As moving the transformer delivers worse results than the tinkered switch mode power supply, I will not bother on better shielding of the transformer.
I think there is no hope on a free SMPS upgrade kit from Jens, so I probably will go for batteries.
SMPS have to much noise at output. Batteries are to weak. The beast consumes to much power.
Here is a simple inexpensive fix: Trafo shielding sheet, 14,90 € that could actually work. Before I get one shipped all the way here maybe someone in the EU can try it? There are also cans like these on eBay that may work: Black Metal Shield Toroid Transformer Cover Chassis (multiple sizes available) | eBay
Switch mode supplies can be low noise or high efficiency or cost effective but not all three. If one of the steel cans or the magnetic tape solution works that's probably the best option.
If I were designing a transformer for this I would cut the flux by about 50% which will reduce the field by a whole lot. However not something you can get off the shelf.
Switch mode supplies can be low noise or high efficiency or cost effective but not all three. If one of the steel cans or the magnetic tape solution works that's probably the best option.
If I were designing a transformer for this I would cut the flux by about 50% which will reduce the field by a whole lot. However not something you can get off the shelf.
Generalize much? It is possible (if not easy) to design an SMPS with whatever output noise you would like, especially if you can post-regulate it.
Try passives and a better regulator next time. Your broad, sweeping, and possibly incorrect generalizations are not helpful. Just like in the OPA1622 thread. Not correct and not helpful.
Should we all just give up then? It has been done by test equipment designers for the last 30 years now. Common-mode chokes can be effective, among other things.
There is already possible evidence in this thread that the SMPS works better than the linear supply for the RTX.
The lowest noise power supply I have is the switcher that powers the HP microphone in the HP sound level meter. This was designed in 1968. The principles have not changed and switchers can be smaller and more efficient today.
The EMU 1616M recording interface also uses several cascaded switching supplies and there is no evidence of them in the analog out or recorded signal. It uses the same ADC as the RTX and has similar performance. The analog front end is not quite as good as the RTX.
Blanket statements are not constructive.
The EMU 1616M recording interface also uses several cascaded switching supplies and there is no evidence of them in the analog out or recorded signal. It uses the same ADC as the RTX and has similar performance. The analog front end is not quite as good as the RTX.
Blanket statements are not constructive.
I think it takes some experience to integrate a switching power into the design for better performance. I have worked on integrating a switching power in an amplifier, it was not easy, and when you want measurement equipment level, it is going to be more tough. For example, I still have a problem that is actually in the low frequency about 120 Hz seemingly due to the phase offset between the +/- outputs driven by different primaries. I was going to use data recording to investigate this more with the RTX. Unfortunately, one of my RTXs now has a problem after the input mods.
When designing a filter for the switching power, passing requirements effected the sound of the amplifier. Since the manufacturer lowered the switching frequency from 110KHz to 60Khz to pass EMI tests, I was able to find a design point so that the noise was out of the conductive test range to around the switching frequency to obtain best compromise, I suspect it would not be best for measurement equipment. I had not had time to investigate the interaction between the amplifier circuit and the power supply in detail to optimize it, just a reason, try, and listen process.
The EMU noise figures are excellent, but the THD is a little bit to high for a meassurment device.
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Hi diyralf,
Your argument simply isn't true this day and age. All the top test equipment manufacturers are using switching power supplies today, and have for years. If nothing else, this is to keep the weight down. My old equipment weighs in at 60 to 80 pounds for the network and spectrum analysers. The current stuff is light as a feather, and that includes the oscilloscopes that cost over $250,000 US. These are making measurements way down in my noise floor with ease, and no switching artifacts. Their bandwidth greatly exceeds the switching frequencies used. Their low noise power supplies and SMUs are also using switching power supplies.
I am using switching supplies in some of my audio designs, and they are not the limiting factor in the design. The limiting factor would be me in this case. I still use linear regulators in high voltage applications.
-Chris
Your argument simply isn't true this day and age. All the top test equipment manufacturers are using switching power supplies today, and have for years. If nothing else, this is to keep the weight down. My old equipment weighs in at 60 to 80 pounds for the network and spectrum analysers. The current stuff is light as a feather, and that includes the oscilloscopes that cost over $250,000 US. These are making measurements way down in my noise floor with ease, and no switching artifacts. Their bandwidth greatly exceeds the switching frequencies used. Their low noise power supplies and SMUs are also using switching power supplies.
I am using switching supplies in some of my audio designs, and they are not the limiting factor in the design. The limiting factor would be me in this case. I still use linear regulators in high voltage applications.
-Chris