I believe the transformer is indeed connected to the mains. The reason given for having one in the first place was, apparently, when the subs were first designed it was felt that having a large toroidal transformer was more of a "prestige way to do it." At some point I very much want to try a DC blocker. For now I switch it off when not in use.
I can't see how a DC blocker could damage the SMPS (or anything else) in the sub. The incoming mains to an SMPS is simply rectified anyway. Adding a couple of inverse parallel diodes in series with the mains (and these are bypassed anyway with lots of uF) can't conceivably alter anything that might upset the SMPS.
Reviving this from way back to make sure what I'd like to do is safe. I'm building a guitar amp, just a 10w SE amp. I would like to put one of these dc blockers between the neutral lug of the switch and the toroid PT's primary. I'm not willing to put anything on the safety ground to the chassis, so I hope it will still work, but I'm fine adding the 220n and 220k cap and resistor between the neutral and hot leads as shown in the Bryston schematic if those are needed.
I have 4 Nippon Chem-con 15,000 uf 63v electrolytics, a 25a 1000v bridge rectifier and a 6a 400v bridge I can use. If I didn't have a spare 320-0-320 toroidal PT sitting around, I wouldn't be considering this.
Both the Bryston and the Westhost schematics make sense if the big caps are just there to smooth out the switching noise, but I was worried about the startup current. Is there a big spike in current to fill the caps initially in both designs?
If there is, since there's so little current flowing after the startup, could I put a 5 or 10ohm resistor on the negative side of each cap without preventing the caps from doing their jobs, and would limiting that inrush be wise?
Thanks for any advice!
I would say not tbh. Certainly for a conventional PSU with a mains transformer the value is far to small. SMPS do not need a DC blocker.
You need big uF (like 10,000uF) at low voltage (16 volt even 6.3 volt is ok) and add the diode protection (bridge rectifier is commonly used) for protection of the caps,
You need big uF (like 10,000uF) at low voltage (16 volt even 6.3 volt is ok) and add the diode protection (bridge rectifier is commonly used) for protection of the caps,
Is this blocker effective and above all safe ...
What is your opinion on the addition of resistor and film cap?
https://ibb.co/WFB6mQb
Cant post images for some reason.
What is your opinion on the addition of resistor and film cap?
https://ibb.co/WFB6mQb
Cant post images for some reason.
It is safe if you install it correctly... meaning physical mounting of it and keeping necessary clearance from other parts of the amp. They can be effective if the real source of the problem is asymmetric mains causing a shift in the notional centreline of the waveform (which is commonly but incorrectly called a DC shift)
Can't see a resistor or cap.
Can't see a resistor or cap.
That sounds like a snubber of some kind although that would mean the cap and resistor in being in series.
Have a look at this:
https://sound-au.com/articles/xfmr-dc.htm
Figure 8 shows the standard circuit.
Have a look at this:
https://sound-au.com/articles/xfmr-dc.htm
Figure 8 shows the standard circuit.
A cap across L and N can be considered as a filter for interference (it must be a cap suitable for that use such as Class X spec)
The 33 ohm is so low in value it can only go across the two series electrolytics but there is no charge to bleed off ofr all practical purpose because the caps see hardly any actually DC across them. The diodes limit the voltage to around -/+1.3 volts.
If the caps are suitably sized in value then the diodes never come into play.
The 33 ohm is so low in value it can only go across the two series electrolytics but there is no charge to bleed off ofr all practical purpose because the caps see hardly any actually DC across them. The diodes limit the voltage to around -/+1.3 volts.
If the caps are suitably sized in value then the diodes never come into play.
The R and C should not be needed. 47000uF tbh sounds to big. Yes it will work but its overkill. Six diodes will allow around -/+ 1.9 volts 'DC' to be developed across the caps. The surge ratings of the diodes is the most important factor. The diodes only conduct in normal use for a few cycles at power on. How big they are depends on the VA rating of the transformer.