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sovtek , JJ or Shuguang ?
thanks
LT
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I've had the Shuguang 5AR4s in my 60 Watt KT88 monoblocks for 2 months now. No reliability issues. As to the sound, I've swapped them with Mullards and Sovteks and have observed the following. The Sovtek sounds grainy in comparison to the Shuguangs. When switching to the Shuguang, the clarity of the highs and liquid of the midrange came as a surprise as the Sovteks sounded fine prior. (I really wasn't expecting there to be any difference.) Between the Mullard and the Shuguang? They are both good sounding. I'd say the Mullard presented a slightly wider soundstage and a little more lower bass. The liquid midrange of the Shuagang and fine highs made the Mullard sound a tad dry and soft.
This is my initial experience with only one set of each brand. I can tell you that all tubes were good and displayed very similar characteristics on my rectifier tube load tester.
I have never "rolled" rectifer tubes before or compared them to SS rectifiers. (After this I guess, I'm going to have to set some time aside for same.) My Shuguangs were purchased from Jim McShane in April 2012.
Jack
Likewise, with the 5V4/GZ32, old tubes, even good used ones, are the clear winner for longevity. Consider buying any of the new rectifiers and risk blowout within two years; Add the cost of two new tubes plus postage over three to four years, if you are lucky, and you quickly realize that good old stuff is the best bet.
Now, tally your current requirements. You might be able to get by with a 5V4GA instead of a 5AR4; much cheaper. Stay within current limitations, of course.
When I hear of all the failures with new rectifiers, my head spins. Depending on the month/year of manufacture...; are they kidding ? Quality control is amiss these days; certainly. Stick with known quality. Buy good used tubes from reputable sources...
Add diodes to the input to take up most of the load so new production will last, especially needed in big amps. It keeps the nice slow warm-up feature the 5AR4/GZ34.It won't hurt the sonics and the newer faster UF4007 diodes may make a noticeable improvement over IF4007 for a few cents more!
If the tube is on a PCB board you can put the diodes in series using heat shrink tubing over the PS transformer secondary B+ leads and even diodes for strength.
Make sure polarity of diodes are correct.
I found this mod 3 yrs ago @ diyaudio by an Engineer Kevin Kennedy whom had been doing it for 10 yrs + with no tube failures after. It's quite popular now.
Lastly it will help the tube last when you have a power failure where it flashes off & on quickly!
Randy
Edits: 06/06/12 06/06/12 06/06/12 06/06/12 06/06/12 06/06/12
I was under the impression that the tube itself blocked switching noise so you didn't even have to use UF4007's in this trick. There is no advantage over using 1N4007's. Maybe someone else could ring in.
Edits: 06/06/12 06/06/12
As UF4007s are about 15 cents each, better (IMO) not having lots of switching noise, to begin with. The difference in the switching noise dept. is substantial between UF400n and the corresponding 1N400n parts.
Eli D.
Right, can't go wrong for the little extra money.
Sovtek. Only one immediate failure out of many tubes. Likely rough handling issue. I only used at 375 volts output.
Avoid the JJs!!
My experience says the Sovtek handles higher currents better than the Shuguang/Chinese. Conversely the Shuguang seems to handle voltages above 450 or so better, but isn't happy with higher currents.
So one of those two will be the best match for your needs.
Jim, if you do the diodes in series trick is it safe to have 40uf or even 50uf right after the new stuff? Also which would you recommend for a Dynaco ST70 and Eico ST70?
Edits: 06/05/12 06/05/12 06/05/12
I'd recommend the Sovtek with the diode mod for either of the two amps. And yes, 40-50uf will be okay there.
Dennis Hadd put a pair of series 1200uf after the gz34..It may have had a slow turn on but YIKES!!
When problems become increasingly difficult,we can always rely on our collective knowledge and seek relief.
Haad abused more than his share of vacuum rectifiers. :> ( That some survived is a miracle.
If you want to use HIGH value cap. I/P filters, SS rectification is a must. Even with SS diodes' toughness, NTC inrush current limiting is in order. Stop power trafo clang.
Eli D.
Hi Eli,
Thus slowing down the HT/B+ a bit more?
Waste of a few cents?
TIA
Note that a post in response is preferred.
Warmest
Timothy Bailey
The Skyptical Mensurer and Audio Scrounger
And gladly would he learn and gladly teach - Chaucer. ;-)!
'Still not saluting.'
I have never found the in rush limiter to reduce voltage on turn on,only current if you were to measure it. It does prevent arcing of tubes and reduces the chance of damage to filter caps ..Mcintosh used them for years in the Mc240,Mc275,Mc225,and the monos with a SS power supply.
They do work well tho.
When problems become increasingly difficult,we can always rely on our collective knowledge and seek relief.
So, a second one on the HT/B+ wouldn't hurt.
There's a snubbed full-wave SS rectifier set-up using way overrated SoftRecovery diodes in each amp, the tech added an NTC on the primary in each.
Since the early 90s I don't do HT work, promised TMFW&F! But I could always solder one in when they've been off a couple of days, no? ;-)!
Note that a post in response is preferred.
Warmest
Timothy Bailey
The Skyptical Mensurer and Audio Scrounger
And gladly would he learn and gladly teach - Chaucer. ;-)!
'Still not saluting.'
So, a second one on the HT/B+ wouldn't hurt.
Its actually preferred.
When problems become increasingly difficult,we can always rely on our collective knowledge and seek relief.
Likely to be rebuilding two TL12 Plus soon. The mono versions with an EF86 input tube. Both small signal tubes will become a 6DJ8 twin-triode one triode only, and a 6CG7 and a FET CCS.
For two bass channels up to 150 - 400 hz 3rd order filter, possibly a knee'd type, a PLL* 1st then cascaded by a 2nd order active low-pass.
20wpc in UL or ?watts in pentode, we'll see!
I'll probably add AC balance pots and a LED to each op't stage in all 6 channels.
*One more question, with Passive Line Level filters, a bandpass filter is possible? Yes?
IE a 1st-order 'matching' high-pass in the bass and a 1st low-pass at 6kHz?
Note that I'll be using the sealed sphere's own 2nd order slope as well. The driver is a WR 5 inch and should be okay power-wise with a 1stord. and the enclosure's own roll-off. I'll need to reduce the Vb with some roof-tilers epoxy/sand mixture.
Three spheres stacked using cut-down basketball hoops and and adjustable height column-stand per side.
Columns? Remember when DOS type computers and their noisy dot-matrix printers needed a 3 shelf thing on 4 rollers? That's where the two columns will come from. Two triangular bases and 2 more matching rollers.
You'll soon have mail.
Note that a post in response is preferred.
Warmest
Timothy Bailey
The Skyptical Mensurer and Audio Scrounger
And gladly would he learn and gladly teach - Chaucer. ;-)!
'Still not saluting.'
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