

[condor22]

Before anyone connects a set of "different" phones to their detector..................

Earphones or earplugs/buds are usually impendence matched to the output signal of the device they are used on. It might be a detector or MP3 player, stereo system, CB radio etc etc. In some instances using the wrong impendence phones or speakers may overload the final output amp or not work properly because the device output isn't strong enough.

Either way you could damage the phones or far worse the detector. Could be an expensive exercise, so as they say, "measure twice, cut once".

 

[Coota]

Thanks for the photo and comments N61753, hope they don't blow a fuse when you plug them in!
Looking forward to your rundown on the performance of the antique 50 odd year old homemade phones, luv em!

 

[outboard]

These early headphones used moving iron drivers, either single ended or balanced armature. The requirement for high sensitivity meant no damping was used, thus the sound quality was crude. They also had very poor comfort compared to modern types, usually having no padding and too often having excessive clamping force to the head. Their impedance varied; headphones used in telegraph and telephone work had an impedance of 75 ohms. Those used with early wireless radio had to be more sensitive and were made with more turns of finer wire; impedance of 1000 to 2000 ohms was common, which suited both crystal sets and triode receivers.

you can test the impedance with an ohm meter and adjust it with resistors (in series to increase it, in parallel to reduce it) as impedance is (in layman's terms) resistance on an alternating current


disclamer: I ain't no electrickery magician so do your own research before taking any of my advice

 

[N61753]

Thanks Condor22 good catch, absolutely right.
I hadn't thought of this.
I know they are very high impedance(resistance).
If I find they still are in working order will make this into a project and post my results.
Will use an impedance matching transformer and some type of volume limiting circuit.
Thanks Outboard, you got me thinking in that direction.
I'll try an make it a proper project which others can use, but then again the phones are probably faulty.
If anyone can recommend a volume limiting device I would appreciate it. I know you can do this with an operational amplifier.
Would like to come up with something everyone could build with a cost of $10.00 or so.

 

[Ridge Runner]

Remember its ok that they are more Ohms But if they are Less than what the detector puts out or what the factory says it puts out then they will Eat Your machines out Put Stage of the Audio Circuit,

The Audio will sound a lot Louder than with normal Phones if they are Less than what they Recommend, Ok

Hope this helps

 

[condor22]

Remember its ok that they are more Ohms But if they are Less than what the detector puts out or what the factory says it puts out then they will Eat Your machines out Put Stage of the Audio Circuit,

The Audio will sound a lot Louder than with normal Phones if they are Less than what they Recommend, Ok

Hope this helps

Conversely, if they are much higher, the detector volumes will need to be cranked and even then may not give a loud enough signal.

That's why it's called Impendence Matching........

 

[Ridge Runner]

Remember its ok that they are more Ohms But if they are Less than what the detector puts out or what the factory says it puts out then they will Eat Your machines out Put Stage of the Audio Circuit,

The Audio will sound a lot Louder than with normal Phones if they are Less than what they Recommend, Ok

Hope this helps

Conversely, if they are much higher, the detector volumes will need to be cranked and even then may not give a loud enough signal.

That's why it's called Impendence Matching........

Yeah, That's why I would rather leave it to the experts or to get one of them test them first, I would go nuts if I did some thing that blew up my machine

 

[condor22]

Here's a good explanation, although somewhat technical

http://hyperphysics.phy-astr.gsu.edu/hbase/audio/imped.html

or an explanation from Jaycar Electronics.

http://www.jaycar.com.au/images_uploaded/impmatch.pdf

It's not really necessary to understand the science/technology of Impedance matching, only that if not considered, things might not work as expected or damage the more expensive part of a system.

Just because a speaker or phone jack fits in a socket, does NOT mean it will work in the same way as the original item.