6J1 9V real tube drive

rybcki_mt · Post by **rybcki_mt** » 02 May 2021, 20:22

Hello,

Yesterday I finished prototype of 6J1 (cheap Chinese tube) drive using 9V

It sounds really awesome so I wanted to share it.

Heaters can be supplied by 7806 or by simple 100ohm resistor (min 0.5W).

R7 can be replaced by potentiometer (10K) to have simple Tone Control there. Or you can add any tone stack in place of R12. It works quite good as preamp with Fender tone stack.
Blue LED can be removed - but it looks so awesome

tonyharker · Post by **tonyharker** » 02 May 2021, 21:57

Any sound samples?

Intripped · Post by **Intripped** » 02 May 2021, 23:35

ppluis0 · Post by **ppluis0** » 03 May 2021, 02:58

Hi rybcki_mt and welcome to the forum.

The heater draws 175mA @ 6.3V, so you can connect it in series with 15 ohm 1W and supply this series with 9Vdc. It's not necessary to feed it with a regulated supply.

Perhaps you can use the second half of your TL072 placed after the tube to drive a tone stack (or volume pot and output jack), due this tiny tube can't handle any load.

If any forum member wish to experiment with tubes (RECOMMENDED !!!) the equivalents of the 6J1 are 6AK5, 6AK5W, 5654, Western Electric 402A, and EF95

Another little tube named EC900 or 6HA5 has the same height (38mm) and heater ratings than 6J1

Cheers,
Jose

rybcki_mt · Post by **rybcki_mt** » 03 May 2021, 07:28

Sound sample.
1 part - neck pickup - ref clean channel of my amp
2 part - neck pickup with tube drive enabled (gain 40%)
3 part - neck pickup with tube drive enabled (gain 40%) and Timmy (gain at 20%) in front of tube drive
4 part - bridge pickup with tube drive enabled and gain 100% (tone stack not corrected so some adjustments required)

paconroll · Post by **paconroll** » 03 May 2021, 11:12

Nice work! thanks for sharing.

I'm waiting for some connectors to try a TUBE-6J1 tube preamplifier for the guitar. My preamp came with 6K4 tubes instead of 6J1 and I got much better audio replacing them with GE-5654W.

Have you tried these tubes instead of 6J1? at least in my preamp they're compatible and way better sounding.

rybcki_mt · Post by **rybcki_mt** » 03 May 2021, 12:26

paconroll wrote: ↑03 May 2021, 11:12 Nice work! thanks for sharing.

Thanks man

paconroll wrote: ↑03 May 2021, 11:12 Have you tried these tubes instead of 6J1? at least in my preamp they're compatible and way better sounding.

Nope. Previously I only worked with ecc83 and higher voltages. I wanted to try if it's possible to supply such small tube with 9V. I've found 6J1. And it works.

ppluis0 · Post by **ppluis0** » 04 May 2021, 01:49

Hi folks,

In the above diagram the 6J1 is a pentode but connected to work as triode by means to tie together pins 6 and 5
The 6HM5/6HA5 suggested to use -if anyone wish to experiment with it- is a triode and the pin 6 must be connected to ground:

https://frank.pocnet.net/sheets/135/6/6HA5.pdf

Cheers,
Jose

dylan159 · Post by **dylan159** » 25 May 2021, 12:32

Nice work. Since you call it real tube overdrive though, are you sure most of the clipping isn't coming from the op amp? because it will clip, sooner or later. Don't know the Vgk but depending on it there might be a point at which the tube clips before the op amp starts to, somewhere on the lower gains.

rybcki_mt · Post by **rybcki_mt** » 26 May 2021, 14:55

dylan159 wrote: ↑25 May 2021, 12:32 Nice work. Since you call it real tube overdrive though, are you sure most of the clipping isn't coming from the op amp? because it will clip, sooner or later. Don't know the Vgk but depending on it there might be a point at which the tube clips before the op amp starts to, somewhere on the lower gains.

Thanks man. It's very good question. Currently OpAmp section has gain of 48dB when gain is set to 50% and 54dB at 100%.
Such gain is needed to push tube to clip. When you remove clipping stage (tube stage) then you will have clean, transparent booster.
Today I made additional test of opamp stage with PAF pickups. OpAmp section has clean sound even with full gain. I was able hear clipping (caused by high current) after connecting output directly to right side of C5 capacitor which is bad idea

as any resistor is needed to limit current. So I'm sure that I have only tube clipping there.

dylan159 · Post by **dylan159** » 30 May 2021, 17:22

While your calculations are correct, I really doubt an op amp can stay clean with that much gain and a 9v supply, especially with humbuckers! The reason might be that the 1k and 100n have an upper cutoff at 1.5k. by 500hz, your gains have dropped to 41 and 35 dB (still a lot!), and since guitar circuits tend to stretch the definition of clean a lot, you might find it pleasing.
Not sure about the current limiting. You don't need a resistor unless you're shorting the output or driving a long cable.

6J1 9V real tube drive [documentation]