Very good reference material when it's completed.   

Having my WA5 open box over a month,  but only then I spent a hour today to clean all pins for this WE tubes set and add adapters for the TSRP/ SYMB driver tubes, WE274A rectifiers (still looking for a pairs of high quality straight adapters for 300B). I managed to have the tubes loaded and prepared to experience the first test drive listening. I would also verify which driver TSRP/ SYMB I like better with the WE300B/ WE274A on my WA5.
 
Now time to power up and ready to rock!
 

 

 

 

 

 

 

 

 

Some of my very lovely vintage rectifier tubes collection Globe WE274A, Engraved WE274B, Marconi 5U4B/ U52 and GEC 5U4B/ U52 to be paired with the WE300B. Your know I spent some years to have them in pairs, no luck in originally matched, but all are tested at NOS level, they should be fine on WA5.

When will your beautiful Woo ever get off that wooden dolly and onto a proper shelf taking center stage in your listening room?  
 
all kidding aside, that's a great selection of tubes.  Listening will surely be a lot of fun.  

t bone said:

  When will your beautiful Woo ever get off that wooden dolly and onto a proper shelf taking center stage in your listening room?  

 
all kidding aside, that's a great selection of tubes.  Listening will surely be a lot of fun.  

Click to expand...

 
I am adding my tube collection and impression to Tube Register & Impression Register, it will end up with 200 tube combinations or so and more than 800 effect with the change of DAC (x2) and signal cable (x2), and over 4,000 impressions when I use different headphone (x5). Yes, that is a lot of fun and full of excitement to discover something impressive.
 
That is a big project to roll over a round for all these possible configuration in tubes, DAC, cable, headphone and other accessories, look like my trial would never finish. My WA5 would be sitting on the dolly at least another few months if not years ......  

Have some interesting DIY work on my WA5 today, I loaded it back on the dolly after the work, and it looks balanced, stand still and stable. I am about to have a follow up listening session, see if it does make a noticeable difference ......

And just completed a follow up session ...... Yeap! What a difference in sonic effect (clarity, resolution of tone, dynamic response), feel like adding another upgrade! SWEET!

Got unboxing and Tube Register another WE300B pairs in their 1960s with double D getter, both tested at NOS level. Just have a trial drive for an initial impression, I would record the difference with the 1950s pairs in the Impression Register after I got into serious listening session.
 

 

 

 

 

 

 

 

 

 

Have my third pairs WE300B Tube Register, vintage tubes in their 1950s, tested at NOS level, D getter with code USN-CW.
 

 

 

 

 

 

WA5 Soft-Start & External Power Switch
 
A simple DIY adaptor to facilitate learning the AC electrical behaviour of my WA5, four AC current were measured with 220V AC supply at initial power up, just before the completion of standby countdown, just after the standby and WA5 run stable some minutes afterwards. I also discounted the ground line (green-yellow wire)/ neutral line (blue wire) without power up to WA5 to verify some interesting finding with my WA5.
 
So I got all answers for my questions in mind today, they do mean something important, and I would go with some optimized work on the AC power supply for my WA5.
 

 

 

 

 

 

 

 

 

I am adding a resistor and a power switch in the AC power circuit to simulate a power soft-start for WA5 and managed to experimenting a best delay interval before bypass the resistor, it seems working (a 3-4 seconds delay before supplying WA5 with full power is feasible) that limited the startup current apply to WA5 (and life safer for my beloved tubes).
 

 

 

 

 

Confirmed that adding soft-start resistor is feasible, I end up making it into a resistor in 450 ohm (= 9 x 50 ohm, 20W in serial). 
 

 

 
And check my experimenting videos without/ with the Soft-Starter Resistor. AC current measured during my WA5 power up in initial 40 seconds. Note that the tubes on WA5 took about 50W power (5V, 10A or about 220V, 0.22A).
 
Stage 0 - Second 00-01 , system power up 0.7A (actually much high and may be over 1A)
Stage 1 - Second 02-24 , tube warm up, falling steadily from 0.7A to 0.4A
Stage 2 - Second 25-25 , B+ activated, radically go up over 1A
Stage 3 - Second 26-40 , system stabilized, falling steadily and keep staying at about 0.7A
 

 
See the difference with the Soft-Start 450 Ohm Resistors installed, and a 30 seconds delay for tubes pre-warmup (under-powered),  the WA5 then supplied with full AC power and lasted for another 15 seconds of tubes warmup,  the internal control circuit now bring in the B+ at second 45 (instead of second 25).
 
Stage 0 - Second 00-01 , system power up, limited max. current under 0.5A (=220V / 450 Ohm)
Stage 1 - Second 02-30 , under-powered tube pre-warmup, falling steadily from 0.27A to 0.18A
Stage 2 - Second 31-44 , tube warm up, falling steadily from 0.42A to 0.4A
Stage 3 - Second 45-45 , B+ activated, radically go up over 1A
Stage 4 - Second 46-50 , system stabilized, falling steadily and keep staying at about 0.7A
 
 

What these videos tell? In this case, the stable condition 0.4A = 0.22A for tubes + 0.18A for other components before the B+ in place. The tubes on my WA5 may be suffering an initial "cold" current over 0.7A (actually higher, maybe over 1A), but they only need about 0.22A in total under normal operating condition according to paper specifications.
 
It worked, the Soft-Start Resistor limited the startup AC current under 0.27A (second 0-30), and 0.42A max (second 31-44) just after supplying WA5 with full AC power, though the internal control circuit now bring in the B+ at second 45 (instead of second 25). It is almost a perfect arrangement with no inrush current over the specifications for normal operations. And believe me, it not only saved your tubes, but also sound much better even with the stock tubes, everything does goes with much more pleasure in sonic effect with this under-powered pre-warmup!  

Also confirmed that my WA5 V2 version has a refined design for rectifier connection, it also used the center tap of the 5V-0-5V, the rectifiers on WA5 may consider working independently in a parallel configuration.
 

 

 

 
Also check the difference in rectifiers wiring in pics from 6moons audio review (upper) & my WA5 V2 (lower).
 

 

 
Now interesting questions ..... can I mix use one WE 274B and one GEC 5U4G on my WA5? And if feasible, what would be the sonic effect? Should it be a new effect differ from that from a pairs of WE 274B and a pairs of GEC 5U4G?!

More about the AC power supply for WA5, I experienced noticeable “hum” noise when the WA5 connected to AC power, but after power up, it just gone and in fact no impact on sonic effect or quality during listening. Disconnecting everything from signal inputs, changing tubes and headphone could not help, but offline the Neutral wire from AC power source did make a difference.
 
I thought that was the AC signal captured by the power transformer in PSU, go via the DC cable to the AMP unit then appeared in the headphone output. To get rid of this "hum", I would like to have a 2P power switch is serial connection with both the Live and Neutral wires, such that it disconnected both wires after power off WA5.
 

 

 

 

 

 

 

With the result from previous experiments for Soft-Start Resistor and the scenario of AC “hum” noise experienced while WA5 power off, I worked out a diagram and decided to DIY an external power switch as shown for my WA5 to life safe tubes and get rid of the “hum”.
 
It is simply composed of a Soft-Start Resistor, 2P power switches and indicators , no delay circuit nor power relay. I would put all components in a palm side alum case (*** caution: chassis properly grounded ***), and attach it aside the WA5 PSU. Full manual operations would be just fine with me, the live operation procedures would be:
 
Power On:
AC In shine -> SW2-ON -> Delay Count -> SW1-ON -> AC Out shine -> SW2-OFF.
 
Power Off:
Confirm SW2-OFF -> SW1-OFF -> AC Out dim.