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beginners ecl82 power supply
beginners ecl82 power supply
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Old 24th September 2004, 03:10 AM   #11
planet10 is offline planet10  Canada
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beginners ecl82 power supply
Quote:
Originally posted by Luke
I have some of these valves and wondering if I should build it with valve rectifier or diode? Doesnt the valve rectifier have no turn on thumps?
Valve rectification gives you slow start... i usually decide based on what power rafo i'm recycling -- you get a significant voltage drop from the valve rectifier so your trafo needs to have higher secondaries.

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Old 24th September 2004, 03:21 AM   #12
Luke is offline Luke  New Zealand
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Sorry Fedgrove, I missed your response to my first question.
I thought as Planet 10 stated a valve rectifier gives slow turn on, doesnt this prevent thumps at power on?
I have a 250 0 250 and an ez81, any advantage to using the valve rectifier, if so whats the maximum capacitance I can put behind this rectifier. If I download the data sheet for an EZ81, will it tell me?

cheers Arthur
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Old 24th September 2004, 03:35 AM   #13
planet10 is offline planet10  Canada
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beginners ecl82 power supply
Quote:
Originally posted by Luke
I thought as Planet 10 stated a valve rectifier gives slow turn on, doesnt this prevent thumps at power on?
What Frank is saying is that the rectifier doesn't cause thumps, the slow turn on may well hide the thump caused by something else.

Quote:
I have a 250 0 250 and an ez81, any advantage to using the valve rectifier, if so whats the maximum capacitance I can put behind this rectifier. If I download the data sheet for an EZ81, will it tell me?
If i'm reading the spec sheet right this combo will give you 245 VDC, use a max of 50 uF input cap. Just about what you want....

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Old 24th September 2004, 04:42 AM   #14
Luke is offline Luke  New Zealand
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thanks Planet 10
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Old 24th September 2004, 07:41 PM   #15
fdegrove is offline fdegrove  Europe
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Hi,

Quote:
I thought as Planet 10 stated a valve rectifier gives slow turn on, doesnt this prevent thumps at power on?
Contrary to transistors, tubes have heaters which are, by their very nature, slow compared to the almost "instant on" action of solid state devices.
This feature alone is often adequate enough to prevent turn-on thimps.

However, it is still good practice to let everything warm-up before playing music through the amps.
The most common practice is to engage the mute switch on the preamp so no DC can develop on the output cap (it's this that's often the cause of loud thumps) while things are settling.

As for the PS, as Planet10 stated, a 47F cap right after the EZ81 will do fine but it won't be the cleanest supply as far as ripple goes.
Therefore I'd recommend a hybrid rectifier (this doesn't require extra heater power) to raise the B+ a little so extra RC elements can be used to reduce ripple on the PS.
This is particularly important for SE amps where there's no noise cancelation since there's no PP action.

For examples of ECL82 amps:

CLAUDIO BONAVOLTA

Disregard the one using the rectified mains supply; this is NOT recommended practice.

The site also contains very useful information for the beginning builder.

Ciao,
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Old 25th September 2004, 05:20 AM   #16
Luke is offline Luke  New Zealand
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Thanks Fedgrove,

I would probably use a crc filter anyway I think, but first I have to finish lingering projects
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