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    Tube vs Solid State Rectifier for VTA ST-120

    audiomaniac
    audiomaniac


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    Post by audiomaniac Tue Oct 01, 2019 11:00 pm

    Hi All,

    I'm new to the forum and need some advice. I'm looking at getting one of Bob's amps, the ST-120, and I'm getting hung up on the decision of going with tube or SS rectification. At first, I was all set on tube but since my speakers right now are pretty inefficient at 84db (Ascend Acoustics Sierra 2), I read somewhere on the forum that SS might be preferable. I know that if I did go SS, I would want to get the TDR mod. But as I understand it, this isn't recommended for tube rectification in case I want to try the tube rectification at a later date.

    My question is, how many of you prefer one over the other and why. Would I be giving up the classic tube amp sound going SS? Would I be sacrificing some tube reliability or have more maintenance going with tube rectification?

    Thanks for the help!
    cci1492
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    Post by cci1492 Wed Oct 02, 2019 7:52 am

    SS rectifiers provide more current, therefore more bottom end (slam). I cannot hear a difference anywhere else other than more punch and only when playing the music loud. There are many high end tube amplifier manufacturers that use diodes for rectification, so it's a perfectly legitimate way to go. I use a gz33 because I like how it looks and its able to get very close to SS levels of bottom end punch (also, money to burn on nonsense). I used the Weber for over a year and loved it. If the gz33s became completely unavailable for purchase, my amps will continue to sound great, would only miss the look of the tube.
    Bob Latino
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    Post by Bob Latino Wed Oct 02, 2019 12:17 pm

    audiomaniac wrote:Hi All,

    I'm new to the forum and need some advice. I'm looking at getting one of Bob's amps, the ST-120, and I'm getting hung up on the decision of going with tube or SS rectification. At first, I was all set on tube but since my speakers right now are pretty inefficient at 84db (Ascend Acoustics Sierra 2), I read somewhere on the forum that SS might be preferable. I know that if I did go SS, I would want to get the TDR mod. But as I understand it, this isn't recommended for tube rectification in case I want to try the tube rectification at a later date.

    My question is, how many of you prefer one over the other and why. Would I be giving up the classic tube amp sound going SS? Would I be sacrificing some tube reliability or have more maintenance going with tube rectification?

    Thanks for the help!

    A solid state rectifier is probably a better choice IF ..
    1. Your speakers are relatively inefficient (88 dB or below)
    2. Your listening room is large (over maybe 400 square feet)
    3. You play music at high volume levels much of the time

    The nice thing about the VTA ST-120 is that you can use either rectifier in the amp. The solid state rectifiers are plug compatible with a 5AR4 tube rectifier. Just pull out the tube rectifier and install the solid state rectifier and rebias the amp (Note > If you have the AutoBias board, you need not rebias the amp as the AutoBias board will make the necessary adjustments for you.) That said, there are many ST-120 users who use a tube rectifier with success. If your speakers are above 88 dB efficient and your room is of modest size, a tube rectifier will work fine with the ST-120. I have had a Tung-Sol 5AR4 tube rectifier in my own ST-120 for about 2 years now .. Works great ..

    Bob
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    Post by audiomaniac Wed Oct 02, 2019 2:37 pm

    cci1492 wrote:SS rectifiers provide more current, therefore more bottom end (slam). I cannot hear a difference anywhere else other than more punch and only when playing the music loud. There are many high end tube amplifier manufacturers that use diodes for rectification, so it's a perfectly legitimate way to go. I use a gz33 because I like how it looks and its able to get very close to SS levels of bottom end punch (also, money to burn on nonsense). I used the Weber for over a year and loved it. If the gz33s became completely unavailable for purchase, my amps will continue to sound great, would only miss the look of the tube.  

    Thanks CC. Great to know.
    audiomaniac
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    Post by audiomaniac Wed Oct 02, 2019 2:39 pm

    Bob Latino wrote:
    audiomaniac wrote:Hi All,

    I'm new to the forum and need some advice. I'm looking at getting one of Bob's amps, the ST-120, and I'm getting hung up on the decision of going with tube or SS rectification. At first, I was all set on tube but since my speakers right now are pretty inefficient at 84db (Ascend Acoustics Sierra 2), I read somewhere on the forum that SS might be preferable. I know that if I did go SS, I would want to get the TDR mod. But as I understand it, this isn't recommended for tube rectification in case I want to try the tube rectification at a later date.

    My question is, how many of you prefer one over the other and why. Would I be giving up the classic tube amp sound going SS? Would I be sacrificing some tube reliability or have more maintenance going with tube rectification?

    Thanks for the help!

    A solid state rectifier is probably a better choice IF ..
    1. Your speakers are relatively inefficient (88 dB or below)
    2. Your listening room is large (over maybe 400 square feet)
    3. You play music at high volume levels much of the time

    The nice thing about the VTA ST-120 is that you can use either rectifier in the amp. The solid state rectifiers are plug compatible with a 5AR4 tube rectifier. Just pull out the tube rectifier and install the solid state rectifier and rebias the amp (Note > If you have the AutoBias board, you need not rebias the amp as the AutoBias board will make the necessary adjustments for you.) That said, there are many ST-120 users who use a tube rectifier with success. If your speakers are above 88 dB efficient and your room is of modest size, a tube rectifier will work fine with the ST-120. I have had a Tung-Sol 5AR4 tube rectifier in my own ST-120 for about 2 years now .. Works great ..

    Bob

    Thanks Bob.
    deepee99
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    Post by deepee99 Thu Oct 03, 2019 8:37 am

    First of all, Welcome to Tommy's Holiday Camp.
    I'm with cci1492 regarding Genyoooowine Mullard GZ-33s: They're the bee's knees aesthetically, tougher than the back of God's hand, live longer than Methuselah, and whatever shortcomings they have in terms of punch as opposed to a solid state rectifier is IMHO not much of an issue. (
    There should be a caveat here: GZ-37s are NOT the same as GZ-33s and while just as tall and sexy, don't have what it takes to run an ST-70, much less a ST-120 or M-125.
    I agree, at $100 each for a strong sexy unblemished tube is expensive. But the Weber WZ-68 copper caps designed to replace them fetch $24 apiece. From my experience with Webers, the Mullards are the cheaper deal. Unless some hole-drilling in the copper caps lets them ventilate and cool, the Webers are definitely a consumable.
    Again, welcome. I'm the long-winded one.
    deepee99

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    Post by deepee99 Thu Oct 03, 2019 8:51 am

    Warned ya.

    But a penny for thoughts. A custom-builder friend of mine came up with the idea of running a pair of GZ-33s in parallel in lieu of just one in the M-125. That really, seemed to me, brought a punchier presence much as solid state. Don't know where on Bob's builds you'd find room for an extra hole; this was a custom chassis. Four GZ-33s lighting up the back of a pair of M-125s was sublime.
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    Post by cci1492 Thu Oct 03, 2019 8:52 am

    Experiment for yourself, that's the fun of playing with this stuff. With an off the shelf SS amp, there's not much tweaking the amp (cables for some, maybe), with Bob's amps, there are options to explore. Only thing to be careful with when swapping between rectifiers (and other tubes), clean and adjust the pins on the sockets as the Weber and the various tubes to try have different size pins (width). A loose fitting tube, especially a rectifier, will cause damage to the amp.
    deepee99
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    Post by deepee99 Thu Oct 03, 2019 9:10 am

    Yes. I redplated a very nice tube with a loose socket fit. They should be uncanny tight. Push the socket springs back toward the centre towards the middle with a jeweler's screwdriver. Then give the tube a little shiny TLC by polishing the pins with a sheet of Mr. Clean's Magic Eraser. There's probably some under the kitchen sink. Amazing stuff.
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    Post by LeGrace Thu Oct 03, 2019 3:43 pm

    What is issue with GZ37?
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    Post by deepee99 Thu Oct 03, 2019 5:54 pm

    LeGrace wrote:What is issue with GZ37?
    The GZ-37 can't handle the voltage swings. (Well, they can: I was using a pair of GZ-37s in one of Bob's amps and they survived all those successive loads over two years unscathed.) I'll leave the technical explaining to Bob L.
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    Post by Bob Latino Thu Oct 03, 2019 6:08 pm

    deepee99 wrote:
    LeGrace wrote:What is issue with GZ37?
    The GZ-37 can't handle the voltage swings. (Well, they can: I was using a pair of GZ-37s in one of Bob's amps and they survived all those successive loads over two years unscathed.) I'll leave the technical explaining to Bob L.

    I have a number of customers using BOTH the Mullard GZ33 and GZ37 rectifiers with no problems whatsoever. The "problem" with both of those is that they are not made anymore and pricing on these has risen over the past few years to about $100 USD a copy.

    Bob
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    Post by deepee99 Thu Oct 03, 2019 8:26 pm

    "GZ33s can handle a much larger first input cap (200uF vs 16uF) thus much higher peak current handling" from Tube Asylum . Unless things have changed, the rectifier greets a 40-uF cap on VTA amps. That's a reach for the 16uF GZ-37,but no issues with the GZ-33's 200uF capacity. At 40 uF it's loafing.
    audiomaniac
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    Post by audiomaniac Thu Oct 03, 2019 9:08 pm

    Thanks everyone for your replies. I called Bob and had a nice conversation with him about my options. With my current speakers, I would have to go with the SS rectifier, which isn't a bad thing. As for the TDR mod, I know that it can be easily disconnected, even with my bad eyes. Which by the way is why I will probably get it wired. So much fun on this board and I'm glad to be here. Very Happy
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    Post by deepee99 Thu Oct 03, 2019 9:25 pm

    audiomaniac wrote:Thanks everyone for your replies. I called Bob and had a nice conversation with him about my options. With my current speakers, I would have to go with the SS rectifier, which isn't a bad thing. As for the TDR mod, I know that it can be easily disconnected, even with my bad eyes. Which by the way is why I will probably get it wired. So much fun on this board and I'm glad to be here. Very Happy
    The Weber Copper Cap WZ-68s get hotter than the hubs of hell and there are heat-sensitive parts in the innards, too. Especially if you've got a difficult speaker load with a very low impedance, if you want to preserve the Webers for more than a few months, here's a cheap trick to making them last much longer.
    Remove the "copper cap" from the tube base. It's just a weak glue holding it on, and you're obviously not disturbing a vacuum, so gently work the cap off. Select a length of dowel that fits just inside the cap. Drill 4-6 quarter-inch holes in the copper-cap so air can flow through it and cool it. Caution: be careful when locating the holes that they do not expose any of the high-voltage stuff in the bottom of that Weber to deliver a very nasty high-voltage shock.
    Having driven the holes, fit the copper cap back on the tube base and secure it with a temperature-insensitive glue.You'll miss the royal glow of a Mullard but some say you'll get a slight edge in sound quality.
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    Post by StevieRay Fri Oct 04, 2019 8:54 am

    I use the Weber WS-1 with thermistor, which is just diodes and a thermistor to bring up the B+ slowly.

    Of course I also use a TDR board.

    This works quite well, and you don't have that dropping resistor inside like a WS-68 that gets 'hotter then the hubs of hell'.

    One caution:  If your line voltage is more than 122 or so volts AC, you might need to use a bucker or variac to get it down to ~117 or so.  I use the filament winding for the rectifier tube (which means I can NEVER use a tube rectifier unless I re-wire it) for bucking down to ~116/117 vac, and my B+ and all other voltages are dead in the middle of the ranges as listed in the instructions when using the WS-1.

    The amp has been rock steady for almost a year now, no problems cheers
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    Post by LeGrace Fri Oct 04, 2019 9:12 am

    deepee99 wrote:"GZ33s can handle a much larger first input cap (200uF vs 16uF) thus much higher peak current handling" from Tube Asylum . Unless things have changed, the rectifier greets a 40-uF cap on VTA amps. That's a reach for the 16uF GZ-37,but no issues with the GZ-33's 200uF capacity. At 40 uF it's loafing.

    GZ-37 has no problem accommodating up to 64uF. So no problem to use it in VTA amps that employ 40 uF first cap, like in my M125's.
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    Post by New2Tubez Fri Oct 04, 2019 4:39 pm

    I'm also using the Weber WS1t in my ST120.
    I use a variac and have the auto bias board installed. I never had an issue with my TungSol 5AR4 but the AB has a delay and the tube rectifier was just another heat source.
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    Post by rjpjnk Fri Oct 04, 2019 6:20 pm

    According to the Weber website the WZ68 is not for use in HiFi. They suggest the WS1 instead. From reading the description of the two it appears the difference is that the WZ68 has a dropping resistor as mentioned above. The WS1 is nothing but diodes and for 2.50 more you can add a thermistor. If you go with the WS1 your B+ voltage may be a bit high and there won't be any sag, i.e., voltage variation as a function of current draw. Guitar players like sag as it's part of the compressive tube amp sound. Not good for HiFi though.

    https://www.tedweber.com/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."

    https://www.tedweber.com/ws1
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    Post by Drummerboy2 Sun Oct 13, 2019 12:24 am

    Bob Latino wrote:
    deepee99 wrote:
    LeGrace wrote:What is issue with GZ37?
    The GZ-37 can't handle the voltage swings. (Well, they can: I was using a pair of GZ-37s in one of Bob's amps and they survived all those successive loads over two years unscathed.) I'll leave the technical explaining to Bob L.

    I have a number of customers using BOTH the Mullard GZ33 and GZ37 rectifiers with no problems whatsoever. The "problem" with both of those is that they are not made anymore and pricing on these has risen over the past few years to about $100 USD a copy.

    Bob

    I use a GZ37 in my VTA-120 now for around 2 years with no issues. My Bias is still right on as when I first biased the amp. I need to buy another one as a back up.
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    Post by Dogstar Sun Oct 13, 2019 9:08 am

    rjpjnk wrote:According to the Weber website the WZ68 is not for use in HiFi. They suggest the WS1 instead. From reading the description of the two it appears the difference is that the WZ68 has a dropping resistor as  mentioned above. The WS1 is nothing but diodes and for 2.50 more you can add a thermistor. If you go with the WS1 your B+ voltage may be a bit high and there won't be any sag, i.e., voltage variation as a function of current draw. Guitar players like sag as it's part of the compressive tube amp sound. Not good for HiFi though.

    https://www.tedweber.com/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."

    https://www.tedweber.com/ws1

    I bought two WZ68’s before the WS1 was available. I’m still using the first one. What are the problems with using the wz68?
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    Post by Bob Latino Sun Oct 13, 2019 9:31 am

    Dogstar wrote:

    I bought two WZ68’s before the WS1 was available. I’m still using the first one. What are the problems with using the wz68?

    There are no problems with using the Weber WZ68 in any of the VTA amps BUT > For some reason the Weber web site gives some warning about using the WZ68 in "audio" amps ? I honestly do not know why they have that little blurb about not using the WZ68 in audio amps ?

    Bob
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    Post by nmchiefsfan Sun Oct 13, 2019 11:19 am

    I built my ST120 in 2012 and am on my 2nd set of KT120s. My amp has the TDR mod. I have used nothing but tube rectification and have had the same Tung-Sol 5AR4 in the amp since 2016. (Probably Jinxed it now). My understanding is that if you think you may use solid state rectification some day, install the TDR. I think it is okay to have the TDR with tube rectification but I have been wrong before! Hope I don't find out the hard way why I shouldn't be using it this way!
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    Post by deepee99 Sun Oct 13, 2019 11:39 am

    Bob Latino wrote:
    Dogstar wrote:

    I bought two WZ68’s before the WS1 was available. I’m still using the first one. What are the problems with using the wz68?

    There are no problems with using the Weber WZ68 in any of the VTA amps BUT > For some reason the Weber web site gives some warning about using the WZ68 in "audio" amps ? I honestly do not know why they have that little blurb about not using the WZ68 in audio amps ?

    Bob

    I think it was the late Kentley (RIP) who noticed this fine print swap-out on the WZ-68 originally. I figured some lawyer knew something we didn't. If memory serves, it had to do with home hi-fi being more demanding of the rectifier than a guitar amp. Again, heat's the devil with the WZ-68. When my last GZ-33 takes its final gasp, I'll probably just sub it with a WS-1 and TDR fix-up.
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    Post by Hops Sun Oct 13, 2019 4:44 pm

    Perhaps it is all the complaints about the heat of the WZ-68, and advice the drill holes in the copper cap in response, that has Weber wary. I bought a WZ68, a WS1 with thermistor, and a Tung-Sol 5AR4. The WZ68 is in the (newish) VTA-120 and is working well ( no holes drilled). If it fails, I will try the Tung-Sol, see if it sounds different, and if it fails try the WS-1. So far the WZ68 is working, the Amp sounds good. I run 113-118 V through a Variac ( target 115 ) with a TDR.

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