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5AR4: Sovtek, Shuguang, or other?

Nirky

Nirky

Active Member
I just purchased a Sherwood mono EL84 amp which uses a 5AR4 rectifier, which is missing.

I know from research that the Mullard (around $100-150) is the preferred 5AR4.

However, cost is a big consideration. So I'm looking towards the new production Sovtek & Chinese Shuguangs. Are there any other reasonably priced 5AR4 rectifiers I should consider, and has anyone had any experience with either of these new tubes?
 
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Here's my documented rectifier failure/replacement timeline for my fully restored Scott LK-72A:

Unit was placed into service on July 28th, 2006.

JJ GZ34S - arc'd at 78 hours (38 days) after installation (Sep 5th 2006). Arcing noises became present intermittently well before that time. Tube was scrapped (then, I found out it was under warranty for 90 days.) DOH!

Installed on Sep 9th 2006 - JJ GZ34S - arc'd at 65 days after installation (Nov 12th 2006). Noises actually became present intermittently after about two to three weeks. Tube was kept after replacing.

Installed on Nov 14th 2006 - Sovtek GZ34 Cryoset - arc'd at startup!!! (same day) then appeared to be fine with some intermittent noises for 93 days (Feb 15th 2007). Noises increased and started about 25 minutes after startup until it eventually made those arcing noises almost all the time.

Installed on Feb 19th 2007 - JJ GZ34S - arc'd at 42 days after installation (Apr 2nd 2007). Noises were occasionally intermittent during that time. Tube was scrapped since it was happening nearly all the time after a month of use, and sometimes started making noises about 15 minutes after startup. Also seems to be happening a bit more frequently.

Installed on Apr 10th 2007 - Sino 5AR4 - Noises noticed 4 hours after installation!!! Never actually saw it arc, but I definitely heard it. Rushed into family room to turn off the amp. Tube was removed after cooling thrown into the metal waste bin at my local landfill the following morning. . .with extreme prejudice.

Reinstalled on Apr 11th 2007 - The Sovtek GZ34 Cryoset is currently back in the amp until replacement arrives. Noises are sometimes now starting only about 10 minutes after startup, and are more frequent.

April 27th 2007 - Sovtek GZ34 - Quiet for four days, but now noises are more frequent and can start happening as soon as 10 to 15 minutes after startup.

After putting a 1961 Mullard 5AR4 in there, the rectifier arcing stopped. It has been fine since I pulled all the new production tubes out and replaced them with vintage.

YMMV

. . Falcon
 
The newer 5AR4s' are just too spotty on quality to form an opinion. Any of the NOS varities are better IMHO. 5AR4s' were generally manufactured from Mullard- Great Britain, Sylvania had a big bulb USA made, GE had a USA made small tube the size of a 5Y3 and there was a Japanese production with various brand names on them but ID'd by a cross seam on the top.
If you don't mind the brand name of "Mullard" not being on the tube, be patient as brand name varibles show up on you know where.
 
Nirky said:
I know from research that the Mullard (around $100-150) is the preferred 5AR4.
Click to expand...


dude...its just a rectifier. A properly designed amp should NOT show any change in sound with different rectifiers.
What does change the sound, is internal resistance (which varies by tube), and that affects how much voltage the tube drops and/or how the amplifier will respond to transients. Maybe mullard had different internal specs, but I wouldn't go insane on a rectifier tube. Just get one thats gonna be reliable. JJ makes a 5AR4 repro that can be had for $15.
 
Scott LK-72 took 7591A tubes, if I am not mistaken. That's a much bigger tube than an EL84. The current demand on the rectifier is going to be much lighter with a mono EL84 amp, and I suspect even the Russian or Chinese cheapies will hold up just fine. I used a Sovtek in my HK A230 amp - it runs four EL84. It never gave me any problems. I've been running "Ruby" branded 5AR4 in my Dynaco Mk3 amps. I'm betting these Ruby tubes are Chinese, probably Shuguang or Sino. The Mk3 draw about 160 mA from the power supply, and the Ruby have never arced or done anything bad.

Thinking about it more, a 5AR4 seems like overkill for a mono EL84 amp. How many pairs of EL84 are on this thing? Is there supposed to be a tuner section attached or something?
 
FalconEddy--Wow that is really depressing, and seems to be a strong indicator of the quality control of new production GZ34's. I was thinking slam-dunk I'd choose a cheaper new production tube, but this makes me think twice.

Thespeakerdude8--
dude...its just a rectifier.
Click to expand...
dude I know but there has to be a good reason the NOS rectifiers are selling from $75 and up, with the most prevalent GZ34 being the $150 Mullard.

Ty--This amp is the S-1000 II and I'm finding out it was made with at least 3 variants, mine uses a quad of EL84's. Another uses a pair of 7591's.

Thanks for the info so far, keep the info coming! I knew about the JJ problems with arcing, but didn't know about the Sovtek & Chinese issues with this rectifier.
 
I'm using a NOS GE 5AR4 in my Supratek preamp, and it definitely improved the sound over the Sovtek that was in there (believe it or not). The GE smoothed out the sound, as did changing the regulator tubes from the stock Sovteks to a pair of real Tung-sol 5881 (got them used, NOS is $$$$).

The NOS GE is a very nice tube, and is easy to spot - it has bright copper sides on the plates. It will last a very long time, is cheaper than the Mullards, and as I said, it did make a positive change in the sound.
 
I'd suspect after SEVEN failing rectifiers that something is wrong with the amp somewhere. Seven different tubes arcing and acting up?.... hmmm.
 
Just as an aside while I know that Mullard's usually go for 100 to 150 you can find them cheaper sometimes. I recently purchased two at once off Ebay for 80 for two new testing ones. I think as someone said that they were labeled something else althought the labels were almost gone except the Made in Great Britain but they had the Blackburn factory codes which is what is important. So if you are patient and watch ebay you can get a good deal as I have more than once on the 5AR4. In fact in the four I have purchased the most I have ever paid was 65 dollars and those were all fairly recent purchases.
 
magmod93 said:
I'd suspect after SEVEN failing rectifiers that something is wrong with the amp somewhere. Seven different tubes arcing and acting up?.... hmmm.
Click to expand...

Welcome to AK.

Yes, one would think that, wouldn't one?

Back when this was an issue, I spent MANY days trying to track this elusive problem down. There was an intermittent slight soft crackling noise that had a very distinct electrical arcing sound to it. I posted the sounds and issues here on AK. We even thought it may be arcing in the windings of the power transformer at one point.

After going through the entire amp one circuit at a time, I had proven that the amp was fine and the restoration (and modifications made) were exactly as they should have been.

The culprit(s) turned out to be the new production JJ 7591S power tubes I was using. After a couple of days, the Mullard GZ34 won the battle. One of the 7591S's brightly arc'd and died. Its replacement (another JJ) started motorboating after a couple more days. I decided to run the original Westinghouse tubes, and the noises stopped. All arcing stopped.

I was also able to find a pair a JJ 7591S's that weren't complete crap and successfully used them for a few months until I saved up enough money to buy a NOS quad of both GE 7591A's, and Westinghouse 7591's.

It wasn't a grid resistor over-value issue because I had installed an adjustable bias control circuit to give me full control over the negative feed voltage to those tubes. Plus, I had their current draw cranked down to 28-30mA each.

So, after I'd determined it was a quality control issue with JJ, I swore it would only be vintage tubes for me from that point on.

. . Falcon
 
Nirky said:
FalconEddy--Wow that is really depressing, and seems to be a strong indicator of the quality control of new production GZ34's. I was thinking slam-dunk I'd choose a cheaper new production tube, but this makes me think twice.
Click to expand...

Actually I've told Falcon before something is wrong with his amp... Yes the Mullard 5AR4 is much tougher then any current production tube but there is absolutely no reason he should experience the problems he has repeatedly with modern production tubes.... Maybe the problem in his amp is to such a small degree that the Mullards better construction is enough to mask the proeblem. I have pretty much stuck with the Sovtek over the years, I have literally hundreds of them out in the field in Scott, Fisher and other vintage amps.... Most customer get 2 or 3 years of trouble free service out of the light load of these amps in properly working order.
I also use the Sovtek and the standard tube in my VRD mono blocks which place a very servere load on them at statup without unreasonable failures...they usually last one or two years in this application...
One thing I did notice is he mentioned Cryo treatment.... Stay away from Cryo treated tubes IMHO.... Tube consist of glass and various metal types and solder connections... All these materials have differnet expansion and contraction rates... Sub arctic freezing will cause server contraction of all these materails, than place then in service and heat causes maximum expansion... These can and does cause fractures especially in the solder connections inside the tube which equated to early failure....
 
I kept wasting dollars on those crappy tubes, so finally decided to run my
LK-72B on a G.E. JAN-CG-5R4GYA. Did this for ten years.
Military-spec. Direct-heated [no slow warm-up], but it never hurt my precious amp.
Finally found a Mullard 5AR4. Used that for a very long time until I
sold the amp. Kept the Mullard [and the G.E.]. Both top brands of tubes.
Both too precious to part with.
I do agree that different rectifier tubes sound different, and most sound better than silicon diodes.
[Not for sale]

Seth
Forever Analog and Covered In Parrot Poop
 
NOS Valves...you make some valid points and I respect your opinion. But I must quote you on something..
"Most customer get 2 or 3 years of trouble free service out of the light load of these amps in properly working order. "
Me: If you use decient NOS tubes they will last much longer! I feel it is unacceptable to replace tubes every couple of years because this is what we have to settle for. Maybe we will see the day when better quality rectifiers will be available.
 
Cryo-treatment of metals is apparently not all snake-oil:

http://www.straightdope.com/columns...arts-sports-equipment-and-musical-instruments

I can't say whether it is appropriate (or effective) for vacuum tubes, but it sounds to me like, if it is to be properly implemented, it should be executed on the internal structure of the tube before it is sealed in the glass envelope...although the heat involved in sealing the glass may take away any benefits of the cryogenic cooling. Hmmm...

--Bob
 
I think we can agree that cryo is not the issue at all. There are other cryo threads out there you can do all the pros & cons.

These new production tubes seem to fail at an alarming rate. Reasons unknown. At best they only last a few years. At worst they fail immediately. So it seems kind of a gamble if you want to try out a new production GZ34 rectifier? Only good option seems to shell out some bucks for a NOS or used OS tube.
 
It's good to hash these things out, BUT let's keep it civil!

Some feel the CRYO treatment helps and is warrented, others find it not the thing to do.

The rectifier deal, same same, some have used the new ones and are not happy with how
long they last and suggest then the use of an old style rectifier, to each his own.

Discussions are good, but out an out calling someone an idiot for believing one or the other
does not fly here, keep your discussions/oppinions/experiences friendly.. :)
 
Kegger said:
It's good to hash these things out, BUT let's keep it civil!

Some feel the CRYO treatment helps and is warrented, others find it not the thing to do.

The rectifier deal, same same, some have used the new ones and are not happy with how
long they last and suggest then the use of an old style rectifier, to each his own.

Discussions are good, but out an out calling someone an idiot for believing one or the other
does not fly here, keep your discussions/oppinions/experiences friendly.. :)
Click to expand...

Thank you, Kegger!

That was my very first experience here being called 'pathetic' due to voicing my well-educated beliefs; which came at quite a surprise since I appear to have been the very first person that formally welcomed him to the AK site.

Perhaps the self-proclaimed S.E.B. in the Custom User Title area wasn't intended to be humorous.

This, too, shall pass.

. . Falcon
 
Antique Electronic Supply sells a 5AR4 that's not very expensive and I haven't seen any negative comments when it was used for guitar amps. I can definitely say that the Sovtek version puts out more B+ than the amp needs/wants/should see, though. I finished recapping my '58 Bassman and the B+ was way high. It's higher than the schematic calls for but it's still within the stated +/-20% voltage range stated on the diagram. I'm using a 5U4 right now and it's working well.

I also have a Fender Vibro Champ that came to me with a Sovtek 5Y3 and it took out the new can cap I bought after the re-cap job. The B+ on that was 505VDC and it's supposed to be 355VDC at the first node. I put an old big bottle Tung Sol 5Y3 in and all of the voltages are really close to the original schematic.

I'd like to see more consistency in tubes. They're getting better but they still aren't where they were.
 
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