Audio Note Meishu Silver Phono - Tube Advice Please!

Okay, I hate to do this, but I feel I must. I have found a profound effect by replacing the 5U4GB rectifier tubes with 274Bs in my 300B amps. I rolled a ton of exotic and expensive NOS 5U4GBs (RCAs Raytheon, Philips, etc.), and even cheap new production 274Bs sounded better. New production 274Bs like the Sophia mesh plates are just sublime. At least to my ears, in my system.

Many people don't believe that rectifier tubes make much of a difference, and I have to admit that I wouldn't believe what I am saying here without experiencing it for myself, but have an open mind and give it a try sometime if you can do so.

YMMV

 

Hi Lee - Yes, I'm using Psavane 2A3 s, which may, by now, be the tube supplied with the amp as I selected mine from a crate-full at the AN factory. I wasn't a big fan of the EH.

Hi Don - I'll shoot the 5687 and post a pic a bit later.

 

Ray - considering that the signal is really a modulation of the rectified, smoothed AC power, how could it be otherwise?

Those who have replaced a resistor in the PS with a choke have experienced a similar revelation.

 

I wrote to Sophia to ask about their 274B tubes and they said that I need to check with my manufacturer to make sure that it is safe to use those in my amp in place of my current rectifier tube.

I wrote to Audio Note asking if it is ok to use the 274B but I still haven't heard back a month later. I know that Martin left Audio Note, so their response is slower, but I thought that I would hear back by now. I might be picking up the phone and calling directly (at 4:00 am!).

Does anyone know if it is ok to use the 274B in my Meishu Silver Phono? David?

 

I don't know. I use Mullard GZ37s in my Welborne Labs 300B amps and twysted (an inmate on AA) told me the TJ 274B worked great, so I bought a pair but never tried them. What's the standard rectifier in yours?

 

The standard rectifier is a 5U4GB. I swapped in a winged c (SED) 5U4G black plate and it was a nice increase in resolution and detail.

 

For the 6X5 you could look for Brimar 6X5GT or the Bendix 5852, the latter being much more expensive but accroding to many the best option

 

When you explain it like that- it becomes obvious. That is why I am trying to learn as much electronic and amp design theory as possible.

 

According to Mission Labs, the ability to use a 274B rectifier tube depends on the value of the capacitor following the rectifier, the AC input voltage, and the DC output:

Maximum ratings.
NOT possible simultaneously
Take one maximum number, you must de rate another
READ all notes at the bottom of this Data sheet.
AC input voltage 550Volts
First capacitor, connected to plates 4uF
DC output current 160mA

"Good care should be taken when making the design of any DH rectifier. It must be prevented to have strong current peaks, through the first capacitor, because consequently this flows through the tube anode, and transformer windings as well. The transformer will produce mechanical hum by this, most specially if windings symmetry fails. Also the tube will suffer. For this reason, the first capacitor (C1) should never be larger than stated in the data sheet. The mechanical transformer hum, and also tube current peaks are greatly reduced by smaller capacitor values, and use higher choke values instead. Although higher capacitor values are at lower cost, using lower capacitors and higher chokes values instead, is always more satisfactory in the end. The result will be: Lower transformer hum, less electrical field radiation into the pre-amp, and more lifetime from the rectifier tube. This is why we recommend using largest chokes. From Lundahl, high value chokes are available at the same price as HiFi capacitors, like from a Mundorf or Black Gate. So we have to go back to the roots, and use high quality, large value chokes, like in the old days of radio design. For best ripple suppression, increase the choke to any value you need, or even use a C-L-C-L-C circuit, as also advised in the historical RCA data sheet."

I'm not sure if this is exactly the same numbers for the Sophia.

 

I might just give that a try at some point. I'm waiting for my speakers to be built, so I am trying to be patient and not make any more changes until they are here and broken in.

 

Wow, that is great information, but I don't have the background to really understand it. I should have taken a class on electrical circuits in high school!

 

Substituting the Bendix 5852 will only work reliably if the transformer feed is uprated to 1.2 amps rather than the 600ma rating of the transformers used in audio notes. Can be straight forward and certainly worthwhile.

 

Don - I'm sorry your question went unanswered. They are in an "all hands on deck" state with the factory move....

In any event, I asked Peter Q your question this morning and he says you should be fine.

 

6SN7 = JAN RCA VT-231 "Gray Glass". I think you will dig it.

But, as mentioned earlier, I think you should give your rig some more time with the stock set-up. You will appreciate and better understand the unique characteristics of each subsequent valve; a kind of knowledge that can't truly be acquired on forums.

have fun.

 

That was nice of you David.

Don, from what I have read about the 274B is that if the tube is not a good match for the amp the tube life is shortened, but it won't hurt the amp.

 

Thank you David. I really appreciate you asking for me. I didn't know that they are moving the factory. That would be a LOT of work!

 

Ray; you're right. I'm tempted to try because of what someone else reported and one tube isn't too bad on the budget.

I just put some more money down on my speakers and had a chance to listen to a pair of not yet broken in AN E SPE HEs. They sounded great with a source that is definitely not as good as my TT, so that's encouraging!

 

Hi Don,

Yeah, I'm happy to conveniently be 3k miles away so that I don't get called in to help with that. Phew! They outgrew the existing space quite a while back and the new space is something like 6x the size, so it will be great once it's done.

The E/SPe has been considered the sweet spot on the E continuum for a very long time and the HE version has inherited that mantle.

 

A little update on my tube rolling.....

I replaced the 5U4GB initially with a SED C 5U4GB and it gave a small but appreciable improvement in resolution over the stock tube.

Later, as in a month or two later, I replaced the SED with a NOS RCA 5U4GB from 1962 and also replaced the 6SN7 with a Northern Electric 6SN7 (a good Canadian tube eh!) and immediately had the sort of sound that I was looking for. The sound was warm without being too much of the 1950s/1960s excessively warm and rolled off. The resolution improved about twice as much as with the SED C and there were minor improvements in other areas such as bass.

Although it isn't a tube being replaced, I was offered a used pair of Audio Note SPx BiWire speaker cables at a very friendly price from my dealer. (He was looking after the widow of an audiophile who had passed away). I was go smacked at the improvement! I gained an extra octave of bass . The cables put everything into focus and in the most natural way. It wasn't an elevated upper midrange and lower treble, just more natural resolution. It was the largest improvement a pair of cables has ever made for me. This be fair, I was using a very cheap and basic Monster Cables before, but this was a very nice surprise. I thought that it would be a minor improvement, subtle at best. Nope, like upgrading a major component such as the amplifier. I have owned several brands of cables over the years and have been happy with some and not so much with others. These SPX speaker cables really match up well with my Meishu Silver and my E SPE HE speakers.

 

I should have added that my favourite 300B tubes gave me a short but exciting light show. One of the two Sophia Royal Princess 300Bs shorted and became bright white for a couple of seconds then took out a fuse. I bought a spare fuse and went back to the stock 300Bs. Still sounds good but I definitely preferred the Sophias.

After reading about PSVane tubes that others loved, I ordered a pair of the Black Treasure 300Bs. I was trying to finish paying off my new speakers, so a new pair of Sophias (US $1299) was out of the question. The PSVanes were US $299/pair, if you are willing to wait for slow shipping. I was!

These new tubes were better than the stock tubes but the improvement was about one third to one half of the Sophias. Pretty good considering the price difference. One day I will buy a pair of ElRog 300Bs, but they are even more than the Sophias

I think that I will also look for a single Sophia, as I had the remaining tube tested and it's still like new. Maybe I will do a tube shoot out with El Rog, Sophia Royal a Princess, stock and PSVane Black Treasure!

 

That seems like a pretty big claim to me. Are you sure something wasn't wrong before. Never heard of a properly made cable cutting off an octave of bass.

 

I certainly have, and then there's the question of how 'properly made' and Monster Cable relate . . . (Oh, this'll raise no end of hackles, I'm sure. Oh well.)

Holy Cow Don! Not Monster to SP/La or Lexus or even SPe, but straight to SPx! Good job seizing the moment. I'd imagine between the changed tubes and speaker cable upgrade, you now get to roll through your whole music collection saying, "What the . .!" and "I never heard . . ." Have fun.

 

Well that's why I was assuming something was wrong like corrosion or manufacture defect. I've measured things like Belden cable which cost less than a dollar per foot and there was no loss in the lower range with my speakers to what the manufacturer says they should reproduce.

I suppose it's possible the monster cable is really poorly designed I've never used them before

 

It was just hyperbole. A small increase in bass extension and control is very noticeable and cables can do that. I'm OK with the exaggeration. Monster Cable have a pretty ordinary sound, although I liked their old Interlink 400 interconnects - terrific shielding.