[Dracule1]

Hi, I have a tube DAC that keeps arcing direct heated rectifier tubes (5U4 and 274B) probably due to large current in rush from a large capacitor bank.  I was told an indirect heated rectifier would be better suited. So I'm looking for a quality 5AR4 tube that will give dynamic sound with extended bass, wide/deep sound stage, and smooth detailed sound. Thanks.

[ltr317]

???  What type is the stock rectifier?  Does that arc also? 

[Dracule1]

Stock is a Russian 5U4 according my DAC designer, but I can find the company on the tube.  And yes it arced.  I tried the Sophia Electric Princess 274B which arced. 

[ltr317]

I don't understand why the designer would design a circuit that would have the rectifier tube arc deliberately and sell it as a finished product.  It would make sense to either correct the problem or design the product with a solid state diode instead. 

[JakeJ]

@ Dracule 1,

NOS Mullard Blackburn.  Yeah, it'll cost a few extra bucks but you'll probably never have to replace it plus it really is the best 5AR4 sonically.


@ ltr317

In another thread the OP posted that he was trying the 274B for it's sonic merits but please know that the device/circuit was originally designed around and supplied with a 5U4.  He even contacted the designer and was told it would be OK.  Unfortunately it wasn't.

Here is the original thread -
http://www.audiocircle.com/index.php?topic=97194.0

[ltr317]

Thanks Jake.  After reading the original thread, it seems the original 5U4 also arced briefly, so I stick with my comments.  I still think it's a poor design.  It's never good for any rectifier to arc, regardless how long.  Steve is right, that 5U4 is probably toast.  The 5AR4 is much more robust.  I would also open up the unit and check for any damage.  I have tried dozens of 5U4 and 5AR4 and agree with Jake, the vintage Mullard is my favorite.   

[Phil A]

I just got Synergy HiFi 5AR4s.  They are not broken in yet (probably a total of just a few hours).  There are reviews of their tubes and technology at 6 moons.  I had a pair of Amperex Bugle Boys made by Mullard in Britain and so far they are comparable and certainly in the same league.  Supposedly, they need 50 hours of break in.

[S Clark]

Another highly regarded 5AR4 is the Sylvania fat bottom.  Even the Sovtek gets good reviews from some.

[Pez]

Best of the best is Mullard skinny bottle 5AR4.

[Dracule1]

Thanks everyone for the recommendations.  I ordered a Sovtek 5AR4 ($22) just to try and see if this tube won't get fried.  If it works fine, I will order the more expensive 5AR4 tubes.  It seems like my DAC is the first to have this problem.  Designer said he burned in the DAC for couple of weeks before shipping and ran into no tube failure.