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The Beyerdynamic DT880 Discussion thread - Page 121

post #1801 of 10426

I'd probably go with the 600 then - if nothing else, they lower the noise floor on tube amp systems.

post #1802 of 10426
Quote:
Originally Posted by liamstrain View Post

the LD Mk II puts out enough power to play nicely with 600 ohm cans. So, really its a question of flexiblity. Do you expect to use the 880 from a portable device (without an amp) at any point? 

Ultimately, I don't think it matters much. I like the 600 ohm version, personally - but I do not think I could choose them in a blind test from the 250s... 

I think you mean to say the LD Mk II outputs enough voltage to drive 600 'phones.
post #1803 of 10426
Quote:
Originally Posted by Chris J View Post


I think you mean to say the LD Mk II outputs enough voltage to drive 600 'phones.
 

Power = voltage x current 

 

I needs enough power (in regards to the sensitivity of the headphones) and enough voltage (in regards to the impedance). So, I suppose, yes, if you want to be a pedant. 

 

The upshot is the same (and there was no confusion over my statement's intent). The 880/600 and the LD MK II, pair just fine both from a technical requirements standpoint, and subjectively (in my opinion) as well. 


Edited by liamstrain - 5/16/12 at 7:59pm
post #1804 of 10426

The 600ohms need plenty of voltage swing...hard to choose the right amp!

post #1805 of 10426
Quote:
Originally Posted by Syan25 View Post

The 600ohms need plenty of voltage swing...hard to choose the right amp!

 

Which is what I was trying to say.....................!

I have an iBasso D12 which works off a 4 Volt battery, that does not drive my 600 ohm 'phones very loud.

My laptop computer does not drive the 600 ohm 'phones very loud either.

And neither do my iPad or iPod.

Why? Because they run out of voltage!

 

Generally speaking:

 - you need enough voltage output to drive 600 ohm 'phones to a reasonable volume

(i.e. you will normally run out of voltage before you will run out of current)

 - and enough current to drive low impedance 'phones to a reasonable volume

(i.e. you will run out of current before you will run out of voltage).

 

But WTF do I know? I'm just a pedantic EE........

post #1806 of 10426

For portable use, I drive the DT880 600ohms with the RSA SR-71B in balanced mode.  Actually, as I am typing this, I am listening to these DT880s using:  iPod 4G running FLAC Player ----> CLAS ----> SR-71B ----> DT880s.

 

Next step, the RPX-33.

post #1807 of 10426

Yo,

 

With the DT880/600Ohm since they are semi-open they will have a lower sensitivity. The general rule is more airflow - more sensitive, lower airflow - less sensitive. Since the DT880 is partially closed this makes them less sensitive. Even though beyer gives you the same numbers as the 600Ohm DT990 (600Ohm, 96dB) the sensitivity is actually lower. When I owned both, the DT880 was not as loud as the DT990 at the same volume setting on my amps.

 

That being said, you should consider a beefy amp. I can recommend the Little Dot MKII, Bottlehead Crack, Decware CSP2+, Woo Audio WA3. All of these have more than enough power for the headphone, so they should be the natural choices. They are OTL tube amps, and as such they can output a large voltage swing an can drive higher impedance loads with ease. I've heard the DT880/600Ohm on a few of these (CSP2+, WA3, Crack) and it sounded beautiful.

 

About OTL:

OTL stands for Output Transformer Less, which means there is no transformer in the signals path nor is the amp coupled to one for buffering. The resulting output impedance of the amp is quite high and can be anywhere from 60Ohms to over 100Ohms. OTL designs generaly have a high voltage swing and are ore efficient at driving high impedance loads. The high impedance will give some headphones a fuller sound and also gives you notice not to use any low impedance loads.

 

*The amps will not perform well with low impedance loads though, as OTL amps are connected directly to the tubes, hence not much current. Low impedance loads crave current, so choosing and OTL design would not be wise. Using low impedance loads on an OTL design will result in a big mismatch as well as audio degrading. he sound would be bloated, hazy, muffled, and messy. The rule of impedance matching will be taking output impedance of the amp and multiplying it by eight. This gives you the minimum impedance of headphone you should use on the amp.

post #1808 of 10426
Quote:
Originally Posted by Zombie_X View Post

Yo,

 

 

 

The rule of impedance matching will be taking output impedance of the amp and multiplying it by eight. This gives you the minimum impedance of headphone you should use on the amp.

 

So, his there a way to figure the output impedance of an amp if it isn't listed?

post #1809 of 10426
Quote:
Originally Posted by gonkulator View Post

So, his there a way to figure the output impedance of an amp if it isn't listed?

 

If the information is not available anywhere and you want to figure it out yourself, you basically need to measure the output voltage of the amp with and without a load (a resistor or even just headphones) while it is playing the same test tone, and the output impedance can be calculated with a simple formula.


Edited by stv014 - 5/18/12 at 7:44am
post #1810 of 10426

So, Zombie_X, can you comment on the RPX-33?

post #1811 of 10426

Hi,

 

I looked at the specs for the amp and it doesn't give you much information. It says it can do a maximum of 700mW, but at what impedance? What's the output impedance? How much voltage does it have to swing? There's not enough info to know how well it will perform.

 

Sorry man, can't help ya.

 

Quote:
Originally Posted by flyfish2002 View Post

So, Zombie_X, can you comment on the RPX-33?

post #1812 of 10426
Quote:
Originally Posted by flyfish2002 View Post

So, Zombie_X, can you comment on the RPX-33?

Based on the sketchy spec they provide, the amp probably outputs 700 mW into 16 ohms.
If this is true and the output impedance is virtuallly zero then the RPX-33 will output enough voltage to drive 600 ohm DT880s.

Looking at the photos, it's built like a tank!
post #1813 of 10426
Quote:
Originally Posted by Chris J View Post


Based on the sketchy spec they provide, the amp probably outputs 700 mW into 16 ohms.
If this is true and the output impedance is virtuallly zero then the RPX-33 will output enough voltage to drive 600 ohm DT880s.
Looking at the photos, it's built like a tank!

 

They give their THD noise spec for a signal at 32 ohms (THD: 0.02% (3Vpp on 32Ohm)) - it's possible they use that as their nominal for their other specs as well. 

post #1814 of 10426

---------------------


Edited by Grado77 - 5/21/12 at 12:46pm
post #1815 of 10426
Quote:
Originally Posted by liamstrain View Post

 

They give their THD noise spec for a signal at 32 ohms (THD: 0.02% (3Vpp on 32Ohm)) - it's possible they use that as their nominal for their other specs as well. 

 

I'm sure everyone agrees with me on this:

Their "spec sheet" is bloody awful!

 

I only used 16 ohms because they rate the output impedance as 16-600 ohms and 16 ohms gives a worst case (based on their sketchy info).

If it is 700 mW at 32 ohms then so much the better.

700 mW @ 16 ohms = 3.34 V rms

700 mW @ 32 ohms = 4.73 V rms..............more voltage to drive 600 ohm 'phones (assuming Zout is virtually zero). 

If Zout is 10 or 20 ohms or higher then there is even more voltage available to drive 600 ohm cans.

 

OTOH, 3 Vp-p @ 32 ohms = 35 mW so it would be fair to say that their THD spec is nowhere near full output.

 

I think it would be reasonable to say that the RPX-33 should be able to easily drive Grados, Sennheisers, AKGs, and Beyers of any impedance, etc.

But I've never heard one so cannot comment on any sound signature.  That would be..........crazyconfused_face_2.gif

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