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Wharfcreek
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Rbertalotto
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    SS vs Tube Rectifier???

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    Rbertalotto


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    SS vs Tube Rectifier??? Empty SS vs Tube Rectifier???

    Post by Rbertalotto Mon Jun 28, 2021 11:35 pm

    I'm sure this has been discussed forever. But maybe there is something new to add.

    Is there any real difference sonically between a solid state and a tube rectifier?

    What are the pros and cons of both.

    Currently my ST120 is running a SS rectifier. Just wondering if there is anything to gain going with a tube.

    I believe I will need to make some internal wiring changes to use a tube?

    Thanks!
    corndog71
    corndog71


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    Post by corndog71 Tue Jun 29, 2021 8:07 am

    The only thing you really gain is another tube to look at. Solid state will likely be more reliable. I’ve burned through a lot of cheap and poor quality tube rectifiers. The yellow sheet mod helps protect the tube rectifier and in my opinion is worth doing.

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    Wharfcreek


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    Post by Wharfcreek Sun Jul 04, 2021 1:53 am

    First, this is a highly debatable subject.  From a purly 'electronic' standpoint, the process of 'rectification' is essentially the same, whether done via a solid state device or a vacuum tube.   However, it's really not quite that simple!!  There are 'characteristics' of both that can come into play in the audio world.  When dealing with solid state rectification, you have a minimal 'voltage drop' as associated with the rectification process. However, as most any solid state device is a 'switching device', this introduced some noise issues with some of the early solid state rectifiers.   This noise was limited by better designs in power supplies, as well as the introduction of better devices.   In today's world, the problem is minimal, but it can still raise it's ugly head from time to time.   As to 'tube' rectification, the problem of 'switching noise' was virtually non-existant.   BUT, you have 2 other things that have to be addressed:  The first is the obvious need for a secondary filament source for the rectifier itself, and the second is the amount of voltage drop associated with the tube being used.   In both cases it is the job of the product designer to address these issues and construct a proper design that results in properly functioning product.   Once that product is in the owner's hands, you now get into that area of 'What if I change things myself?' This is where you simply have to know what you're doing.....or risk the consequences.  

    To directly answer your question, the simple fact is that if you use a solid state device as a replacement for a 'tube' rectifier, you'll likely encounter a change in voltage supply to the amp.  This change in voltage can often result in a change in sonic signature.  This 'change' is not the same in all amps........so to attempt to describe it is really somewhat futile.   BUT, this is really no different than what one might experience if, for instance, you had an amp that was designed to use a 5U4 rectifier, and you decided to replace that with a 5AR4 rectifier.   The difference here is roughly 40 volts INCREASE within the power supply.   If you changed a 5U4 to a solid state rectifier, it would increase even more.   And, this 'increase' in voltage would likely result in a change in the characteristics of your amp.  This, in turn, might be simply boiled down to 'accuracy'!  If the original design of the amp in using the 5U4 produced the most accurate frequency response, then the increase in voltage would likely alter things such that an 'inaccuracy' could now be measured at some points within it's audio frequency response.   To some, this might sound better!!   To others.....not so much.   But, were you to swap out a 5U4 with a solid state rectifier circuit that would emulate the 5U4 voltage response, then you might end up having very little if any detrimental affect on the amps distortion levels.

    In the hi fi world, this is pretty critical stuff...as 'accuracy' is really the primary target.   In the musical instrument amplifier world, it's a different story.   There the swap from a 5U4 rectifier to a 5AR4 or a solid-state 'plug' type rectifier can affect the amp in a very favorable way......if you're the musician!  Of course, the amp's power supply filter section may ultimately fail and need to be replaced and updated...... as the increase in voltage may simply be too much for old filter capacitors.   But, that's what happens in the guitar amp world!!   In the Hi Fi world, the need for all the considerations is a bit different, as the 'results' of this kind of a change is NOT always in the best interest of reproducing music accurately.   But, if proper attention is paid to all the variables associated with making the change, then at the very least, the system will likely benefit by the reduction in demand from the power transformer to light up the rectifier.   Beyond that, if the desing calls for 400 volts, and that's what you get with your Tube rectifier, and if you change to solid state and 'adjust' to maintain 400 volts (which is the proper thing to do)..... then as long as the rest of the amp's power supply is doing what it should to support the current demands, you should experience virtually no difference in the sonic performance from an 'audible' perspective......or so I believe to be true.  Likewise, if you go with a Tube Rectifier FROM a Solid State rectifier, again, as long as both the voltage and current requrements of the amp are met by the divices chosen, then all you're really doing is (as stated above) adding another tube to look at, and another filament to power up, and you'll likely hear no difference at all. Just my opinion, but I'm stickin' to it!!

    Tom D.


    Last edited by Wharfcreek on Sun Jul 04, 2021 1:57 am; edited 1 time in total (Reason for editing : Added a closing comment.)

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    Rbertalotto


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    Post by Rbertalotto Sun Jul 04, 2021 2:01 am

    Thanks Tom, I learned a lot right there! Appreciated!
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    Wharfcreek


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    Post by Wharfcreek Sun Jul 04, 2021 2:45 am

    Like I said, it's kind of a 'debatable' subject, just like the subject of 'Can you hear a difference between a 5AR4 from Mullard vs one from JJ?'. Or worse, the debate over which 12AX7 sounds better? I tend not to enter into such discussions. BUT, when it comes to distinctions between types of rectifiers, or rectification, there is distinct 'voltage' characteristics involved there, as well as 'current' aspects as well. Not only are there deviations in 'voltage drop', but also in 'current capability'. A rectifier that cannot supply the needed current, even though it CAN supply the proper voltage, that will also generate the potential, and in fact likelihood, of sonic distortion that will be 'audible', particularly in high demand (volume) circumstances. To me, the first question really is: Did the designer of the amp do his job properly? That is often never known, as the 'upper management' can often require changes for 'cost' reasons that might have a detrimental affect on the original design. Then you have 'Production' issues that can also come into play! The 'sourcing' of component parts in which to build the product can some times result in additional corner-cutting, again all for 'profit' reasons, although some times it's just to keep production rolling when 'original' parts aren't available. But, if you assume that once you've got it and once you confirm you like it, then from there any 'mods' you make are purly at your own discression. The idea that any amp can be 'improoved' is probably true..... but at some point you end up being further ahead just to buy a different amp....or build one! But, it's also an 'educational' thing.....and 'modding' also 'teaches'. So, have at it! Good luck, and I hope it works out for you! Tom D.

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    Rbertalotto


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    Post by Rbertalotto Sun Jul 04, 2021 4:23 am

    My VTA ST120 has the proper SS rectifier circuit and a SS rectifier. It sounds fantastic and I'm going to leave well enough alone....."If it ain't broke........"
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    nuketech


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    Post by nuketech Sun Jul 04, 2021 4:37 am

    I prefer the “soft start” of tube rectification for preamps.  No power up thumps. I believe tube rectifiers are easier on the downstream components of the power supply on all amps and preamps. IMHO.
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    Rbertalotto


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    Post by Rbertalotto Sun Jul 04, 2021 4:50 am

    If you install the "Time Delay TRelay" board from Bob, there is no thump or surge from a SS rectifier....

    "This is a "time delay relay" board" for tube amps and preamps.
    The time delay allows the tube filament heaters to come up before any high voltage is applied. The time delay is nominally about 17 seconds but may be adjusted for more or less delay at the discretion of the user. There are complete instructions for the assembly and installation of the board. In a stock ST-70 the board replaces lugs 5, 6 and 7 of the 7 lug terminal strip. In a VTA ST-70/ST-120 tube amp kit, the VTA-TDB replaces the 3 lug terminal strip. The VTA-TDB may also be easily retrofitted to any VTA ST-70/ST-120 tube amp kit.

    The board is 1 7/8 inches wide by 2 1/2 inches long. It takes about 1/2 hour to assemble and is powered by a 6.3 volt AC line taken off V2. When the board is powered up a RED LED lights up to show that the board has power. About 17 seconds after power is applied, a GREEN LED comes on, and the relay kicks in to apply high voltage to your amp. Another nice thing is that if you are in an area that has quick ON/OFF/ON power interruptions the board will automatically reset itself. In other words, if your power goes OFF and then ON again a split second later the board will automatically reset itself and no high voltage will be applied for another 17 seconds.

    This is only a delay board - you still need a solid state or tube rectifier to plug into the rectifer socket. If you use a GZ34 tube rectifier IMHO you can get by without it. If you use a solid state rectifier like the Weber WZ68, which only has a 3 to 5 second delay, I think it is helpful. It would also be helpful if you have the quick ON/OFF/ON power interruptions.

    This board is to be used ONLY for solid state rectifiers. If used with a TUBE rectifier, the TDR can cause problems with the normal slow warm up of the tube rectifier and may damage a tube rectifier. If you intend to use a TUBE rectifier ONLY with your amp, you do not need the TDR. If you do use a tube rectifier with the TDR, you should BYPASS the TDR. Instructions are included with the TDR on how to bypass the TDR."
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    Post by DavidR Sun Jul 04, 2021 9:16 am

    Rbertalotto wrote:If you install the "Time Delay TRelay" board from Bob, there is no thump or surge from a SS rectifier....

    "This is a "time delay relay" board" for tube amps and preamps.
    ..........................................................................................................................................................

    This is only a delay board - you still need a solid state or tube rectifier to plug into the rectifer socket. If you use a GZ34 tube rectifier IMHO you can get by without it. If you use a solid state rectifier like the Weber WZ68, which only has a 3 to 5 second delay, I think it is helpful. It would also be helpful if you have the quick ON/OFF/ON power interruptions.

    This board is to be used ONLY for solid state rectifiers. If used with a TUBE rectifier, the TDR can cause problems with the normal slow warm up of the tube rectifier and may damage a tube rectifier. If you intend to use a TUBE rectifier ONLY with your amp, you do not need the TDR. If you do use a tube rectifier with the TDR, you should BYPASS the TDR. Instructions are included with the TDR on how to bypass the TDR."

    My ST120 came with a TDR and tube rectifier - a Sino 5AR4. I had it for about 3 years now and no issues (I swapped the Sino out with a Tung Sol for no specific reason other than to have all Tung Sol tubes.
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    nmchiefsfan


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    Post by nmchiefsfan Mon Jul 05, 2021 7:42 am

    I don't see any reason that the TDR board would be a problem if you use tube rectification. I included the TDR board when I purchased/built my Latino 120 back in 2012. I thought that it was good insurance against short cycling the amp due to power blips. I have been using the same Tung-Sol 5AR4 (purchased from Jim McShane) since July, 2016. It must have 5000 hours on it. I bias the amp at .5V (50mA) per tube as I have very efficient speakers and and I listen at moderate levels. I have 2 spare Tung_Sols but haven't needed them yet...though I may have just jinxed myself.


    Last edited by nmchiefsfan on Mon Jul 05, 2021 7:43 am; edited 1 time in total (Reason for editing : typos)
    Tubes4ever
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    Post by Tubes4ever Tue Jul 06, 2021 3:38 am

    nmchiefsfan wrote:I don't see any reason that the TDR board would be a problem if you use tube rectification.  

    The reason that the TDR shouldn't be used with tube rectification is due to a condition called "Hot Switching". Since the rectifier cathode is already hot when the voltage is applied and the filter capacitor is not charged, a high inrush current through the rectifier is created. There is a spec. for Hot Switching current in the tube spec. sheet. If there isn't sufficient resistance in the power supply circuit, you will exceed that current spec. The VTA 70 and 120 don't have enough supply resistance to keep the surge current within limits.

    This all doesn't mean the tube will fail immediately, it just means that the condition is hard on the tube.
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    Post by nmchiefsfan Tue Jul 06, 2021 4:00 am

    Tubes4ever wrote:
    nmchiefsfan wrote:I don't see any reason that the TDR board would be a problem if you use tube rectification.  

    The reason that the TDR shouldn't be used with tube rectification is due to a condition called "Hot Switching". Since the rectifier cathode is already hot when the voltage is applied and the filter capacitor is not charged, a high inrush current through the rectifier is created. There is a spec. for Hot Switching current in the tube spec. sheet. If there isn't sufficient resistance in the power supply circuit, you will exceed that current spec. The VTA 70 and 120 don't have enough supply resistance to keep the surge current within limits.

    This all doesn't mean the tube will fail immediately, it just means that the condition is hard on the tube.


    Gotcha. I never considered that. I put the board in to protect against hot cycling. Your post most likely explains why I blew through several Ruby and Sovtek rectifiers. Maybe I have the best Tung-Sol 5AR4 ever made but I have an incredible amount hours on it. After my post yesterday I thought it would for sure blow up but I ran the amp for another 12 hours.

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    Post by Tubes4ever Tue Jul 06, 2021 7:41 am

    nmchiefsfan wrote:After my post yesterday I thought it would for sure blow up but I ran the amp for another 12 hours.

    I know what you mean.  Maybe it didn't hear you typing. Very Happy

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