33 Ohms impedance audio signal

[danytremblay]

Hi, I would like to feed existing 33 Ohms impedance input amplifiers with sound coming from a computer audio line out.
From what I found, the computer audio output is about 1 VRMS and can be considered as a 600 Ohms impedance.
I was thinking of using some audio isolation transformers to match the 600 Ohms to the 33 Ohms input but I figure that it can't be done since there won't be enough power from the audio card to supply the amplifiers input.
The other solution I tough was to use a small 2 watt 8 Ohms output amplifier with adjustable gain and use a resistor at the amplifier output to match the 33 Ohms amplifiers inputs requirements but I really don't know if that could do the job and how to calculate the required resistor value or if there is another better solution ?
Any help will be greatly appreciated !

 

[Salt]

Hi, I would like to feed existing 33 Ohms impedance input amplifiers

Could You name this singularity?

 

[Blumlein 88]

Sure this is not 33 kohms? Yes, naming the amp and model would help.

 

[danytremblay]

Could You name this singularity?

This 33 Ohms audio signal is feeding existing GaiTronics paging system amplifiers like the above:.

 

[danytremblay]

Sure this is not 33 kohms? Yes, naming the amp and model would help.

Yes it is 33 Ohms, see previous response with amplifier model

 

[Blumlein 88]

Input impedance is 50 kohms. Page 2 below. The 33 ohms is probably for its electrical load.

https://hubbellcdn.com/installationmanuals/SKU-GTC-Manual-42004-210B.pdf

.5 volt input for rated output.

Direct connection should work, don't see which type of input jacks it uses. As long as you can adapt the sound card out to the type jack at the input everything should be good. No need for anything else.

BTW, Welcome to ASR, just noticed you were a new member.

 

[Salt]

Don't think this one is meant as 'power ampifier' ...

 

[solderdude]

Hi, I would like to feed existing 33 Ohms impedance input amplifiers with sound coming from a computer audio line out.
From what I found, the computer audio output is about 1 VRMS and can be considered as a 600 Ohms impedance.
I was thinking of using some audio isolation transformers to match the 600 Ohms to the 33 Ohms input but I figure that it can't be done since there won't be enough power from the audio card to supply the amplifiers input.
The other solution I tough was to use a small 2 watt 8 Ohms output amplifier with adjustable gain and use a resistor at the amplifier output to match the 33 Ohms amplifiers inputs requirements but I really don't know if that could do the job and how to calculate the required resistor value or if there is another better solution ?
Any help will be greatly appreciated !

If that were really 33 ohm input resistance than simply using the headphone out of the computer instead of line-out would have been an easy solution.

But as @Blumlein 88 already mentioned it is 50k input R (and 500mV sensitivity with the internal volume control set to max.)
It can clearly only be used for paging workers in a plant(factory) when looking at the frequency response: 250Hz – 4kHz, -3 dB
It is designed to deliver power to paging-speakers/headsets in production plants and is fed with a 'safe' (low voltage) 24VDC power supply.

https://hubbellcdn.com/installationmanuals/SKU-GTC-Manual-42004-139D.pdf

 

[IAtaman]

If that were really 33 ohm input resistance than simply using the headphone out of the computer instead of line-out would have been an easy solution.

But as @Blumlein 88 already mentioned it is 50k input R (and 500mV sensitivity with the internal volume control set to max.)
It can clearly only be used for paging workers in a plant(factory) when looking at the frequency response: 250Hz – 4kHz, -3 dB
It is designed to deliver power to paging-speakers/headsets in production plants and is fed with a 'safe' (low voltage) 24VDC power supply.

https://hubbellcdn.com/installationmanuals/SKU-GTC-Manual-42004-139D.pdf

I understood plant as in eukaryotic kingdom of living things plantae, not as factory or workshop, and was very confused with the term Plant Paging Amplifier.

 

[danytremblay]

Input impedance is 50 kohms. Page 2 below. The 33 ohms is probably for its electrical load.

https://hubbellcdn.com/installationmanuals/SKU-GTC-Manual-42004-210B.pdf

.5 volt input for rated output.

Direct connection should work, don't see which type of input jacks it uses. As long as you can adapt the sound card out to the type jack at the input everything should be good. No need for anything else.

BTW, Welcome to ASR, just noticed you were a new member.

Could it be that the total impedance of all the amplifiers connected on the same audio line input signal (there might be up to 50 amplifiers) may go as low as 33 Ohms ?
How do we calculate the total input impedance of 50x amplifiers in parallel (if the input impedance is 50K). Is it like 50 x 50K resistors in parallel ?

I'm confused about this 33 Ohms, why do they sell a 600 Ohms to 33 Ohms converter GaiTronics 370-301 600 Ohms to 33 Ohms Converter
On sheet 10 It says 33 Ohms max. audio Out is 1.5Vrms.

I took measurement on 3 audio lines (different number of amplifier and total cable length) with a Tenma Model 72-6948 audio impedance tester and got these readings: 14 Ohms, 20 Ohms and 23 Ohms.

If 1,5 Vrms is required on a 33 Ohms impedance audio line it needs 0.068 Watt of power, does a computer sound card produce enough power for this ?

IF not, is there some preamps that are having a mute input signal that could do the job ?

I was also thinking of using a small 2 watt / 8 Ohms amplifier like Vicking PA-2A and add a resistor on the amplifier output to adjust the total audio line impedance to 8 Ohms (for example, 20 Ohms line + 15 Ohms resistor = 8.5 Ohms total) but I would get an audio signal maximum voltage of 4 V rms, this is too much voltage for the speakers amplifiers (should be somewhere between 0.5 and 1.5 VRMS from the documentation). Any tricks I could use to match it ? (600:150 audio transformer ?)

Thanks

 

[egellings]

Hi, I would like to feed existing 33 Ohms impedance input amplifiers with sound coming from a computer audio line out.
From what I found, the computer audio output is about 1 VRMS and can be considered as a 600 Ohms impedance.
I was thinking of using some audio isolation transformers to match the 600 Ohms to the 33 Ohms input but I figure that it can't be done since there won't be enough power from the audio card to supply the amplifiers input.
The other solution I tough was to use a small 2 watt 8 Ohms output amplifier with adjustable gain and use a resistor at the amplifier output to match the 33 Ohms amplifiers inputs requirements but I really don't know if that could do the job and how to calculate the required resistor value or if there is another better solution ?
Any help will be greatly appreciated !

If the input impedance were just 33 ohms, you'd need a small power amplifier to drive that.

 

[Blumlein 88]

Looks like these units are connected together over either 33 ohm or a 600 ohm network. The input impedance to the unit is still 50 kohm. If you connect multiple units then it is one of the other values. It appears it also drives directly 33 ohm or 600 ohm speakers. Looks like 600 ohm speakers, phone handsets etc are something of a standard.

So exactly how are you wishing to use this unit? Some PA speaker sending out announcements over a PA or what?

 

[IAtaman]

Looks like these units are connected together over either 33 ohm or a 600 ohm network. The input impedance to the unit is still 50 kohm. If you connect multiple units then it is one of the other values. It appears it also drives directly 33 ohm or 600 ohm speakers. Looks like 600 ohm speakers, phone handsets etc are something of a standard.

So exactly how are you wishing to use this unit? Some PA speaker sending out announcements over a PA or what?

You are right.

I was intrigued, so did some reading. This amp seems to be part of a Page/Party (r) system that has various intercom stations that connects to the network which has 33 ohm ratings such as this beauty here.

And for the 600/33ohm converter

The Model 370-301 Dual Channel 600-Ohm to 33-Ohm Audio Interface allows GAI-TRONICS’ Page/Party® systems to connect with standard 600Ω networks for one- or two-way communication between dissimilar transmission mediums. Suitable 600Ω systems include central amplifiers, PABX paging ports, Programmable Logic Controller (PLC) alarm outputs, and computer sound cards.

There is even a 33ohm network to VoIP converter.

SP2 Page/Party® Interface | 370-901 | GAI-Tronics

SP2 is one of GAI-TRONICS’ most advanced paging and intercom systems. Combining the simplicity of “press to page, release to party” operation with cutting-edge multicast Voice over Internet Protocol (VoIP) technology, SP2 is capable of providing virtually instant communication in the most...

www.hubbell.com

And one more thing I learned today, if you have a page/party system, you press to page, release to party.