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Full sized amps with low output impedance

post #1 of 42
6/20/12 at 7:19am
Thread Starter 

Besides the O2, and all Meier Corda amps, what other amps have low output impedances?

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post #2 of 42
6/20/12 at 1:40pm

Musical Fidelity has two headphone amps.  The budget one is called the V-CAN II ($200) and it has an output impedence of 5 ohms.  Musical Fidelity makes a point of highlighting this.  The higher-end one is called the M1 HPA (something like $800), it lists 1 ohm as the "source impedence", not sure what this means, but I imagine it's also very low output impedence.

I have the V-CAN II along with Musical Fidelity's V-DAC II ($350), which I'm using to drive the LCD-3.  It sounds awesome.  However, I have no reference point because I don't have any other desktop amps.  So, I'm not at all an authority when it comes to amps.

 
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post #3 of 42
6/20/12 at 1:44pm

Grace Design m903:  Headphone output impedance = 1.2 Ohms

http://www.gracedesign.com/products/m903/m903.htm

 

Headroom's Balanced Ultra Desktop Amp:  Headphone output impedance = .5 - .6 Ohms

http://www.head-fi.org/t/512731/buda-impedance-and-output-spec

 

Benchmark DAC1 Pre: Headphone output impedance = < .11 Ohms

http://www.stereophile.com/content/benchmark-dac1-usb-da-processor-headphone-amplifier-specifications

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post #4 of 42
6/20/12 at 9:05pm

The Liquid Fire has an output impedance of about 0.25R.

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post #5 of 42
6/21/12 at 4:14am
Quote:
Originally Posted by fusionramjet View Post

The higher-end one is called the M1 HPA (something like $800), it lists 1 ohm as the "source impedence", not sure what this means, but I imagine it's also very low output impedence.

 

 

Yes, source impedance is another way of saying "output impedance".

 

here's a fairly low output impedance unit:

Matrix M Stage:   5 ohms

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post #6 of 42
6/21/12 at 5:59am
Thread Starter 
I know the fiio portable line has a near zeto output impedance too. I hatr starting yo adk for suggestions so early but for around 250 what would be a good amp for grados and denon headphones?

haha zo2+e9+ Arietta into cash into another solid state, any say?
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post #7 of 42
6/21/12 at 9:56am

I think you probably won't do much better than your Arietta for the price.  I guess if you wanted better volume control and a worse looking design (and almost the exact same sound) then you could get an O2.  It is really difficult to find amps in this price range with a low enough output impedance for Grados, and especially Denons.

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post #8 of 42
6/21/12 at 5:51pm

Damn near every solid state amp has a low output impedance.  Centrance and the original Burson being the exceptions.  Most transformer based tube amps also have a low output impedance in relation to headphone impedance.  These aren't 4 ohm speakers after all ;)

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post #9 of 42
6/21/12 at 6:37pm
Thread Starter 
I just found it quite hard to follow the one eighth rule when it comes to the denon
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post #10 of 42
6/21/12 at 9:04pm
Thread Starter 
Quote:
Originally Posted by runeight View Post

The Liquid Fire has an output impedance of about 0.25R.

Wow and a tube amp! XD Definitely want to hear one but I don't want to sell any more body organs as of now.

 

Quote:
Originally Posted by haejuk View Post

I think you probably won't do much better than your Arietta for the price.  I guess if you wanted better volume control and a worse looking design (and almost the exact same sound) then you could get an O2.  It is really difficult to find amps in this price range with a low enough output impedance for Grados, and especially Denons.

Have you heard both? I did shortly and I agree with you that they sound about the same. I'm just wondering if I sell it, and sell the E9, and sell the ZO, would I be able to get some improvement. Thanks for the input!

 

Let's get back to the topic, keep listing guys!

 

And another question, how do you measure the output impedance?

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post #11 of 42
6/21/12 at 9:21pm

You know, plenty of people report Grados and Denons running just fine on high-Z output sources.  Damping factor is probably not such a big deal for these headphones which have a pretty flat impedance across frequency (pretty much resistive).

 

Quote:
Originally Posted by mrAdrian View Post

And another question, how do you measure the output impedance?

 

Output a constant tone and take a couple of voltage readings.  Cheap multimeters are under $10.  You just need two different resistors, or for a little coarser estimate, just a couple different headphones with known impedances at the frequency of the test tone you're using.

 

V_L = V_s * Z_L / (Z_s + Z_L)

 

V_L is voltage you measure across the load (resistor or headphones).

V_s is voltage output from the source, unknown.

Z_L is load impedance, which should be known.

Z_s is source output impedance, unknown.

 

So with two different readings using different loads, you have two different (independent) equations and two unknowns.  Solve for Z_s.

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post #12 of 42
6/21/12 at 10:02pm
Thread Starter 

I'll give that a try with my DV336 after my exams. Interesting note on the Denon and Grado's FR vs impedance graph. Sounds to me the Arietta is a keeper for my solid state amp.

 

Is it particular harder to achieve near zero output impedance for a tube design? How about hybrids?

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post #13 of 42
6/22/12 at 3:56am
Quote:
Originally Posted by Solude View Post

Damn near every solid state amp has a low output impedance.  Centrance and the original Burson being the exceptions.  Most transformer based tube amps also have a low output impedance in relation to headphone impedance.  These aren't 4 ohm speakers after all wink.gif

The Beyer A1 has an output impedance of 100 ohms......rather high.
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post #14 of 42
6/22/12 at 4:41am

That's because Beyer still believes in the IEC 120Ohm spec.  Its on purpose and from a time when cans were 600+ ohms.

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post #15 of 42
6/22/12 at 7:12am
Quote:
Originally Posted by mrAdrian View Post

 

Have you heard both? I did shortly and I agree with you that they sound about the same. I'm just wondering if I sell it, and sell the E9, and sell the ZO, would I be able to get some improvement. Thanks for the input!

 

I own both the O2 and the Arietta right now and used to own the E9.  I think after the Arietta, you would have to spend much more than $250 to get a decent upgrade that will really make you feel like you got an upgrade.  I think Audio-GD makes some decent amps with low output impedance, you might look into that.  I haven't ever heard one, but I have considered buying from them.

 

As for tube amps with low output impedance, they have to be transformer-coupled tube amps.  These can get really expensive because the transformers used in the output stage are pretty hard to find and often hand wound.  I wouldn't be surprised if there were some Tube-hybrid amps with low output impedance, but from my research I found most of them too noisy for the sensitive Denons.  Once again, didn't actually hear any of them myself.  I also happen to own a Little Dot I+ hybrid amp and it performs quite well with my Denons.  It sounds warmer than my SS amps, but other than that I don't really feel it performs as well as O2 and Arietta.  I also saw that the maker of the LDI+ claimed it to have 32 ohm output impedance, so not exactly low.

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