[mplee79]

I recently purchased a Fatman I-red itube: Link: Fatman iTube Red-i with Speakers

This amp does not provide a headphone jack and only really has speaker outputs.

Is there anyway to rewire my Sennheiser HD580 so that I can power them with this amp? Specifically, i was wondering if there was an adapter to connect my headphones to the speaker output?

Is this even advisable given the specs of the amp?

* Power Output: 25Wx2
* Frequency Response: 20Hz - 20KHz (±1.5Db)
* Harmonic Distortion: ≤0.5%
* Signal-To-Noise Ratio: ≥86Db
* Input Impedance: 100KΩ
* Output Impedance: 4Ω, 8Ω
* Valve Type: 2x6N1(ECC85)
* 1x6E2(EM87)
* Power Supply: AC100~120V/50~60Hz, AC220~240V/50~60Hz
* Dimensions: Amp: 450x220x210 mm ( WxHxD), Speaker: 330x315x210 mm ( WxHxD)
* Weight: Amp: 5.8kgs, Speaker: 6.8kgs


Thanks

 

[mplee79]

any gurus out there that could help this noobie out?

 

[Sherwood]

There is no commercial adapter I know of, so you'll need to make one

This is probably not advisable, as you could absolutely destroy your headphones at worst, and it may well sound bad at best, but it's certainly worth a try if you're careful.

The problem is twofold: one is output impedance. Your fatman is designed for 4-8 ohms. Your Sennheisers present a nominal impedance of 300 ohms. It'll work, but it's not what the amp was designed for. The other is power rating. The Sennheisers like about 200 mW into their 300 ohms. You're outputting about 100x that. Again, it'll "work", but it's not ideal.

Still, man, forge new trails. The high impedance offsets the power issue somewhat, so if you keep the volume low you'll be okay.

 

[mplee79]

Thanks for your comments. I have little to no idea about how to wire it myself. Total DIY noobie. Do you have any idea where i could get a headphone adapter like that?

Someone else mentioned placing a 8 ohm resistor parallel to the speaker output. Again, completely clueless...sigh

Thanks guys

 

[Sherwood]

Unfortunately, my search turned up nothing commercially available. AKG made something like it to connect the AKG K1000 headphone to a speaker amp, but it had the wrong plug on one end.

You wanna learn how to make one?

 

[mplee79]

Yes please !

 

[mplee79]

If i get a line level converter, will my headphones still receive any power from the amp (will this be sufficient to power my hd580)

Parts-Express.com:*Audioplex SPKCNV Speaker Level To Line Level Converter | speaker jacks speaker jack rca jacks rca jack rca converter rca power converter power amplifier power line level converter line level line converter jacks jack ev converters

 

[Sherwood]

That's not what you want. For one, you can't plug your headphones into those RCA sockets.

First off, this will require some soldering. Do you have access to a soldering iron and some solder?

 

[mplee79]

Yes i do.

Headphone Adaptor for Power Amplifiers

It seems that this schematic is designed for 120 ohm impedance headphones. Not sure it will work for the 300 ohm 580s.

Maybe i'm just in way over my head...

 

[Sherwood]

That schematic is actually very helpful. 120ohms will run the HD580s just fine.

 

[Thermionic Dude]

It will not only work, but will probably also work WELL with your HD580!

Contrary to popular opinion/belief, this type of voltage divider is exactly how most commercial manufacturers add headphone jacks to power amps (few actually employ the "cheap" op-amp circuit that a lot of people around here deride). It will allow you to experience the full sonic signature of your amp, just with voltages and currents scaled-down for headphone drivers. The amp itself will be loafing along, and will have no trouble at all keeping up with the demands of the headphone drivers during complex/loud musical passages. (BTW how is the Red-i over speakers? I've been intrigued since it came to market.)

Given the design of your amp (tube gain stages, transistor output), the changes in impedance "seen" by the amp circuit with these mods in place should not cause any problems (the effect will be that the outputs "see" a higher impedance vs. speakers, resulting in lower output current). With solid-state (output) amps, the main thing to avoid is a dead short or multiple speakers connected in parallel such that the total impedance is less than the minimum specified by the manufacturer.

Given the specs of the Red-i, I would use the resistor values designated for a 30 wpc amp. Since only six are needed, I would go for the best quality metal film types I could find (such as Vishay RN series-Digikey and Mouser have them); this will help to ensure that these additional components are as sonically-transparent as possible.

 

[mplee79]

Do you think I could use something like ProCo HJ-4P Headphone Junction box to connect the itube carbon amp to my hd580s?

Here's the user manual: http://www.procosound.com/downloads/datasheets/hj4p.pdf

Could someone take a peak at the second page with the tech specs to let me know if this would be appropriate?

Would this addition change how I experience the sound (will the sound be good)?

Thanks