Sophia Princess Upgrade for the WooAudio6



Though the WooAudio6 is a very good amp for the price, people are constantly looking for ways to upgrade its performance. One way to upgrade the WooAudio6 is by replacing the stock rectifier to the Sophia Princess Rectifier, which WooAudio sells for $150.

It may come with a cheap looking packaging, but the Sophia Princess tube is an awe to behold. It sized much bigger than the stock Tung-Sol rectifier and it’s really a piece of art made from glass and metal. When turned on, the tube lights with a beautiful V-shaped pattern. It’s really mesmerizing. Even if it yields absolutely no sonic improvements, some people (me included), would happily pay $150 just so my amp can look better. (Fortunately, the WooAudio6 is not mine) For people who’s serious about audio, the question is, how much better does the Sophia Princess rectifier perform from the stock Tung-Sol? Having both tubes in our review room, I gave both a listen.


This WooAudio6 comes with the PDPS upgrade from WooAudio, and it’s already a very fine amp to begin with. However, I really wouldn’t compare it to other amps in the $1,000+ range, as the WooAudio6 can’t compete with the higher priced amplifiers in terms of refinement, details, imaging, et cetera. With the Sophia Princess rectifier, you’re not changing the sound signature of the WooAudio6. After all, why mess with such a great musicality? The Sophia Princess rectifier, however, takes the stock WooAudio6 and adds a level of refinement normally only found on more expensive amplifiers.


The soundstage is improved, and not only does the Woo sounds more open, but its imaging is also significantly improved. I really like the imaging performance of the WooAudio6 with the Sophia Princess, so much that I find myself comparing it to the SPL Phonitor amplifier, which is a high-end solid state monitoring headphone amplifier with a superb imaging. Though the SPL Phonitor has a bigger soundstage than the WooAudio6, the Woo with the Sophia Princess gives a more pleasant imaging that’s both intimate and yet well separated.

Ambience, subtle nuances, and decay also sounds more natural and real. Even though I didn’t notice any improvements in detail level, these improvements brought by the Sophia Princess makes the experience more engaging and real. Having listened to the Sophia Princess, I also feel that the low bass bump that I associate with the WooAudio6 is actually caused by the Tung-Sol rectifier, and is now eliminated by using the Sophia Princess. Bass extension is now smoother and more natural.


Having heard the Sophia Princess, now the same amplifier with the Tung-Sol rectifier sounds very closed and congested. It’s really hard to go back to the stock rectifier. I also think that the $150 spent on the Princess is well worth the upgrade, as now the WooAudio6 feels more like a $1,000 amplifier, and it hangs pretty confidently next to the Phonitor, the Auditor, the Grace, and the Beta22.

System for auditioning:
Headphones: Sennheiser HD800, AKG K501, AKG K701
Source: MacPro via Toslink to Lavry DA11, CEC TL51XZ via Coaxial to Lavry DA11
Amplifier: Lavry DA11, Grace m902, WooAudio6 with PDPS and Sophia Princess, SPL Auditor, SPL Phonitor.
Interconnect: Transparent Musiclink Plus XLR, Purist Audio Design Maximus XLR, Stereovox Digital Interconnect, DIY Copper with Eichman Bullet RCA

Rate this post


  • Reply February 21, 2010


    Dear author,
    Great micro-review!

    I was wondering how well did the WooAudio6 fare with the K701,with and without the Sophia Princess rectifier tube,in relation to other amps youve sampled.
    I ask because many say the K701 needs a powerfull amp to not sound sterile and boring.

  • Reply July 26, 2011

    Larry Ganz

    I absolutely agree 100% with what you heard.  I posted the same type of things when I upgraded to the Sophia Princess 274b rectifier tube in my Woo WA6 back in 2008.  Interestingly, changing the 6DE7 tubes to different brands of 6DE7 didn’t have as big of an effect in the sound as changing the rectifier did.  (However, changing to a different tube type altogether, like a 6FD7 or a 6SN7 with adapter also makes a big difference).  

    I still own my maxed WA6 three years after the Sophia tube upgrade, even though I have more expensive amps that surpass it in sheer performance, because it just offers such a great bang for the buck that it’s hard to part with it.  Compared to the Woo WA22 or Eddie Current ZDT the WA6 still has a little more forward presentation with a narrower soundstage, but the quality of the reproduction is still top notch.

    • Reply July 26, 2011


      …and I still need to get a woo6. If only I didn’t have too many household expenses 🙂

    • Reply July 27, 2011


      The WA6 is one of the good deals out there. $700 for the non SE version
      and that gets you a very good amp. The Rectifier tube upgrade does
      upgrade the sound quality. I’ve tried however two WA6 models with two
      different 6DE7 tubes that have quite a different sound signature. One is
      dark and bottom heavy, the other one is much lighter in tone. Don’t
      remember the tube brands though.. it may have been a different tube like
      the 6FD7 or the 6SN7 like you said.

  • Reply December 29, 2011


    Hey Mike,

    I have a question about tubes. 274B, 5U4G, 6DE7: What are these model numbers? are they actual types of tubes or types of the connection the tubes use. I understand that Sophia Electric is a company such as Tung-Sol but are these model numbers universal; for example would both companies have tube type 6DE7 or is that company specific.What is OTL/OPT/etc.Could tube selection be seen as cable selection? kinda.Sorry maybe I should be asking this in the Q&A.

    • Reply December 29, 2011


      274B, 5U4G, 6DE7 are the types of tubes. An amplifier that’s designed to use 6DE7 should only be used with 6DE7 tubes, but these can be from different brands: Tung-Sol, GE, Sylvania, etc. Each brand may have different types of 6DE7 as well, i.e Sylvania grey plate, black plate, black glass, etc. This applies to all short of different tube types. 

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.