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Full sized amps with low output impedance

Jun 20, 2012 at 10:19 AM Thread Starter Post #1 of 43
mrAdrian

mrAdrian

Headphoneus Supremus
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Besides the O2, and all Meier Corda amps, what other amps have low output impedances?
 
Jun 20, 2012 at 4:40 PM Post #2 of 43
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.
 ​
 
Jun 20, 2012 at 4:44 PM Post #3 of 43
Jun 21, 2012 at 7:14 AM Post #5 of 43
Quote:
fusionramjet said:
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.
 ​
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Yes, source impedance is another way of saying "output impedance".
 
here's a fairly low output impedance unit:
Matrix M Stage:   5 ohms
 
Jun 21, 2012 at 8:59 AM Post #6 of 43
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?
 
Jun 21, 2012 at 12:56 PM Post #7 of 43
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.
 
Jun 21, 2012 at 8:51 PM Post #8 of 43
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 ;)
 
Jun 21, 2012 at 9:37 PM Post #9 of 43
I just found it quite hard to follow the one eighth rule when it comes to the denon
 
Jun 22, 2012 at 12:04 AM Post #10 of 43
Quote:
runeight said:
The Liquid Fire has an output impedance of about 0.25R.
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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:
haejuk said:
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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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?
 
Jun 22, 2012 at 12:21 AM Post #11 of 43
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:
mradrian said:
And another question, how do you measure the output impedance?
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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.
 
Jun 22, 2012 at 1:02 AM Post #12 of 43
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?
 
Jun 22, 2012 at 6:56 AM Post #13 of 43
solude said:
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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The Beyer A1 has an output impedance of 100 ohms......rather high.
 
Jun 22, 2012 at 7:41 AM Post #14 of 43
That's because Beyer still believes in the IEC 120Ohm spec.  Its on purpose and from a time when cans were 600+ ohms.
 
Jun 22, 2012 at 10:12 AM Post #15 of 43
Quote:
mradrian said:
 
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!
Click to expand...

 
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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