5AR4 rectifier tube question

I am sort of shopping for one or more 5AR4s for a Cary SLP05 power supply because I’d like to have at least one spare and because I’d maybe like to roll two or three ad see if I can hear an improvement or vice versa. I make no claims of knowing much about the vacuum tube game; occasionally I get lucky & stumble on something that really works for me. As far as the 5AR4, I did a hit at Uncle Kevin’s site, and there were some that looked interesting (I am thinking of one in particular, it had a Japanese sounding name that started with a ’M’) but when I click on it, all I get is a picture of Uncle Kevin’s screaming face telling me "not to buy tubes" (later, when I finally took time to read, apparently his tube tester is down).

So I started doing hits on Ebay, and oh my gosh! I was inundated with choices and the variation in prices! Which do I stay away from and which should I be interested in? Would a 5AR4 from Bugera also be suitable for what I’d want to use it for? Could a rectifier tube provide a big sonic upgrade if I spent enough money on it? Can I make a sonic upgrade from what I believe (I haven’t opened up the power supply yet) is the stock EH 5AR4 without breaking the bank? I would be totally good with the $50.00 range and picking up 2 or 3 different ones to play with if those with experience thought I could improve the power supply in that range. If I had to I guess I could go more (the $100.00 range) but I probably wouldn’t be buying too many of them, and I was kind of HOPING not to go much over that.

Anyway, thanks in advance for the input; I always consider it part of my education.


Upscale is selling tubes again but with some limitations. I would not say you are buying spare tubes but I think tube rolling would be acceptable reason (better would be your tube failed). Probably only able to order 4 tubes every 180 days per his email. Oh. The tube tester is back online..

All Kevin's showing for sale are the four Russian new production brands which are pretty much the same tube with different labels and boxes. For NOS 5AR4's that work and may outlast you call Andy at Vintage Tube Services.  Don't waste your effort with e-mail.  The Matsushita 5AR4 which was made in a plant built and tooled with Mullard are very good tubes for under $100.  He also has couple of American made ones that are similar priced from Sylvania and GE.  If you just need one really good tube that will be the standard for comparison just buy a Mullard from him and be done. They have climbed to around $200 in the last couple of years.  Buying 5AR4's on Ebay is a serious crap shoot.

Stick to the American, British and Japanese made back in the days of yore! Current production Czech, Russian and Chinese may have reliability/longevity problems. No need to "tube roll" for the 5AR4/GZ34. The music signal does not pass through the rectifier tube. 

@russ69 oops, I forgot about the whole tube hoarding thing. And I wasn’t even thinking about it along those lines; ever since I bought that pre I’ve been considering tube upgrades and a spare rectifier in case the stock one takes a crap, so I wouldn’t be down, but I see what you mean.

@jackd okay, thank you for that, and I will consider Andy.

@jasonbourne52 I am confused on that; I understand that the rectifier tube is not in the signal path, but then I have read people talking how a different rectifier tube improved their unit’s sonic performance. As an example, I think I remember a blurb from Uncle Kevin talking about a rectifier tube upgrade for that tubed Prima Luna CD player he sells on his site. As I said, I am confused on that subject.


Sure it does. All the signal does ultimately is to modulate the power supply DC.

The music signal does not pass through the rectifier tube.

Andy's got a 70's Sylvania that he likes that's the same price as the Matsushita so if you want to try two to see if you hear a difference you could buy those two for less than the price of one Blackburn Mullard.  Be warned though that Andy is way behind and Brett's stock of 5AR4's is wiped out. I've got two of the Mullard's and one Matsushita and I have tried with two different preamps to hear any appreciable difference and couldn't. The Matsushita's are that good and should be. 

     +1s, for those that recommended NOS Mullards as the go-to, for tube rectifiers.                       Especially: look for those manufactured in the Blackburn plant.

     In SS, linear power supplies: upgraded rectifiers and regulators, often makes some of the most audible and dramatic improvement in presentation.     The same applies to tube components, BECAUSE (in every gain stage):

"All the signal does ultimately is to modulate the power supply DC."


     Keep in mind: there's a plethora of variables, between that 5AR4/GZ34 and what you ultimately perceive (media/components/room/ears/brain/perspectives).

                  OH, and: NEVER accept info, from a bogus* Intelligence Operative! 

                           *What they offer will typically be in character 

                                  Happy experimenting and listening!

I've tried a variety of 5AR4/GZ34 rectifiers, from a metal base, a fat base, to a JJ new production and a few in-between these extremes.

Audible sonic difference = zero. 

The fat base popped after a couple weeks of use.  Oh well.

I think there may be a case for differences in guitar amps but only from what I have read on those forums - their version of a tweak?

{I see that my metal base might be worth a few bucks on eBay these days..}


The first valve I changed on my SLP-05 was the rectifier. I started with stock tubes and finished with Blackburn. Day 1 and 2. I left the rest. They were matched very well.

Did it make a difference? I was going to sell the unit if I couldn’t contour the tone. It added greater detail in every region. I ordered a STR-1002-SUPER rectifier from STL. I also ordered their passive tube 15 band EQ with a STR-1001 for it. BOTH are "Super" rectifiers. I use a STR-1001 on a Decware ZP3, literally night and day.

Does it make a difference? This discussion reminds me of cables and fuses. There is the "show me", bunch and there is the "I tried it" bunch.. I’m in the latter. Everything matters, even driving home with the window down before a listening session.



I have a Cary SLP 05 too and have used several different rectifiers after the stock Sovtek failed after three months and took both fuses with it.  

I rate the Sovtek as OK sounding and poor on reliability. 

I tried a Gold Lion and it was a mixed experience. Good dynamics but poor transparency and detail.  

For NOS I tried an off label Amperex and it had quite a bass punch but the treble was not refined.

Next was a Mullard f31 and it was excellent but not quite as good as the Mullard f32 which is cheaper and easier to find.  

The NOS Mullard f32 can be found on ebay under a variety of labels that Mullard made them for, e.g. Haltron, RCA and Westinghouse.  

There are a number of very knowledgable and trustworthy tube guys on ebay and they have served me well for NOS rectifiers and 6SN7 tubes for my Cary. 

The Mullard f32 sounds so much better in my system than any others.  Speed, dynamics, transparency and seperation, refinement, bass, midrage, treble, etc.  Reliability is by all accounts a last a life time purchase, mine has lasted 9 months and going strong. 

Mullard NOS GZ34 / 5AR4 f32 date code.   If you keep looking you should be able to find an unused version for -$150 or so.  

i still have quite a stash of nice old stock 5ar4/gz34 (uk holland japan) so if folks are desperate for a few of them i may be able to assist, just pm me... only in usa or canada please - i am not currently using gear that runs these...

i had accumulated quite a few these from the 90's and 00's when i was running my wavelength cardinal se amps (one in each mono block) so being the hoarder i am i stocked up way back then

I only use Andy of Vintage Tube Services.  Due to high demand (panic) he is running 2 to 3 months behind in filling orders but really knows his stuff and has never let me down with superior, fairly priced tubes. 

After extensive rectifier rolling in my SLP 05 I settled on 1959 Mullard Fat Base GZ34/5ar4 rectifier tube. 

Andy is real good. I would recommend doing a browser search for DubStep Girl’s Massive 5ar4 Shoot-Out. It is comprehensive and has her comments on the sonics of each tube. I have a number of these rectifiers. My fav, which is not a direct equivalent, is a GEC u52. I’ve had them as brown base and black base. I own several different old Mullards, including a NIB/NOS Philips/Miniwatt metal base- it sounds dramatically different than the GEC.

Some of this is probably due to the circuit, so I’d think you’d want to compare notes with somebody who has rolled using at least the same component. In my case, it was an Allnic phono stage with outboard power supply.

Thank you to all for suggestions and information.  I have made some notes and I put some 5AR4s on my ebay watch list so that I can find them easier if I decide to pull the trigger.  I also went back to upscale audio and I clicked on a 5AR4 to rad the blurb, and once again, all I got was Uncle Kevin's screaming face telling me not to buy tubes.

@whart I am about to do a search on that.  Thanks.

How much money do these mainstream rectifier tubes cost currently? I got off this train about 3 years ago when I bought a separate power supply with two 2.5 volt rectifier tubes that crushed all of these mainstream rectifier tubes for about $10-20 per tube.

      Not certain about many of the NOS rectifiers, out there, but: a Mullard Blackburn, GZ34, in pristine condition, will always bring above $150, from what I've seen of late.

      One reason for the demand and price, is the presentation, which (of course) is a matter of the palate.

      Another huge one: typically, the tube will still be testing GOOD, long after the first purchaser has expired.

     I'm sorry, "...VALVE..." (in case there are any Brits in the audience).

Another huge one: typically, the tube will still be testing GOOD, long after the first purchaser has expired.

@rodman99999 ’s point is the key one here, as far as i am concerned - when rectifiers fail, they usually do some ancillary damage to the circuit, big or small - so to me the most compelling case for these old stock 5ar4 is their tremendous durability...

i myself went through a period using dan wright’s modded cd players, which in turn use his sweet sounding outboard power supply based on the 5ar4 rectifier... these were initially shipped with the grim sovtek 5ar4, two of which failed over the course of the first 12-18 months, and i got tired of the smell of electrical components burning, then shipping to darn ps back to dan in washington for repairs to the pcb

Rectifier tubes drop the B+ voltage by different amounts. 5AR4 vs. 5V4 vs. 5U4 vs. 5Y3/80 vs. ... and they are rated for different current handling. Find a copy of Vacuum Tube Valley and read the article/survey of different rectifier tubes. Changing the B+ voltage in a tube circuit will also change the various operating parameters in the circuit. That is why it is best to stick with the designer's choice of recrtifier tube. Otherwise performance will be compromised! 


There is NO music signal passing through a rectifier tube. Unlike an output tube! All a rectifier tube does is take a pulsing AC voltage and smooth it out before passing it over to some capacitors and/or a choke. Capesce?

Or four diodes can be used in a bridge configuration to replace the rectifier tube. These have the advantage of greater current handling, unlimited life and zero voltage drop. Plus way cheaper!

                                                      One more time:

     In SS, linear power supplies: upgraded rectifiers and regulators, often makes some of the most audible and dramatic improvement in presentation.     The same applies to tube components, BECAUSE (in every gain stage): what the signal does is modulate the power supply's DC, into a stronger signal, until it ultimately reaches your speakers and ears.

                                    iow: You're listening to your power supply!


                                                       (of course not!)


Post removed 

According to Cary Audio:


If you have not had it done to your favorite Cary Audio piece, the Hexfred option makes an awesome difference! Hexfreds are high speed low noise rectifiers and replace your existing standard rectifiers in the power supply. You will notice more speed, air, detail, imaging and tighter bass, yet a cleaner clearer sound quality. The Hexfreds help to provide a cleaner, faster DC voltage which shows up very noticeably in the sound quality. There is one more layer of hash and hardness (noise) that is removed so that you can just enjoy the music! Bass is faster with more details and the midrange and highs are cleaner and clearer. You will hear more detail with less bite.

     From those that I've spoken to, component designers/manufacturers are well aware, whatever active gain devices* they choose to incorporate in their components: the quality of presentation will be directly proportionate to the quality of the DC *they modulate, as controlled by the signal they're presented.

     Note the number of times, "power supply upgrades" and, "HEXFREDs" are mentioned, in the following upgrades/paths/offers.    Bybee Rails are another power supply upgrade/tweak, btw.



     Odyssey used to offer HEXFREDs (ultra fast/ soft recovery) as an upgrade, but: now, just as a standard parts.


                                            Happy listening!

Bah, humbug, snake-oil!

I went ahead & pulled the trigger on a couple of vintage 5AR4s (a UK Amperex and a Hitachi) on ebay. I bid on a couple of Mullards as well, but I am not planning on going any higher and there are still a bunch of days left until those bids close, so I completely expect to be outbid.

Post removed 

@immatthewj -

     It’s hard to go wrong with Amperex, regardless of the context.

     When you receive yours: look for date codes like: F32/B4J1 or: F32/B4H5, etched into the glass.    Also: for a hole in the guide pin.

     Those would indicate that your Amperex was manufactured by Mullard and rebranded.

     Many of the better tube companies rebranded/sold Mullard’s wares.


                                            Enjoy the journey!

dutch made amperex are every bit as good as uk made, though heerleen/dutch production volume was earlier and in smaller numbers

uk made gz34’s were sold under many many names - iec, rca, h-p, sylvania, even realistic/radio shack, rogers (canada), siemens, miniwatt and so on...

I have an amperex and it sounds good.  just a bit of a bass peak that can be annoying and slightly ill refined treble.  

the stock sovtek sounded better imho.  

keep an eye out for an f32 mullard or made by mullard.  

I have an amperex and it sounds good.  just a bit of a bass peak that can be annoying and slightly ill refined treble.  

the stock sovtek sounded better imho.  

not sure what unit/gear you are using, but this doesn't seem right... might be your amperex rectifier is bad

the sovtek 5ar4's are grim, compared to properly working uk or dutch real deal ones (my experience from modwright gear/tube power supplies, wavelength, cary, primaluna amplifiers)

would say it is definitely worth your trouble to try another one

Nope. The smoothing is done elsewhere. Rectifiers also introduce voltage sag, modulation, harmonic distortion and switching noise. 

All a rectifier tube does is take a pulsing AC voltage and smooth it out


the UK Bugle Boy arrived today.  I can not find any actual ETCHING in the glass, just what is printed on the glass.  It does state that it is a Bugle Boy "MADE IN GT. BRITAIN" and in very light, hard to read print, underneath the "5AR4-GZ34", it says "B5L2."   In the approximate middle of the glass, underneath the "Amperex" logo, is a "66" with a "14" underneath it. And there is a hole in the guide pin.

I am going to install it right now.

     The hole in the pin is a giveaway and with the code’s starting with a B: should be a Mullard from the Blackburn plant.

                How many teeth are there, in each side of the top mica?

Cary could have made a removable access panel for the tube in the side of that power supply.

But, @rodman99999   I should have read your reply more carefully before I took it apart again and then put it back together.  I seem to believe in measuring once & cutting twice.

However, if I counted correctly (& I did actually count twice) there appear to be ten total teeth in the top mica (so I am ASSUMING) that there are 5 per side).  The top mica is a shiny silver like color.  The bottom (mica?) is clear and has two semi circular notches in it.  As does the top shiny mica, 2 notches with the teeth in between.

Does ten sound right?  I was bitching about Cary not putting an access panel in it, but it's really not that hard to get down and remove the bottom, so I can easily look at it again.  I've got the rectifier tube warming up right now, but I haven't lit all the other tubes yet.


    Some have four, some seven, but: forget the notches.

                                Not important!

                               How's it sound?


     Here's something you may find interesting.

     There are some Mullards compared, for plate structure, etc and the last two both have the 5 tooth, top mica.

      Just a way to close in on the valve's year, but: not nearly as important as the condition, strength and sound.


I went through the same exercise with a Modwright Pre-Amp w/ outboard power supply.  After listening to a number of NOS options I ended up with a metal base.  It was expensive but had the most positive impact to SQ of any tweak i’ve done.   I think it was a ‘56 or ‘57.   

@rodman99999 thanks! I did a quick skim of the URL you posted & I quickly caught this from one of the people who answered on one of the forums:

The Mullard GZ34 has a hole in the guidepin and the upper micas have 5 teeth per side. On a new NOS Mullard the flashing extends down BEYOND the level of the mica.

so I am not sure what "the flashing" is referring to, but I am petty sure I must have 5 teeth per side. . . .

Some have four, some seven, but: forget the notches.

Not important!

How’s it sound?

Well, it sounded good tonight . . . but here is the thing--it was not sounding bad before, and I frequently confess to not possessing The Golden Ear (& I don’t intend any sarcasm whatsoever with that term). I seem to hear incremental changes when they get worse more than I do when they get better. When things get incrementally better, I seem to get more comfortable & relaxed . . . but the thing on that is: it takes a while for me to fully realize & appreciate that feeling. I am absolutely horrible at doing A/Bs (unless what I am comparing is just radically different), & therefore I hate doing A/Bs. It would be hard to A/B rectifier tubes in this pre, as it would require getting it down & then pulling the bottom cover off.

But: I did like the way everything felt tonight.








                                    Just relax and enjoy the music.

     Its a lot easier to obfuscate issues with a quick A/B comparison, than over the long term.   That, "comfortable and relaxed...feeling", in YOUR listening room, over the long term, is ALL that's important.

      Keep in mind: valves typically take something like 50 hrs of use, before they sound their best.    Some will claim such is a result of ones ears adjusting.   

      This is a verbatim quote, from a letter Brent Jessee sends, whenever one buys valves from him: 

New tubes need a break-in period before they can fully exhibit their true sonic character when used in audio circuits. Preamp tubes especially benefit from a good break-in. This period may vary widely, but NOS vintage tubes usually need at least 48 hours of use, sometimes up to 100 hours. New current production tubes need 24-48 hours typically.
Good break-in can be accomplished by either leaving your tube unit turned on in a no-signal condition for 2 days, or you can just enjoy the tubes for several hours each evening and they will be broken in after several weeks. New tubes, especially NOS vintage tubes, may sound a bit edgy at first, but after the break-in period will mellow out and sound wonderful."

                                             Enjoy your jams!

 btw: That, "flashing" mentioned is the main component of a tube’s gettering system.

                                         Here’s some info:



I need to stop visiting ebay when I’ve been drinking; I just won a bid I placed on a Holland Amperex 5AR4. This one was not branded as a Bugle Boy.