I replaced it with a Lundahl LL1572 transformer.
But I can't say that there is difference. I may say that the best sound is on a secondary spdif input (I use the fourth input) that has one 75ohm resistor parallel with the spdif entrance and one capacitor.
I found an electronic repair shop and they were kind to receive me yesterday to test the board with an oscilloscope. Grid input was clean. We found 1.5v on heaters. I also had with me an external board, a dc step down with potentiometer. I removed the parts from the onboard LM317 regulated circuit. I used a bridge rectifier with the external board and set it to 6.3VDC. Clean when not connected to the DAC board, same problem when connected. I browsed the schematic again and saw that the DC heaters is not grounded there, but it is grounded (common ground with anode voltage and digital ground) on this board. So today or tommorow I'll try to cut the traces that put the minus of the heaters to ground and I'll feed them from the external board. If it cures the problem I might build a new board with LM317, a Tentlabs clone probably.
Where dit you find the board you are using for heaters? Have you cut the board traces before second cap?
But I can't say that there is difference. I may say that the best sound is on a secondary spdif input (I use the fourth input) that has one 75ohm resistor parallel with the spdif entrance and one capacitor.
I found an electronic repair shop and they were kind to receive me yesterday to test the board with an oscilloscope. Grid input was clean. We found 1.5v on heaters. I also had with me an external board, a dc step down with potentiometer. I removed the parts from the onboard LM317 regulated circuit. I used a bridge rectifier with the external board and set it to 6.3VDC. Clean when not connected to the DAC board, same problem when connected. I browsed the schematic again and saw that the DC heaters is not grounded there, but it is grounded (common ground with anode voltage and digital ground) on this board. So today or tommorow I'll try to cut the traces that put the minus of the heaters to ground and I'll feed them from the external board. If it cures the problem I might build a new board with LM317, a Tentlabs clone probably.
Where dit you find the board you are using for heaters? Have you cut the board traces before second cap?
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The heater psu board I use was made by a fellow Diya member a while ago.
This is his ebay listing:
DIY PCB Board - Tube Amp - LV Tube Heater DC Power Supply - 6.3VDC from 6.3VAC | eBay
The first listing picture is the older version, the revised version is in the following 3 pictures. That’s the one I’m using. It has it’s own GND point which I connect to the Dac board GND terminal. I did not cut any traces on my board. The heater psu wires connect to the +/- pads where C9 was installed.
This is his ebay listing:
DIY PCB Board - Tube Amp - LV Tube Heater DC Power Supply - 6.3VDC from 6.3VAC | eBay
The first listing picture is the older version, the revised version is in the following 3 pictures. That’s the one I’m using. It has it’s own GND point which I connect to the Dac board GND terminal. I did not cut any traces on my board. The heater psu wires connect to the +/- pads where C9 was installed.
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thanks for the link!
I'll buy one if i'm not going to kill the hum with my ideas posted above.
I see some naked resistors on IV on your board. Mundorf EvoOil on anode B+, some changes in resistors in SRPP. and, also, tantalum capacitors replace oscons around ad1865. some notes on sound chages?
I'll buy one if i'm not going to kill the hum with my ideas posted above.
I see some naked resistors on IV on your board. Mundorf EvoOil on anode B+, some changes in resistors in SRPP. and, also, tantalum capacitors replace oscons around ad1865. some notes on sound chages?
)
Hmmm....
Very strange Gionloc, our boards are the same. The differences I see are: I’m using the on-board regulated HV psu and the interstage transformers and much less exposed wires around the board.
I also installed the “naked” resistors, they definitely didn’t add any noise.
Do you have the transformer shield, external heater psu gnd and earth gnd tied to a single point with a wire connecting to the onboard GND terminal?
Very strange Gionloc, our boards are the same. The differences I see are: I’m using the on-board regulated HV psu and the interstage transformers and much less exposed wires around the board.
I also installed the “naked” resistors, they definitely didn’t add any noise.
Do you have the transformer shield, external heater psu gnd and earth gnd tied to a single point with a wire connecting to the onboard GND terminal?
of course, the ground is a star, where DAC board, chassis, filament, transformers shields meet and go to earth pin on iec.
this is the third board i build using the same principles, first one is in CDPlayer, which has 5-6years (and which I would like to sell if I am going to cure the hum in this DAC) with signal from CDPro direct to CS8414, no filters. second one is same with the third one, boards bought together - same metal chassis and components, different colours. and this last one is the only one with problems.
this is the third board i build using the same principles, first one is in CDPlayer, which has 5-6years (and which I would like to sell if I am going to cure the hum in this DAC) with signal from CDPro direct to CS8414, no filters. second one is same with the third one, boards bought together - same metal chassis and components, different colours. and this last one is the only one with problems.
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I tried to increase capacitance on anodes, following some advices given by Lampizator in an old post from his blog.
I changed C2 from 10uFMKP to 680uF FTCap electrolytic and C1 from 100uF MKP to 2x270uF electrolytic (Chemi-Con) with 1k between them.
Hum is vastly diminished, you have turn the amp volume 1/3 to start hearing it, 1/2 to be noticed from listening position with no music. And, when playing music, there is no way you go there with volume. So, it may not be a healing, but at least the DAC is operable... I'll try to increaae capacitance on C3 from 0.1uF (mkp) to at least 10uF (mkp) to see if there is some improvement.
nevertheless, increasing capacitance it made the sound much better, it has more body, bass improbed considerably, authority. impressive! i was against electrolytics in tube anode psu, but this is a good lesson!
I changed C2 from 10uFMKP to 680uF FTCap electrolytic and C1 from 100uF MKP to 2x270uF electrolytic (Chemi-Con) with 1k between them.
Hum is vastly diminished, you have turn the amp volume 1/3 to start hearing it, 1/2 to be noticed from listening position with no music. And, when playing music, there is no way you go there with volume. So, it may not be a healing, but at least the DAC is operable... I'll try to increaae capacitance on C3 from 0.1uF (mkp) to at least 10uF (mkp) to see if there is some improvement.
nevertheless, increasing capacitance it made the sound much better, it has more body, bass improbed considerably, authority. impressive! i was against electrolytics in tube anode psu, but this is a good lesson!
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