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Dynaco ST120 rectifier

Aw Hell. IF (and it's a BIG IF, based on looking at the pics on Bob's site)!
1.) The Transformer can handle the extra load from the 5V heater tap,
2.) And There's space for one on top,
Why not Use paralleled 5AR4's. It looks like the CAN CAP can be installed underneath leaving enough space for a 2nd 5AR4. Looks wise it would look more balanced than it is now with that skyscraper can cap.
 
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The WZ68 actually has a built-in NTC thermistor. I don't remember the specs at the moment, but it is present. I don't see the need for an additional thermistor with the TDR and the WZ68.
 
All done and back up . I like the WS1 and TDB working good. I'm using my ST120 to bi-amp the top end and it now sounds more "punchy" but not bright. I mounted the LEDs inside the vent hole in front of the rectifier for some eye candy . I think I will roll some 12AU4's on L&R I have one that fails grid leak . I have one those VU meter kits from China but the meters were just a little to big to fit in the output power socket holes (I was thinking about , probably better off they didn't fit). I did connect the two lower pin holes on those sockets to ground for hands free biasing .Webber told me the WZ68 will give about 5 seconds of delay . Later
 
So, take a photo of your LED arrangement. I'd be interested in seeing how it turned out. And yes, the WZ68 produces current equivalent to two 5AR4/GZ34 rectifiers.
 
eickmewg said:
The WZ68 actually has a built-in NTC thermistor. I don't remember the specs at the moment, but it is present. I don't see the need for an additional thermistor with the TDR and the WZ68.
Click to expand...

I thought so too but one fell open on me and I did not see the thermistor inside. Only 2 diodes.
 
20171115_091210.jpg Do you WZ68 users notice the "Sag" that Webber Speakers talks about ?
eickmewg I used 5 second fix to hold the LEDs in place ,the green fell in a little . It would have been more work to mounted them in output socket pins and in hindsight the green always on might have gotten annoying . They are visible on top if you want to see them . I thought abut making some kind of LED holder but they are so small . The 5 second fix is working so far .
 
calman46, your setup looks interesting. You must have pretty long leads on those LEDs. As far as "sag" goes, I never measured B+ voltage after going to the WZ68. How much did you have to dial down on the bias pots with the WZ1? Finally, I took the cap off my WZ68 to drill some ventilation holes. IIRC, I am pretty sure the guts consist of two diodes, two high-power cement resistors, an NTC thermistor, and a spring between the resistors to force them against the copper cap.
 
The leads ,maybe 6 inches . When you order any copper cap rectifier from Webber there two options , with a thermistor or not . My WS1 does not get hot and you can disconnect the tube filament voltage wires ,or not ,or use it for something else . I just left it alone
 
From what I can tell, only the WS1 has the option for a thermistor. No such option for the WZ34 or WZ68, both of which I am pretty sure include the thermistor. That WS1 appears to pass twice the current of a WZ68 and 4 times the current of a WZ34. That's lots of juice!
 
I have a tube question on amp. The 3 12AU7 could you run two 12BH7 (L&R sockets 1&3) and one 12AU7 ? (in the center)
 
I run two 12bh7's with an e80cc in the center. If you have the bigger power transformer, yes you can. The original Dynaco power transformer doesn't have enough heater current for the 12bh7, e80cc, ecc90, ect. Thats what ive been told anyway.
 
You have plenty of heater capacity. Get a tube adapter and try a 6SN7 or CV181z in the center position. I believe either option will best a 12AU7.
 
The amp came with 3 NOS GE 12AU7. One the them shows fluctuating grid leak on my Mighty Mite VII. So that tube is out. Now I have the two GE's in #1 & #3 and a RCA 12AU7 in the #2 socket . The RCA tested real good , flaking red printing. I'm going to try 12BH7 in #1#3 and some different 12AU7 . I have all these tubes .
I'm not sure if I have the heater capacity you mention .
 
From the description of the VTA ST70 on Bob's tubes4hifi page. And note the VTA ST120 power transformer has higher ratings in general but I see no maximum 6.3 V heater winding amp value. I assume the value is at least that of the VTA ST70 transformer and, more likely, greater.

"2. The new USA made power transformer has a higher stack lamination than the original Dynaco power transformer and is rated
for 120 volts instead of 115 like the old design. The two tube heater legs are rated for 5 amps each instead of 3 amps each
like the old design."

"5. The upgraded VTA driver board uses three new 12AU7 or 12BH7 triodes in place of the two mediocre sounding 7199 pentode/triode tubes."

If you can use three 12BH7's you have plenty of current for 6SN7's which also draw 600 mA at 6.3 V. Therefore, you are good to go. I have seen a number of evaluations where the 12BH7 was deemed superior to the 12AU7, and the 6SN7 is also highly valued as a preamp tube.
 
You it would be safer to use just one 6SN7 in the Center and 12BH7 #1 &#3 . So you can mix and match the tubes but keeping the #1& #3 the same type .
 
Yes, you could do a 6SN7 in the center amplification position and either 12BH7 or 12AU7 phase splitters in #1 and #3. If you already have the 12AU7's, I'd leave then in #1 and #3 for now and go for a 12BH7 or 6SN7 in the center. I have had rather bad luck with new production 6SN7's being rather noisy. You could keep an eye in the Barter Town-Parts for nice old NOS or high-testing used Sylvania 6SN7's. And remember to get the tube adapter if you plan to try the 6SN7 route. The 12BH7 goes into the original socket. See what you like, but you have no heater current worries anyway you choose to go.
 
Some here really like the 12bh7's and 6sn7's in the center. The old stock E80CC and JJ ECC90 are a couple more that sound nice
 
I'll try the 12bh7 in center with the 12au7 @ # 1&#3 . I have some 6sn7 ,there're used but the bags are marked EX and GOOD . I'm reading the 6ns7 draws twice the current.
 
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