Seem like my measurement is nothing near yours, the table below is where I checked voltage at each pin. How did you get 6.xx?
Does your chassis is aluminum? Steel got hum. When I put the toroidal on top the wood, the hum went away.
My outlet currently between 120v and usually drop up to 115v so I have 290vDC at 120vAC so it's right at 280vdc when drops. I will order the choke later since it's working fine. Hope the choke will improve more.
Check the manual again on page 6 and 8, it does say R18 is 300k, not 300r. Why it didn't happen to you, I am not sure but my filament shut down in 5 mins with 300r that got spark and blew off parts on PS. For safety, you may want to replace to 300k on R18.
Another issue is filament, without tubes is 12.5vdc, however; when inserted the tubes, it drops to 9.5vdc constant. Have you checked to see if it's at 12vdc and what values you have for both of them? I am setting 12v where R20: 1.07k and R21: 124r. I tried R20 @ 1.5k or R21 @ 100r but it didn't do anything. Look like his formula is wrong too, it's support to be R20/R21 but he has R21/R20 ...lol...What a crazy manual.
My input/out grounds are separated, only connect the IEC ground to the House GND on PCB.
What kind of input selector you use?
Does your chassis is aluminum? Steel got hum. When I put the toroidal on top the wood, the hum went away.
My outlet currently between 120v and usually drop up to 115v so I have 290vDC at 120vAC so it's right at 280vdc when drops. I will order the choke later since it's working fine. Hope the choke will improve more.
Check the manual again on page 6 and 8, it does say R18 is 300k, not 300r. Why it didn't happen to you, I am not sure but my filament shut down in 5 mins with 300r that got spark and blew off parts on PS. For safety, you may want to replace to 300k on R18.
Another issue is filament, without tubes is 12.5vdc, however; when inserted the tubes, it drops to 9.5vdc constant. Have you checked to see if it's at 12vdc and what values you have for both of them? I am setting 12v where R20: 1.07k and R21: 124r. I tried R20 @ 1.5k or R21 @ 100r but it didn't do anything. Look like his formula is wrong too, it's support to be R20/R21 but he has R21/R20 ...lol...What a crazy manual.
My input/out grounds are separated, only connect the IEC ground to the House GND on PCB.
What kind of input selector you use?
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sunil,
So far I got the hum down to 1 channel and heater filament fixed because of wrong jumpers. It's stable at 12.4v.
I am using R18 and R19 as in the image. Do you have the same value? As he mentioned around 75v at B+ 300v but somehow my V1 and V3 seem high so I think the hum may cause by high cathode voltage. All voltages are almost identical except cathode voltages on pin 7 and 8. I am not sure how to balance these voltage since they're shared the filament which they should be divide equally. Swapped tubes around still have the same problem. Other than that, I really can't think what cause the hum.
So far I got the hum down to 1 channel and heater filament fixed because of wrong jumpers. It's stable at 12.4v.
I am using R18 and R19 as in the image. Do you have the same value? As he mentioned around 75v at B+ 300v but somehow my V1 and V3 seem high so I think the hum may cause by high cathode voltage. All voltages are almost identical except cathode voltages on pin 7 and 8. I am not sure how to balance these voltage since they're shared the filament which they should be divide equally. Swapped tubes around still have the same problem. Other than that, I really can't think what cause the hum.
That's the voltage divider section. Most of his designs are using 300k for R18 and 47k or 100k for R19. If you use 300r, the voltage at pin 7 and 8 are around 600v according to the formula.
By the way, I got the hum figure out.
1. Wrong jumpers for 6.3v, that's why DC with load at 9.5v
2. One of the cathode resistor burned out may cause by the problem above.
3. All voltages are the same now except the cathode voltage at V1 and V3 are about 3-5v higher than V2 and V4. Even thought all the component values are the same. B+ is stable at 290v
4. Steel chassis hum with toroidal
5. Only a small hum when 50k alps pot at 95-100%
I saw you use 8uF for coupling cap where he mentions 1-4uF? What do you get out of it? More bass?
By the way, I got the hum figure out.
1. Wrong jumpers for 6.3v, that's why DC with load at 9.5v
2. One of the cathode resistor burned out may cause by the problem above.
3. All voltages are the same now except the cathode voltage at V1 and V3 are about 3-5v higher than V2 and V4. Even thought all the component values are the same. B+ is stable at 290v
4. Steel chassis hum with toroidal
5. Only a small hum when 50k alps pot at 95-100%
I saw you use 8uF for coupling cap where he mentions 1-4uF? What do you get out of it? More bass?
I thought the big coupling cap is for subwoofer where I saw he mentioned in the old rev. manual where you can add 1M resistor and 4-10uF for sub. I will check the manual again.
The sound is great, midrange and bass are well balance so I won't add the tone control. I plan to add digital selector input and xlr option for both input/output. It actually sound different from the ss preamp.
How does the ACF-2 sound?
The sound is great, midrange and bass are well balance so I won't add the tone control. I plan to add digital selector input and xlr option for both input/output. It actually sound different from the ss preamp.
How does the ACF-2 sound?
The ACF-2 is nice. No sound of its own that I can hear. The sources are hooked up to it since I want to have two Preamps that will have two amps each.
I've built two TSEs of Tubelab - 2A3 and 300B and am building two SSEs with a bunch of tubes.
Yup, the midrange, highs and bass are great with the Aikido.
I've built two TSEs of Tubelab - 2A3 and 300B and am building two SSEs with a bunch of tubes.
Yup, the midrange, highs and bass are great with the Aikido.