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    Rectifier options M-125/kt120

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    Dahlberg

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    Age : 55
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    Rectifier options M-125/kt120

    Post by Dahlberg on Tue Sep 27, 2016 5:59 am

    First post on this forum  Smile

    I bougth the M-125 mono amps yesterday and have a few questions that I
    thougth could just as well be asked here as sent as mail so....

    Hello.
    I’m in the process of picking up the missing parts and I have a few questions regarding the rectifier.
    Would you recomend either the EZ-33 or the solid state rectifier, based on bass resolution and dynamic drive?
    The amps will only work from 50 to 350hz in an actively crossed over three way system.
    I have already bought the Tungsol KT-120 tubes, would it be possible (and a good idea?) to use the WS1 copper
    cap instead of the WZ68 or will the lesser voltage drop be a problem? (that's if I go for the solid state one).

    WZ68 FOR USE IN GUITAR AMPS. Not designed for use with HIFI tube amps, tube radios, etc. -
    Try the WS1 instead. Equivalent of 2x GZ34/5AR4 (dual rectifier). Voltage drop: 17V at Maximum Current: 450ma.

    WS1 Replaces any rectifier tube with solid-state rectifiers for no sag. OK to for use with HIFI tube amps,
    tube radios, etc. Diodes and Limiter only, No Sag. Voltage drop: 1V max at Maximum Current: 1000ma.


    Edit: I belive I found one answer all by myself
    Can I use this WS1 Copper Cap in an amp that doesn't have a standby switch?
    No, there is no inrush current limiter on the WS1.

    Best regards. Bengt

    mazeeff

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    Re: Rectifier options M-125/kt120

    Post by mazeeff on Tue Sep 27, 2016 8:17 am

    I have been using the Weber WS1 in two of my VTA-70s for the past year. The only issue that I have had is high B+ voltage. My house voltage is 125V. With a 5ar4 installed, my B+ was 456V. With the WS1 installed, my B+ was 496V! This is too high a voltage for modern EL34's, so I have to use a variac to drop my line voltage down to 110V. This drops my B+ back down to 460V. I still get the full benefit of a solid state rectifier, with reasonable EL34 reliability. Your case may be different with the M125, but I just wanted to share my experience with the WS1. You may also hear a lot of concerns about "Cathode Striping", and other major issues as well, regarding the use of a straight diode rectifier. I have been using solid state rectification for 10+ years in all of my amps, and never experienced any issues, other than the high B+. For myself, the main benefit of SS rectification, is extremely tight bass. My speakers have 15" woofers, and the bass is much cleaner, without the sag and compression of a tube rectifier.

    Bob Latino
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    Location : Massachusetts

    Re: Rectifier options M-125/kt120

    Post by Bob Latino on Tue Sep 27, 2016 8:40 am

    Contrary to what Weber says > The Weber WZ68 works just fine in any of the VTA amps and does have a short 3 to 5 second delay built in. That said > If you do not have the high voltage system wired properly, then you will destroy the WZ68 when you start the amp up for the first time. If you intend to use a Weber solid state rectifier, you should probably start your kit amp up the first time with a tube rectifier just to make sure that the high voltage system works OK. If the amp works OK, biases up properly and does not blow a fuse then pull out the tube rectifier and install the Weber WZ68. Remember also to rebias the amp after you switch to the Weber. Different rectifiers will cause the amp to have different bias points.

    In most cases a 5AR4 or GZ33 or GZ37 tube rectifier will work fine in any of the VTA amps and does provide a slow warm up. Unfortunately, the Mullard GZ33 and GZ37 are not made anymore and those still in existence are getting pretty pricey.

    Why would you need a solid state rectifier? If your are operating your music system under the following conditions
    1. At very high volume levels much of the time
    2. Into a room that is very large
    3. Into low efficiency speakers which are 83 to 88 dB efficient

    then a solid state rectifier will provide more current for the amp under these conditions.

    Advice > try a 5AR4 tube rectifier first and see how the amp sounds to you.

    Bob

    Dave_in_Va

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    Re: Rectifier options M-125/kt120

    Post by Dave_in_Va on Tue Sep 27, 2016 10:30 am

    Bob,
    Is there any advantage (other than cool looks) to using a GZ33 or GZ37 in a VTA ST70? If so, which one? Does it matter?
    I'm currently using a Sylvania 5AR4 and my wall voltage (with a bucker) is about 116 volts.
    Thanks.

    Bob Latino
    Admin

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    Re: Rectifier options M-125/kt120

    Post by Bob Latino on Tue Sep 27, 2016 11:02 am

    There is no real advantage in using a GZ33 or a GZ37 instead of a 5AR4 in any ST-70 amp. In a VTA ST-120 or the VTA M-125's a GZ33 or a GZ37 tube rectifier can provide more current at very high volume levels than a 5AR4.

    The GZ33 and the GZ37 look alike and have very similar electrical characteristics. In the VTA amps, there is no real advantage of one over the other.

    Bob

    peterh

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    Re: Rectifier options M-125/kt120

    Post by peterh on Tue Sep 27, 2016 4:42 pm

    An ordinary GZ34 aka 5AR4 will do.
    What kills tuberectifiers is short power interruptions ( in order of 0.1 to 10s ) where the cathode
    still is hot but the caps has been discharged. The current rush that results might vaporize parts
    of the cathode, and any vapor inside a tube will cause a flash. The flash in turn will burn
    away more material resulting in an even larger flash and dislodging of material. The tube is
    usually destroyed after a flash, and even if it "seems to work" have a high probability to flash or
    short.

    Stand-by switches might also create surges if activated when the cathode is hot.

    A turn-on delay of 15-20s after application of mains power will be an effective protection. So will
    a relay that trips when power fails( and needs a manual reset which usually occurs after several minutes )

    Dahlberg

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    Re: Rectifier options M-125/kt120

    Post by Dahlberg on Tue Sep 27, 2016 6:09 pm

    Thanks for all input. I have a pair of gz-34 to start with just to make shure everything is in order.
    If the main advantage is current capasity I might have a way to decrease the need for that by
    some rewiring of the midbass section. I would loose 3.5db/2,83v of output going from
    2x8/3=5,33ohm to 3x8/2=12ohm nominal load. There should be enough power to pull
    that of even when counting for that I will need some extra power for dipole compensation.

    I will do as adviced, try the gz34 first.



    Last edited by Dahlberg on Mon Oct 03, 2016 3:37 am; edited 2 times in total

    pedrocols

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    Re: Rectifier options M-125/kt120

    Post by pedrocols on Tue Sep 27, 2016 10:22 pm

    Running the webers WZ68 solid state for almost two years and never have a problem. I also have a pair of GZ33s but can't hear a difference and sometimes switch between the two just because I can... Cool

    Dahlberg

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    Re: Rectifier options M-125/kt120

    Post by Dahlberg on Mon Oct 03, 2016 3:38 am

    Dahlberg wrote:Thanks for all input. I have a pair of gz-34 to start with just to make shure everything is in order.
    If the main advantage is current capasity I might have a way to decrease the need for that by
    some rewiring of the midbass section. I would loose 3.5db/2,83v of output going from
    2x8/3=5,33ohm to 3x8/2=12ohm nominal load. There should be enough power to pull
    that of even when counting for that I will need some extra power for dipole compensation.

    I will do as adviced, try the gz34 first.


    A bit to quick in my thinking  Embarassed  Current discussion was of cource "bias-current" related.
    Just to get it straight then, a GZ34 would handle 4 output tubes @60mA + input tubes ?
    Feels like I would be pushing it a bit ? How wide is the bias regulating area ?

    LeGrace

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    Join date : 2016-08-07

    Re: Rectifier options M-125/kt120

    Post by LeGrace on Mon Oct 03, 2016 6:12 am

    I went through 2 5AR4's within my first month of M125 ownership. The best life I've gotten so far is about 3 weeks. I'm off tube rectification for now pending applying the diode mod, then I plan to try again with Genalex 5AR4 recommended by Jim McShane.

    Dahlberg

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    Re: Rectifier options M-125/kt120

    Post by Dahlberg on Mon Oct 03, 2016 7:44 am

    LeGrace wrote:I went through 2 5AR4's within my first month of M125 ownership. The best life I've gotten so far is about 3 weeks. I'm off tube rectification for now pending applying the diode mod, then I plan to try again with Genalex 5AR4 recommended by Jim McShane.  

    Ok, thanks.

    10-E-C

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    Re: Rectifier options M-125/kt120

    Post by 10-E-C on Mon Oct 03, 2016 3:18 pm

    I have M-125's and been running Mullard GZ37s for 20 months and it's as solid as the day I installed them.

    TM

    LeGrace

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    Re: Rectifier options M-125/kt120

    Post by LeGrace on Mon Oct 03, 2016 5:24 pm

    10-E-C wrote:I have M-125's and been running Mullard GZ37s for 20 months and it's as solid as the day I installed them.

    TM

    I would love to have a set of those! Why doesn't anyone make them anymore?

    Kentley

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    Location : Worcester, MA

    Re: Rectifier options M-125/kt120

    Post by Kentley on Mon Oct 03, 2016 6:35 pm

    "Why doesn't anyone make them anymore?"
    That may be a rhetorical question, but it deserves an answer.
    First, the market for tube rectifiers is quite small. The only need for them is vintage toobies, like many of us, and guitar amps. So much of the hi-fi market has switched to SS rectification - even the 10 or so percent who are toobies. So what of the guitar market? Simple - most guitar amps I'm familiar with have a limited space for tubes. Big-bottle stuff, like the rather tall and fat GZ-33/37 simply will not fit.
    And frankly, even if someone decided it was worth their while to tool up to make these beasts, there's no guarantee that they'd be anywhere near as good as the vintage Mullards. Lots of work for little return. So the answer, in short -- Economics, my dear, er, LeGrace.
    GZ-37s are still around, and good ones - at $80 and up - WAY up. GZ-33s are practically Dinosaurus Wrecks. No

    pigface

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    Re: Rectifier options M-125/kt120

    Post by pigface on Mon Oct 03, 2016 6:46 pm

    I got 4 1/2 years + out of the GZ-33 in my ST120 before it gave it up and took out a bias resister  .  
    I bought a couple spares back then too . Smile

    10-E-C

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    Re: Rectifier options M-125/kt120

    Post by 10-E-C on Tue Oct 04, 2016 6:49 am

    pigface wrote:I got 4 1/2 years + out of the GZ-33 in my ST120 before it gave it up and took out a bias resister  .  
    I bought a couple spares back then too . Smile


    I have one GZ-37 spare and a set of GZ-33s also as spares.

    TM

    GreggW

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    Re: Rectifier options M-125/kt120

    Post by GreggW on Tue Oct 04, 2016 11:11 am

    I've been using the same 5V3A for a year now in an ST120. Plate voltage is between 450-460, the same as when it was installed. Bias remains steady, with infrequent, small adjustments.

    LeGrace

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    Join date : 2016-08-07

    Re: Rectifier options M-125/kt120

    Post by LeGrace on Tue Oct 04, 2016 3:51 pm

    Just added some beefy UF5408 diodes. Now the clock starts to see if I can exceed 3 weeks when running with tube rectifiers. The ones Jim sent are stamped U77/GZ34 as opposed to 5AR4. Any difference?

    peterh

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    Re: Rectifier options M-125/kt120

    Post by peterh on Tue Oct 04, 2016 4:19 pm

    LeGrace wrote:Just added some beefy UF5408 diodes. Now the clock starts to see if I can exceed 3 weeks when running with tube rectifiers. The ones Jim sent are stamped U77/GZ34 as opposed to 5AR4. Any difference?
    GZ34 and 5AR4 is the same spec, the first is european (Mullard-Philips tube designation) standard, the second US RETMA standard.

    skriefal

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    Re: Rectifier options M-125/kt120

    Post by skriefal on Tue Oct 04, 2016 9:51 pm

    Right - different label but same tube. Like 12AU7 = ECC82, or 6DJ8 = ECC88.

    Dahlberg

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    Re: Rectifier options M-125/kt120

    Post by Dahlberg on Wed Oct 05, 2016 7:06 am

    Lets say that I would like to try the "WS1 Copper Cap" rectifier and as a safety precaution
    limit the inrush current with a thermistor at the AC-line. What would be the parameters to
    look for in that thermistor? I have "zero power resistance@25dgr C",
    "maximum current@steady state 25dgr C" and "maximum energy" at the Farnell catalog
    to work with.

    I did a search filtering for thermistors from 7-15 amps and got "zero resistance" from
    0,7-20ohm.

    "Maximum energy" differs from 40-500 J


    KT120's arrived today Very Happy

    Dogstar

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    Re: Rectifier options M-125/kt120

    Post by Dogstar on Wed Oct 05, 2016 9:22 am

    A few years ago I installed the Weber WZ68 in my ST-120 after going through a few rectifier tubes in my amp. Since then I haven't had a problem. I bought two just to have an extra on hand. And now I see Weber specifically states that rectifier should not be installed in hifi amps. The spare has never been used. I'm wondering if I should contact Weber to see if they be willing to exchange it for the rectifier they currently recommend? I know this is of no concern for Tubes4Hifi but I'm not just expressing a thought.

    deepee99

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    Re: Rectifier options M-125/kt120

    Post by deepee99 on Wed Oct 05, 2016 4:00 pm

    Dogstar wrote:A few years ago I installed the Weber WZ68 in my ST-120 after going through a few rectifier tubes in my amp. Since then I haven't had a problem. I bought two just to have an extra on hand. And now I see Weber specifically states that rectifier should not be installed in hifi amps. The spare has never been used. I'm wondering if I should contact Weber to see if they be willing to exchange it for the rectifier they currently recommend? I know this is of no concern for Tubes4Hifi but I'm not just expressing a thought.
    My guess is some lawyer made them put that language in for whatever reason.
    Only problem I ever had with the WZ68s is when I had about a 1-ohm speaker load (Maggies and ESS Heils strapped parallel). They didn't like that! With a nominal load of 4 ohms I've never had one choke on me, albeit, like tubes, they are consumables. I prefer the aesthetics of the old Mullard GZ33 and -37s, but they are getting spendy so some day it will be Weber City, I suppose.


    Dahlberg

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    Re: Rectifier options M-125/kt120

    Post by Dahlberg on Thu Oct 06, 2016 5:43 am

    Went on a shoppingstreak Cool so now I have gz34's, gz33's, wz68's and
    a couple of octal tube bottoms to make my own rectifiers.

    Dahlberg

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    Re: Rectifier options M-125/kt120

    Post by Dahlberg on Fri Oct 07, 2016 6:03 pm

    Ok, an idea. Lets say that I would build a solid state rectifier on a socket and ad the
    ntc thermistor there (at the ac input). They get pretty hot but it will be at the outside so....?
    I'm still trying to figure out what values I'm supposed to look for. Putting it at the high voltage
    beetwen the transformer and the rectifier would lower the current demands for the device.
    Still fumbling around in the dark here Embarassed Any input would be appreciated Smile

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