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TDK-Lambda Single, Bipolar and Triple Output Switching Power Supplies for Audio Projects

Posted: Tue Mar 20, 2018 5:00 pm
by mediatechnology
I had a chance to test the TDK-Lambda 35W 5V 3A, +/-15V 650 mA switching supply.

TDK-Lambda CUT35-5FF Rating: Excellent

Mouser CUT35-5FF product page: https://www.mouser.com/ProductDetail/TD ... TIWQ%3d%3d
TDK CUT35 datasheet: https://www.mouser.com/ds/2/400/cut35-1101382.pdf
Mouser Project Manager for TDK CUT355FF power supply and mating connectors/pins: https://www.mouser.com/ProjectManager/P ... 65b59a493a

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TDK-Lambda CUT35-5FF 5V 3A +/-15V 0.65A Triple-output Power Supply

The CUT35 is a mixture of TH and SMT. The 8 pin DIP switcher ICs appear to be a Lambda proprietary part.

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TDK-Lambda CUT35-5FF 5V 3A +/-15V 0.65A Triple-output Power Supply

Note that there are dangerous potentially lethal line voltages on the primary side of this supply. Use caution when handling and bench-testing.

The CUT35-5FF is small measuring about 2" by 4".
One unique feature is that the bipolar output and 5V output are isolated and do not share a common ground.

The unloaded outputs measure almost exactly on-target.
The 5V is adjustable.

A minimum load is not required for start-up but it was found that a +/-15V (30V) pre-load current of 15 mA was required for low-noise operation.
If the CUT35 is started without pre-load and the load then added it remains somewhat noisy with sawtooth ripple in the 10s of millivolts.
With the 15 mA pre-load applied at startup, ripple and noise is exceptionally low <4mV P-P measured on the scope.
With a board connected having a 50 mA load I saw no issues with noise.

Measured with the HP400FL analog meter the output noise is -62 dBu (100 kHz filter) and -44 dBu (4 MHz). (-3dB points.)

The CUT35 appears to have two separate converters one for the 5V the second for the bipolar 15V.
It also has two transformers.
The bipolar supply uses a center-tapped transformer with half-wave rectification.
The 5V supply uses a single output winding and a dual diode half-wave rectifier connected in parallel.
There are 4 opto-isolators which cross the galvanic barrier.
The 5V may have one for voltage feedback and the second to detect over-current.
The second pair of optos, on the bipolar supply, along with a second convertor IC suggest voltage feedback for at least one of the channels if not both.

I measured the noise floor of the MS-II connected to the TDK CUT35-5FF and it was as quiet as when powered from the linear bench supply.
That's good enough!

Re: TDK-Lambda Single, Bipolar and Triple Output Switching Power Supplies for Audio Projects

Posted: Thu May 03, 2018 3:30 pm
by mediatechnology
I needed to run a Phono Transfer System on overnight burn in and do final QC so I used the TDK CUT35-5FF.

I couldn't distinguish any difference in noise floor between running the low-level preamp on the TDK switcher and a linear bench supply.

The TDK CUT35-5FF triple-output bipolar supply rocks! I think its my "goto" switcher. To bad they don't make it in a desktop.