I am not building any DC filters yet, no worries. Not today, at least...I would first confirm that it is DC by making something similar. If it is DC that cause buzz... Should manufacturers take it into account? Do they? A lot of questions, but let's check first
In any case, this is only one out of three similar size transformers where the hum or buzz was noticeable, in the same test.
I got a pair of 800 va 18vac transformers from the group buy. They both have a mechanical hum, one much louder then the other. I tried a dc blocker to no avail. I contacted the manufacturer and they offered to replace the noisier one. I don't know if it's worth the hassle/expense of shipping back and forth.
Some background:
these units replace 400 va antek transformers that were quiet in the same amps.
The amps are mono blocks using two bridge rectifiers crclc
30,000 .12r 30,000 .3mh 100,000uf
Checking voltage drop across the first r it looks like a 3.9 amp draw per rail.
I have been wondering if the noise is caused by my power supply, or if it's just inherent in the transformers.
Evan
Some background:
these units replace 400 va antek transformers that were quiet in the same amps.
The amps are mono blocks using two bridge rectifiers crclc
30,000 .12r 30,000 .3mh 100,000uf
Checking voltage drop across the first r it looks like a 3.9 amp draw per rail.
I have been wondering if the noise is caused by my power supply, or if it's just inherent in the transformers.
Evan
Well that sucks. I wonder what causes the hum? It must be mechanical. Why would one company's assembly process cause more hum? They've been making transformers long enough to iron out any problems. Does the hum come out of the transformer itself or does the vibration transfer to the chassis? Can it be quieted with more careful mounting?
Does potting fix a hum problem?
I haven't used my transformers yet and will be a while before I do. I hope they don't have problems. However, I have four so I don't think odds are in my favor.
The manufacturer is in Canada so shipping is outrageous.
Does potting fix a hum problem?
I haven't used my transformers yet and will be a while before I do. I hope they don't have problems. However, I have four so I don't think odds are in my favor.
The manufacturer is in Canada so shipping is outrageous.
If I am doing the math correctly, then this is about the same power, relative to the specified VA rating, compared to my randomly chosen test point.
In round numbers, you would have ~4A at 25V DC per rail... 100W per rail total from a toroid rated at 800VA. I am testing at 50W/rail, from a transformer half your size.
Interesting that one was louder than the other. That would seem to suggest something related to individual transformers, not related to power quality.
My dc voltage drops to +-21.16vdc under load. The 400va anteks dropped to +-20.5vdc.
I tried mounting a bit tighter and looser, extra padding over/under the transformer, no big change.
I need to remind myself that although the humm seems loud standing over the amp in a silent room I certainly can't hear it from my couch even between tracks.
I tried mounting a bit tighter and looser, extra padding over/under the transformer, no big change.
I need to remind myself that although the humm seems loud standing over the amp in a silent room I certainly can't hear it from my couch even between tracks.
In my case it comes from the transformer itself, even if it is sitting on the bench on a foam pad. It is not transferred to my chassis, as far as I can tell.
A 2-3% difference makes sense, the Anteks were closer to their rated load. The rest of the voltage drop is just the normal power supply drop under load.
I have the same issue. I tried the dc blocker to no avail.
Primrose stood behind their product and offered to replace the noisier of the two 800 va transformers I have. I did not take them up on the offer.
I also wonder if my power supply is causing the noise.
crclc 30,000uf .12r 30,000uf .3mh/.1r 100,000uf
Primrose stood behind their product and offered to replace the noisier of the two 800 va transformers I have. I did not take them up on the offer.
I also wonder if my power supply is causing the noise.
crclc 30,000uf .12r 30,000uf .3mh/.1r 100,000uf
No, it is a mechanical issue. I tested with purely resistive loads, and Lamp loads with no rectifier/filter supply connected. All you need to verify is a couple 250~300W light bulbs, and some sockets w. holders from Home Depot. When the current gets high enough, the transformer will start to hum. around 25%~30% of full load is enough to cause it.
Not saying that the current spikes produced when the rectifiers turn on and off could not cause noise, but that is not the case here.
Well this sucks. I probably won't use my transformers for a while, but don't look forward to dealing with a noise issue. I wish we were made aware before we purchased that it may be a problem. Maybe could have had them potted or some other process to correct it. Sending them for replacements is too costly.
It may only be a few out of those that were made. I have only seen posts from two people, besides me.
Easiest way to test is with some dummy loads, as I said above. You do not even have to be close to the rated transformer load.
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