Head-Fi.org › Forums › Equipment Forums › Headphone Amps (full-size) › speaker amplifier to drive headphones
New Posts  All Forums:Forum Nav:

speaker amplifier to drive headphones

post #1 of 11
7/12/01 at 3:55pm
Thread Starter 
Someone mentioned a headphone amplifier I hadn't heard of before (the QED MB45), so I went looking around for the information on it -- seems pretty reasonable at CA$225 -- and found this other thing which got me to thinking. They have this device, the MA18 headphone volume control, which is designed to be connected to the speaker outs of your regular power amplifier...has anyone tried this yet? What does it do, shunt some of the power into head? How is the sound quality? I really want to try this with some insanely high quality amp, like my Manley Stingray (integrated tube amp) or my Musical Fidelity A3CR...what would that sound like without a preamp, I wonder? Also, I'm not sure I would need a volume control on an integrated amp, so my question becomes, what else does it do, besides convert the speaker binding posts to a 1/4 inch headphone jack? Does it shunt any of the power into heat, convert amps to volts, what?

http://www.qed.co.uk/files/qed_acc.pdf
Reply

Gear mentioned in this thread:

Sennheiser HD 238 Stereo Open Aire Headphone
post #2 of 11
7/12/01 at 6:46pm
Are you sure this thing will work? I mean some amp outputs 300W RMS, how is that QED going to down size that amount of power into a pair of headphones?
Reply
post #3 of 11
7/12/01 at 7:31pm
Awhile ago, I posted on Headwize that I had tried using my vintage Dynaco ST-70 power amp with my headphones. I discovered this little box, in my basement, which I used 30 years ago with some really cheap headphones. It hooks up to the speaker terminals of the amp and has a 1/4 jack in it. Apparently this box contains some resistors which limit the amp's power to the headphones. There is a schematic and directions on Headwize in one of the librarys for attaching 120 ohm resistors to your amps terminals so that you could try this out yourself without purchasing the item you mention.
Here's the link: http://headwize.com/faqs.htm#amp
Unfortunately, I was not impressed by the sound quality at all.......muddy, noisy, basically pretty poor!
Your amps will hopefully yield better results. Hope this helps.
Reply
post #4 of 11
7/12/01 at 8:31pm
I used the circuit on HeadWise (100 ohm/2 watt in series and 10 ohms in parallel with the speaker outputs) with a 3.5 watt SET amp with excellent results. It's a cheap setup, so why not give it a try.
Reply
post #5 of 11
7/29/11 at 9:07pm
Quote:
Originally Posted by KurtW View Post

I used the circuit on HeadWise (100 ohm/2 watt in series and 10 ohms in parallel with the speaker outputs) with a 3.5 watt SET amp with excellent results. It's a cheap setup, so why not give it a try.


I did not see HeadWise but a similiar idea occured to me.  Power amps usually have series resistors or some means of not smoking headphones so I plugged in with 10 ohm parallel resistors. I was testing Sennheiser HD238 which has mushy bass and weak mids. There seems to be some improvement.

 

I read somewhere that amp impedance should be 1/8th of the phone impedance. It should < 4ohms for the HD238 and others like it.  But the Fubar has 100ohm series resistance and the HA11 has 47ohms. My crappy old Sony phones sound the same in every jack but not the HD238 which seems to need a LO-Z amp.

 

 

Reply
post #6 of 11
7/29/11 at 9:23pm
i can't go to the link you posted op. but i know what your talking about. you can DIY cheap if you want but it'll be pointless in a way unless your power amp has no headphone out in the front(like integrated or receiver) cause all these speaker amps use is a simple dropping resistor for both the left and right channel from the power amp section to the headphone out so building a box will do the same thing. only difference is it'll be easier to swap resistors and experiment. you can also if want just re-cable your headphones to be used directly from the speaker outputs but you'll have to be very careful and always keep the volume at 0 on start up and be useful to have a ''muting'' button as well if going that route.
Reply
post #7 of 11
7/30/11 at 1:03am

It will also depend on how quiet your amp is.  2A3 amps are ideal, but there is heater hum to deal with and even some cap-coupled amps are pretty noisy through high sensitivity headphones.  Direct coupling causes the biggest hum problems for headphones.  However, the various incarnations of the Moth head amp (discontinued) were quiet.  I hear that Craig Uthus, the original designer, is thinking about re-introducing the Moth, which would be cool.

Reply
post #8 of 11
7/30/11 at 3:26am

This is like a STAX adapter, back from when headamps aren't widely used, but theirs is an active design with its own volume control. I'm not sure but perhaps it can be used without a preamp upstream. ALO sells a pure passive adapter for $100. If you already have the amp, this idea is worth trying, especially if you'll just DIY.

Reply
post #9 of 11
7/31/11 at 12:10pm
Quote:
Originally Posted by ProtegeManiac View Post

This is like a STAX adapter, back from when headamps aren't widely used, but theirs is an active design with its own volume control. I'm not sure but perhaps it can be used without a preamp upstream. ALO sells a pure passive adapter for $100. If you already have the amp, this idea is worth trying, especially if you'll just DIY.


 

The Stax boxes are actually transformers.

Stax headphones are driven by several hundred volts, no normal amp can deliver those voltages so they devised a transformer.

Reply
post #10 of 11
7/31/11 at 12:54pm

For the past month or so I've been driving my D7000's from the output of my Crown D-75a.  I do not use any sort of series resistor or L pad on the output.  With the Crown it is particularly convenient as there is a headphone jack on the front panel.

Reply
post #11 of 11
8/4/11 at 4:24pm

Make a proper voltage divider network, add a headphone jack, and you can drive headphones with just about any audio amp that you want to. About the simplest project you could undertake. You can add a switch and tailor it to specific impedances by switching between different voltage divider networks.

 

If you didn't stay awake in high school physics class, find somebody that did with an interest in electrical or electronic circuits. 

Reply
New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: Headphone Amps (full-size)

Gear mentioned in this thread:

Sennheiser HD 238 Stereo Open Aire Headphone
Head-Fi.org › Forums › Equipment Forums › Headphone Amps (full-size) › speaker amplifier to drive headphones