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Sophia 274B meshplate

Discussion in 'Headphone Amps (full-size)' started by tony3d, Jul 14, 2013.
  1. tony3d
    Please tell me I didn't just throw out $160.00. I just ordered the Sophia 274B mesh plate for my WA6. Thing is I have a very early WA6 late 2007 I think. From what I'm piecing together here, it may not work correctly do to the first Capacitor after the rectifier needing to be 10uf. I'm wondering if mine is using a higher maybe 20uf. How can I find out? Does anyone here have an early product run, who's using the Sophia 274B Mesh plate? I should have made sure of this before I ordered it on WooAudio's site. The reason I'm suspicious, is because on their tube chart it says the WA6 is not compatible, yet they offer it as an upgrade. This makes me believe they may have changed something along the way. Any input would be great. Thanks.
  2. tony3d
  3. clowkoy
    I think all WA6 are using 330uf as first capacitor. It's the capacitor in the middle of the board located near the transformer at the back held by zip tie and glue. The label is hidden by positioning it towards the board.
    I've stopped using the Sophia after I learned of this. Some say you can get away with it since it's drawing only small current but I think it's still not a good idea. You can't lower the value because of hum issue.
  4. tony3d

    Why do they sell it on their site as an upgrade for the WA6 then? That's pretty misleading. Did it seem to work alright? How did it sound. Why did you stop using it, and what year was your amp built? I'm contacting them first thing tomorrow. Supose it can really impact the life of the tube.
  5. clowkoy

    It worked fine and sounded good. I only had it for about =30-40 hrs. It's built in '11. Some brands of 274B would even spark on start-up. It will definitely shorten its lifespan.
    From sophia website:
    Note(*): 274B is direct heating tube. The indirect heating 5AR4 may turn on slower, however, people who buy 274B is for its superior sonic performance. To fully utilize its benefits, it may require first stage capacitor (capacitor input) to be less than 10MFD, or would shorten the 274B life span (very much like smoking is bad for your health). It would not be a problem with common choke input. Please consult to your amplifier maker or refer to a tube manual. This 274B is an update of the NOS WE 274B, so both share with same characters. In 1930s, WE 274B was the rectifier choice for 300B single ended theater amplifier in the US.
    Please let us know of Jack's reply but I'm sure he'll say it's fine.
    It's the reason I'm selling it.
  6. fhuang
    so using 5ar4 is safer/better/"healthier" for the amp and/or the 300b? 
  7. tony3d
    Tried emailing them several times, but no reply yet. Does anyone have a phone number? I'd really like to cancel this order before it ships.
  8. tony3d
    They did issue my refund. Very pleased. 
  9. clowkoy
    Did they reply to your email?
  10. tony3d
    Yes they did, and they were able to stop the order before it shipped.
  11. namhkim
    This is three yr old thread, I'm not sure who will revisit here, but I'd like to add my findings from a great magician/electrician that I recently found from YouTube. He is Mr Carson, and is extremely well versed in EE design.
    He posted this timing circuit to cure directly heated tubes spark symptoms.
    Basically, it's an N-channel FET linked to a capacitor to gradually charged to work as a delayed timing circuit under DC influx. Looks like a very simple circuit, yet what a genius way to handle the spark ! I was in awe when I found this, or any other of his videos for that matter. So worth my time (hrs) to watch his videos.

    I think WA6 has similar circuit, but if not, and if some 274b tubes do Spark, it's well worth to add diy for the price of ~10 seconds of delayed start.

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