SCT2000 transformer alternative

[ElSmurf]

Late August I ordered an SCT2000 PSU from Thomann, only to find the transformer hummed. I had a similar issue with the micparts PSU that came with my V251 kit. This was resolved by Matt sending me a tested transformer that didn't hum. Hoping I just got a unit from Thomann with a bad transformer, I returned it and got a replacement. Long story short, I just plugged in the third one they sent me and it also hums, so I'm looking to go a different way.

My goal is to build a PSU for my 251 clone, and the SCT2000 route would've been the easiest since I could've just plopped in one of Dany's PSU PCBs. I might still go that route, depending on what transformer I can score. Which is my first question - where would I be able to source a transformer, preferably in Europe, that would do the job. Are there custom made options I'm unaware of? My plan B was to have a custom toroidal with shielding built by Audiophonics in France, who do a great job, but their lead time is a few months.

And a more general question - what is up with mains transformers that produce sound? One of the transformers in my D-EF47 PSU also hums (or is it the choke?) and I haven't had the courage, or taken the time, to troubleshoot it. Maybe I'm overlooking something... All my other gear on the same circuit is dead quiet, commercial or DIY.

Any suggestions or insights would be greatly appreciated.

 

[kingkorg]

Late August I ordered an SCT2000 PSU from Thomann, only to find the transformer hummed. I had a similar issue with the micparts PSU that came with my V251 kit. This was resolved by Matt sending me a tested transformer that didn't hum. Hoping I just got a unit from Thomann with a bad transformer, I returned it and got a replacement. Long story short, I just plugged in the third one they sent me and it also hums, so I'm looking to go a different way.

My goal is to build a PSU for my 251 clone, and the SCT2000 route would've been the easiest since I could've just plopped in one of Dany's PSU PCBs. I might still go that route, depending on what transformer I can score. Which is my first question - where would I be able to source a transformer, preferably in Europe, that would do the job. Are there custom made options I'm unaware of? My plan B was to have a custom toroidal with shielding built by Audiophonics in France, who do a great job, but their lead time is a few months.

And a more general question - what is up with mains transformers that produce sound? One of the transformers in my D-EF47 PSU also hums (or is it the choke?) and I haven't had the courage, or taken the time, to troubleshoot it. Maybe I'm overlooking something... All my other gear on the same circuit is dead quiet, commercial or DIY.

Any suggestions or insights would be greatly appreciated.

You hear the hum in the audio, or is the case and the transformer itself humming?

 

[pasarski]

Sorry can't answer your question, but going to think out loud. Does it actually matter if it hums? In a very quiet recording space, recording very quiet source probably yes. But in a not so quiet place recording close miced vocals for example? Also, I think it's not very uncommon that a mains transformer hums IIUIC? I was just about to order couple of these btw.

(Edit: seeing the post above, I assumed the latter)

 

[ElSmurf]

You hear the hum in the audio, or is the case and the transformer itself humming?

The transformer itself is humming.

In a very quiet recording space, recording very quiet source probably yes.

The PSUs are less than a meter away from the mics in a small and very quiet vocal booth. With louder vocals this is indeed not a big issue, but since I know these transformers can also be dead silent I'd prefer to have on that doesn't hum.

 

[rock soderstrom]

The PSUs are less than a meter away from the mics in a small and very quiet vocal booth. With louder vocals this is indeed not a big issue, but since I know these transformers can also be dead silent I'd prefer to have on that doesn't hum.

I can relate to that, it bothers me too.
I've already had 19" effect units that did that.

And a more general question - what is up with mains transformers that produce sound?

As far as I understand it, the 50Hz magnetic field of the alternating current excites the mechanical structure of the transformer to resonate. This is not intentional and I believe that is why transformers are usually potted to prevent this. Some do it anyway or develop this behaviour over time.

 

[ElSmurf]

As far as I understand it, the 50Hz magnetic field of the alternating current excites the mechanical structure of the transformer to resonate. This is not intentional and I believe that is why transformers are usually potted to prevent this. Some do it anyway or develop this behaviour over time.

Then my conclusion would be the problem is one of build quality and QC. Which makes me think getting a good quality transformer for the PSU would be the better route to go.

Which brings me back to my first question - do I get a custom transformer made for the PSU, or are there commercial alternatives available?

Another possibility would be to find a readily available transformer, that wouldn't necessarily have the same secondary voltages, and then adapt the circuit. Which is a bit above my pay grade though...

 

[ElSmurf]

I think I figured it out, just stumbled onto this part of the C12 clone thread where the two options I have in mind are discussed - either a custom job from Audiophonics or this guy from Toroidy. I'm assuming the 9V will be sufficient to drive heater circuit since it's regulated and adjustable.

 

[kingkorg]

The transformer itself is humming.


The PSUs are less than a meter away from the mics in a small and very quiet vocal booth. With louder vocals this is indeed not a big issue, but since I know these transformers can also be dead silent I'd prefer to have on that doesn't hum.

Maybe contact UTM, they might have something.