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Tube buffer using 12AU7

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tube buffer USING 12au7

dear all,
the circuit is a tube buffer using 6dj8 and low power supply.
can i use 12au7 to replace it?
if yes, need to change any resistor?

any any reference circuit that using a 12au7 to construct a tube buffer?

THANKS
 

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12au7/ECC82

Hi Takashi,
I have used a ECC82 in place of a 6DJ8 in a headphone amp. The amp worked off a 36 volt single supply. The tube had about 18 volts across Plate and cathode.
It worked . It also sounded OK. The measured distortion is higher than the 6DJ8. The 6DJ8 tube sounded better - more open and clearer. Quite noticeable but not an enormous difference. You could live with the 12au7 till you get a 6DJ8.
Cheers,
Ashok.
 
12au7 seems OK.

I checked the circuit. The 12au7 will work as is but it will have far more distortion. Running it at a higher plate current will be better say around 1 mA at least.

Make R3 = 820 ohms and R4 = 4.7K if you plan to use the 12au7. It should sound good. You will have to try out the 6DJ8 or any other tube to see how good (or bad) the 12au7 is. IMHO the sound depends on more than just the tube and so you can't trash the 12au7 because it sounds bad elsewhere. Maybe that was the wrong application ! Here I think it should be OK .
Remember that gain is less than one ( about 0.85 or so ). Distortion at 0.707volts (rms) input is just over 0.1%. Looks like you can feed about 5 volts peak at the input without clipping into 1M load.
Cheers.
ashok.
 
6N1P

Hello,

I am so very new to tubes and would like to start my journey with a tube buffer such as the one shown above (takashi's post). I would like to build it because it uses low supply voltages so I can start asap. However, I can only find the 6N1P tube locally, can I use it in place of the 6DJ8? If not, which resistors must I change?

Thanks in advance,
JojoD
 
You can use a constant current source at the cathode and you will get a huge reduction in distortion . That is not because the ccs does any magical thing but just because the ac load on the tube is now much higher ( in ohms !) than if you used a resistor in place of the ccs.
You could try setting the current at 5mA for the ccs. The 6N1P also might work well here , without any changes. I don't have its data sheets .

Leave out the input capacitor . A capacitor at the output is essential though it needn't be very high voltage types. However if you pick a 'botique type ' cap it might just be a HV type.
Have fun.
Cheers.
 
I checked the circuit. The 12au7 will work as is but it will have far more distortion. Running it at a higher plate current will be better say around 1 mA at least.

Make R3 = 820 ohms and R4 = 4.7K if you plan to use the 12au7. It should sound good. You will have to try out the 6DJ8 or any other tube to see how good (or bad) the 12au7 is. IMHO the sound depends on more than just the tube and so you can't trash the 12au7 because it sounds bad elsewhere. Maybe that was the wrong application ! Here I think it should be OK .
Remember that gain is less than one ( about 0.85 or so ). Distortion at 0.707volts (rms) input is just over 0.1%. Looks like you can feed about 5 volts peak at the input without clipping into 1M load.
Cheers.
ashok.
Hi ashok!
What should I change the schematic if the buffer with C5N instead of using PCC88 .
I can go with vekim voltages to the example of + /-30V?
thank you
 
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This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.