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Primrose(SumR Audio) Toroid GB

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Measurements

I'm not trying to stir the pot. I simply wanted to offer some measurements that may inform other folks here. With the test rig noted in an earlier post, here is what I found:

I'm reporting the DC current through and voltage across the load at which I could hear the transformer buzz from a distance of approximately 1 meter (measured). The transformers were NOT mounted and simply rested on a large sheet of Baltic birch ply, supported off the floor by saw horses. There was a computer case fan running approximately the same distance behind me and it was audible. Point is, I heard transformer buzz above other background noises.

Methodology: I turned up the VAC on the primary side of the transformer with a VARIAC until I could hear the buzz from the Device Under Test (DUT). The output of the each DUT was connected to a rectifier/capacitor unit to create a +/- Vdc output. The output was then fed to the 'load' of 300W light bulbs. (Pictures previously posted)

Unit 1 (24+24, 800 VA, potted)
Idc = 2.14 A
Vdc = 7.5 V

Unit 2 (24+24, 800 VA, potted)
Idc = 2.08 A
Vdc = 6.6 V

Unit 3 (25 + 25, 400 VA, non-potted)
Idc = 2.77 A
Vdc = 15.4 V

Unit 4 (25 + 25, 400 VA, non-potted)
Idc = 2.8 A
Vdc = 15.9 V

Other notes... These are threshold values. As I increased above these state points, the buzzing increased. I didn't run the test long enough to feel a temperature rise in the transformers. I did place my hand on the them so I could feel the mechanical vibrations.

Comments/suggestions? I've e-mailed Primrose to get instructions on how to return these. I understand these things happen in manufacturing processes.

Ryan
 
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Joined 2010
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Hi Ryan,
Thanks for take your time and send us your results.
I have two 600VA 24+24 in the drawer taking dust and I forgot to have them
Should be interesting to know what's the primerose reply.
I am in korea and I will not spent others money to ship them back but is really a pity.
Best Regards,
Enrico
 
Sorry for resurrecting a really old thread.

I recently used the SumR toroids I got from this GB and they all buzz pretty loudly (I can easily hear them a few meters away). I tried using a DC blocker on the mains with no effect.
I also tried contacting Richard from SumR but he just blamed anything else in the power supply. After directing him to this thread asking if he found the cause and a solution, all I got was radio silence.
It seems that SumR doesn't stand behind their products anymore, even those from their Primrose line.

Lesson learn about spending any money on their transformers in the future, but I was wondering if there was any way to salvage these toroids? Has anyone had any success?

Thanks

Paul
 
I finally installed the SumR transformer as part of the group buy (400VA, 22VAC) and it mechanically buzzes badly, not usable for my standards.

While I was waiting for the SumR transformer I was testing a single channel F4 with a 120VA, 22VAC Plitron and it was dead silent at full bias.

I would suggest everyone involved in the group buy test their transformers before too much time passes.

BDP

I received replacements for both and the replaced units were silent, I hope you have success in getting them replaced.
 
can they be potted in epoxy or something?

2 of them are the potted version and 2 of them are non-potted. The potted versions buzz less loudly but still much above background noise. So it may be a solution for ones that only buzz slightly?

Unfortunately it doesn't seem like SumR wants to recognize that the problem has something to do with their fabrication, like some other toroids from the same GB. At least that's my interpretation from SumR's silence after my last email (which was a month ago).

Paul
 
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