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Old 2nd March 2007, 09:23 PM   #1
Cobra2 is offline Cobra2  Norway
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Default Tube rectifier help

I was wondering, do the rectifier tube need to be matched to the load? - can I use a GZ34 or similar also for a preamp?

Better suggestions for both pre-amp & power-amp diode-tubes?

Arne K
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Old 2nd March 2007, 09:59 PM   #2
Sherman is offline Sherman  United States
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You don't have to "match" the rectifier to the load (except in the case of not exceeding the rated capacity). The circuit will draw what the circuit will draw and the rectifier will happily provide whatever is needed up to its rated current.
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Old 2nd March 2007, 10:20 PM   #3
Cobra2 is offline Cobra2  Norway
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So a oversized tube will be ok...
(maybe waste more heat?)

The 5AR4 / GZ34 seem to be common for many of the constructions I'm looking at.
But NOS tubes seem expensive...

Is there any other similar alternative?

Arne K
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Old 2nd March 2007, 11:18 PM   #4
ulibub is offline ulibub  France
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Hi Arne!

Why using NOS tubes? JJ is producing a GZ34, and their tubes have a very good quality. Also, some newer russian 5Y3GB-tubes have systems nearly identical to GZ34 - maybe with a bit less plate dissipation. And they are really cheap. Or use EZ 81, EZ 80. I use a small EZ 90 (6 X 4) in my preamp. All these tubes aren't expensive. No need at all to use over-priced NOS tubes. I wouldn't pay 100% more for a Telefunken or Valvo-stamp on the bulb.....

But in general, I would generously oversize rectifier tubes. This reduces their forward drop, increases lifetime and adds to the stability of a power supply.

Good luck!

Uli
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Old 2nd March 2007, 11:38 PM   #5
Cobra2 is offline Cobra2  Norway
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Thanks, you are right, NOS are getting way too expensive...
I would rather use a ~ $ 2 SS rectifier...
But have heard/read a lot of bad experiences with the "modern" 5AR4 / GZ34.

More reading to do...

Arne K
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Old 2nd March 2007, 11:47 PM   #6
Zen Mod is offline Zen Mod  Serbia
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Quote:
Originally posted by Cobra2
Thanks, you are right, NOS are getting way too expensive...
I would rather use a ~ $ 2 SS rectifier...
But have heard/read a lot of bad experiences with the "modern" 5AR4 / GZ34.

More reading to do...

Arne K

you can always use tv tube dumper diodes.........commonly dirt cheap everywhere

anyway-for preamp is everything OK ,regarding current capability;
which rectifier you'll use is more matter of availability or taste ; better smaller old one than biggie new one.

tip-you can always find good rectifiers (NOS) on fleabay-look for russian (or ex-russian) dealers .
there is somewhere fine thread about russian toob dealers in last few days
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Old 2nd March 2007, 11:55 PM   #7
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Remember to check the filament current required if you switch a rectifier tube type, some transformers may not be rated for the higher filament current. Also, there are octal plug-in solid state rectifiers, but if using these (or diodes in general), it's best to have HV standby switch, so as not to apply the HV current to the output tubes until they are warmed up.
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Old 3rd March 2007, 12:04 AM   #8
ulibub is offline ulibub  France
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Yes, TV booster diodes like the ever-present PY 88 are sufficient even for very powerful amps.

I did a look on my favourite tube dealer ;-), BTB-elektronik (www.btb-elektronik.de) in Nurnberg, Germany:

5Y3GT for 7,57 Euros
GZ34 (unbranded) for 10,63
GZ 34 JJ for 12,90
EZ 81 JJ for 7,50

The PY 80, 81, 82, 83, 88 between 1,50 and 2,60 .....
Even the mighty PY 500 A for only 4,63 .....

From the single (booster) diodes you'd need at least two....

GZ 34 can be a bit sensitive to arcing due to its very low interior resistance (very small cathode - anode distance). Watch for careful current limitation.

Uli
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Old 3rd March 2007, 08:24 AM   #9
Cobra2 is offline Cobra2  Norway
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Quote:
Originally posted by frank754
Remember to check the filament current required if you switch a rectifier tube type, some transformers may not be rated for the higher filament current. Also, there are octal plug-in solid state rectifiers, but if using these (or diodes in general), it's best to have HV standby switch, so as not to apply the HV current to the output tubes until they are warmed up.
- "filament current required"...I have seen that mentioned lots of places. Is there any problem, as long as your trafo has enough juice? (As in SS, I tend to make trafos 2-100 times larger than needed...)

A "555" relay-delay is quick & easy to set up...for HT.

A resistor, or better, a thermistor would maybe be used to current-limit the filament "inrush/startup" current.
Is there a common thermistor with lower resistance than, say CL-60?

Arne K
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Old 3rd March 2007, 11:30 AM   #10
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I am buying NOS-tubes, all kinds AND rectifier tubes at www.tubesandmore.com. When looking for rectifiers for small poweramps and preamps I sometimes pick odd tubes like metal cased 5Z4, 5T4 or glass 6BW4 and 6X4.
Cannot say how much they are but a few USD.

I have been using Chinese Valve Art 5AR4 from TubesAndMore and they work OK and are rather cheap.
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