Missing something
Hi,
Just wondering what goes in the through holes perpendicular to D1. Looks like its on the trace from power IN to the pot.
Aside from that build it in about an hour. I received 4 of the 647 transistors and no 667 so im waiting.
I was also missing 2 resistors and got four .68 uf caps instead of the four 1uf caps. Kind if annoying but what do ya do?
Thanks
Hi,
Just wondering what goes in the through holes perpendicular to D1. Looks like its on the trace from power IN to the pot.
Aside from that build it in about an hour. I received 4 of the 647 transistors and no 667 so im waiting.
I was also missing 2 resistors and got four .68 uf caps instead of the four 1uf caps. Kind if annoying but what do ya do?
Thanks
Success
Hi,
So follow up on build with missing parts. I had some poly film caps laying around to replace the missing 1uf caps. These are 500v power caps.
Local electronics place had some NET31 transistors that are a close sub for the missing 667s.
For power supply I took a 12v dc Walwort and bypassed the bridge and connected directly to the secondary of the transformer.
Turned it on and had hum on right channel. Wiggled the tube and no more hum. I think the pins were oxidized or something.
Anyway no hum! I expected the worst reading this thread. I was prepared for some mods. But a couple hours of listening now with perfect clarity.
Listening to some 24bit flac on sound cloud with headphones.
So maybe the NET31 or the power caps but sounds great. Very pleased.
Hi,
So follow up on build with missing parts. I had some poly film caps laying around to replace the missing 1uf caps. These are 500v power caps.
Local electronics place had some NET31 transistors that are a close sub for the missing 667s.
For power supply I took a 12v dc Walwort and bypassed the bridge and connected directly to the secondary of the transformer.
Turned it on and had hum on right channel. Wiggled the tube and no more hum. I think the pins were oxidized or something.
Anyway no hum! I expected the worst reading this thread. I was prepared for some mods. But a couple hours of listening now with perfect clarity.
Listening to some 24bit flac on sound cloud with headphones.
So maybe the NET31 or the power caps but sounds great. Very pleased.
As you know DC-DC converters are produce some interferes (RFI). Tube-01 have a DC-DC converter made as separate pcb. I did not have any problems with RFI from this pcb but I decided to do steel shield. And I made it from a steel shield, which I removed from an old printer. Very simple and I recommend this modding for all users.
Attachments
Ok
After a lot of research, this is for me the best 6j1 board to buy, i have it installed on my system. No hum, no noise, and very good sound coming out of it. I use other equivalent tubes.
HIFI 6J1 Preamplifier Board Tube Pre-Amp Assembly Board 2018 New | eBay
After a lot of research, this is for me the best 6j1 board to buy, i have it installed on my system. No hum, no noise, and very good sound coming out of it. I use other equivalent tubes.
HIFI 6J1 Preamplifier Board Tube Pre-Amp Assembly Board 2018 New | eBay
Did you test all the other in this thread? The green one people have raving about..?
I have the green one but get some background noises..
Green One
I have the green one, on my system it is very quite, most of the noise has to do with good grounding with the rest of your equipment. But if you want something quite from the beginning the one i propose is an upgraded version of all the rest of the 6j1 ones here.
I have the green one, on my system it is very quite, most of the noise has to do with good grounding with the rest of your equipment. But if you want something quite from the beginning the one i propose is an upgraded version of all the rest of the 6j1 ones here.
Since the lockdown, I started debugging this board and found disconnecting the switch does reduce the hum slightly. But the main problem i found is the power supply for the tube filament. Checked with oscilloscope and there was saw tooth output from the diode which the low capacitance capacitor is doing next to nothing. So added more capacitance 2200 35v x 2 and the Peak to Peak amplitude is reduced. how ever, i found new problem.. I am powering this setup with 12 AC transformer. but the actual RMS value will be higher. So checked the voltage and i am getting around 15.x volts after the 2.2ohm resistor. further checking the filament voltage, i found each filament is getting 8v which is way higher. So after some basic calculations found that i can add a 17ohm resistance to that 2.2ohm resistor in series to reduce the voltage. Since lockdown no shops were open but i have 100ohm resistors laying around so added 5 of them in parallel to get around 20ohm. added that in series and filament voltage is now 6.7v. which is within 10% as per manufacturer. BTW i'm using GE 5654 tubes. With khadas tone board as DAC and this tube as pre amp and LM4702 as poweramp with 5200 and 1943. Extremely detailed sound and holographic imaging. I'll further improve this build!
Attachments
Hi All,
I have the FX Audio Tube-01 and I would like to modify it so it can accept proper 150VDC for the the tubes, beside removing the DC converter what else should I add\remove\modify so the circuit will handle the 150VDC voltage?
I noticed that when I remove one tube there is no sound at all, I was expecting that removing 1 tube will affect only 1 channel but it appear that it affects both of the channels, Does anyone have an explanation for that?
I have the FX Audio Tube-01 and I would like to modify it so it can accept proper 150VDC for the the tubes, beside removing the DC converter what else should I add\remove\modify so the circuit will handle the 150VDC voltage?
I noticed that when I remove one tube there is no sound at all, I was expecting that removing 1 tube will affect only 1 channel but it appear that it affects both of the channels, Does anyone have an explanation for that?
I have not used FX tube amplifier so without having a look at the circuit, i cant help you. The reason removing 1 tube will shut both channels is because the heater coil is connected in series for the both tubes. So removing 1 tube will effectively shut both tubes.
I just received a similar preamp with 6j3.
Except for the caps, all the other components are smt. Not sure if it's going to last coz the case feels warm to touch, probably operating at 40ish 50 degC.
There are a couple of things I couldn't reconcile. With the psu and tubes removed:
1. I measured about 10kohms across the hot and ground of the input rca.
2. I opened up the case and got 48.xkohms across the 2 extreme pins of the volume pot. One of them is confirmed the ground.
3. When I measured across the Hot on the rca to the other pin of the pot, I got around 58.x kohms.
I just couldn't figure out how the inputs are wired! ��
4. Then I measured the Hot on the output to ground and it was nowhere near 100kohms. Does the remnant 25.xV on pin 5/6 has an effect on this?
Hope someone can shed so light on the above.
TIA
Except for the caps, all the other components are smt. Not sure if it's going to last coz the case feels warm to touch, probably operating at 40ish 50 degC.
There are a couple of things I couldn't reconcile. With the psu and tubes removed:
1. I measured about 10kohms across the hot and ground of the input rca.
2. I opened up the case and got 48.xkohms across the 2 extreme pins of the volume pot. One of them is confirmed the ground.
3. When I measured across the Hot on the rca to the other pin of the pot, I got around 58.x kohms.
I just couldn't figure out how the inputs are wired! ��
4. Then I measured the Hot on the output to ground and it was nowhere near 100kohms. Does the remnant 25.xV on pin 5/6 has an effect on this?
Hope someone can shed so light on the above.
TIA
i m trying this idea for remove hum in my 6j1.......
but why it still hum in my speaker??
any idea...??
built my $10 kit using GE 5654 and swapping for UF4007. the 2.2ohm resistor was upped to 5w. replaced caps with nichicons. resistors upped to 1w. power supply 17v as it drops about 2 volts when powered on. no hum and it rocks!
the power supply is the trick; not enough juice and the left speaker and bass don't come alive.
I'm impressed!
I hear Russian 6J5P (6ZH5P) sound better. don't know.
the power supply is the trick; not enough juice and the left speaker and bass don't come alive.
I'm impressed!
I hear Russian 6J5P (6ZH5P) sound better. don't know.
Okay,I'm back!
Tried the 2x 2200uf caps in parallel and the 20ohm resistor subs.,in addition to the 470uf cap from the 2 resistors to RCA phono jack ground methods, and......... NO HUM!
Dead silent.
The resistor reaches nearly 150 deg. farh. with AC power source under 12v;use a high wattage one.
Thank you.
The question is why was it dead silent initially and then (after a month)the hum began.....
Noticed that one 470uf cap dropped to 420 while the others remained at 475-80uf and one transistor's HFE dropped,or no longer matched(2sb647).
Time will tell how long this cheap,but good sounding,pre lasts. It's not a sub for the real deal. But fun to play with.
Tried the 2x 2200uf caps in parallel and the 20ohm resistor subs.,in addition to the 470uf cap from the 2 resistors to RCA phono jack ground methods, and......... NO HUM!
Dead silent.
The resistor reaches nearly 150 deg. farh. with AC power source under 12v;use a high wattage one.
Thank you.
The question is why was it dead silent initially and then (after a month)the hum began.....
Noticed that one 470uf cap dropped to 420 while the others remained at 475-80uf and one transistor's HFE dropped,or no longer matched(2sb647).
Time will tell how long this cheap,but good sounding,pre lasts. It's not a sub for the real deal. But fun to play with.