Carver C-4000 Preamp and Beyerdynamic DT990 Edition

[l_pad]

Hello,

I have a Carver C-4000 preamp and understand that it (and the C-4000t) employs the RC4136N opamp for the headphone stage, and has a maximum output of 400mW in that unit.

The service manual states in section 2.10 "Headphone Amplifier: Power output is no less than 2.2 Vrms into 160 ohm loads for distortion levels below 0.05% THD. Frequency response is within 1 dB, 20 Hz to 20K Hz."

The user guide (nay, book!) says the headphone output will handle any headphones from a couple Ohms to a couple thousand Ohms.

That seems all well and good, but I am not able to discover the output impedance of the headphone amp so that I can make a proper determination of what impedance headphone to purchase, for I recently stumbled upon the 1:8 rule (or preference?), which goes something like this: if a headphone amp's output impedance cannot be at zero, it should at least be no more than 1/8th the input impedance of the headphones.

In trying to decide between the Beyerdynamic DT 990 Edition, 32 Ohm vs 250 Ohm, I find I am stymied without knowing the output impedance of the Carver C-4000's headphone amp.

Help!

 

[fmw]

Don't worry about it. The headphone impedance only determines where you need to set the volume control. Buy whatever sounds good to you.

 

[l_pad]

Don't worry about it. The headphone impedance only determines where you need to set the volume control. Buy whatever sounds good to you.

Thanks for the reply. I guess I left off one important thing: the amp's output impedance is supposed (?) to match the "rule" in relation to the headphones in order to properly electrically damp the driver's movement. I am concerned that this will be an issue with the unenclosed drivers on the DT990. What do you think?

 

[fmw]

I already told you what I think.

 

[tyhjaarpa]

I would get the DT 990 600 Ohm, you have nothing to worry about your amp.

 

[PENG]

Even 32 ohm should not be a problem. I can't imagine any solid state amp would have output impedance high enough to worry about a 32 ohm load, and you don't have an extra long cord assume.

 

[l_pad]

I already told you what I think.

Okay! Thanks!!

 

[l_pad]

I would get the DT 990 600 Ohm, you have nothing to worry about your amp.

Thanks! I am beginning to think that when the manufacturer says the preamp will work fine with headphones as low as "a couple ohms" that it implies output impedance is not an issue. Also, it seems that 400mW is pretty high, so maybe the 600 ohm DT990 would be a great choice.

 

[l_pad]

Even 32 ohm should not be a problem. I can't imagine any solid state amp would have output impedance high enough to worry about a 32 ohm load, and you don't have an extra long cord assume.

Thanks! Given your reply, and those of others here, it seems that my choices are more flexible than I thought! Regarding the length of the cord, I might use a six-foot extension of high quality with gold plated connectors and all that (especially for movie watching in my apartment - my neighbors don't appreciate my subwoofer the same way I do for some reason?!), but in normal use I would just use the headphone's own cord direct to the preamp.

 

[l_pad]

Even 32 ohm should not be a problem. I can't imagine any solid state amp would have output impedance high enough to worry about a 32 ohm load, and you don't have an extra long cord assume.

Thought you'd like to know I made up my mind to go with the 32 Ohm version after remembering that I had a Sony Dolby Pro Logic IIx/Virtualphones Technology processor and amp for watching Blu-ray movies, which I hadn't been using since I moved to my new residence a couple years ago. So, I dug it up and checked the specs. By the way, the headphones (which I have been using for stereo listening) that came with the processor are 24 Ohm at 100dB/mW sensitivity, and are an open air design with 40mm drivers hovering about 1/4 inch from any contact with my ear. All nuances aside, I am pleased that the Beyerdynamic DT990 is physically similar in relation to position and orientation to the ear, and an open air design, too. So, I put it all together, and took some notes about the various volume settings and output levels. With all volume controls at about 70% (VLC player, Windows7 OS, and the Sony processor), the sound borders on "very" loud. So, with the 32 Ohm and 96dB Beyerdynamic DT990, I think I should be in good shape. As well, I would rather not take chances on anything being too hard for that Sony processor to drive.

 

[PENG]

Thought you'd like to know I made up my mind to go with the 32 Ohm version after remembering that I had a Sony Dolby Pro Logic IIx/Virtualphones Technology processor and amp for watching Blu-ray movies, which I hadn't been using since I moved to my new residence a couple years ago. So, I dug it up and checked the specs. By the way, the headphones (which I have been using for stereo listening) that came with the processor are 24 Ohm at 100dB/mW sensitivity, and are an open air design with 40mm drivers hovering about 1/4 inch from any contact with my ear. All nuances aside, I am pleased that the Beyerdynamic DT990 is physically similar in relation to position and orientation to the ear, and an open air design, too. So, I put it all together, and took some notes about the various volume settings and output levels. With all volume controls at about 70% (VLC player, Windows7 OS, and the Sony processor), the sound borders on "very" loud. So, with the 32 Ohm and 96dB Beyerdynamic DT990, I think I should be in good shape. As well, I would rather not take chances on anything being too hard for that Sony processor to drive.

Thanks for the feedback. I am happy to know it works out for you.