Tone Control with EF86 / EF 80

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Tone Control with EF86 / EF 80

Post by JDL-TAIWAN on Tue Jan 07, 2014 12:17 pm

Hello made ​​friends of the tubes,
I'm going to build a tone control and want to use EF80 or EF86.
I started, but unfortunately I have a humming at the Input.
The heating is in DC. Has one a good idea for me.
I apologize for my English but written as with the Presentation I'm German and I live in Taiwan.
Thanks in advance
Jonny

I Test a tone controller with two ECC83 is a 3 band Tone Controller is super nice 16 - 18 dB.

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Re: Tone Control with EF86 / EF 80

Post by Dr. Radio on Tue Jan 07, 2014 6:24 pm

Sometimes it's just the basics.

"Lead dress" can make a difference sometimes. When audio lines aren't kept short or close to the chassis, they can pick up noise from power supply wires and the related circuitry. If you are just using regular wires, you may have to shield them--either use shielded wires or wrap the wires tightly with wires that get grounded to the chassis.

What are you using for a power supply? If using modern diodes, strapping a small value like .001 microfarad capacitor across each diode can shunt noise spikes and switching noises. Clean filtering is a key too. Need ample size capacitors for the power supply configuration.

Lastlly, don't rule out the tubes. Sometimes "good" tubes can have grid issues or heater issues causing the hum right there inside the tube.

Do you have a schematic of your design?
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Re: Tone Control with EF86 / EF 80

Post by JDL-TAIWAN on Wed Jan 08, 2014 12:20 pm

Dr. Radio wrote:Sometimes it's just the basics.

"Lead dress" can make a difference sometimes. When audio lines aren't kept short or close to the chassis, they can pick up noise from power supply wires and the related circuitry. If you are just using regular wires, you may have to shield them--either use shielded wires or wrap the wires tightly with wires that get grounded to the chassis.

What are you using for a power supply? If using modern diodes, strapping a small value like .001 microfarad capacitor across each diode can shunt noise spikes and switching noises. Clean filtering is a key too. Need ample size capacitors for the power supply configuration.

Lastlly, don't rule out the tubes. Sometimes "good" tubes can have grid issues or heater issues causing the hum right there inside the tube.

Do you have a schematic of your design?



Hello and thank you for the quick response.
I use a 300 V DC power supply. Linear regulator with 50uF choke 5Henry and again 50 and 25 uf.
I am experimenting on I've only tested a design with EF86.
I try on the weekend to make another test with an EF86.
Here is the first test.

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Re: Tone Control with EF86 / EF 80

Post by JDL-TAIWAN on Wed Jan 08, 2014 12:24 pm

One more thing I want to say here, I am just starting with the tube technology. My real passion is measuring devices Grundig 1960 - 1990
But when I start something, I want to get right. Smile 
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Re: Tone Control with EF86 / EF 80

Post by codefox on Tue Oct 07, 2014 12:04 pm

The EF86 will almost certainly need a properly grounded tube shield; can't tell from the picture whether you used one or not.

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Re: Tone Control with EF86 / EF 80

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