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    Choices in rectifier tubes for VTA?

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    LEVLHED

    Posts : 21
    Join date : 2009-10-26

    Choices in rectifier tubes for VTA?

    Post by LEVLHED on Wed Nov 18, 2009 10:31 am

    I've been throughly enjoying my VTA ST-70, recently picked up a Dared SL-2000A preamp and it seems like the perfect match. Now I'm looking into trying some different tubes.

    Since I've already got some Mullard input tubes order and I've got driver tubes on a few Christmas lists (Smile) I was wondering what peoples experiences are with different rectifier tubes for this unit.
    Mine currently has a Sylvania. I have no idea how it compares to the myriad of other choices out there.

    Bob Latino
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    Re: Choices in rectifier tubes for VTA?

    Post by Bob Latino on Wed Nov 18, 2009 11:14 am

    LEVLHED wrote:I've been throughly enjoying my VTA ST-70, recently picked up a Dared SL-2000A preamp and it seems like the perfect match. Now I'm looking into trying some different tubes.

    Since I've already got some Mullard input tubes order and I've got driver tubes on a few Christmas lists (Smile) I was wondering what peoples experiences are with different rectifier tubes for this unit.
    Mine currently has a Sylvania. I have no idea how it compares to the myriad of other choices out there.

    Hi,

    Probably the best GZ34 rectifier tube ever made was the Mullard GZ34 but they are expensive at $50+ (used) and $150 or so NOS. Your USA "Sylvania" could be a Mullard. Look on the bottom of the center pin. If there is a little hole in there it was probably made by Mullard. Your Sylvania could also be an older USA production tube which were usually very well made. Your Sylvania is probably a better tube than any GZ34 produced today.

    Of the current choices out there for newer production tubes there is the JJ, the Sovtek and the Ruby GZ34. Of the three tubes mentioned IMHO the Ruby is the best of the bunch and seems to last longer than the JJ or Sovtek tubes in an ST-70. A friend of mine mentioned to me that a lot of guitar players like the Ruby GZ34 in their tube guitar amps.

    Bob

    LEVLHED

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    Re: Choices in rectifier tubes for VTA?

    Post by LEVLHED on Wed Nov 18, 2009 12:00 pm

    I'll check the center pin when I get home, thanks for the tip.
    Though I could also ask, have you sold any completed kits recently with a Mullard? Seeing as how I just bought this from a guy in Puerto Rico who'd recently bought it from you as a completed kit!
    I'm certain he did not replace any tubes, they are all the same ones as when he bought it.

    Bob Latino
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    Re: Choices in rectifier tubes for VTA?

    Post by Bob Latino on Wed Nov 18, 2009 12:17 pm

    LEVLHED wrote:I'll check the center pin when I get home, thanks for the tip.
    Though I could also ask, have you sold any completed kits recently with a Mullard? Seeing as how I just bought this from a guy in Puerto Rico who'd recently bought it from you as a completed kit!
    I'm certain he did not replace any tubes, they are all the same ones as when he bought it.

    Hi,

    I had a few Mullard GZ33's (not GZ34's) at one time and did sell a few out with some of the kits (at extra cost for the Mullard tube). Unfortunately I don't have anymore of these here in stock ... The GZ33 is taller than a GZ34 and is not an exact replacement for the GZ34 as it draws a little more current. I wouldn't use it in a STOCK ST-70 but it will work OK in your amp which has an upgraded power transformer. The height of this tube may also be an issue if you use a tube cage on your amp. I am not sure if a tube cage will fit on the amp with a GZ33 in there. Upscale Audio sells these Mullard GZ33's for $90 each + shipping. This is less money than you would pay for a new Mullard GZ34 - IF you can find one anywhere for a reasonable price. Most new NOS Mullard GZ34's are well over $100 each ...

    Bob

    LEVLHED

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    Re: Choices in rectifier tubes for VTA?

    Post by LEVLHED on Wed Nov 18, 2009 12:34 pm

    This would've been a completed amp that you built probably 3 or 4 months ago and sent to a customer in PR. Are you building and selling so many of these that you can't keep track of what went where? I hope that is the case!

    Lets say it doesn't have the hole that indicates it's a Mullard (which it sounds like that is likely the case), are there other date codes/etc to indicate if it's one of the older USA production runs?

    Bob Latino
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    Re: Choices in rectifier tubes for VTA?

    Post by Bob Latino on Wed Nov 18, 2009 12:54 pm

    Hi,

    The amp that I sent to Puerto Rico went out over a year ago in February of 2008 .... The ORIGINAL buyer did not buy that wired ST-70 from me recently although the person that you bought the amp from could have purchased it recently from the original buyer within the past few months?

    Sylvania hasn't made any tubes in at least 20 years. I don't know the production codes for these tubes. Maybe you can find some information on your Sylvania GZ34 if you ask the question on the Tube Audio Asylum here > Tubes Audio Asylum

    Bob

    LEVLHED

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    Re: Choices in rectifier tubes for VTA?

    Post by LEVLHED on Wed Nov 18, 2009 1:21 pm

    The seller made it sound like he'd bought it directly from you, maybe I was reading into how recent it was based on the number of hours he claims it was run. If I had to guess, this is the one you shipped 02/2008 and I bought it from the original owner...who apparently hardly used it!
    His ad read:
    For sale a used Dynaco Stereo 70 built by Bob Latino. It was built from new parts by Bob Latino and performs at its best. I estimate this unit has between 50-100 hours at the most. This one has the tube cage also which is $50 more to the listed price. I purchased this one completely assembled by Bob. Google Bob Latino ST-70 for more information.


    Thank you for your help and info! I truly appreciate it.

    LEVLHED

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    Re: Choices in rectifier tubes for VTA?

    Post by LEVLHED on Wed Nov 18, 2009 2:36 pm

    Since I'm fortunate to not only have a job, but to also have one that is about a half mile from my house, I went home for lunch to investigate. I found what appears to be a "hole" in the center pin! I'd call it more of an indent than a hole, but judging from what I've seen so far this would indicate that it was in fact made by Mullard? Sorry the pic is a little blurry, I was being a bit hasty.



    LEVLHED

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    Re: Choices in rectifier tubes for VTA?

    Post by LEVLHED on Wed Nov 18, 2009 3:11 pm

    I suppose if it were made by Mullard, it'd be marked as made in Gt Britan, not U.S.A

    Still must be a good tube though.

    Jhoman

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    Re: Choices in rectifier tubes for VTA?

    Post by Jhoman on Sun Jan 17, 2010 12:20 pm

    I found an old RCA 5U4G that appears to be in good shape. Big coke bottle glass. Has anyone used one of these in place or their 5AR4? I understand the B+ voltage is not quite as high and it will require re-biasing.

    I was just wondering if it was doable.

    Jeff

    Bob Latino
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    Re: Choices in rectifier tubes for VTA?

    Post by Bob Latino on Sun Jan 17, 2010 3:01 pm

    Hi Jeff,

    You can use a 5U4 in place of a 5AR4. The only issue you may run into is that a 5U4 has a higher voltage drop than a GZ34 and your B+ voltage will be lower which will result in the loss of a few watts of total output. I suggest a 5U4 as a BACKUP rectifier in the ST-70, ST-120, Mark II, Mark III or Mark IV. The nice thing is that you can find quality older USA made 5U4 rectifiers at much lower prices than older USA made 5AR4's. Many older tube color TV's of the 1960's used a 5U4 for a rectifier so the supply of 5U4's as used tubes is still fairly plentiful.

    As to rebiasing > Anytime you change the rectifier tube you should rebias even when changing one 5AR4 for another 5AR4 of the same brand. Each rectifier tube is slightly different from the next and will provide a slightly different B+ DC high voltage.

    Bob

    Jhoman

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    Re: Choices in rectifier tubes for VTA?

    Post by Jhoman on Sun Jan 17, 2010 3:33 pm

    Well, the RCA 5U4G coke bottle never lit up, nothing so I tried a GE 5U4GA that has dots in the shape of a D below the 5U4GA. Had to bring the bias up from .34 to .55 VDC, I really don't miss any power, actually this is the best this amp has sounded since I got it. What gives with this? I did order 2 Ruby 5AR4's and will try them when they get here, but I think I'll be hard pressed to improve off the old GE 5U4GA!

    Thanks Bob!

    Bob Latino
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    Re: Choices in rectifier tubes for VTA?

    Post by Bob Latino on Sun Jan 17, 2010 4:27 pm

    Jhoman wrote:Well, the RCA 5U4G coke bottle never lit up, nothing so I tried a GE 5U4GA that has dots in the shape of a D below the 5U4GA. Had to bring the bias up from .34 to .55 VDC, I really don't miss any power, actually this is the best this amp has sounded since I got it. What gives with this? I did order 2 Ruby 5AR4's and will try them when they get here, but I think I'll be hard pressed to improve off the old GE 5U4GA!

    Thanks Bob!

    Hi Jeff,

    The fact that the 5U4 possibly sounded slightly better may have something to do with the lower voltages of the 5U4. Possibly the amp may now have a "more rounded tone" with the lower voltages involved. Your KT88's are now being operated at voltages considerably below the level that they were designed for. If you keep the 5U4 in there you should get "more mileage" (longer tube life) out of those KT88's.

    Bob

    RichJB603

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    Re: Choices in rectifier tubes for VTA?

    Post by RichJB603 on Wed Sep 08, 2010 9:12 pm

    Would there be any advantage to using the GZ33's over the 5AR4 in a standard VTA-120 with upgraded caps? Other than it being slightly cheaper than std mullards?

    Bob Latino
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    Re: Choices in rectifier tubes for VTA?

    Post by Bob Latino on Wed Sep 08, 2010 9:25 pm

    Hi,

    No other real advantage of using a Mullard GZ33 other than they are cheaper to find NOS than a NOS Mullard GZ34. One other thing about the Mullard GZ33. It is a lot taller than a GZ34. If you have a tube cage on your amp, I am not sure that a Mullard GZ33 will fit under the tube cage. If someone is using a GZ33 with their ST-70 or ST-120 and has a tube cage maybe they could comment here?

    Bob

    RichJB603

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    Re: Choices in rectifier tubes for VTA?

    Post by RichJB603 on Wed Sep 08, 2010 9:39 pm

    I just had seen this thread and picked a pair of them up from the uk fairly cheaply and wondering if there will be much of a difference. You mentioned it would draw more current and the transformers would be ok with this, does this also mean it will output slightly higher power or does it not quite work that way?

    Bob Latino
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    Re: Choices in rectifier tubes for VTA?

    Post by Bob Latino on Thu Sep 09, 2010 5:07 am

    The GZ33 draws more current but won't give higher voltages than a GZ34. The power in your amp with a GZ34 or a GZ33 should be about the same.

    Bob

    Dynalover

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    Re: Choices in rectifier tubes for VTA?

    Post by Dynalover on Thu Sep 09, 2010 8:23 pm

    5AR4 are pricey, but not THAT big a deal. Used, tested, delivered to your door, under 50 bucks -- http://www.tubesandmore.com. They charge 50 for NOS, but are zero balance right now. Anyone try
    5Y3??

    Have not had good results with modern 5Ar4 reissues, so for me it isn't worth the money "saved". Be frugal, but don't be cheap!

    RichJB603

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    Re: Choices in rectifier tubes for VTA?

    Post by RichJB603 on Fri Sep 10, 2010 11:29 am

    I keep a pair of mullard 5AR4's on hand, but I was just looking to try something different, and if perhaps the GZ33's yeilded more power or some other benefit it would be an added bonus IMO.

    RichJB603

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    Re: Choices in rectifier tubes for VTA?

    Post by RichJB603 on Mon Sep 13, 2010 9:24 pm

    Well today I got in those GZ33's I ordered online. They appeared to be in excellent condition which I mostly expected (they were listed as NOS http://cgi.ebay.com/GZ33-CV5745-MULLARD-NOS-/260546680022?pt=UK_Consumer_VintageAudio_RL&hash=item3ca9cad4d6). I ordered two, since it seemed like a good idea at the time. This is what I found

    Overall the amp seems to be a little hotter running after a few hours of continuous play. The GZ33 now sits what seems to be about 3/4" and maybe a full 1" higher than the middle transformer. I don't run a cage on my ST-120 so this for me is a non-issue. I don't know offhand (possibly bob might?) what kind of room you have in there. Worst case (and you wanted to be able to use one of these) you could tape it fairly well and use a hole saw to cut a nice hole in the cage with a drill press or something like that perhaps and it might look 'ok'. As much as I don't believe this should/could make the amp sound any different there seem to be some small tonal differences. When listening to some jazz (Somethin Else, Miles Davis/Cannonball Adderley) it seemed a little brighter on the high end, cymbals, trumpet, and other similar instruments seemed to have more 'bite' although I wouldn't necessarily equate that with a harshness, just sharper and in a good way. Perhaps this is some side effect of the sag characteristic of this tube thats different than the GZ34? I did bias things a little over (.560 vs .550) or perhaps it's just a factor of biasing things a little high?

    davidness

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    Choices in rectifier tubes for VTA

    Post by davidness on Fri Sep 17, 2010 1:02 am

    I just received one of those NOS Mullard GZ33, and agree with everything said above. I like the sound of it. I also feel 'safer' with this tube than the Ruby 5AR4's I've been using, but that's just a psychic vibe. It's tall, and I would think that it's too high for a cage, but I don't have one so can't say for sure.

    Even though I have a NOS Mullard GZ34 coming in, and two Weber GZ68's, I like this Mullard GZ33 just fine, too, so I ordered 2 more just to have around for future use. I'll have enough rectifiers to last a lifetime.

    JunkyJan

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    MESA GZ34/5AR4 - ugh!!

    Post by JunkyJan on Sun Sep 19, 2010 3:21 pm

    Hi guys

    Just wanted to add to this thread... Somewhere else on this forum I posted that I bought a MESA GZ34 from a local musical instrument supplier. I stated in that post that it seems to work fine in my ST-70.

    Well, yesterday I finished the second of a pair of Dynakit Mark III amps, bought from Dynakitparts, and where the first amp fired up and biased beautifully first time, the second one would just splutter a few times, arc for a split second and then blow the fuse... Nothing wrong with the wiring that I could see... On a whim I plugged in the Ruby GZ34 that I tested the other Mark III with, and that cured it - works perfectly fine. Refusing to believe that the MESA rectifier is bad, I tried it again - and it just blew the fuse again.

    The bizarre thing is that this MESA GZ34 seems to work fine in my ST-70 - but flatly refuses to work in any of my Mark III amps, and perhaps it would probably cause damage to the other tubes (thank you, fuse!). The Ruby just takes it all in its stride - works perfectly fine no matter what it is plugged into.

    Is the MESA a bad tube? As far as I know, a GZ34 is a GZ34 - it's not like you get different grades of GZ34 tubes, do you?

    Thanks
    -- 'Jan in BC, Canada

    JunkyJan

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    Re: Choices in rectifier tubes for VTA?

    Post by JunkyJan on Mon Sep 20, 2010 12:29 pm

    JunkyJan wrote:...Is the MESA a bad tube? As far as I know, a GZ34 is a GZ34 - it's not like you get different grades of GZ34 tubes, do you.....
    Just wanted to add - according to some of the guitar playing forums, the Mesa/Boogie GZ34 is a rebranded Sovtek GZ34/5AR4. Physical comparison seems to bear it out - plate construction and physical appearance is identical.

    Sovtek makes good stuff IMHO - I guess I just got one that was made on a Friday afternoon then.

    -- 'Jan in BC, Canada

    davidness

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    Re: Choices in rectifier tubes for VTA?

    Post by davidness on Mon Sep 20, 2010 1:12 pm

    By the way, the NOS Mullard GZ33 stands right at 5" floor to ceiling when installed, for those inquiring as to cage compatibility.

    anbitet66

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    Re: Choices in rectifier tubes for VTA?

    Post by anbitet66 on Mon Sep 20, 2010 2:31 pm

    I have a question about a substitute for the stock 5AR4. My ST70 is nearly all original except for two of the output tubes (even then, they are the same Mullard type that used to say GE made in Great Britian) and I found in my posession a 1N2389 plug in rectifier. Has anyone ever tried one in a tube amp? The specs seem to be 600mA and breakdown voltage of 1600. The pinout seems compatible with the 5AR4. I don't currently need to use it, just curious. BTW, the dishwasher will most likely remove the weak paint on the glass just as if you wiped it with a clean cloth.

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