• 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.

Tube Buffer 6J1 / 5654 (6AK5)

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#81
I bought the PCB from a local shop.

Using Russian 6N23 tubes (same in my MF Tubalog). Using Wima's & Rubycon in signal path. EPCOS, Rubycon, United Chemicon for the other parts. The A42, A92 and all resistors are generic and was purchased from the same shop. Using IN4004 (extra's from my upgrading my two pairs of Quad 33/303) in-place of IN4007. LED is green as per suggested by other forums to be less noisy than the rest.

When I tried with another wall PSU - 13V and 800mA in-place of the 12V 500mA PSU, sounded brilliant for a few seconds before it returned to the "breaky" output.

I am suspecting a voltage/mA issue rather than parts. When I searched other forums, someone did mention they could not a make MF based tube buffer kit sound nice with 12V and had to use 2x - but no mention of the actual kit or PCB variation used.

Thanks!
 
#82
Update.

I managed to locate a 24V 200mA wall PSU from my storeroom and using it in-place of the suggested 12V 500mA.

WOW WAT A DIFFERENCE!

Now sounds really nice .... with much potential for further tweaks!

So confirm it is due to voltage.
 
#84
Yes, but the original design was awful! Getting the voltage up is a good idea (assuming the "designer" of the piece used caps with reasonable voltage ratings).

The stuff about green LEDs being less noisy is questionable. In that position, the LED has zero to do with noise, and the noise of any LED is ridiculously low.
 
#85
Another update. Went back to the local shop and obtained a unregulated 12V 500mA off-the-wall PSU. Works fine.

Lesson for me. Unregulated off the wall PSU is with a wave-ly line on the power source output. Regulated output has a bar with 3-dots over it.
 
#96
Ghost22

Do You actually own any of the tubes you wish to substitute or is it as I suspect a hypothetical question?

Quite frankly anybody with half a brain could deduce from the data sheets any changes, physical or electrical that would be needed.

The Valve Wizard -Cathode Follower

the 6J1 buffer is a crap design, originally designed using a 7pin EF95/6sh1 Pentode, Triode strapped. the 6DJ8 and 6n23 are 9pin Dual Triodes.

The other Yaquin design - CD3 uses Dual 6SN7 in parallel, both it and CD1 at an insanely non-linear operating point.

Regards

John

Both designs basically put 150v on the Anode and 80v across the tube at 1mA.

As buffers, these sort of currents will be unable to drive the capacitance of a chocolate fireguard let alone a long Interconnect (Slew Rate).
 
#98
The song may remain the same but the quality suffers

Cookj said:
Ghost22

Do You actually own any of the tubes you wish to substitute or is it as I suspect a hypothetical question?

Quite frankly anybody with half a brain could deduce from the data sheets any changes, physical or electrical that would be needed.

The Valve Wizard -Cathode Follower

the 6J1 buffer is a crap design, originally designed using a 7pin EF95/6sh1 Pentode, Triode strapped. the 6DJ8 and 6n23 are 9pin Dual Triodes.

The other Yaquin design - CD3 uses Dual 6SN7 in parallel, both it and CD1 at an insanely non-linear operating point.

Regards

John

Both designs basically put 150v on the Anode and 80v across the tube at 1mA.

As buffers, these sort of currents will be unable to drive the capacitance of a chocolate fireguard let alone a long Interconnect (Slew Rate).
Click to expand...
That reminds me of this as to the quality of it ability to drive The chocolate fireguard experience Paranoid performed by The Chocolate Fireguard Experience at The Kings Arms in Colchester - YouTube
 
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