Pro-95
Member
I need to lower the headphone output down to line level. Would simple resitors work? How much or how many? Headphone output is for a 246T.
Headphone to line level output
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JnglMassiv
Member
I've always used the built in attenuator...
...Which is the volume knob. Experiment a little to get the settings right.
...Which is the volume knob. Experiment a little to get the settings right.
JnglMassiv said:
LOL...
I've done the same. I cut tiny squares from CD-label stock and affixed them as hash-marks, next to the volume knob on two of my scanners, so that I know exactly where to set the volume.
Pro-95
Member
Yeah I could turn down the volume. But where's the fun in that. :lol: :lol: :lol: :lol:
N
N_Jay
Guest
Pro-95 said:
It probably does not matter most of the time, but the correct way is to load the output within its designed specifications and tap it with 600 to 1000 ohms.
The problem with this is you will probably have low output.
The other proper way is to use a matching transformer 8ohm to 600 (or 1K).
Thi sis one of the areas where the wrong way often works just fine.
Put a resistor in series, or just turn down the volume.
The matching transformer is the best way, considering that on some scanners the headphone jack has a floating ground. I don't know if that's the case with the 246T. The ground side of the headphone jack on my Uniden BC895XLT is at true ground (same as the chassis), but if I clamp the jack's ground on my RS PRO-95 to radio's chassis ground, the headphone output volume goes *way* up. I can still use it for a line-level input, but the volume has to be almost completely down.
N
N_Jay
Guest
PhilJSmith67 said:
Thats because you are not loading the output.
It is also a good way to get lots of noise and to introduce RFI suceptability.
Same load, without grounding the headphone jack, and the volume level does not shoot skyward. Other PRO-95 owners have actually wired the headphone jack to the antenna BNC ground to increase the volume; it's a known condition.
N
N_Jay
Guest
PhilJSmith67 said:
I was refering to fact that you have to keep the volume turned way down.
The speaker amp is probably designed for 8 to 16 ohms, the headphone jack is 8 to 100 ohms.
Your line in connection is 600 to 1000 ohms and often higher.
Put a 100 ohm resistor across the line and the volume control will work better.
10-4...
Halfpint
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Radio Shack *used* to sell both a cable and an `adapter' that attenuated audio signals from earphone jacks for use with recorders. I've got a couple of each that I bought years ago and I can testify that they actually work quite well. (I actually used to recommend them to customers when I had my Stereo / Hi-Fi repair shop and only got `carped at' by one *supposed* `Golden Eared Audiophile' who was the type who wouldn't be satisfied if G_d himself had given him an answer and it didn't co$t him `an arm and a leg' to purchase. {WAN GRIN!} IE: The poor schmuck equated `expen$ive' with `quality' whether or not it actually worked. The last time we saw him he was looking for `oxygen free' copper wired connecting cables w/ platinum plated connectors for his system because he'd heard that it would make an audible improvement! While we'd heard of the `oxygen free' copper wire we hadn't ever heard of, or seen any adds for, platinum plated connectors and still haven't. Dunno if he ever did find them but *if* he did I'd bet that he paid dearly for them and *still didn't* get any improvement. When we heard about the so-called `directional' hookup cables a few years back he was the first person we thought about who'd be going out and buying into the theory and wasting his money. {VBE GRIN!} BTW, *both* `oxygen free' copper wire and `directional' hookup cables are a load of fetid dingo's kidneys. Neither one will do anything to improve the sound of one's sound system. Also... In 99% of the cases out there neither will gold plated connectors. The 1% where gold plating has shown an ability to improve the sound has been with the connectors with a few `moving coil' cartridges that have *very* low output *and* expect to see a specific capacitance. Most of those could only be found in recording studio / record pressing company QA departments like that of MFSL and the likes had. [And who's records usually sold for around $35 - $50 apiece!]) If you've got a RS nearby maybe you could peruse the audio cable and adapter section and see if they still have them. If I `disremembers prezactly I think' they weren't all that expensive even if it was the cable/attenuator assembly one bought. You will still have to be careful about where you set your volume control but it won't be as `twitchy' as it would be without it or with some of the other suggestions here. Too bad that quite a few of these newer radio's volume controls don't actually control the actual signal volume anymore as it'd be fairly easy to just tie into the input side of the control and use that instead. (The `up side' to doing the volume control with a VCA is that there's less chance of the control itself causing problems with the signal since all it's doing is controlling just a voltage rather than the signal itself. IE: VCA stands for `voltage controled amplifier'.)
Just an `Olde Fart's' 2¢ worth. {WAN GRIN!}
Just an `Olde Fart's' 2¢ worth. {WAN GRIN!}
MacombMonitor
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Radio Shack still does sell what you need! It was a little hard to find, but click here:
http://tinyurl.com/dt74f
6.5' Attenuating Dubbing Cord
$4.29 Brand: RadioShack
Catalog #: 42-2152 Model: 42-2152
http://tinyurl.com/dt74f
6.5' Attenuating Dubbing Cord
$4.29 Brand: RadioShack
Catalog #: 42-2152 Model: 42-2152
bsavery
Member
Or if you prefer to make something......
Audio Transformer
I would think using a transformer would be better since it would eliminate any problems with ground hum.
You could cut your existing cable in 2, wire the transformer in the middle, and record away!
Bob
Audio Transformer
I would think using a transformer would be better since it would eliminate any problems with ground hum.
You could cut your existing cable in 2, wire the transformer in the middle, and record away!
Bob
N
N_Jay
Guest
MacombMonitor said:
These cables are usually designed to drop the signal to Mic level (Way below TRUE line level)(1vp-p at 600 ohm).
Hi guys,
Aw cummon, KISS. (keep it simple stupid) That's not an insult, rather the electronic way of saying don't over complicate things. A plain, ordinary 600 ohm pot dug out of the parts junk box is all you need if you don't want to play with the volume control which can get tricky. The idea of attenuating the output is to get a finer adjustment on the volume control taking the "sweet spot" up off the bottom of it's range while keeping it below the point where the audio becomes distorted.
I suggested 600 ohms because it's a nice average and works well. A transistor is a current device and hates too low a load impedance, too little and it draws too much current and POOF, blown transistor. On the other hand unlike a tube it doesn't mind an open circuit, no current flows at all. Frankly it likes anything in between although those audiophiles will argue with that. Then again you're not doing hi-fi, you're dealing with a scanner. That's why you don't have to mach the line input impedance either.
Aw cummon, KISS. (keep it simple stupid) That's not an insult, rather the electronic way of saying don't over complicate things. A plain, ordinary 600 ohm pot dug out of the parts junk box is all you need if you don't want to play with the volume control which can get tricky. The idea of attenuating the output is to get a finer adjustment on the volume control taking the "sweet spot" up off the bottom of it's range while keeping it below the point where the audio becomes distorted.
I suggested 600 ohms because it's a nice average and works well. A transistor is a current device and hates too low a load impedance, too little and it draws too much current and POOF, blown transistor. On the other hand unlike a tube it doesn't mind an open circuit, no current flows at all. Frankly it likes anything in between although those audiophiles will argue with that. Then again you're not doing hi-fi, you're dealing with a scanner. That's why you don't have to mach the line input impedance either.
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