[Renderman]

   
This morning found some time to compare the ECC31, the National Union 6SN7GT and the Sylvania 6SN7W. Of course, neither of the 6SN7s match the ECC31 on bass, but otherwise, they are very similar. I find the Sylvania to be the most similar to the ECC31 in the mids and highs, while the NU is just a bit darker.
 
On a side note, I modded my HD700 last night and I am very pleased. The edge is gone and the treble is much smoother.

Thank you for confirming this gibosi! I'm glad others hear this as well and it's not just me being unable to hear more of a difference. I like both the NU 6SN7GT Black Glass and CNU 6SN7 Grey Glass, they sound similar to me.
 
Which mod did you perform on your HD700? I'm still contemplating doing something similar to my T1s however, I must admit I have some reservations operating on 1000 dollar headphones..

 

 

[gibosi]

  Which mod did you perform on your HD700? I'm still contemplating doing something similar to my T1s however, I must admit I have some reservations operating on 1000 dollar headphones..

 

 
Takato has posted three mods to his 700s. I decided to skip the earpad mod and the foam backwave-damping mod. It seems to me that they are primarily aimed at modifying the bass response. However, the filter-paper mod, intended to attenuate the highs, is incredibly easy, cheap and reversible, so decided to go for it. And I really like what I am hearing.

 

[Renderman]

   
Takato has posted three mods to his 700s. I decided to skip the earpad mod and the foam backwave-damping mod. It seems to me that they are primarily aimed at modifying the bass response. However, the filter-paper mod, intended to attenuate the highs, is incredibly easy, cheap and reversible, so decided to go for it. And I really like what I am hearing.

Great! Even if I don't own a HD700 I'm reading this! Maybe there is a way to easily tame the T1's as well! Thanks.

 

[Shaffer]

Philco BNIB 6FD7 came in today. I was hoping for a tapered bottle, but no. Just the standard GE-made fat bottle. They seem to be early-60s production. Smooth, dimensional sound with an excellent sense of depth. I'm really enjoying them.

 

[Shaffer]

Very happy with the Elise and her current tubes. Now to get back to what it's all about... the music.

http://recycledplastics.bandcamp.com/music

Minimal Dub and Minimal Techno. Similar to Brother Blue. Most of the titles are free.

 

[mordy]

Hi Gibosi,

Couln't read the Taka mod post due to the foul language. Would you mind summarizing the mod you did if it might apply to other headphones? I have a set of Yamaha MT-220.

 

[Shaffer]

As on the LD, I would hope that there would be a current / voltage rating printed on the transformer.....

Herein lies the problem. There's nothing on the transformer. Zilch. I suspect, perhaps, Woo winds their own. It's significantly larger than the LD's, if that means anything.

The official word from Woo is 1.2A for each signal tube and 4A for the rectifier, max. I might take the chance with 6BL7s. If the amp starts to get very hot, it'll be the end of that. What do you think?

Edit: Mordy, apparently I'm locked out of the old Elise thread, which makes finding the information difficult. Going through my purchases, these are the tubes you want:

http://www.ebay.com/itm/NOS-NIB-RCA-6BQ7-A-Power-Pentode-AUDio-AMp-Radio-Vacuum-tube-white-label-/201457341404?

I had another seller with the same product at a lower price, but cannot access the thread.

 

[gibosi]

Couln't read the Taka mod post due to the foul language. Would you mind summarizing the mod you did if it might apply to other headphones? I have a set of Yamaha MT-220.

 
I find the HD700 to be overly bright, so I have been searching for a way to attenuate the highs. Tak uses the the filter paper used in surgical/medical face masks, the non-rigid type, as damping material. This filter paper has three layers, each somewhat different. He separated them, and then tried various combinations of these layers inserted between the driver and the dust cover.
 
I agree that the language is very foul, but if you believe your headphones are too bright, I would encourage you to grit your teeth and read through it. But if your Yamahas are not too bright, then it very likely isn't worth the effort.
 
Cheers

 

[MIKELAP]

 

As on the LD, I would hope that there would be a current / voltage rating printed on the transformer.....

Herein lies the problem. There's nothing on the transformer. Zilch. I suspect, perhaps, Woo winds their own. It's significantly larger than the LD's, if that means anything.

The official word from Woo is 1.2A for each signal tube and 4A for the rectifier, max. I might take the chance with 6BL7s. If the amp starts to get very hot, it'll be the end of that. What do you think?

Edit: Mordy, apparently I'm locked out of the old Elise thread, which makes finding the information difficult. Going through my purchases, these are the tubes you want:

http://www.ebay.com/itm/NOS-NIB-RCA-6BQ7-A-Power-Pentode-AUDio-AMp-Radio-Vacuum-tube-white-label-/201457341404?

I had another seller with the same product at a lower price, but cannot access the thread.

Used these tubes in the LD amp with adapters if i remember those adapters were wired  to use one triode per tube later made an adapter that used only 1 tube but both triode   and they are plug &play in WA2  sounded nice   for the price                                                                                                                                                      

 
       
 

 

 

 

[mordy]

Hi Mikelap,

Appreciate that you posted the pictures - found that I have 5 of these tubes under the 6BZ7 designation. Gonna try them tomorrow - thanks.

 

[gibosi]

Herein lies the problem. There's nothing on the transformer. Zilch. I suspect, perhaps, Woo winds their own. It's significantly larger than the LD's, if that means anything.

The official word from Woo is 1.2A for each signal tube and 4A for the rectifier, max. I might take the chance with 6BL7s. If the amp starts to get very hot, it'll be the end of that. What do you think?

 
I very well could be wrong, but I don't think the rectifier pulls 4A. That is the theoretical maximum "Transient Peak Plate Current per Plate, Maximum Duration 0.2 Second". The heater for a 5AR4 draws 1.9A. The heater for a 6DE7 draws 0.9A per tube. So the total current needed to run the heaters of these three tubes is about 3.7A. A 5AR4 puts out about 0.25A maximum. So I would guess that in that configuration, the Woo will need about 4.0A total out of the transformer. Running a pair of 6BL7's, that number would be about 5.0A. I fear that 5.0A may well be at, or above, the rated maximum for the transformer. But of course, there is no way to know for sure....  You might be able to get away with it for a short time.... But if it was mine, I wouldn't do it.....  

 

[MIKELAP]

 

Herein lies the problem. There's nothing on the transformer. Zilch. I suspect, perhaps, Woo winds their own. It's significantly larger than the LD's, if that means anything.

The official word from Woo is 1.2A for each signal tube and 4A for the rectifier, max. I might take the chance with 6BL7s. If the amp starts to get very hot, it'll be the end of that. What do you think?

 
I very well could be wrong, but I don't think the rectifier pulls 4A. That is the theoretical maximum "Transient Peak Plate Current per Plate, Maximum Duration 0.2 Second". The heater for a 5AR4 draws 1.9A. The heater for a 6DE7 draws 0.9A per tube. So the total current needed to run the heaters of these three tubes is about 3.7A. A 5AR4 puts out about 0.25A maximum. So I would guess that in that configuration, the Woo will need about 4.0A total out of the transformer. Running a pair of 6BL7's, that number would be about 5.0A. I fear that 5.0A may well be at, or above, the rated maximum for the transformer. But of course, there is no way to know for sure....  You might be able to get away with it for a short time.... But if it was mine, I wouldn't do it.....  

This i got from Mike Liang at Woo                                                                                                                                                        

 

[gibosi]

OK....  But still, it is not clear that if a rectifier pulling only 2A of heater current is used, the remaining 2A can then be used to run driver/power tubes that draw more than 1.2A. That portion of the transformer which supplies the driver/power tubes may not be able to handle 1.5A. After all, they assume you will use something like the 6DE7, 0.9A, and 1.2A  provides a cushion of 0.3A. A 6BL7 exceeds that cushion by another 0.3A. Anyway, I urge you to be cautious. Replacing a custom Woo transformer is likely not cheap.

 

[hpamdr]

  OK....  But still, it is not clear that if a rectifier pulling only 2A of heater current is used, the remaining 2A can then be used to run driver/power tubes that draw more than 1.2A. That portion of the transformer which supplies the driver/power tubes may not be able to handle 1.5A. After all, they assume you will use something like the 6DE7, 0.9A, and 1.2A  provides a cushion of 0.3A. A 6BL7 exceeds that cushion by another 0.3A. Anyway, I urge you to be cautious. Replacing a custom Woo transformer is likely not cheap.

You are right gibosi, the question is more to know the  heating circuits design to know what could be burned !
 
if you have overload protection on each heating section you will brake nothing or just a fuse but it will not work corectly !
(on the folowing i use rectifier for a curcuit that stabilize voltage and current and not for the rectifier tube )
 
Common heating circuit with single rectifier -> you will be safe balancing heating power between tubes.
 
Common heating transformer with different rectifier section -> you will probably burn the rectifier ....
 
Single transformer with dedicated outputs  and rectifier you can burn both rectifier and transformer.
 
Multiplte transformers an rectifier you will burn only the overloaded circuit..

 

[Renderman]

  You are right gibosi, the question is more to know the  heating circuits design to know what could be burned !
 
if you have overload protection on each heating section you will brake nothing or just a fuse but it will not work corectly !
(on the folowing i use rectifier for a curcuit that stabilize voltage and current and not for the rectifier tube )
 
Common heating circuit with single rectifier -> you will be safe balancing heating power between tubes.
 
Common heating transformer with different rectifier section -> you will probably burn the rectifier ....
 
Single transformer with dedicated outputs  and rectifier you can burn both rectifier and transformer.
 
Multiplte transformers an rectifier you will burn only the overloaded circuit..

Indeed! I had a similar experience running 6BL7s as driver in the Elise, she is pretty resilient but started to get hotter the longer these tubes were in there. Sounded quite good and I can understand Shaffer for wanting to try these tubes. I don't expect the transformer would get fried right away but I don't think it would be a sustainable option. I would never recommend others to use these tubes as driver tubes in the Elise.