Since I first bought this GA-TRP a little over two years ago, I've gone through three new rectifier tubes, though I've only played these tubes for very short periods of time. They sound fine at first, then no output at all within less than 100 hours. Tube socket is tight. All else seems normal. I'm led to believe something in the DAC is causing the tubes to fail. I ordered a new Sophia Aqua to install, but now I'm doubtful I'll install it until I know more about whether I have an internal electronics issue. I have measured pin voltage, finding that to be at specification. I'm considering whether the filter capacitor at input power supply is either the wrong value (too high?) or not functioning as intended/designed. I may not be able to diagnose this myself/DIY. I'm entirely open to suggestions at this point.
Why Is My Lampi DAC blowing Rectifier Tubes
- Thread starter GoodGroove
- Start date
Unlikely. The fact that rectified voltage is as expected almost guarantees there is no excessive current draw. Too high an input capacitor sounds a little fantastic, a capacitor which has developed leakage is certainly a possibility but very likely will bring the plate voltage down.
If you really want to know, find a way to insert a small resistor, perhaps 10 or so ohms in series with the rectifier's cathode and measure the voltage drop across that resistor. In case there is no easy way to do this, consider a socket extention to a second socket and insert the resistor between the two sockets.
Imho, you have just had bad luck with the rectifers.
Thanks so much for your feedback and possibly helpful suggestion. At $250-$300 each, plus hours and hours of diagnostics of all sorts, I began to consider an SS rectifier; and, I hated the thought of sending the unit back, only to find nothing is wrong with it.
Psvane Acme 274b; Sophia Electric Aqua (1) 274b. I've ordered an Aqua ii 274b for replacement.
Hmmm...others can weigh in, but I wonder if the fact that these are Chinese-made rectifiers may be a potential answer. There are known quality-control issues with tubes manufactured in China.
This could be a likely factor; although, I've not seen much, anecdotally, where Sophia Electric has been cited as of questionable statistical reliability. But, I suppose, just because one doesn't see much about it, doesn't mean its not occurring. Perhaps my experience is an outlier, or due to shipping(?}. I'll see how the replacement performs in due time; that will tell me more.
Here's a fairly discussion of Sophia's rectifiers. I did not look into it deeply, but glanced at in the past and it just stuck in my mind.
Forums - Be careful buying Sophia Electic tubes
If you are in US I would definitely reach out to @LampiNA (Fred) or @DSG Rob (Rob) and talk to them about what you can troubleshoot on your own or arrange a trip to either local tech in USA or back to Poland.
PS: I do not have any experience with Sophia Electric tubes. I have been using mostly NOS rectifiers in my Lampizator DAC.
PS: I do not have any experience with Sophia Electric tubes. I have been using mostly NOS rectifiers in my Lampizator DAC.
Upon further reflection, I realize my thread post header should not have asked, "Why is...blowing rectifiers?", as that assumes, a priori, the Lampi is causing the problem. Rather, the header should have read something like, "What may be causing rectifiers used in my Lampi DAC to fail?" In addition, the header as posted could be understood to include negative inferences about my Lampi (or potentially others); and I wouldn't want that.
I have been in contact with LampiNA/Poland. They have walked me through some diagnostics, including pin voltage measurements and specs; which, as I've said, are spot-on. I also checked the tube socket integrity and cleanliness, and connection. These diagnostics would seem to be sufficient (inasmuch as I know) to likely rule out the DAC causing the tube failures. Thus, unless I learn other possible causes, I'm back to focusing on the tubes themselves. In such case, I've paid the extra forty bucks for a 1-year warranty on the replacement Sophia.
I failed to mention the CLC filter as something that could affect the rectifier tube. Perhaps that is very unlikely; if so, perhaps that is why the folks at Lampi did not raise this possibility during our communications.
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