• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

beginners ecl82 power supply

Status
Not open for further replies.
Jump to Latest
#5
Here is it ! but i have messure the voltage and it is 247 Volt!!!
 

Attachments

  • neu bitmap.jpg
    neu bitmap.jpg
    37.5 KB · Views: 559
#6
emil_86 said:
Here is it ! but i have messure the voltage and it is 247 Volt!!!
Click to expand...

I don't doubt !
Wanted to have a look at the schemo before making any suggestion !

I can't see it here, is it the one drawn in the referenced link ?

Anyway, do you measure voltage with or without load ?
Each amp will probably consume some 30 to 40 mA.

Nevertheless, there is no risk to try, at least for few minutes, the time to take voltage while working.

Yves.
 
#7
emil,

i built the same project, and my power supply is almost 300v.
I have tried using 240v (two identical transformer back to back) I didnt like the 'thin' sound i get. so i think yours is just fine.

If you really want to lower it, 1.5k resistor 25w to replace the (100R 5w) should do the trick.

But i think within <250v is fine. It runs hotter but it sounds richer
 
#11
Luke said:
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?
Click to expand...

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.

dave
 
#12
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
 
#13
Luke said:
I thought as Planet 10 stated a valve rectifier gives slow turn on, doesnt this prevent thumps at power on?
Click to expand...

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.

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?
Click to expand...

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....

dave
 
#15
Hi,

I thought as Planet 10 stated a valve rectifier gives slow turn on, doesnt this prevent thumps at power on?
Click to expand...

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 47µF 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,😉
 
Status
Not open for further replies.
Top Bottom