[Tech2]

I am very seriously considering the purchase of a Woo Audio 6. I will be using it to drive both my Grado 325i and Senn HD600.

The stock tubes that are supplied with the amp are two 6DE7 driver tubes and a single 5U4G or 5AR4 rectifier tube. These tubes probably are just fine for my purposes, at least initially, but I have some n00b questions regarding tube-rolling with this amp.

Which tubes will have the most pronounced effect on the sound of the amp? The way I understand it is that the driver tubes are the output tubes. I would assume these would have the greatest effect on sound if I were going to roll the tubes. Correct?

Will rolling the rectifier tube also have a pronounced effect on the sound?

Are there any other options (direct substitutes) for the stock tubes listed above? The reason I'm asking is because I would like to know what some of my tube options are before I purchase the amp.

 

[sacd lover]

Quote:

Originally Posted by Tech2 /img/forum/go_quote.gif I am very seriously considering the purchase of a Woo Audio 6. I will be using it to drive both my Grado 325i and Senn HD600. The stock tubes that are supplied with the amp are two 6DE7 driver tubes and a single 5U4G or 5AR4 rectifier tube. These tubes probably are just fine for my purposes, at least initially, but I have some n00b questions regarding tube-rolling with this amp. Which tubes will have the most pronounced effect on the sound of the amp? The way I understand it is that the driver tubes are the output tubes. I would assume these would have the greatest effect on sound if I were going to roll the tubes. Correct? Will rolling the rectifier tube also have a pronounced effect on the sound? Are there any other options (direct substitutes) for the stock tubes listed above? The reason I'm asking is because I would like to know what some of my tube options are before I purchase the amp.

The 6de7 is a dissimiliar twin triode. The tube has an input/ gain triode for preamlification or voltage gain and an output triode to drive the headphones .... both in the same tube. Any 6de7 you receive will be a nos tube as they are no longer manufactured .... so you will likely be getting a good 6de7 to start with. The 6de7's were made by GE/RCA/Sylvania and Tung Sol for sure; maybe Raytheon too. These tubes are inexpensive and easy to find.

There are other dissimiliar triodes but their amplification factor for the gain stage triode and voltage handling can be quite different; even with some that will be listed as potential substitutes. This type tube is also tricky because either triode can have different voltage maximums. The 6de7 has a 330 volt maximum for the gain triode and a 275 volt maximum for the output triode. Looking at some other dissimiliar triodes they flip the voltage maximums. Furthermore, some of the other dissimiliar triodes have a much higher voltage gain which will cause the most problems with compatibility. I would get a recommendation from the manufacturer who knows the limits and operating points of the circuit. As a starting point, the 6ew7 would seem to be the most likely candidate as a sub.

A rectifier tube can definitely impact the sound. The one I like for the best sound / cost ratio is the 5u4g. Good 5u4g's were made by all the major tube manufacturers and they are about $30-40 most places.

 

[Tech2]

Thank you.

So any 6DE7 will work? I did a quick google search but didn't find many 6DE7s available, which concerns me.

I also read the entire Woo3 mod thread, and it appears that there are many more tube options for that amp, but I figured that the 6 would be better suited to my two main phones, which are a Grado 325i and Senn HD600. My understanding is that the Woo3 can have trouble driving Grados, whereas the the Woo6 will drive either. I have also read that replacing the 6AS7 power tube with a Tung Sol 5998 allows the Woo3 to more efficiently drive the 325i. So now I'm wondering if I should just get the Woo3 and replace the power tube?...or spend the extra $100 for the Woo6?

Arrrgh...if I had hair I'd be pulling it out by now.

 

[sacd lover]

Quote:

Originally Posted by Tech2 /img/forum/go_quote.gif Thank you. So any 6DE7 will work? I did a quick google search but didn't find many 6DE7s available, which concerns me. I also read the entire Woo3 mod thread, and it appears that there are many more tube options for that amp, but I figured that the 6 would be better suited to my two main phones, which are a Grado 325i and Senn HD600. My understanding is that the Woo3 can have trouble driving Grados, whereas the the Woo6 will drive either. I have also read that replacing the 6AS7 power tube with a Tung Sol 5998 allows the Woo3 to more efficiently drive the 325i. So now I'm wondering if I should just get the Woo3 and replace the power tube?...or spend the extra $100 for the Woo6? Arrrgh...if I had hair I'd be pulling it out by now.

If a tube is a 6de7, the tube will have been made with the same identical specs regardless of the brand .... thats the way the system was designed. The 6de7's are easy to find and generally cost about $4 each. Give me 15 minutes and a phone and I could obtain hundreds for you; not that you need that many.

The 5998 has a lower output impedence than the 6as7g but the 6as7g will pass more current. Neither tube has an output impedence that will work that well with the grados or low impedence / low sensitivity headphones like the AKG 701.

5998 = 350 ohm plate resistance/ mu of approx 5 = 70 ohms.

6as7 = 280 ohm plate resitance/ mu of 2 = 140 ohms.

I thought the Woo 3 was noisy and lacked transparency. I owned one. I would stick with the Woo 6 or go in another direction. The Mapletree ear+ drives grados very well for $595 assembled. But I have never liked the sound of my senn 580/600's with the ear+. The tube amp I like around this price is the Singlepower PPX3 SLAM.

The SLAM sounds great with grados or senns, is very quiet and has tons of low cost tube choices. But the SLAM would run you $899. Looking at your options and assuming you want to keep the cost down around the $600 price point ..... I think you have the right choice in mind with the Woo6.

 

[sacd lover]

EDIT .... the dreaded double post.

 

[Jon L]

5U4G is the way to go for rectifiers, and yes it'll make a significant difference.

Tung Sol top-getter 5U4G is my fave, but the much cheaper Tung Sol 5U4GB can give many 5U4G's a run for their money. RCA 5U4G bottom getter tubes are much more common, and they are good too.

 

[sacd lover]

Quote:

Originally Posted by Jon L /img/forum/go_quote.gif 5U4G is the way to go for rectifiers, and yes it'll make a significant difference. Tung Sol top-getter 5U4G is my fave, but the much cheaper Tung Sol 5U4GB can give many 5U4G's a run for their money. RCA 5U4G bottom getter tubes are much more common, and they are good too.

I agree Jon, the TS 5U4G is my favorite too. I really like all the 5U4G's though. The Raytheon is a clean, clear sounding tube I enjoy, as is the Ken Rad. The non ST rectifier type I like is the brown base Sylvania 5931.

Tech2 .... ST stands for shoulder tube .... which are the coke bottle shaped tubes. The 5931 is referred to as a straight bottle tube.

Left to right .... Raytheon, Ken Rad, two TS and the brown base Sylvania 5931.

 

[Rob N]

5AR4/GZ34 are also good although can be expensive especially the metal base version

 

[Tech2]

Thank you all, especially to sacd lover for taking the time to take and post pictures.

To complicate matters, I emailed Jack Woo and he said that a Woo3+ is now available. He wrote:

"We have a new solution to compliment some of the matching issues with low gain phones. That is the WooAudio3+ we recently developed as an upgraded version on the WA3. The WA3+ features a filter choke that increases the output power."

There is also a review of the Woo3+ and Woo6 in Tone Audio magazine (link on Woo's site) which says the Woo3+ has a "solid state rectifier", whatever that means.

Anyway, I'm looking to go with something that will drive both, and even Jack Woo said that the Woo6 is the way to go if I want to drive both of my headphones. Apparently the Woo3+ is $495. With the Woo6 being only $75 more, I'll probably go in that direction.

And yes, I would love a Singlepower amp, but I don't want to spend the money. I'd rather get the Woo6 and use the extra funds for some tubes.

Thanks again for all of the responses.

 

[sacd lover]

Quote:

Originally Posted by Tech2 /img/forum/go_quote.gif Thank you all, especially to sacd lover for taking the time to take and post pictures. To complicate matters, I emailed Jack Woo and he said that a Woo3+ is now available. He wrote: "We have a new solution to compliment some of the matching issues with low gain phones. That is the WooAudio3+ we recently developed as an upgraded version on the WA3. The WA3+ features a filter choke that increases the output power." There is also a review of the Woo3+ and Woo6 in Tone Audio magazine (link on Woo's site) which says the Woo3+ has a "solid state rectifier", whatever that means. Anyway, I'm looking to go with something that will drive both, and even Jack Woo said that the Woo6 is the way to go if I want to drive both of my headphones. Apparently the Woo3+ is $495. With the Woo6 being only $75 more, I'll probably go in that direction. And yes, I would love a Singlepower amp, but I don't want to spend the money. I'd rather get the Woo6 and use the extra funds for some tubes. Thanks again for all of the responses.

SS rectification means just that. SS parts are used for retification instead of a tube. You can also have SS or tube voltage regulation.

rec·ti·fied, rec·ti·fy·ing, rec·ti·fies

To set right; correct.
To correct by calculation or adjustment. See Synonyms at correct.
Chemistry To refine or purify, especially by distillation.
Electronics To convert (alternating current) into direct current.
To adjust (the proof of alcoholic beverages) by adding water or other liquids.

I would still get the Woo6 vs the Woo3+.

If you need some tube help give me a pm. I am sure I can save you some money while helping you find what you want.