How much ripple is acceptable?

[Morden2004]

This is a technical question, and I'm hoping EchoWars and/or any/all of the other technicians will jump in with answers and additional info. This is very basic troubleshooting and is useful for all owners to have this knowledge.

Q: How much ripple do you accept as allowable on the DC rails of a vintage Sansui (or, I guess, any vintage) audio gear?



If the answer is none, then I'm about to dig into a couple of units

I assume that it will be the relative % of a/c on top of the DC since 100MV of ripple on a 6VDC is more significant that the same amount on 45VDC, right?

Paul

 

[EchoWars]

True...100mV would be a real problem on 6V.

To be honest, It's not something that I regularly measure. If I hear no hum or 120Hz or harmonics thereof at the output, and the amp can reach its rated power (plus some for good measeure), and the DC voltage reading is about what it is supposed to be, then I figure that the filter caps are OK.

With no load though, I would assume that anything over 250mV on the high voltage supply might raise an eyebrow. Still, I wouldn't be overly concerned about ripple unless there is an obvious symptom.

 

[Rob]

Morden,

Ripple is usually expressed as a percentage of the DC voltage but can also be specified as an absolute crest to trough value, such as 15 millivolts P-P ripple. One volt P-P ripple on top of 100 volts DC would be 1% ripple.

I don't know what the acceptable ripple specs are for consumer SS gear such as Sansui. It will be worst at the main supply capacitors, the rails, and less elsewhere after further decoupling for lower voltage stages.

 

[Morden2004]

Great! I sort of thought that it was a non-issue if no apparent hum (60 or 120) appeared at the output.

I do sometimes see a bit of ripple on the speaker outputs but I guess that a lot of that can be induced and is not necessarily DC ripple. Also, nowhere have I seen any info from the manufacturers as to how 'clean' their DC is expected to be.

These older supplies are, I think, less likely to induce audible noise unlike the newer switching supplies.

Thanks for the comments.

Paul

 

[Rob]

Switching supplies in hi-fi gear? uke: Well I guess it was inevitable since sand is cheaper than copper or iron. I haven't owned anything SS new enough to see this. For land based applications give me a reliable mains frequency power supply with a big power transformer any day thank you.

I see they are putting switchmode PS's in microwave ovens now. I haven't found one of these at the landfill site yet but was taking the regular ones home regularly to salvage the HV xfmers and a few other parts from. These transformers are useful for some projects and the magnetrons contain awesome fridge magnets!

I'll be looking for ways to use the HV switcher when I do run across one. Could lead to some interesting applications.