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    two GZ 34 rectifiers

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    ac2

    Posts : 28
    Join date : 2014-03-01

    two GZ 34 rectifiers

    Post by ac2 on Mon Mar 03, 2014 8:21 pm

    Howdy folks!

    I was wondering on the M-125 since I will be using dual rectifiers, should I run them parallel or similar to the Scott LK 150? Or, is the Scott what parallel looks like? To me parralell means exactly as it sounds, pin to pin. Its been many years and I forgot probably much of what I knew but even that was not a great deal, lol.

    I was also considering A WZ38 with a 5Ar4 if that would work and last the GZ33 but my concern is I don't see how that is much better than a single 5AR4 and my concern is that it will not be able to drive the amp to full power. Aside from the cost, which is not a deal killer, just hard to swallow that price for a rectifier.


    My tubes will be the KT120 and yes I know it will be easier using the WZ38 but I don't want to. I want either a single or dual tube rectifiers and would love to have dual coke bottle type 5UAR4's but voltage drop rules them out.

    I am building a custom chassis so I have all the room I need even adding another TX for the rectifiers if I have to.


    Any and all suggestions are welcome except for a solid state rectifier. No thank you.
    Oh, and I am not worried about giving up some on the LF, I have subs that will take care of all my needs.


    Thanks guys in advance!!

    stewdan

    Posts : 160
    Join date : 2010-03-07
    Age : 78
    Location : Houston Texas

    Re: two GZ 34 rectifiers

    Post by stewdan on Mon Mar 03, 2014 9:19 pm

    Hi AC2 -- In some of the ST70 upgrades that I ran across in the early 1990's they put two GZ34's in Parallel (as you say, pin to pin) to provide more current , thus better punch to the sound.

    So, with that same logic when dealing with Bob's M-125's, two copper top (WZ68) regulators would be better than one and you would have twice as much current available.

    However, some of the folks on the Forum have used a single Mullard or Marconi GZ37 Regulator tube on the M-125.

    Bob Posted a Table here a few years back that gave specs for all the currently available Tube Regulators.

    On my M-125's I use a single WZ68 Copper Top and either KT-88's or KT-120's and the sound seems very good to me.   I have some GZ37's but have not tried them yet.

    Have fun,
    Stew

    sKiZo

    Posts : 1285
    Join date : 2013-04-01
    Location : Michigan USA

    Re: two GZ 34 rectifiers

    Post by sKiZo on Mon Mar 03, 2014 11:40 pm

    If it helps any, I've been using a NOS GZ37 driving a quad of KT120's in my ST120 for a while now with no issues. The GZ37 can flow quite a bit more current than a GZ34 or 5AR4 - if I remember right it's something like 250mA vs 160mA, but don't quote me. Doesn't feel like it's working as hard as it did with the smaller rectifiers, which should be a good plus for durability ...

    I'm thinking the GZ37 has an added benefit if your house current is high in that it does drop the B+ about 10 or thereabouts. I recently added a bucking transformer to the power side of my amp and the B+ tests at just below minimum listed for the amp's specs, but it still biased up at 55mA with room to spare ...

    ac2

    Posts : 28
    Join date : 2014-03-01

    Re: two GZ 34 rectifiers

    Post by ac2 on Tue Mar 04, 2014 2:43 am

    Thanks guys! I need to know the difference between the GZ33 and the GZ37?

    Got it on the GZ34, thanks stwedan!
    sKiZo, how are you wiring your bucking transformer?

    Thanks again!!

    ac2

    Posts : 28
    Join date : 2014-03-01

    Re: two GZ 34 rectifiers

    Post by ac2 on Tue Mar 04, 2014 11:24 am

    Skizo, I found the post on your bucking transformer. Basicly an isolation thransformer and using gfi as switch?

    Im stable on my incoming power....but....I was thinking if I ran my variac to boost my incoming voltage could I compensate for the voltage drop using parallel 5UA4G's?

    I dont see why that would not work as long as my variac is rated to cary the load. Hmmm. Next question would be how that would affect my fillament voltages.

    ac2

    Posts : 28
    Join date : 2014-03-01

    Re: two GZ 34 rectifiers

    Post by ac2 on Tue Mar 04, 2014 11:30 am

    On second thought....might just keep it simple...two 5AR4's or one CZ33/37...... I found the chart Bob posted on rectifiers but do not see anything on CZ33/37.

    ac2

    Posts : 28
    Join date : 2014-03-01

    Re: two GZ 34 rectifiers

    Post by ac2 on Tue Mar 04, 2014 1:06 pm

    Tube Type DC mA PIV FIL AMPS MaxACV DCV DCV DROP

    5AR4 / GZ-34 250 1500 1.9 450 415 10
    5V4-GA 175 1400 2 375 400 25
    GZ37 350 1000 2.8 450 388 37
    5U4-GA 250 1550 3 450 381 44
    5U4-G 225 1550 3 450 381 44
    5U4- 275 1550 3 450 375 50
    5Y3-G/GA 125 1400 2 350 365 60
    5R4GYB 250 3100 2 900 362 63
    5R4G/GY/GYA 250 3100 2 750 358 67

    I don't see how much is gained using a single GZ37.....trying to find specs on the GZ33

    ac2

    Posts : 28
    Join date : 2014-03-01

    Re: two GZ 34 rectifiers

    Post by ac2 on Tue Mar 04, 2014 1:08 pm

    Looks like dual 5AR4's would be better than a single GZ37 but the GZ37 has it beat on aesthetics, how is it on sound?

    ac2

    Posts : 28
    Join date : 2014-03-01

    Re: two GZ 34 rectifiers

    Post by ac2 on Tue Mar 04, 2014 1:13 pm

    GZ33

    tubedata.milbert.com/sheets/129/g/GZ33.pdf

    GZ37 seems like a better option than the GZ33 but will it output full power to a pair of KT120's?

    Bob Latino
    Admin

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    Re: two GZ 34 rectifiers

    Post by Bob Latino on Tue Mar 04, 2014 1:22 pm

    I do not recommend running TWO 5AR4/GZ34's off the power transformer of the VTA ST-120 or the VTA M-125. The power transformer on BOTH amp kits use a 5 volt @ 5 amp rectifier line. Two 5AR4's @ 2.5 amps each = 5 amps. Using TWO 5AR4's, you would be running the rectifier line on the power transformer right at the limit of the rectifier line's ability to supply current which is not a good thing. A single 5AR4 is operated near its ability to supply current in the VTA ST-120 or M-125. A single 5AR4 does work OK as long as you do not have speakers that present a complex load to the amp OR you have very inefficient speakers. A better solution is just to use either the Weber WZ68 (450 milliamp current flow ability) solid state rectifier or a GZ33 or a GZ37 tube rectiifier. Both the GZ33 and GZ37 can supply 300 milliamps of current as long as you use a choke input. 300 milliamps is slightly beyond what a VTA ST-120 or M-125 will use under any playing conditions. GZ33 specs below in pdf format as issued by Mullard. The GZ37 specs are about the same ...

    GZ33 specs

    Bob

    deepee99

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    Location : Wallace, Idaho

    Re: two GZ 34 rectifiers

    Post by deepee99 on Tue Mar 04, 2014 1:24 pm

    Nothing tops a half-century old Mullard GZ-33, and I think Dr. Latino would concur, but I gotta tell you, since I got the speaker load back up to 6 ohms, the big Weber WZ 68 solid-state copper cans are cheap, safe and reliable, and until the third bottle of Lookout Ridge red has been opened and consumed, I can't hear the difference. I keep the glass rectifiers in their boxes until royalty drops by, which is not as often as it ought to be. The GZ-33s do help heat the house during sub-zero weather, however.But I've never had a Weber fail so totally that it takes out an output tube; when it gives up the ghost it just takes the fuse with it. Those are about 10 cents.

    sKiZo

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    Re: two GZ 34 rectifiers

    Post by sKiZo on Tue Mar 04, 2014 3:11 pm

    My VOM readings are also posted in the bucker thread - with, without, and pre/post thermistor. The bucker itself is just built on an old power strip that already had a switch and breaker onnit. The bucker box itself plugs into a non-latching GFCI adapter to prevent fast cycling of the amp if the power blips.

    Getting some miles on the setup now, and all is well here in sKiZoLand ...

    I also experimented with a Phillips 5R4GYS and had good results with it. Problem being, after about a month, the tube started going weak ... I was losing a few points on bias every time I started the amp. Not sure I can blame that on the tube type ... more likely just the tube.

    And ya ... the GZ37 or GZ33 are hands down the prettiest option!  tongue 

    Oh. And just to regurgitate ... I'm driving a quad of KT120's with the GZ37 and it's doing a bang up job.


    deepee99

    Posts : 1260
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    Location : Wallace, Idaho

    Re: two GZ 34 rectifiers

    Post by deepee99 on Tue Mar 04, 2014 3:16 pm

    sKiZo wrote:My VOM readings are also posted in the bucker thread - with, without, and pre/post thermistor. The bucker itself is just built on an old power strip that already had a switch and breaker onnit. The bucker box itself plugs into a non-latching GFCI adapter to prevent fast cycling of the amp if the power blips.

    Getting some miles on the setup now, and all is well here in sKiZoLand ...

    I also experimented with a Phillips 5R4GYS and had good results with it. Problem being, after about a month, the tube started going weak ... I was losing a few points on bias every time I started the amp. Not sure I can blame that on the tube type ... more likely just the tube.

    And ya ... the GZ37 or GZ33 are hands down the prettiest option!  tongue 

    Oh. And just to regurgitate ... I'm driving a quad of KT120's with the GZ37 and it's doing a bang up job.


    Winter solstice photo to follow, I'm sure

    ac2

    Posts : 28
    Join date : 2014-03-01

    Re: two GZ 34 rectifiers

    Post by ac2 on Tue Mar 04, 2014 5:57 pm

    Thanks guys, Okay dual 5AR4 tube rectifiers out.

    Solution almost settled,

    WZ68 when watching movies...
    GZ37 when listening to music or when I just want to show off my baby's, :)I'm sure I will have to reset bias when I swap so I will see how all that plays out, but hey if we like the tubes we have to like the tinker right? Wink

    Now one last question guys if you will bare with me, I like the GZ37 because its wider (57.5mm, vs 45mm) so it has a more pronounced "coke bottle" look. They are both the same height but do they both glow the same? Sorry for being a little picky here but its not like I can run over to best buy and take a peek Wink The filament current is a tad bit more on the GZ33, probably not enough to make a difference but I have to ask Smile

    I am running JBL 3722 screen array speakers at 4ohms. I am setting up my HT for movies and music. I have a few more questions but will post a new topic so this one does not get off track.

    Thank you Bob, sKiZo, and deepee99 for the replies, much appreciated!!

    deepee99

    Posts : 1260
    Join date : 2012-05-23
    Location : Wallace, Idaho

    Re: two GZ 34 rectifiers

    Post by deepee99 on Tue Mar 04, 2014 6:06 pm

    ac2 wrote:Thanks guys, Okay dual 5AR4 tube rectifiers out.

    Solution almost settled,

    WZ68 when watching movies...
    GZ37 when listening to music or when I just want to show off my baby's, :)I'm sure I will have to reset bias when I swap so I will see how all that plays out, but hey if we like the tubes we have to like the tinker right? Wink

    Now one last question guys if you will bare with me, I like the GZ37 because its wider (57.5mm, vs 45mm) so it has a more pronounced "coke bottle" look. They are both the same height but do they both glow the same? Sorry for being a little picky here but its not like I can run over to best buy and take a peek Wink The filament current is a tad bit more on the GZ33, probably not enough to make a difference but I have to ask Smile

    I am running JBL 3722 screen array speakers at 4ohms. I am setting up my HT for movies and music. I have a few more questions but will post a new topic so this one does not get off track.

    Thank you Bob, sKiZo, and deepee99 for the replies, much appreciated!!

    Webers are for everyday life. GZ33s are for impressing chicks. Will you not learn? sunny 



    ac2

    Posts : 28
    Join date : 2014-03-01

    Re: two GZ 34 rectifiers

    Post by ac2 on Tue Mar 04, 2014 6:13 pm

    My drivers:

    Frequency Range
    30Hz to 18kHz

    Frequency Response
    40 Hz - 18 kHz (±3 dB)

    Sensitivity
    104dB, 2.83V @ 1m (3.3ft)

    ac2

    Posts : 28
    Join date : 2014-03-01

    Re: two GZ 34 rectifiers

    Post by ac2 on Tue Mar 04, 2014 6:31 pm

    "Webers are for everyday life. GZ33s are for impressing chicks. Will you not learn?"



    Lol.....after almost 30 years of marriage the only chicks I can impress are my granddaughters and they already think i'm the best haha....  Smile

    I just cannot see myself being happy without that glowing tower beaming its power right smack in the middle of my monoblocks!

    Nooooo wayyyyy Smile


    Last edited by ac2 on Tue Mar 04, 2014 7:23 pm; edited 1 time in total

    deepee99

    Posts : 1260
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    Re: two GZ 34 rectifiers

    Post by deepee99 on Tue Mar 04, 2014 6:53 pm

    ac2 wrote:Lol.....after almost 30 years of marriage the only chicks I can impress are my grandaughters and they already think im the best haha....  Smile

    I just cannot see myself being happy without that glowing tower beaming its power right smack in the middle of my monoblocks!

    Nooooo wayyyyy Smile


    Well, you could always go with a quad system, or one of them 7-channel thingies.

    ac2

    Posts : 28
    Join date : 2014-03-01

    Re: two GZ 34 rectifiers

    Post by ac2 on Tue Mar 04, 2014 7:21 pm

    Eventually I will add three VTL-120 for my 6 JBL 8340a surrounds. All my speakers are JBL pro, use horns and are very efficient.

    I have a 7 channel Emotiva amp for the surrounds but I want an all tube system with the exception being my subwoofers, they will stay solid state.

    I kind of changed horses in the middle of the stream and after getting my amps I decided to go tube. Most of this was due to the pleasant surprise of how good the JBL 3722 speakers sound.

    My only concern was finding a tube amp with at least 100wpc. Bob took care of that for me plus some!!!

    ac2

    Posts : 28
    Join date : 2014-03-01

    Re: two GZ 34 rectifiers

    Post by ac2 on Thu Mar 06, 2014 12:14 am

    Made the plunge... three Mullard GZ37's on the way.

    Im working on the layout of my new chassis....will post a new thread.

    Skizo, may have to pick your brain a lil bit...I love the way your amp looks....I will be adding a meter too.

    sKiZo

    Posts : 1285
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    Re: two GZ 34 rectifiers

    Post by sKiZo on Thu Mar 06, 2014 12:44 am

    Pick away ... and thanx for the flowers!

    Covered most of the bases on the build here, start to finish ...

    http://dynacotubeaudio.forumotion.com/t1656-custom-chassis

    Other than the chassis, internal Y adapters, meters, dual volumes and larger chokes, it's pretty much a stock ST120 ...

    Meters I used are off the Velleman store on FleaBay, but there's other options available. I liked the larger scale, and they're rock steady. I just use them for quick checks when I fire it up. The circuit gave me some issues - short version - mV meters are impossible to find in that range, but I found out I could use mA meters by clipping the internal shunt and adding a trim pot to match them to the bias pots. That's all covered in the link.

    Oh. You also mentioned GZ37 glow?




    ac2

    Posts : 28
    Join date : 2014-03-01

    Re: two GZ 34 rectifiers

    Post by ac2 on Thu Mar 06, 2014 2:41 am

    Sweet! Thanks, I will read the thread Smile

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