Quad 405 with Hifiman He-400i

[Peeno]

Hello everyone,

I have been reading this forum and getting a lot of useful info. However I am kind of stuck now as I am currently trying to build a speaker/headphones switch from my Quad 405 (100w max into 8ohm) speaker outputs. Speakers are Celestion 66, 4 to 8 ohm.
I would like to power my Hifiman HE400i (2016 edition, planar) which have the following specs:
Impedance : 45 ohm
Max power rating : 2W
Max voltage: 9V
Efficiency : 93dB/mW , 106dB/V

I'm trying to find the value of the resistors needed to complete this circuit. How to calculate for this particular pair of headphones?
If you think of any other way I could use my headphones, feel free to mention it.

Thanks in advance for your help!!

 

[staticV3]

Hi @Peeno! Welcome to ASR.

I'd just do this:

Using these:


It won't sound any worse than jerry-rigging the 400i onto the Quad's speaker output.

 

[Peeno]

Thanks for your reply.

Fair point! However I am often listening to vinyl also. I think your suggestion would not allow for this to happen!

Maybe I can try something from the tape output of the Quad33 into some headphone amp?

Probably easier to wire this way also…

 

[staticV3]

However I am often listening to vinyl also. I think your suggestion would not allow for this to happen!

Why not?

Both the Quad and Headphone Amp have simple, single-ended Line in, right?

 

[Verig]

You can connect your sources to amp and use tape out for the headphone amp. Tape out is before volume and tone controls so it works fine.

 

[Verig]

Your original idea of using speaker outputs. Please don't, it won't work well. Ever. (There are some really hungry headphones that can actually be driven directly without any mods but 400i are not one of those.)

 

[Mr Swing King]

I echo the above post. Speaker amp + headphones is a recipe for blown up transducers. Even very hard to drive headphones have died that way. Methinks it’s one of the main reasons we don’t see many original HE6 on the market today. They died at the hands of audiophiles who believed in the ol’ moar power = better sound quality.
It seems a little silly though…why hook any headphone up to an amp where you’re never going to use more than say 5% of it’s juice - always struggling to have any sort of volume control?
It’s like trying to slice garlic with a twohanded sword.

 

[solderdude]

Should you want to use a speaker amp to connect headphones to read this:

Power amp adapter

home back to Learn published: Apr-5-2013, updated: Feb-09-2022 Can I use the speaker output terminals of a power amp to drive headphones ? Yes and No…. Yes, because high impedance (> 300Ω) head…

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You can use speaker amps when there is no other option. The above attenuator is preferred over the usual > 100ohm series resistor headphone out socket of most integrated amps/AVR/receivers.

 

[restorer-john]

Go with a series pair of 330R 2W resistors and see how you go.