5670 tube buffer issues

[Sandm0n]

Hello,


I have a cheaply made tube buffer that I removed from a non brand finished product that I wish to modify so I can connect it to a DAC output.
The tube buffer is based on single 5670 tube .



I have 2 issues with it:


1. lower signal output compares to the original signal connected to my amplifier.


2. reduced bass output compare to the original signal, when I connect my source directly to my amplifier there is more midbass and bass but using the tube buffer in the middle the midbass and bass significantly reduced.


I attached a drawing for a reference.


Any help will be appreciated.

 

[Kay Pirinha]

Well, your 0.1 µF/10 kOhm output combination forms a LFP with a 160 Hz rolloff…
Best regards!

 

[nigelwright7557]

Interesting you have bigger caps on inputs compared to outputs.
It should be other way around.
1/(2 pi RC) gives break point frequency.

 

[Ketje]

Try it like this 🙂
Mona

 

[Sandm0n]

Thanks for you both (-:


Any suggestions for input capacitor value? and output RC filter?

 

[Sandm0n]

Try it like this 🙂
Mona

Thanks

 

[Sandm0n]

Try it like this 🙂
Mona

Which type of capacitors you recommend?

 

[Sandm0n]

BTW what is the cause for the lower signal at the output compare to the original signal ?

 

[kodabmx]

Buffers are less than unity gain.

 

[Kay Pirinha]

Wrong biasing. See Ketje's addendum.
Btw, a cathode follower's gain always is somewhat below unity.

Best regards!

 

[gerrittube]

Hi, I don’t get why you use such a high filament voltage. From the datasheet I get:

Filament Vf 6.3 Volts / If 0.35 Ampere / Indirect / Parallel, (AC/DC)

If your DC is too high, you can use a series resistor to get to 6.3 Volt.

Regards, Gerrit

 

[Ketje]

Which type of capacitors you recommend?

Whatever you find, providing the voltage rating is high enough.
Minimal voltages, 10µF/150V, 0µ68/100V, 0µ1/50V.

BTW what is the cause for the lower signal at the output compare to the original signal ?

The bad circuit you used.
Mona