There's a good time to use the Weber WS-1 SS rectifier...

...and that is when your line AC is low consistently. Mine has been running as low as 114.8 VAC and no higher than 118 VAC. That was lowering my B+ voltage to the lowest of its recommended range of 370-410 VDC when using a 5AR4, and not much higher with the usual Weber WZ-34. The WS-1 contains no sag resistors, so it must be used only in units with some soft-start mechanism. And it can raise the B+ to dangerous levels if your line voltage is normal. But here in my humble adobe, it works perfectly. Result is crisper sound up and down and particularly a real solid, deep bass response. Never thought I'd love pure SS rectification, but we can teach old canines new games, apparently.
BTW audiobill - Engineer Extraordinaire, agrees that this an elegant solution. And he is practically a god...kinda.
P.S. Because of zero resistance, the WS-1 runs cool, unlike the WZ=34, which is known to melt in your amp, though not in your hand.

Yup... IMO there is nothing special about using a tube rectifier to convert AC to DC in an audio amp.  Tubes are a very inefficient way to do that.  Large B+ voltage drop that varies with current draw and 10-15W of power burned up just heating the rectifier cathode.  SS rectifier better regulates an unregulated power supply.  Tighter bass and imaging are just a few sonic benefits of more efficiency topping off the power supply caps.  The amp runs cooler as well.  Tube guitar amp different story in using the voltage sag as part of the feel of the amp.

Which amp are you trying this in (370-410V DC)?  Doesn't sound like your ST-120.

You are correct to stress the warnings.  Higher B+ due to less voltage drop.  SS rectifier operation most certainly requires a delay to give the audio tubes time to sufficiently warm up before applying B+.  I have been happily running a WZ1 in my ST-120 for 2 years without issue.  I do though have the unused rectifier +5V heater transformer winding wired up as a bucker to the incoming AC voltage.  Reduces secondary voltages about 4% and keeps B+ right at 500Vdc with 120Vac coming in.  Initially my biggest worry was heater voltages dropping too low to reliably operate but I have seen line voltage down to 114Vac and up to 122Vac and my bucker wired ST-120 never skips a beat.  And I am using heater heavy draw KT-120s and one CV-181 as well.  SS rectification can sometimes add diode hash noise induced by the faster switching on and off of SS diodes.  I've had no issues with this type noise using a WZ1 or WZ68 in the ST-120.  

It has been an win-win: better sound, less heat, constant maintenance costs seeking out beefy, old Mullard tube rectifiers, or occasional rectifier fireworks drama when one blowns.

"Which amp are you trying this in (370-410V DC)? Doesn't sound like your ST-120."

That's the B+ as measured on the driver board.

Kentley wrote:"Which amp are you trying this in (370-410V DC)?  Doesn't sound like your ST-120."
That's the B+ as measured on the driver board.

OK, that makes sense with the voltage drop downstream for the board. Thanks

There is one thing to consider for tube rectifiers, ( other than the simple fact they are vacuum tubes and not sand ) tube rectifiers don't have switching noise.

I was using a WZ68 with TungSol KT120's and did not notice any difference in sonic quality compared to a tube rectifier. In my younger days when I was a self proclaimed audiophile I'd swear I could hear the difference between all comparable audio components. Nowadays maybe my ears are tired (though recently I had a hearing test and the audiologist claimed I did very well) and I just don't care to think that there is enough of a sonic difference to make chasing that last little nuance necessary.

Tubes4ever wrote:There is one thing to consider for tube rectifiers, ( other than the simple fact they are vacuum tubes and not sand ) tube rectifiers don't have switching noise.

I've heard about this switching noise, looked around but can't find much about it, is this some constant noise or?

jfine wrote:

Tubes4ever wrote:There is one thing to consider for tube rectifiers, ( other than the simple fact they are vacuum tubes and not sand ) tube rectifiers don't have switching noise.

I've heard about this switching noise, looked around but can't find much about it, is this some constant noise or?

https://electronics.stackexchange.com/questions/217212/how-can-i-observe-rectifier-switching-noise


An excellent explanation of "ringing" and switching noise with some equally excellent illustrations and demonstrations. Upshot of which: Not to worry at the levels under discussion here.

Diode switching noise "sounds" like buzzing or frying versus plain ole 50/60Hz hum.  The power supply filter caps and choke (inductor) form a resonant circuit and if the rectifier switching artifacts stimulate this resonance then you have the ringing as Peter mentions.

Here's some food for discussion and thought.  If you use the yellow sheet diode mod the 1N4007 diodes turn on/off faster than a tube rectifier is capable.  As a result these SS diodes are probably doing the bulk of actually turning AC into DC in your amp.  You may actually have SS rectification with a slower reacting tube in series.  The tube's slowness in turning on may block any SS diode ringing but it's tardy turn off could also pass the more abrupt SS diode's turn off ringing.  

Fortunately, the ST-120 is heavily filtered and likely the power supply resonant frequency is very low and seems impervious to any type switching noise.  I have built many guitar amps with much lighter filtering and more gain.  They will chatter readily with switching noise when using modern, fast switching SS diodes.  ("Ain't rock and roll unless you have some noise" a guitar tech told me once).

Just my experiences and observation.  Not trying to flame anyone's senses or say I am an expert.  Use what you like best and be happy about it!

arledgsc wrote:If you use the yellow sheet diode mod the 1N4007 diodes turn on/off faster than a tube rectifier is capable.  As a result these SS diodes are probably doing the bulk of actually turning AC into DC in your amp.  You may actually have SS rectification with a slower reacting tube in series.  The tube's slowness in turning on may block any SS diode ringing but it's tardy turn off could also pass the more abrupt SS diode's turn off ringing.  

I was wondering about this, applying the 1N4007's seems to negate whatever reasons you might want to run a rectifier tube, I mean at that point, might as well use the weber?

jfine wrote:I was wondering about this, applying the 1N4007's seems to negate whatever reasons you might want to run a rectifier tube, I mean at that point, might as well use the weber?

Perhaps... On my tube rectified guitar amps, to avoid switching noise, I use a single SS diode protector directly downstream of the tube rectifier. In this case the diode is always conducting and never switches on and off. The tube does all the rectification. On power failures the single diode protects in the same way as the dual upstream diodes. Solved the issue with noise and gave me peace of mind. 1N5408 diodes with a 3A continuous current limit are great choice for downstream diodes.