HI 6v6 Dude.No it's nothing serious but it's fun to experiment with it. I've just build another one and will try to put passive Baxandal between the two to see if it has enough gain for at least 1:1 output with it.
I am in the process of completing my first kit as my first entry to DIY vavle hifi (with nice power levels that dont bite ) If I read correctly, your post suggests to take two kits... and 2 is twice as good as one?????? Would this mean each kit would essentially be a single channel preamp and combined to be a stereo pre amp?
Cheers
TN
these mods will remove 100% of the hum in the fever 6j1 tube preamp. it took a little more than i originally thought. the first post had a pic but i am reposting it because you only have to add one cap <snip>
@gmcdonld
Thank you very much for this amazing solution, works really good
I purchased four kits supplied with Chinese 6J1P tubes . The tubes supplied , upon inspection , appear to be a mixture of pulls and used . Bent pins and pin scrapes too which are clear sign of use . Only four out of the 8 tested acceptably . One had inter-electrode shorts , 4 had heater to cathode insulation issues (two tested acceptably after a burn in at 10 volts) . One had low emission . So it's no wonder why so many stuff GE Mullard etc in these cheap kits and boxes and get instant better results
316a
316a
99% reduction in hum with just 2 wires and 3 cuts that separate the filament supply ground from audio ground.
A separate heater supply with full wave rectifcation and 7812/1N4001 regulstor would probably nail the hum down even more . Isolating the PCB AC traces around the pot switch and bypassing upstream even better
316a
I've had one of these for a while now but cast it aside because it sounded pretty bad so I'm happy to have stumbled upon this thread!
3 questions if I may:
Which of the 2 mods are most effective in terms of hum removal (or are they much of a muchness)?
The first mod has an external switch added - what is its purpose?
What power rating does this preamp require?
Thanks!
3 questions if I may:
Which of the 2 mods are most effective in terms of hum removal (or are they much of a muchness)?
The first mod has an external switch added - what is its purpose?
What power rating does this preamp require?
Thanks!
Found the answer to the last question for anyone interested:
Also, for entertainment value:
【Power input】 AC AC12V 0.8A
Also, for entertainment value:
the entire audio system to bring a sweet Natural "bile"6J1 fever gall bladder before the board is imitation machine music fax
I’ve one I use everyday - I modified it into a follower though. I can post pics when I get home. It was actually a pretty straightforward mod n the end and a good fun to $$ project. I didn’t have any hum issues at all though - so the heater circuit has been left as is for me.
I actually bought another two, with a view to trying a few extra mods like boosting the ac voltage, dropping in a 12V regulator on the heater, and popping a current source in instead of the resistor loading the tube.
No real reason to mind, just thought I'd give it a try and see if it sounds different, or measures differently.
No real reason to mind, just thought I'd give it a try and see if it sounds different, or measures differently.
Any noticed improvement with the 2 extra preamp ?
Little bit off context but where can I purchase these nice copper rings around the tubes ?
I don’t even know how it’s called so I can do a proper search on e-pay...
Thanks in advance
Eric
Little bit off context but where can I purchase these nice copper rings around the tubes ?
I don’t even know how it’s called so I can do a proper search on e-pay...
Thanks in advance
Eric
Attachments
Another 6j1
I recently got this pre amp.
But on connecting in the chain there is a constant noise even at nil volume level from speakers.. noise sounds like radio turned on at high volume but without anything being played.
Unit comes with a dc wall socket- could this be power supply issue or the tubes issue!?
Pic of the board:
If it's to do with tubes then planning to get GE substitute and for powerfully issue, i have R core with regulated dc power supply which might need tweaking for that 12 volt input (at present output is at 15volts)
I recently got this pre amp.
But on connecting in the chain there is a constant noise even at nil volume level from speakers.. noise sounds like radio turned on at high volume but without anything being played.
Unit comes with a dc wall socket- could this be power supply issue or the tubes issue!?
Pic of the board:
If it's to do with tubes then planning to get GE substitute and for powerfully issue, i have R core with regulated dc power supply which might need tweaking for that 12 volt input (at present output is at 15volts)
Last edited:
I’ve one I use everyday - I modified it into a follower though. I can post pics when I get home. It was actually a pretty straightforward mod n the end and a good fun to $$ project.
Just wondering if you had a chance to get some pics yet?
Cheers!
Mods 6J1
And there you go! Grid referenced to gnd and not -ve, as is the output node, plate load is gone, and the cathode load is now 4K7.
Works fine, and I really should have a play with some of the others.
And there you go! Grid referenced to gnd and not -ve, as is the output node, plate load is gone, and the cathode load is now 4K7.
Works fine, and I really should have a play with some of the others.
Attachments
Any noticed improvement with the 2 extra preamp ?
Little bit off context but where can I purchase these nice copper rings around the tubes ?
I don’t even know how it’s called so I can do a proper search on e-pay...
Thanks in advance
Eric
Guys if anyopne wants one of these i have one of these new never used that i have no use for. i can send it to you shipped for 22 bucks shipping included or i can also add a pair of real new in box NOS GE jan 5654W for 30 bucks. I have no use for it and i bought for 32.5 bucks.
- Home
- Amplifiers
- Tubes / Valves
- 6J1 China preamp thoughts