Lil' Knight
Headphoneus Supremus
- Joined
- Sep 16, 2007
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That's an awesome explanation, Uncle!
Originally Posted by orkney /img/forum/go_quote.gif Great stuff, UE! One quick question, I've read in various places that the way that OTLs couple to tranducers means that the quality of the tubes can matter even more than in transformer designs -- is the case? I own various tube gear made by Cary, Manley and now an EMP OTL design, and I must say that the differences in rolling the EMP are pretty stark. Just like a baby -- what goes in comes out. best, o |
Originally Posted by LeMat /img/forum/go_quote.gif I have an OTL amp on its way, the Woo Audio 2, while I own a K701... Reading this truly informative thread, I start to feel I made a mistake... or at least, didn't get the best matching amp. Should I worry ? |
Originally Posted by bobsmith /img/forum/go_quote.gif I think you will be fine. Jack Wu specifically told me that the K701 is an excellent match with the WA2. I also seem to recall reading a thread (can't find it now) where Jack quoted the actual impedance output of the WA2, and it was pretty close to the impedance of the K701. If you are unsure, write and ask Jack for confirmation, but I am pretty sure that the K701 is one of the headphones that is most commonly used with the WA2. |
Originally Posted by Uncle Erik /img/forum/go_quote.gif I haven't compared tubes in the OTL and transformer coupled amps I have. Part of the reason for the, er, collection is to get a taste for as many different tubes and topologies as possible. The current project (HeadWize - Project: Brute Force In A Line Stage by Eric Barbour) has a 12SN7 pushing a 6BL7GT. I haven't played with the 6BL7GT before and I've been wanting something with tube regulators, so this was an easy choice. An Eric Barbour (of Vacuum Tube Valley (Vacuum Tube Valley)) pedigree isn't so bad, either! VTV is a terrific resource for anyone wanting to learn more, as well. There's a nice headphone amp project in issue #16, a little transformer coupled amp meant for Grados. I built one a couple years ago and it's been a lot of fun. It uses Hammond output transformers which are affordable and good enough. But there are lots of variables on how tubes perform - where the designer set the operating points at, other tubes in the circuit, how good the power supply is, and so on. Tube rolling does give you different sound, but I've never gotten too far into it. I look at it as like going to a favorite restaurant. The steak will never be exactly the same each time you go. But you still love going there and know you're going to have a great meal even if it isn't precisely the same as last time. Same with tubes. I managed to kill a 6SL7 on the Zana a few weeks back and put in a new one. It's a little different, but it still sounds good and I'm enjoying the slightly different sound. It'll change when this one burns out, but that's OK. |
Originally Posted by LeMat /img/forum/go_quote.gif Jack indeed has been very helpful and told me it was a good match (better than the WA6) but I still tend to trust more users feedbacks than vendors' one... question of habits. |
So just when I thought I was beginning to understand all of this, I go to the Woo Audio site and find that the WA2 is a SE OTL unit while the WA6 is transformer coupled. Shouldn't the WA6 be a better match for the 701 than the WA2, or did the designer do something special with the WA2 to make it more compatible with the low impedance 701 than the WA6?!?!![]()
You're right, the WA6 should indeed be a much better match for the K701. The post above you wasn't accurate in saying the output impedance being close to the headphone impedance being ideal. You want the output impedance of the amp to be lower than the impedance of the headphone, ideally much lower.
Yes. The role of the output transformer is to lower the output impedance of the amp.