Did you add that 270K to ground or -28V. If it is ground, that I think would change the 6J1 grid bias from about 0.8V to about 11V. The tube would run in Class A2. At a relatively low voltages and current, nothing will burn up. It will definitely give a different sound.
Yes i did add it to the Ground. I could try testing it with the -28 volts instead of GND
Update:
After adding the 270K to GND i was able to hear the clicky sound in the left ear again. More investigating have to be done to remove it. Might try to get a decade box and try different values of the resistors i added
Update:
After adding the 270K to GND i was able to hear the clicky sound in the left ear again. More investigating have to be done to remove it. Might try to get a decade box and try different values of the resistors i added
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Hi Mona
I've do the Deecee tricks. the hum is present but lower than stock pre and no, trafo is not hot..
Do you think that this pre is a total crap?
I think adding extra distortions is not what we want.
Let me see if I get this thing right:
There is some guy in China, who copies an old tube stage circuit, he found a schematic of, somewhere on the net. Then he “optimizes” the circuit until it hardly works, by taking away any component that costs more than a quarter of a Cent or whose function he does not understand. Which are quite a lot. Now he sells it as a kit on eBay, with a description made up from English words, he suggests describe high end audio products. The kit lacks even a schematic, because he does not know how to do one. Take into account, the only thing he has learned less from than electronics design, is a foreign language.
Now he waits until an international team of highly educated audio electronic specialists, on a regarded internet forum, optimizes his junk design, until it is tuned into a usable product. If most specialists agree, that now, this is a decent design, our Chinese high end designer will put it on eBay, with flowery words, praising the advantages of version 2.0
The guy sure feels like he was a genius. Maybe he is...
There is some guy in China, who copies an old tube stage circuit, he found a schematic of, somewhere on the net. Then he “optimizes” the circuit until it hardly works, by taking away any component that costs more than a quarter of a Cent or whose function he does not understand. Which are quite a lot. Now he sells it as a kit on eBay, with a description made up from English words, he suggests describe high end audio products. The kit lacks even a schematic, because he does not know how to do one. Take into account, the only thing he has learned less from than electronics design, is a foreign language.
Now he waits until an international team of highly educated audio electronic specialists, on a regarded internet forum, optimizes his junk design, until it is tuned into a usable product. If most specialists agree, that now, this is a decent design, our Chinese high end designer will put it on eBay, with flowery words, praising the advantages of version 2.0
The guy sure feels like he was a genius. Maybe he is...
IF anyone needs a tabarnac of 6J1 tubes for cheap: 6J1P-EV 6ZH1P-EV (EF95 / 6F32) Voskhod New 24 pcs 70-79 years of production | eBay
Link to Hum correction on 6J1 buffer
Hi Puffin, do you have the pictures on the link you posted because there gone!
I have a big hum problem with the same 6J1 buffer but with a green
printed circuit! Components values could be different but same configuration...
People asked to reprint the pictures but no answers
Thank you,
Gilles
Hi Puffin, do you have the pictures on the link you posted because there gone!
I have a big hum problem with the same 6J1 buffer but with a green
printed circuit! Components values could be different but same configuration...
People asked to reprint the pictures but no answers
Thank you,
Gilles
Hi Decee1,
I have same big hum problem. I noticed the AC 12V input is connected to the sound ground in-out! That could be the problem. Never seen that. Why not isolate AC in and those sound ground? Adding a resistor changes the tube bias and could lower gain + hum.
Did you make other changes to values?
Thank you for your pictures!
Gilles
Attachments
I had problems with the DIY kit 6j1 board and GE5654Ws. Put them in and two of the capacitors melted. Prior to that it had been fine using Mullard 8100s and Voskhods. Must be a "feature" of the GEs. Anyone else had this problem?
complete hum removal from china 6j1 tube preamp
they can talk trash about this preamp all they want but the kit with board and parts can be purchased on ebay for less than 10$. i use mine as a mic preamp and it adds a nice warm smooth tone. yes it has hum but is easy fix. most of the hum is in the heater (filament) circuit. it uses only 1 diode and a 470 or 680 mfd capacitor. add a 2200 mfd 16 v cap across the original cap. if there is still a little hum left do the other mod posted, which is add a 470 mfd cap from the junction of the 2 47 ohm resistors to ground. the positive leads go to ground and neg to the resistor junction, use your voltmeter and you will see why. you have to add 2 470 mfd caps because there are 2 sets of 47 ohm resistors. so 1 2200 mfd and 2 470 mfd caps and absolutely no hum at all. the preamp has a gain of about x10 max as it it is. works great with this really simple fix. i used an oscope to find the 60 hz ripple
they can talk trash about this preamp all they want but the kit with board and parts can be purchased on ebay for less than 10$. i use mine as a mic preamp and it adds a nice warm smooth tone. yes it has hum but is easy fix. most of the hum is in the heater (filament) circuit. it uses only 1 diode and a 470 or 680 mfd capacitor. add a 2200 mfd 16 v cap across the original cap. if there is still a little hum left do the other mod posted, which is add a 470 mfd cap from the junction of the 2 47 ohm resistors to ground. the positive leads go to ground and neg to the resistor junction, use your voltmeter and you will see why. you have to add 2 470 mfd caps because there are 2 sets of 47 ohm resistors. so 1 2200 mfd and 2 470 mfd caps and absolutely no hum at all. the preamp has a gain of about x10 max as it it is. works great with this really simple fix. i used an oscope to find the 60 hz ripple
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Thanks gmc .. i used your cap mod but i didnt have a 2200 so i removed the 680 and put in a 3300uf and then i dd the other mod, 2 -470uf at the resistor junctions and there is zero hum so thank you !!
nope not me..thats odd.. im using the GE5654 tubes and nothing like that has happened. hope you find the issue.
im using the GE5654 tubes with no issues.. must be the version of the board you have or something. i didnt even fire up the ones that came with the kit. i ordered the GE tubes separate.. all good here. hope you figure it out.. my kit was called
"fever 6j1 pre-amp kit" if it matters
nope not me..thats odd.. im using the GE5654 tubes and nothing like that has happened. hope you find the issue.
im using the GE5654 tubes with no issues.. must be the version of the board you have or something. i didnt even fire up the ones that came with the kit. i ordered the GE tubes separate.. all good here. hope you figure it out.. my kit was called
"fever 6j1 pre-amp kit" if it matters
Would it be possible to post some pictures of this mod? Would be really grateful if you could show exactly where it fits on the board. Thanks.
i see you did the mod but the mod at the 47 ohm resistors originally posted by someone else is not entirely correct. i rechecked it to be for sure and i change it on my board. one of the caps has negative to ground and one has pos to ground.
here is the picture of the 6j1 hum removal modification
