[Vandal]

Just noticed on Woo Audio's website, that all the OTL amps have a better spec versus transformer-coupled amps for signal-to-noise and THD.
http://wooaudio.com/products/wa6se.html
http://wooaudio.com/products/wa2.html
 
S/N is 95 for transformer coupled and OTL is 98
similarly
THD for OTL <=0.08 and for transformer coupled <=0.3
 
The spec for THD especially seems to have a huge difference.
 
For many like me, who are still saving up for something spectacular like a WA6SE, because we use low impedance cans, is this bad news? 
What does this translate to, in real life listening?
 
Should I switch attention to the WA2 instead of the WA6SE. Financially, it's not a big deal, because both are the same price, and I thank the lord for that...

 

[nikongod]

Once you pass ~80db of SNR the AUDIBLE differences become very very very small.
 
Both numbers posted are actually pretty good for THD, but somewhat meaningless as given. This is actually quite common in headphone-amp-land, but should come as no surprise because very few people really give a darn in speaker-amp-land either. For the numbers to be comparable they must both be run under the same conditions: since the conditions of the test are not given you can not assume that they were tested similarly. Getting better results under easier test conditions is not a better achievement.
 
For example they should both be run at 1v into 300 and 32 ohms, per the (almost) standard RMAA headphone amp tests. 
 
Not to knock Woo, since this applies to the majority of OTL headphone amps, but OTL amps with no global feedback flat out suck when measuring THD when driving a low impedance load. This is not to say they dont sound good, because at low volumes OTLs can sound good with low impedance headphones, but the performance of the OTL amp generally falls much faster than the transformer coupled amp as you ask more of it.... As an educated guess, at equal levels into 32 ohms the Woo6se dominates the Woo2 for THD. 

 

[Vandal]

Thanks Nikongod, that was helpful. Looking at your last sentence, if I swap out a Grado (low impedance), for something like a T1 (high impedance), the situation is a mirror reverse?

 

[nikongod]

Its much harder to generalize which will work better with the high impedance headphone because they could both work outstandingly well here. For this you really need to test.
 
As a tangent...
Something that Woo does that is particularly neat in his transformer coupled amps is that he uses transformers with multiple secondaries. One of the largest issues with building a transformer coupled headphone amp is that headphones can be any impedance from 24-2Kohms, but transformers are designed for a specific impedance. The way to get around this problem is to use a transformer designed for 2 or more impedances, thus the high and low settings on his transformer coupled amps, designed for high and low impedance headphones.

 

[Vandal]

Once again, Nikongod, thanks for your time and insights.
 
I had emailed Jack some 8 months ago, and had almost decided on a WA6SE. But then I moved with my job and my savings for the amp were consumed with shifting house. Have started saving up again, hopefully another 7-8 months and I'll be able to pick up the WA6SE, this time however, I might opt for some upgrades.
 
Am diligently "not" reading up on amps much, because it took me 6 months to decide on the SE in the first place. No chance of auditioning any gear in India, so I have to go on here-say and hope for the best.
 
I will keep my RS1i, and also save up for a T1, selling off my other cans. Hopefully, the WA6SE will do justice to both since they're poles apart in terms of impedances i.e. 32 - 600.