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| AWG Buffer Amp |
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| mawyatt:
The JunTek supplied 12V 5A SMPS is better than most cheap types we have, but certainly not lab grade. You could use a linear ~12V supply if switching noise is an issue. After studying the JunTek some the power input voltage can be greater than 12 volts since it feeds a XL6012 SMPS chip and the input filter cap is rated at 35VDC, it also uses dual LC low pass (2 inductors) filters on the +- 26 volts to reduce the switching noise to the LM1875 amps. What power supply did you select to replace the JunTek supplied device? Best, |
| ExaLab:
Safety and noise are the reasons that led me to replace the SMPS. Many unbranded chinese SMPS do not respect the most basic safety rules and this represents a risk both for the operator (e.g. for me) and for the relative instrumentation. For less than 25€ I bought a branded chinese device which meets all safety regulations (Mean Well GST60A12-P1J). More, as mentioned above, the original supplied smps is not equipped with the earth pin and this (for emi reasons) makes it substantially not recommended for lab use (these kind of devices are generally used as strip led drivers...). If the noise related to the internal XL6012 will be unacceptable for some lab uses, I am thinking of equipping the DPA-1698 with an additional power input so that it can be powered, if required, also with an external dual linear power supply. |
| mawyatt:
Mean Well SMPS seem to have a good reputation, good selection. I've found that the noise on the DPA-1698 output is higher on one CH1 than CH2 (same for DPA-2698) and doesn't depend on the input SMPS or Linear Supply much. Bringing in external +-26VDC will power the dual LM1875 but you'll need ~12VDC for the fan. You'll need the the fan since the LM1875 draws considerable power even static. Best |
| mawyatt:
Just got the Juntek DPA-2698. It's based upon a high speed op-amp being buffered by a pair of BUF634 and the outputs tied together via 1 ohm resistors. Power is from a XL6012 creating +-15VDC. The case is the same as the DPA-1698 and also has a fan which is also somewhat loud. The bandwidth is ~50MHz at 4VPP, 40MHz at 10VPP with 50 ohm load, and drops to ~10MHz at 25VPP (100 ohm load). Rise and fall time is ~12ns at 10VPP with 50 ohm load, and 2-Tone IMD at 1MHz with 2VPP signals is ~-53dB. IMD is better than this but that's as good a source (SDG2042X) as we have. Noise is rather high and higher on CH1 with ~100mvPP, CH2 27mvPP. The fan seems to have an effect on the noise, as it's lower with the fan unplugged by over 2X. Here's a couple images disassembled. Best, |
| Noy:
You should add a gapfiller and check the soldering. I did.. And maybe solder a SMD cap directly on the backside from the fan? |
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