Power Supply Considerations for LDR3x Boards & LDR3.V2 & V2K

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tortugaranger

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As a result of shipping our latest LDR3.V2 and V2K(kit) model preamps we now strongly suspect that poor power supply quality may adversely affect their ability these preamps to perform auto-calibration properly. And since the introduction of adjustable input impedance requires auto-cal to work properly this becomes all the more important to be aware of and to mitigate.

We've been shipping the LDR3.V2/V2K's with our standard issue 12 VDC wall-wart power supply. This is the same PS we used going back almost 3 years now which worked fine with the earlier versions of preamp controller boards before we came out with the LDR3x.V2 board. However, it's now clear these same wall-wart PS's are too noisy for auto-cal.

This came to light today based on the fact that one of the LDR3.V2's we had shipped got hung up during auto-cal whereas we had never encountered that problem in our shop. Then I realized we had in fact NOT used the wall-wart PS during commissioning of the unit but had instead used our own high quality SMPS source which we know to be decently clean and low noise.

So I went ahead and tested the two PS sources - our own SMPS and the wall-wart shipped with the LDR3.V2's and V2K's. Below you can see the results. Clearly the wall-wart PS truly sucks.  :nono:

As a result, we WILL be replacing the wall-wart PS's already shipped with our LDR3.V2 and V2K models. I've identified a candidate linear PS replacement that should perform quite well. One of our customers has already tried an available linear 12 VDC alternative and his unit no longer has any issues with auto-cal.

For those of you who own our DIY LDR3x.V2 and V2.1 preamp controller boards, we've been advising that most any 12 VDC wall-wart PS should be adequate for powering these units. I'm now updating our guidance to be very careful using a switching wall-wart type PS. They may work just fine but I recommend you first verify their noise/quality. Ironically, the SMPS wall-wart we'd been using actually came with very decent specs - trust yet verify.

Please note that are LDRx and LDRxB models are not affected by this because we use our own internal power supply with these units which are reasonably quiet.

Lastly, we will soon be adding a suitable linear wall-wart style PS to our product list - one that we KNOW will be a good fit for your DIY project.  :thumb:

          High quality Tortuga Audio SMPS                   Noisy Wall-Wart style SMPS