I could not resist placing my 2 cents worth... 
... to complete Ray's anecdote, the reason why the stacked transformers got very hot real quick has to do with fact the magnetic field of each transformer is really dense at the centre of the doughnut, and a magnetic field is basically very lazy, it will want to find the easiest return path in avoiding to do any work. So, now stack a second magnetic field producer on top the first, and the 10% or so of leakage fields start the ball rolling, encouraging more lazy field out of the winding area, adding up, concentrated in the tie-down bolt, which will easily form a "third winding" "if" both ends of the bolt are touching common metal (the chassis); that third winding is essentially a very, very low impedance circuit and will draw most of the available transformed energy, leaving very little voltage developed in the other secondary windings (regulation drop)... and the primary winding current supplying this third winding will be higher than it's wire sized rating. The bigger the transformer, the more current and chassis meltdown could occur. All hell can break loose.
P.S. ... why use toroids? Unless these are higher grade (larger cores than needed) they come off the shelf with core sizes that are just right size to handle the rated load without sine wave distortion which occurs with core saturation. Cores move towards saturation as the primary current increases, and leakage current increases as load current increases. Now, the toroid, by definition, is very possessive of fields, leaving only about 10% escape outside the wire area... and this happens to create it's downfall. House current is often, if not always "biased" into a d.c. potential, either +/- by several/many volts depending on the Utility's line loads. Unbalanced lines create the d.c. bias relative to ground. Each of the three phases coming from the Utility's substation power transformer(s) feed single phase lines, one of which races power to your regional distribution transformer, and that single phase transformer has a secondary winding tapped in it's centre which forms the return "white" lead that is grounded. Currents all return to the substation via ground. Any line unbalance shows up there.
So why use toroids?.. their "off the shelf" cores could/will approach saturation more easily by fact their already working by the d.c. bias current, and distort the wave shape, meaning that harmonics are passing through the "high end" power supply. Real high end audio equipment will make good use of audio quality grade toroids (special order if you know the manufacturer real well), or separately mounted EI cored transformer/supply modules.
Leakage fields alone should not govern the transformer choice. An EI cored transformer can be oriented such that the leakage field is not directed at the signal processing area of the chassis. The lower the power, the more the EI design will be attractive. Leakage field can be an asset in high end audio.
There, I went and did this... opened myself up for comments.
... to complete Ray's anecdote, the reason why the stacked transformers got very hot real quick has to do with fact the magnetic field of each transformer is really dense at the centre of the doughnut, and a magnetic field is basically very lazy, it will want to find the easiest return path in avoiding to do any work. So, now stack a second magnetic field producer on top the first, and the 10% or so of leakage fields start the ball rolling, encouraging more lazy field out of the winding area, adding up, concentrated in the tie-down bolt, which will easily form a "third winding" "if" both ends of the bolt are touching common metal (the chassis); that third winding is essentially a very, very low impedance circuit and will draw most of the available transformed energy, leaving very little voltage developed in the other secondary windings (regulation drop)... and the primary winding current supplying this third winding will be higher than it's wire sized rating. The bigger the transformer, the more current and chassis meltdown could occur. All hell can break loose.
P.S. ... why use toroids? Unless these are higher grade (larger cores than needed) they come off the shelf with core sizes that are just right size to handle the rated load without sine wave distortion which occurs with core saturation. Cores move towards saturation as the primary current increases, and leakage current increases as load current increases. Now, the toroid, by definition, is very possessive of fields, leaving only about 10% escape outside the wire area... and this happens to create it's downfall. House current is often, if not always "biased" into a d.c. potential, either +/- by several/many volts depending on the Utility's line loads. Unbalanced lines create the d.c. bias relative to ground. Each of the three phases coming from the Utility's substation power transformer(s) feed single phase lines, one of which races power to your regional distribution transformer, and that single phase transformer has a secondary winding tapped in it's centre which forms the return "white" lead that is grounded. Currents all return to the substation via ground. Any line unbalance shows up there.
So why use toroids?.. their "off the shelf" cores could/will approach saturation more easily by fact their already working by the d.c. bias current, and distort the wave shape, meaning that harmonics are passing through the "high end" power supply. Real high end audio equipment will make good use of audio quality grade toroids (special order if you know the manufacturer real well), or separately mounted EI cored transformer/supply modules.
Leakage fields alone should not govern the transformer choice. An EI cored transformer can be oriented such that the leakage field is not directed at the signal processing area of the chassis. The lower the power, the more the EI design will be attractive. Leakage field can be an asset in high end audio.
There, I went and did this... opened myself up for comments.
Any experience with tubed output-stages with the EZ-DAC ?
I have never build/modified anything with valves/tubes but I am currious to know more about that field.
So I thought that perhaps I should try valves/tubes with the EZ-DAC which I hopefully get assembled this year (or perhaps this decade ?).
I think perhaps a textbook mu-follower based on 6922 or something like that and then lower the passive I/V-resistor to a value that corresponds with the amplification of the mu-follower in order to maintain around 2V output.
Any comments are welcome
I have never build/modified anything with valves/tubes but I am currious to know more about that field.
So I thought that perhaps I should try valves/tubes with the EZ-DAC which I hopefully get assembled this year (or perhaps this decade ?).
I think perhaps a textbook mu-follower based on 6922 or something like that and then lower the passive I/V-resistor to a value that corresponds with the amplification of the mu-follower in order to maintain around 2V output.
Any comments are welcome
ezkcdude (Evan?):
Some of the ezdac images at your Shiny Metal site are not showing up, e.g. the PCB images - something about account inactive for 90 days:
ShinyMetal
Or am I the only one see this?
Some of the ezdac images at your Shiny Metal site are not showing up, e.g. the PCB images - something about account inactive for 90 days:
ShinyMetal
Or am I the only one see this?
Thanks for bringing this to my attention. I didn't know they had that kind of restriction. Anyway, I logged into photobucket. Hopefully, that is all it will take to restore the pics.
It's the same link, but without the "th":
An externally hosted image should be here but it was not working when we last tested it.
I was hooking up power to my ezdac using the ezdual and 9v regs. I tested the outputs of the ezdual and got ~+15/-15v out, and about 9v out of the 9v regs.
I started to smell something, so I unplugged the power. Checked it over, and discovered that R1A & R2A & R3A started to discolor.
I can replace the resistors no problem. But what may have cause the unit to start to fry like that?
I hope I didn't cause any harm to the ezdac.
Any clues?
I started to smell something, so I unplugged the power. Checked it over, and discovered that R1A & R2A & R3A started to discolor.
I can replace the resistors no problem. But what may have cause the unit to start to fry like that?
I hope I didn't cause any harm to the ezdac.
Any clues?
Well, first thing I would do is fix the ezDual and see if that's working o.k. The +/-15V is only used for the opamps, so any damage should be limited to them only. If you have a small adjustable bench supply, you can gently increase the voltage and see what happens. You can insert a 100 ohm resistor in series, as a protection against too large currents. The on-board LM317 should output +12V. Then check the connections to the ezDAC, make sure V+ is connected to V3 and there's no jumper to V2, and V- is connected to V4. G goes to G3 or G4. Make sure there are no solder splashes that cause shorts to the ground plane, and beware of small wire cuttings on the table...
Regards,
Ray
Regards,
Ray
USB input still on?
Any progress with the a USB interface?
I am at that stage , having received the ezDAC board, where I must adopt/adapt an I2S converted USB input to the DAC. I intend to start with this step and firstly populate needed components on a PCB that I can mount adjacent the USB terminal. Second step will be to add any switching/relay as input selector and manage the CS8416 in/out of circuit when using SP-dif or USB respectively.
What approach have you taken? Your input would be well appreciated.
Thank you,
Louis
Any progress with the a USB interface?
I am at that stage , having received the ezDAC board, where I must adopt/adapt an I2S converted USB input to the DAC. I intend to start with this step and firstly populate needed components on a PCB that I can mount adjacent the USB terminal. Second step will be to add any switching/relay as input selector and manage the CS8416 in/out of circuit when using SP-dif or USB respectively.
What approach have you taken? Your input would be well appreciated.
Thank you,
Louis
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