Sennheiser wireless headphones - alternative transmitter options?

[fstarockr]

Hi - picked up a pair of sennheiser HDR120 phones at a thrift store, but no transmitter. My knowledge of eletronics is as such: black/green is usually earth and red positive, and soldering on a live wire causes a small explosion in your face.

Now onto the question.. is it possible to use a generic FM transmitter in the same frequency/range? The original unit takes a power and audio cable and transmits what I believe is a FM signal. The phones have a tune button and here are the specs of the transmitter:

https://en-us.sennheiser.com/downloads/efbf450aa83156c4c25fc77f25977144.pdf


Technical Data – TR 120 Transmitter
Carrier frequencies
..........................
863 MHz variant: 863.3 MHz,
864.0 MHz, 864.7 MHz,
926 MHz variant: 926.1 MHz, 926.8 MHz, 927.5 MHz
Range .................................................................up to approx. 100 m
Modulation........................................................................... FM stereo
Signal-to-noise ratio
........................................................... > 65 dBA


Could I get a cheapo FM transmitter with an overlapping range and tune in? I will be sitting VERY close to it (max 9 ft)..


tx in advance!

 

[ramuna]

Hi,
Before searching for the transmitter at those frequencies, have you a suitable receiver for receiving such transmissions ?

 

[fstarockr]

well the headphones seem to be the receiver? or am i missing something here

 

[fstarockr]

theres a $10 thing on ebay that says :"requencies: 88.0 FM to 108.0 FM", - since the headphones are 863-927 they overlap right?

 

[ramuna]

Hi,
My error , should have read the specs before asking my question. Yes, the receiver is integrated into the headphones. And no, 88 to 108 MHz is the normal commercial FM VHF band. You need frequencies in the UHF range, around 8 times higher.

 

[ramuna]

Have a look at https://en-de.sennheiser.com/accessories--rs-120--tr-120-8

 

[fstarockr]

ah thanks, any cheap options out there? what would the consumer name be - uhf transmitter? cos im getting all kinds of expensive stuff.. or would it be unreasonable to change the headphones receiver? are the higher number more powerful or just because they arent commercially used? sorry for my noob questions

 

[fstarockr]

so am i looking uhf explicitly or just any transmitter in that range? just trying to broaden my search scope..

 

[fstarockr]

so this should work? **broken link removed**

any commercial audio transmitter in the right range basically?

I can get a working set for $40 on ebay, so dont wanna go too $$ on this.. trying to make this thing usable as cheap as possible..

 

[ramuna]

Hi,
I just searched to see if I could find a matching transmitter at a less expensive price than the one in post #6. Unfortunately, I drew a blank. The Sennheiser 864 MHz transmitter is especially tailored to match up with its 864 MHz headphone receiver (ditto with the 926 MHz). I also could not find general purpose FM transmitters at both the requisite frequencies and at a lower price during my search.

 

[fstarockr]

much appreciated! so these are fixed, I understand now.. so basically im stumped. lots of 900mhz things on ebay. so basically I need a transmitter exactly on one of those frequencies then..

 

[ronsimpson]

Found what appears to be a complete working headphone on e-bay for $50 with free shipping.

You might put them on ebay. There is probably someone with a broken head set and a good transmitter.

 

[fstarockr]

could I not change the receiver in the phones? just curious now solder in a diff frequency or something..

 

[fstarockr]

guess thats what i gotta do, they feel so nice!! ah well

 

[fstarockr]

how mch does the tuning knob do? does it go from the lower to the higher range?? ie if i got a transmitter within 863-927 could i tune in or does it have to match exactly down to the decimal? thanks!

 

[ramuna]

fstarockr said:
could I not change the receiver in the phones? just curious now solder in a diff frequency or something..

how mch does the tuning knob do? does it go from the lower to the higher range?? ie if i got a transmitter within 863-927 could i tune in or does it have to match exactly down to the decimal? thanks!

Both the Sennheiser receiver and matching transmitter almost certainly use tailor-made crystals for controlling their frequencies. So the only way to change the frequencies of one or other or both is to change the crystals. Moreover the circuitry is almost certainly surface mounted. Performing crystal-swapping surgery on such pcbs is ill-advised, because (1) it would be hard to source matching crystals, and (2) you need special equipment to desolder and resolder the crystals.

Edit: A general purpose tunable transmitter will not have both the stability required and the low cost you want.

 

[fstarockr]

awesome - tx for the nice straight answers. ive learnt a bit today