If an amp is designed for an 5AR4/GZ34 (which is the same thing just European and American names) dropping in a 5U4 is not a direct replacement. It may work but it will draw more current on the filament (it may smoke the filament winding of your PS transformer) and has less voltage output and warms up much faster which puts additional strain on a circuit designed for 5AR4 on start up. It will "probably" work but you amp will put out less power and the filament transformers will be stressed along with the entire amp on start up. There is even a slight chance it is wired differently and won't work at all. I would be very careful especially with a vintage amp.
I wasn't suggesting that it necessarily was but my amp can run either and the difference was conclusive to me and my dealer.
These are the stock tubes provided with my LS100 preamp: Tube Complement: (2) 6SN7 driver tubes; (1) 5AR4 rectifier tube (may also use 5U4GB and 5V4GB). These are what they suggest as upgrades: Output Tube: Sophia Electric 6SN7 Rectifier Tube: Mullard, Amperex or Philips GZ34 Made in Holland. I guess it’s best to stick to the official specified designations. There seems to be a fair choice.
you can do much better than the sophia electric. there is a big thread about 6sn7 shootout. quick recommendation are NOS sylvania 6SN7 GTA. A good match pair ~ $200.
Since you can use a 5U4GB I would suggest checking one out you can get them NOS pretty cheaply, RCAs and GEs have worked for me.
I think I’m more than OK in the 6SN7 department. It’s the rectifier I’d like to match to the performance level of the outputs if possible.
For 5U4 I've had good results with CBS Hytron and Sylvania in my deHavilland. I don't recall them being very expensive, either.
Seriously though, what I’m looking for now is a rectifier that can possibly match the SQ of my outputs.
I've read or heard this before as well. I wonder if it's really true or just something someone says and then it becomes "fact"? What are these toxic and super rare materials?
Here is a fair, brief summary: https://www.antiqueradios.com/forums/viewtopic.php?p=2180166&sid=d2e22372237898eb53a02e4bb332ee9e#p2180166 I don't think it is just a materials issue, but also involves tooling, know-how and perhaps, exposure to materials that have not been approved. I don't know if anybody has directly compared a period WE 300b to the better modern recreations, but there is certainly a tendency to give the nod to the original era tube. For me, I have some high end rectifiers, including those mentioned upthread-- the GEC u 52, the early metal base Mullard from Holland, and a number of others. Each sounds different. The supplied tube did not reveal the actual capability of the component, but I've found that to be true in a number of cases- how is a manufacturer going to be able to supply vintage tubes? (I have no idea what Shindo stuff is available right now, that was one of his things). Even the 6H30, which is a more modern tube, appearing in ARC and BAT stuff, isn't supplied with period tubes from the DR Reflecktor era, due to cost. (I think when Victor owned BAT, he had a stash and since I use that tube too, I've had to hunt to find good period replacements). They simply sound different than the modern production. More power to you if your gear sounds good with modern production tubes. It can get costly.
The best 5U4 I know is the United USAF-596. Sort of a pain to use (for probably obvious reasons) … but more than worth the effort to get it set up. Years ago, I used one in a single-ended 45 power amp, together with another in a 76-based preamp. If you have 6SN7 preferences already and don’t need recommendations, I’ll hold my tongue. No reason to pressure that market even the slightest bit. To my last point (and I’ve said this before on this forum), this is absurd. Sorry to say, but these were the “stock tubes” we were junking 20 years ago in favor of the good stuff
To my last point (and I’ve said this before on this forum), this is absurd. Sorry to say, but these were the “stock tubes” we were junking 20 years ago in favor of the good stuff [/QUOTE] I have tried many others in my system and these sound the best. If you have a suggestion I doubt a single comment will inflate the others more than they already are....... Please feel free.
Khorn , Certainly not trying to alarm you, but when the stock Sovtek 5AR4 blew in my ModWright LS100, the fuse didn't catch it and the result was a 'fried trace' in the circuit board. Sent back to ModWright for repair and they had to replace the entire board, as they couldn't jump around the bad spot in the trace. Luckily the Preamp was still under Warranty, so I was only out shipping costs. I picked up a pair NOS 5AR4's made by Mullard for Hammond, a much better tube sonically and for dependability.
Good story m. Makes me glad the original Sovtek blew just the fuses in my preamp and the sound does not make them worth the risk ! Do your Hammonds have date / build codes?
It's been 3-4 years ago when I picked these up, IIRC $180. for the pair. They were NOS and certainly looked the part.
I would also like to know what tubes were in favour over the "junk Sylvania 6SN7GTA" 20 years ago. Cheers, Robert
Thing is why would ModWright outfit their preamps with the Sovtek if there were a good chance they could fail and damage new equipment? I certainly have the utmost trust in my output tubes and they are also also new stock. I would of course want to obtain the best (sounding) rectifier tube I can lay my hands on.
I certainly understand your faith in Dan's choices of tubes in his gear. But, there are very few manufactures that provide anything beyond the quality of Sovtek, JJ, EH, etc. in new equipment. I am NOT an electrical savvy guy at all, but I feel like that the fuse 'should' have preempted the damage to the circuit board when the rectifier blew, but it didn't. Or is not designed to protect the circuit if a Rec tube blows, IDK. I'm thankful that the Pre was still under Warranty, if not I would imagine replacing the board is an expensive endeavor.
The story of the Modwright damaged by a failed rectifier tube is as frightening as it is surprising. I, too, would have thought the boards should be protected by a fuse. However I guess there is more than one way a rectifier can fail, some more potentially catastrophic than others. I had a PrimaLuna Evo400 preamp with two stock PL 5AR4 tubes, which are a Chinese-based tube to my understanding. One failed at around 30 days of use (I purchased the preamp new in box). It took out the main fuse, though at the time I did not know WHAT caused the fuse to blow. I spoke to PL service at Upscale and they were great at assisting in troubleshooting. They sent me two new rectifiers and all was well for the next year until I sold the unit. However I've definitely read endless accounts of OS tubes, including rectifiers, lasting much, much longer than new production. Also read that with rectifiers specifically the oldies tend to last seemingly forever, particularly for less demanding duty like powering a preamp. So a good NOS or little used OS pull should typically last many years. Cheers, Robert
