[Zorander]

I have re-cabled another K340 with a balanced configuration. I'm considering whipping up a set of cable adapter (XLR-to-banana/spades) so I can connect the headphones directly to the speaker output of my Cyrus amp. Are there issues on this that I should be aware of before I proceed?

Cheers!

 

[krmathis]

Speaker amplifiers are designed to drive different loads (4 and 8ohm) than headphones.
It sure might work, but be very careful with the volume control.

 

[Zorander]

Quote:

Originally Posted by krmathis /img/forum/go_quote.gif Speaker amplifiers are designed to drive different loads (4 and 8ohm) than headphones. It sure might work, but be very careful with the volume control.

Definitely will be careful with the volume control (and I believe I can tweak the input sensitivity of the Cyrus so overly high gain should not be an issue). I am concerned though if the amp can safely (to itself, not so much to the headphones) drive 300-to-600Ohm loads, which are significantly higher in impedance than what it is designed for.

 

[slwiser]

You are connecting the grounds of the amp at the headphone which was not part of the original amp design. This can have issues. I just read a thread about this somewhere and that was the response that I remember.

This is not the link that I remember but it does have some information:
http://db.audioasylum.com/cgi/m.mpl?...er&r=&session=

 

[PeterP]

Even though many amps will be just fine with a high impedance load, it would be best to put a load right at the speaker terminals. An 8-10 ohm resistor (of the appropriate wattage) would do the job. Take a look at:
http://www.radioshack.com/product/in...entPage=family
Since you are using balanced headphones, that eliminates other potential problems.
Please watch that volume level. If it is too much you may want to consider using a resistor divider to pad down the output.

Take care,

Pete.

 

[krmathis]

Quote:

Originally Posted by slwiser /img/forum/go_quote.gif You are connecting the grounds of the amp at the headphone which was not part of the original amp design. This can have issues.

No, he's not connecting the grounds of the amplifier.
Cause he stated that he have a K340 with balanced configuration, meaning no common ground.

 

[slwiser]

Quote:

Originally Posted by krmathis /img/forum/go_quote.gif No, he's not connecting the grounds of the amplifier. Cause he stated that he have a K340 with balanced configuration, meaning no common ground.

Of course you are right, but in general one needs to make sure that you do things properly or you will get surprised and possibly not pleasantly.

 

[Zorander]

Quote:

Originally Posted by slwiser /img/forum/go_quote.gif You are connecting the grounds of the amp at the headphone which was not part of the original amp design. This can have issues. I just read a thread about this somewhere and that was the response that I remember. This is not the link that I remember but it does have some information: http://db.audioasylum.com/cgi/m.mpl?...er&r=&session=

I have the headphones in a balanced configuration (and hence separate grounds for each channel). I wouldn't combine the grounds of my speaker amp in the first place.

My concern lies in any possible issues on running the amp on loads with non-conventional impedances (outside 4-8 Ohm range).

 

[Zorander]

What about this DC Offset thing I hear so often here? Do they apply to speaker amps?

 

[krmathis]

Quote:

Originally Posted by slwiser /img/forum/go_quote.gif Of course you are right, but in general one needs to make sure that you do things properly or you will get surprised and possibly not pleasantly.

Then we agree.

 

[JadeEast]

The original brochure for the AKG K340 mentions driving them directly from a power amp. I've done it with a few there have been a few issues with one tube amp that had a bit too much noise and I did run them from a Tripath based amp. The tripath amp is supposed to have a rising response into a high load so I figured the response was less than optimal. Watch the volume pot and possible turn on thump.

I would just be cautious with you ears at first, you can't buy new ones on ebay.

 

[balou]

Zorander: yes, definitely check DC offset first before you plug in your headphones. There are DC protection circuits for power amps that cut off at 600mV DC - which seems to be a safe region for loudspeakers, but you will fry or at least damage your phones with 600mV

 

[Zorander]

Quote:

Originally Posted by balou /img/forum/go_quote.gif Zorander: yes, definitely check DC offset first before you plug in your headphones. There are DC protection circuits for power amps that cut off at 600mV DC - which seems to be a safe region for loudspeakers, but you will fry or at least damage your phones with 600mV

How do I check for DC offset? I am not familiar with doing that. Otherwise, I can always send an e-mail to Cyrus but how should I word the question (as they would undoubtedly try to steer me towards using the built-in headphone jack instead)?

 

[swt61]

I had warrior05 build me a set of the same cables you refer to, and I used them to drive my K340s with a Parasound Zamp. The amp was rated at 30 WPC, and I had no issues whatsoever driving the K340 that way.

 

[Zorander]

Cool! Thanks for the assurance. My amp is rated at 70WPC (or perhaps 80) but I'm sure things should work out. This amp is particularly powerful and bold-sounding so the K340 should match nicely with it.

Cheers!