Finally they are arrived – two custom toroidal transformer from Primrose Audio (also known as Richard Sumner Technology). This is Canadian based company specialized in manufacturing the toroidal transformer. For regular customer, they use SumR name, while for the audio specialized version, they name it as Primrose Audio.

Probably you will ask me why Primrose Audio? Simply because I don’t have much options around for custom toroidal transformer and it seems the designer also quite serious to build a transformer for audio purpose. So why don’t I give it a try?

Again, seeing the specification on their website, this company is really serious building the stuff for audio. Definitely they know what those ‘audiophile’ wants in terms of the transformer design (like electrostatic screen, core band for magnetic shielding, potted design, etc).

I decided to order two version: one for my QLS QA-660 and the other is for my ASUS Xonar Essence One.


The lead out is using high quality cables. The outputs are set on the side, quite neat. Although on some parts, we can see this is a real “DIY hand-made” production (not the best in terms of the precision of the cutting, labeling, etc). But as long the sound is not impacted, then I don’t really give a care ;-).


Label is printed and put on the side of the transformer.


Well, they also provide a datasheet for each transformer. As this is a custom version, therefore they will carefully write down the details only for this transformer. I believe the datasheet is quite detail, including some basic actual measurement from each transformer.


Comparison with my standard toroidal transformer: Talema. On similar VA rating, I think they are quite similar in terms of the diameter. Only the Primrose is a bit taller.


Will see how does this transformer could perform on my QLS QA-660 and ASUS Xonar Essence One.