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Need some advice on compatibility issues with different types of rectifiers. I want to substitute a GZ37 or 5V4G or 5R4GB or 5U4G for the standard 5AR4 in my 300B amp. What options do I have? Suggested types? Thanks.
Follow Ups:
Quite a heated discussion below...My advice is just get another 5AR4....but just buy the SOVTEK 5AR4 that was made recently. Whatever you get you get value for money..I've got one in my tube amp now. It's been in there for 24 hours now...and no problems at all ;-).
If someone like Gordon Rankin says they sound superb.. I believe him.There are 2 way's to go IMHO. Buy the best money can buy knowing that quality like that is propably not going to come around ever again. Or just buy good value for money stuff from the people that still make the darn things..You see.. that way future generations can also enjoy the sound of tubes. Because if everyone just bought NOS no-one would bother to making these things anymore. Just my 5 cents worth.
And for the cynical people out there. No I'm not posting this so I can hog all the NOS for myself.... :-) If you're filty rich just buy both old and new tubes and post us your findings...
I'm a lucky guy. A good friend just stopped by to drop of a beautiful Great Britain made Bugle Boy GZ-34. He found it at a local TV repair shop and paid $7.50 for it! I owe him BIG TIME.
Codes:
f32
86C4I would not trade it for a box full of new Sovtek 5AR4's!
My point here is that these are not hard to find, they can be had for not all that much if you buy used, they last a long, long time, and are nearly indestructible. I have purchased about 15 over the last year at about $20 average price and I am yet to buy one and have it sound bad. That includes pulls, burnt glass, you name it. They all sound great.
And yes, the Matsushita ones are also a good deal, and sound great as well. I have two that I paid about $15 for.
You are lucky.Maybe in the States you can find them easily.
But not over here in Holland. I to would love to hear NOS, ya know so I could hear what everyone is raving about. But because I can't get them for reasonable prices, I can't be bothered at all. I've been a hifi freek long enough to know that all that glitters is not gold.
Cheers
American designation 5AR4, European GZ34 are one and the same, and there is no proper substitute for this unique, indirectly heated cathode type-- the Mullard version is perhaps the best rectifier tube ever. Definitely do not sub 5R4, 5U4 or any filamentary cathode type; they produce DC almost immediately which could cause cathode stripping on your precious 300Bs (and any other tubes) Micronetics in Switzerland (Tubes@mnfoc.com)is a great supplier of this and many other scarce tubes. I e-mailed them yesterday; they have nearly a thousand (!) Mullards, as well as hundreds of Valvo and metal-base Philips GZ34. The Mullards are $65 per-- considering the alternative of paying $14 for a Sovtek which will never come close to the Mullard in performance and will last perhaps 20% as long as a Mullard, $65 is not too bad. Ebay is another source, as is Brent Jesse Recording online. His prices are great and he is a decent guy. Andy Bouwman of Vintage Tube Services (616)454-3467 may also have these, but his specialties are VT231/6SN7, 6922/7308, and ECC European series tubes. Hope this helps, Chris
There are many varieties of Mullard branded GZ34/5AR4, ranging from excellent (early versions, particularly the military fat brown base version) to acceptable (70's versions).The metal base GZ34 also came in a number of versions. The one with the stellar reputation is the double D-getter version.
Micronetics sells a version with a single round plate getter. These were made neither by Mullard in the Blackburn factory or by Philips/Amperex in Holland, from the date codes, they appear to have been made in the Philips Scarborough, Ontario factory. They, unlike Mullard or Amperex production, do not have the characteristic seams on top and the getters are a murky caramel color.
Unfortunately, these sound about as good as the common black base US GE 5AR4 - average, not particularly special.
That's why Micronetics sell them cheap - for metal base - or, IMO - expensive for domestic production.
Well, I guess I jumped the gun. There is absolutely, positively no version of the blackburn Mullard with cross-hatch glass. Those would be 70s Matshushitas. As in Japan. If that is what you are used to, its understandable that you find them mediocre. Try a real Mullard someday. Cheerio!
No, not cross-hatch seams - a straight faint seam across the top, the hole in the guide-pin, and the silvery getter.I have no Matsushitas. But people tell me they don't sound too bad.
When you get those Micronetics jobs, you will see the pround plate getter, murky caramel colored getter, and the absence of a hole in the guide pin(which is only there on UK production).
You will also note the factory code. You will also see the top of the glass has not only no seams, but a slightly pointed shape.
Of course, because I know real Mullard sound, it is easy to tell even without these clues, but you may find them perfectly fine.
Robert: Thank you very much for clarifying this... before I sent any money off to Switzerland! Inmates like yourself who have the real low-down are what makes this forum great! Thanks again, and all my best. Happy listening! Chris
Thanks for your help Chris and others. Very informative.
Chris, what do you mean by cathode stripping. Have not heard that term before.
TD-- glad I could provide some small measure of help. I make no claim of being an expert, and am patently unafraid of being proven wrong. That's how I learn. Beware of people who never post ANYTHING except a self-indulgent, ego boosting, security-blanket post that points out small inaccuracies in information that is by and large accurate-- their points almost never have anything to do with the matter at hand, and they never stoop to answer a legit question, only to self-aggrandize. Cathode stripping, now that I've stepped off my soap box of self-righteousness, occurs when filamentary rectifiers like the 5U4 or diodes are used instead of indirectly heated types like the GZ34; the diodes and 5U4 types apply B+ DC voltage to the tubes before their own cathodes are properly heated, and as they warm up, the strong attraction of the plate will strongly draw electrons from the small hot spots on the cathode, sometimes causing small amountsof the powdery cathode chemistry to literally blast off from the surface. Ouch! Hope this helps; I always try to help those with legit questions, even if I'm only making a good-faith guess. My errors are usually highlighted by the supercilious set, so one way or another you'll get the correct info. Happy Listening! Chris
Chris, you claim that you are patently unafraid of being proven wrong, but go on to rant quite obviously about my post above where I point out that you are giving out wrong advice. I think you DO quite clearly from this post have a problem when your inaccuracies are corrected. It is NOT a small inaccuracy to recommend to another newbie that he get some of the Micronetics GZ34's which are quite clearly not the ones with the rep among those who know these tubes. There is a HUGE differences between a Blackburn produced Mullard and a Canadian produced one.Coming back with both knees jerking to say that Mullards do not have cross seams, so the Micronetics ones are the ticket and I have Japanese is pretty stupid. I just checked ALL my metal base GZ34's ( 8 of them, all in original boxes) and they all have the seam on the top, the hole in the centre guide pin, the double-D getter, the silvery getter, and the right date codes. Obviously, it is you who have the fakes - not a surprise. Been buying from Bugleman again?
I don't doubt that you are making a good-faith guess, but you also seem to like to jump in when newbies ask a simple question with wrong advice, and unfortunately, because you position yourself as an expert and defend that as you did above, people without experience actually then go out and spend their money, so good faith or not - please get the facts BEFORE you post.
It's not good enough to rely on the experienced people to correct your errors - if you don't know in the first place, ASK instead of taking a wild guess and posting as fact. We of the "supercilious set" sometimes will jump in when it gets particularly silly, but sometimes stuff is so far off the mark people don't even bother to try.
For a variety of reasons, none of the types you mentioned is a good 5AR4 substitute. The GZ33 is a good 5AR4 substitute.The 5V4/GZ32 could be OK, IF its maximum ratings are not exceeded in the application.
Eli D.
Gz34 is the perfect replacement of 5ar4.
You have no other choice.
5u4, gz37 and so on do work well, but show a lot of voltage drop.
which is not neglectable.
5U4G does NOT work as a 5U4G sub, as it draws 50% more current from the power transformer than a GZ34 !!In a LOT of amps this will quickly cause the power transformer to be overheated and killed.
In an amp designed around 5U4G, it is possible to safely sub many others - GZ34, 5R4, etc.. but the issue of voltage drop is correctly pointed out, in some cases, this may produce a sound more to your liking, in others not.
The issue of cathode stripping the 'expert' above describes is really only an issue with SOME solid state rectified amps, particularly those with very high plate voltages on the tubes and no SS delay in the start-up to the heaters. Those produce the roughest start, and over time the cathode coating will 'flake', leaving a deposit which will cause the tube to become extremely - unlistenably - noisy, even though it will test very well. On indirectly heated rectifiers, such as GZ34, the start-up is softest because of the inherent delay in applying B+, however, even with a directly heated rectifier (such as the 5U4G) there is a lesser, but still present, delay in B+ as the rectifier warms up. But the danger of cathode stripping is really present primarily in poorly designed solid-state rectified amps.
Heavy duty. Doesn't have the sag of a good Mullard (if this is going into a guitar amp---that is an important feature of the Mullard).But, for hi-fi amps---a good NOS 60-70's big Sylvania is a good rectifier. Watch out for clearance of the side (side to side). Try to catch these now, as the prices are reaching Mullard range.
I've used TFK made GZ34 (early 60's). Black base and no serations on plate. Slightly taller than the Mullards, of the time. Great tubes---but, I kinda think NOS is extinct.
You waht to know something funny? I've found 1/2 used 1960's Mullards that give steadier voltage and sound better than brand new Chinese or Russian 5AR4s. Well, maybe not THAT funny.
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