The Can Opener - Passive Headphone Jack

After seeing the Vinyl Flat thread on here, I went to their site and found this: http://www.vinylflat.com/canopener.html

Does anyone have experience with it? I'm considering buying one since my integrated doesn't have a headphone amp. I guess it's not the easiest thing to use since I would have to unplug my speakers and plug this thing in every time. But it's nice that it doesn't need a power source, and it's pretty cheap.

 

Cool. I didn't know Vinyl Flat made something like that.

There are some other companies making the same sort of thing. They're sometimes called headphone taps. There are also some DIY schematics available to make your own.

They have a network of resistors inside that lowers the output wattage down to a level that is headphone friendly. Side effect is that a design like that will have a high output impedance. A headphone output with high output impedance can affect the sound and frequency response of low impedance headphones. Some headphones will have more of a frequency response alteration than others. Here's a long manifesto on output impedance and how it can affect headphones. With the right headphones those headphone taps can be very useful. For example, with orthodynamic headphones. Ortho headphones aren't affected by high output impedance. Or with high impedance headphones like 600 ohm Beyerdynamic headphones.

You also need to do a bit of homework before using a headphone tap if your speaker amp is in any way unusual. A TRS (tip ring sleeve) headphone jack shares the ground and some speaker amp designs will not like that at all if you hook up a TRS headphone tap to the speaker outputs. If a shared ground won't work with your amp you can get headphones rewired to do "balanced" which means four signal wires in the headphone cable and no shared ground. And use a headphone tap that has a four pin "balanced" headphone jack.

 

I'm sure it's just a set of resistors to load down the wattage from your speaker outputs. Still, it's a very good price, and would be a great way to add cans to something like an old Scott tube amp. I'm intrigued.

 

It'd be nice if the description had more info.

Do you guys think it would work with a Line Magnetic 216IA and a pair of Senn HD580s?

Admittedly, a lot of this impedance stuff is over my head. But thanks for your thorough reply, Ham.

 

as an example the Fisher 500c.

schematic:

http://www.freeinfosociety.com/electronics/schemview.php?id=1972

more useful technical info :

http://sound.westhost.com/project100.htm

 

I just emailed VinylFlat to ask about compatibility. He said as long as my amp has a common ground connection between the two speaker outputs, then it will be fine. I'm not sure if it does, so I sent an email to ToneImports asking about the 216IA. I'll report back when I find out.

 

Bridged is what I was trying to remember. Bridged amps (and any similar designs) will not work with a TRS headphone tap and may damage your speaker amp if you try.

This style of resistor network connected to the speaker amp was a common way for older receivers and integrated amps to wire the headphone jack. You can check the schematics for older amps and you'll usually see resistors connected to the headphone jack. Modern receivers though now often just use an inexpensive dedicated headphone amp to power the headphone jack.

 

I checked with the dealer and my Line Magnetic 216IA is apparently ok to use with the Can Opener.

I'm still a little hesitant about using it since it will involve unplugging my speakers and plugging this thing into my speaker outputs every time I want to listen on headphones. The only other option I can think of would be to get a dedicated headphone amp, which would involve unplugging my preamp from my integrated and wiring it into the headphone amp. I feel like RCA jacks are more durable than banana plugs, and would hold up longer. So maybe a dedicated headphone amp is the better option.

Does anyone know of any other solutions?

 

From what I can gather, your Line Magnetic amp doesn't have any line outs. If that is correct you can't connect a headphone amp to it.

You say you have a pre-amp? Could you use 'Y' cables here, the single end leaving the pre-amp, one of the pair of ends going to a headphone amp, the other to your integrated amp?

 

It attaches to the speaker taps, not line out.

My guess is they don't supply much information because the guts of it aren't really that much, just a resistor network at most, and possibly just series resistors. You're basically paying for the enclosure, speaker jack, and speaker taps. For vintage integrated amps, it's not worth it. Almost all vintage amps already have this built in as shown in the Fischer schematic linked above. It has 330 ohm series resistors which is typical.

These became popular on head-fi with the introduction of the new HiFi Man orthos that are incredibly power hungry. Amps under 100 watts have problems driving the HE-6 from the headphone jack.

 

Good headphone amps are cheap, why mess around?

I made my own headphone distribution box ages ago, just a box, some good jacks and a few resistors, but I needed a loud source for half a dozen sets of headphones.

 

GOOD headphone amps are rare. Most are made by small , often one-man companies with a firm focus on high-end looks, high end mumbo jumbo, a ludicrous amounts of output power and a complete disregard for even the most basic protection circuitry.
Hooking up a pair of cans that need 0.2 mW to reach 90dB to a 1500mW amplifier is like hooking up a pair of 90dB/w loudspeakers to a 7500 watt amplifier. Now imagine that amplifier lacking any kind of DC offset protection, or (i many cases) even a simple relay to prevent power-up/down thumps.....

I recently discovered by accident that my Stello HP100 had enough DC on its output to damage headphones.
While using it as a pre-amp I discovered one of my Marantz MA-24 mono's would not switch on because of DC it received from the Stello. If I had not done that, I would not have found out anything was wrong untill the Stello fried my Denon AH-D7000, and even then I might have attributed the damage to spontaneous driver failure and might have ruined another set of premium cans before suspecting the amplifier was to blame.

I bought a Sony TA-F5000 to replace the Stello: Yes is had high output impedance, causing a bit of coloration, but it also has much more sensible output power, and all the protection circuitry you get in a Japanese amplifier.

Using a device like the Can-opener can be a great way to get a headphone output on your system without compromising the safety of your precious cans.

 

So I would need 1 Y cable for each channel? Wouldn't that degrade the signal?

 

I've the original version from back in the 1980s:



It's just some sockets and a couple of big resistors in a box. Assuming a nice amp / system upstream it sounds very good indeed. I've never compared it to a traditional headphone amp though. It's very useful if you really want to know what's coming out of your amp compared to the speaker / room interface too, so can be a useful fault-finding tool. I use it now and again with my HD-600s.

 

Yes, therefore you need two 'Y' cables. I wouldn't have thought the signal would degrade. You would only have one amp on at a time.

This site shows two possibilities:

http://www.thatcable.com/category/RCA-Splitter-Y-Audio-Cable/sub

In the middle is one with two female RCA fittings. You can therefore attach your own choice and length of cables to connect your two amps.

On the right is the complete split cable.

 

Thank you, that's quite helpful.

My only concern is with adding another connection to the signal might degrade the sound a bit. Does anyone have experience with Y splitters, and if they reduce sound quality at all?