[Rawrbington]

i think the output impedance on the WA2 is around 80 ohms.
for dynamic headphones you'll probably be best served with cans 250 ohms and higher.  but that said my beyer 770 80 ohms sound very good out of it as well.  just not as tight as my HD 650's or 990 600 ohm were

 

[MacedonianHero]

Quote:

i think the output impedance on the WA2 is around 80 ohms.
for dynamic headphones you'll probably be best served with cans 250 ohms and higher.  but that said my beyer 770 80 ohms sound very good out of it as well.  just not as tight as my HD 650's or 990 600 ohm were

The output impedance of the amp being OTL, depends on the impedance of the headphones plugged into it.

 

[ardilla]

5998/7236 gives 10% extra power according to Jack Woo by email

Read the power ratings here:
http://wooaudio.com/docs/wooaudio_amplifier_comparisons.pdf



Output impedance is supposedly rated 60 ohm according to Jack Woo

ref:
http://www.head-fi.org/t/392549/woo-audio-wa2-and-the-pdps-mod#post_5165787

 

[ardilla]

Can you elaborate this, dear Mr. MacedonianHero?
Quote:

The output impedance of the amp being OTL, depends on the impedance of the headphones plugged into it.

 

[Efjay]

Quote:

5998/7236 gives 10% extra power according to Jack Woo by email

Sound qualities aside, that the use of the 7236 adds only 31 milliwatts (assuming it is as simple as 10% more power than the rating with the stock tubes) of power over the stock tubes for the WA2 is sort of surprising. When I purchased my amp, I was recommended those tubes for use with my headphones to make certain I had enough power. I tend to doubt I was short just 10% (and I should probably see what it sounds like with the stock tubes, they've been in their boxes since the day I got my package.)

 

[ardilla]

Me: How much do the output power of the WA2 increase with the 5998 and 6H13-type tubes?
 
Woo: With 5998, it increases about 10%. 6H13 is similar to 6080’s.

 

[Efjay]

Quote:

Me: How much do the output power of the WA2 increase with the 5998 and 6H13-type tubes?
 
Woo: With 5998, it increases about 10%. 6H13 is similar to 6080’s.

 I wasn't doubting you, merely noting that I don't usually associate the phrase "greater power" to mean a 10% increase.

 

[ardilla]

10% is 10%...... That beeing said, I too expected it to be more. Have you tried the stock tubes yet?

 

[Efjay]

Quote:

10% is 10%...... That beeing said, I too expected it to be more. Have you tried the stock tubes yet?

 Not yet. I may give it a spin this weekend.
 
I suspect I will try the HE-500 with my WA2 at some point. I have to admit that I don't have a clear understanding of why exactly I should have difficulty driving them.
 
A calculator at Apex's website concludes:
 

Headphone sensitivity (dBSPL @ 1 milliwat)	89
Headphone impedance (ohms)	38
Desired loudness (dBSPL)	110
Required power (milliwatts)	126
Required voltage (volts RMS)	2.19
Required current (millamps RMS)	57.6

 
The same calculator also produces (based on the stock tubes):
 

Power (milliwatts)	310
Impedance (ohms)	38
Voltage (volts RMS)	3.43

 
All of which the WA2 should easily produce. I admit to not really understanding the science behind this stuff. And I thought the psuedo-dual power supply was supposed to address the issue of driving low imp headphones.
 
At any rate, in the event I'm wrong, I have the option of returning the headphones or replacing my amp. (I could just leave the WA2 as amy pre-amp if it comes to that I suppose.)

 

[MacedonianHero]

Quote:

5998/7236 gives 10% extra power according to Jack Woo by email
Read the power ratings here:
http://wooaudio.com/docs/wooaudio_amplifier_comparisons.pdf
Output impedance is supposedly rated 60 ohm according to Jack Woo
ref:
http://www.head-fi.org/t/392549/woo-audio-wa2-and-the-pdps-mod#post_5165787

 
Correct. Jack confirmed as such to me too when I bought my WA2 a few years back.
 
Quote:

Can you elaborate this, dear Mr. MacedonianHero?

 
Basically there is no transformer to control the output impedance....so the output impedance of the WA2 will depend on the impedance of the headphones plugged into it.

 

[Rawrbington]

how does a high z can affect the output impedance vs a low z can?

 

[ardilla]

Correct. Jack confirmed as such to me too when I bought my WA2 a few years back.


Basically there is no transformer to control the output impedance....so the output impedance of the WA2 will depend on the impedance of the headphones plugged into it.

Ok, that makes somewhat sense, but what does it mean? Is all this fuzz about impedance matching with the wa2 irrelevant? Where does this leave Jack's 60 ohms?

 

[Efjay]

Quote:

Ok, that makes somewhat sense, but what does it mean? Is all this fuzz about impedance matching with the wa2 irrelevant? Where does this leave Jack's 60 ohms?

 
I don't have an answer but I would note that in my email regarding powering the He-500 or LCD-2, Woo's 'concern' was not about the impedance of the headphones but about the sensitivity.

 

[1audioz]

Anyone using the Philips JAN 6922? I got them a few days ago and I'm absolutely loving them. Rock music in particular seems to have greater attack, bass extension and quantity seems to be greater than Japanese made Counterpoint 6922 (stock) tubes.
 
Still waiting on a pair of Svetlana 6H13C from Ukraine.

 

[hodgjy]

I've used both of these tubes you mention in my WA3.  The JAN Phillips 6922 is a good tube, but it's more grainy than the JAN Sylvania 6DJ8.  I like both, but prefer the latter. 
 
The Svetlana is an underrated tube around here.  It's warm and smooth, but has a little veil to it.  Overall, I like it.  Very, very low noise.  The lowest noise I've ever experience on that family of tube types.
 
Quote:

Anyone using the Philips JAN 6922? I got them a few days ago and I'm absolutely loving them. Rock music in particular seems to have greater attack, bass extension and quantity seems to be greater than Japanese made Counterpoint 6922 (stock) tubes.
 
Still waiting on a pair of Svetlana 6H13C from Ukraine.