[Lil' Knight]

That's an awesome explanation, Uncle!

 

[orkney]

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

 

[Uncle Erik]

Quote:

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

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.

 

[Brighten]

The scientist has gone mad!

So I take it the RS-1/Eddie Current EC-01 is a no go?

 

[freakmax]

Great thread ,Uncle!
Thanks.

 

[LeMat]

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 ?

 

[bobsmith]

Quote:

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 ?

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.

 

[LeMat]

Quote:

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.

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.

 

[terriblepaulz]

Quote:

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.

I think the amp I had built is the design you refer to above (w/ Hammond transformers). The builder mentioned Eric Barbour and VTV Magazine. Feel free to chime in Erik. Pics:

Picasa Web Albums - hagbard - Tube Amp

 

[bobsmith]

Quote:

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.

Well, there aren't that many people who have used/reviewed the WA2, so I am not sure how much user feedback you are going to find. Also, I found the post with the impedance specs:

http://www.head-fi.org/forums/5165787-post9.html

So, apparently, the WA2 has an output impedance of 60 ohms. Since the K701 has an impedance of 62 ohms, it seems to me like a pretty ideal match. But I am pretty much a newbie at this...

 

[listen2themusic]

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?!?!

 

[Skylab]

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.

 

[listen2themusic]

Quote:

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.

 
Soooo...
 
In order to assure that a low impedance set of cans like the K701 will be able to be driven well enough, it's the output impedance of the amp that should be closely looked at, not whether it is a hybrid transformer coupled amp or an OTL? I guess I should look to see what the output impedance of the WA6 is compared to the WA2.
 

 

[Skylab]

Yes. The role of the output transformer is to lower the output impedance of the amp.

 

[listen2themusic]

Quote:

Yes. The role of the output transformer is to lower the output impedance of the amp.

But I suppose it must be generally true then that a hybrid amp will meet this lower impedance requirement more than an OTL?
 
And by output impedance, that's not the same as headphone impedance is it? Trying to figure out where this measurement is on Woo's amp specs.
 
Sorry, just trying to get a grasp on all this!