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Swapping class AB amp linear supply with a SMPS - incl measurements

dlaloum

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SMPS sure have their advantages and nowadays you will not see any PA amplifier without it. But their reliable life time is limited, usually to about 10 years. For Pro PA not a problem at al, as it is their usual service life too. But for private home use, recapping after 25 years is normal. Regularly swapping SMPS? I doubt.

Some posts earlier the Perraux amplifiers came along as a kind of reference example. These are beautiful amps. Despite the design is rather simple, they have precise and smooth mids and highs and a huge bass drive. Nevertheless they are never fatiguing and almost indestructible. Recently I did restore a over 25 years old 3370 model and a 3400 model Perreaux, rated at 300W_rms continuous. I considered also putting a SMPS into it. But as they are, these beasts can spit out over 25 amps at 80 V_peak for short burst periods, thanks to its large rail buffer caps. That is more than 2 kW peak! Hard to find a suitable SMPS of plus and minus 90V that can deliver that peak power and fit. So I left the heavy tranny at its place for another happy 25 years :)
My lightly used Crown XLS' are about 15 years old now... had a hard 2 to 3 years in professional use before I bought them... and since then, they idle along at a lazy 1 to 4 W
 
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McFly

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That is more than 2 kW peak! Hard to find a suitable SMPS of plus and minus 90V that can deliver that peak power and fit. So I left the heavy tranny at its place for another happy 25 years :)
hypex smps3ka700 would probably do the trick :p
 

dlaloum

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hypex smps3ka700 would probably do the trick :p
Presumably that heatsink would need to be thermally connected to a "real" case size heatsink to support this level of output for any substantive period of time?
 

dlaloum

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Home HIFI? Using 1/8th rule, very likely not.

Running flown PA at a concert, yes.
But wouldn't that reduce the gears life expectancy ?

Attached to a "proper" heatsink, it would remain no more than lukewarm under any normal use - and heat is the main cause of reduced life expectancy...
 

Piere

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Thanks for the suggestions. Hypex products are well known to me and I already fitted a Hypex inrush limiter in those amps. Apart from the smps3ka700 doesn't fit, I will not gain anything with it in this case. Only lose some weight, for the amp as well as in the pocket.
 
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McFly

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Hypex do an inrush limiter? huh.
 

fpitas

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Presumably that heatsink would need to be thermally connected to a "real" case size heatsink to support this level of output for any substantive period of time?
Yes. But home use for music isn't like that. The peaks are 15dB above the average. PA use, driving a shake table, or used as a lab amp, yes, a real heatsink becomes necessary.
 
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McFly

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Haha I just pictured a perreaux amp sitting under the paint counter at bunnings :D
 

fpitas

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Haha I just pictured a perreaux amp sitting under the paint counter at bunnings :D
When you need high fidelity shaking!
 
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McFly

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If there's any distortion in your paint shaker, well... you don't wanna know what happened to those guys that used crown class D amps. They never got the color they wanted.
 

fpitas

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If there's any distortion in your paint shaker, well... you don't wanna know what happened to those guys that used crown class D amps. They never got the color they wanted.
Well...we do also use shake tables to perform vibration testing of equipment. But that really may not take much more fidelity.
 

restorer-john

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If there's any distortion in your paint shaker, well... you don't wanna know what happened to those guys that used crown class D amps. They never got the color they wanted.

Yeah, much darker black backgrounds with a big Perreaux installed under the paint shaker. Bit of a ripple-like sheen in the finish if you look really hard.
 

Doodski

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I had not browsed the Perreaux website in some years and wow what a change there has been. Brightly colored components but still in their typical high quality. Check out all the colors available in this integrated amp. (Downpage) Perhaps this is industry leading stuff and we will see colorful stuff in the future?
 

Doodski

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I hope not. :)
It's ballsy for sure or perhaps somebody is having some sort of crisis? :D The interior of the smaller power amp, smaller integrated amp, phono amp and the big pink power amp all look OK.
z p a.png

z p b.png

z p c.png

z p d.png

z p phono amp.png
 
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McFly

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Yeah the stuff that came out of Napier in the 80s and early 90s is the lateral mosfet stuff. They likely had a big design change when the mosfets were EOLd and the owner sold, the company moved south.

The newer stuff looks good, but too expensive for me to grab one and measure! Maybe in another 10-15 years who knows.

Not sure about the Colors on the current stuff. Different than the usual silver and black tho.
 
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restorer-john

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Yeah the stuff that came out of Napier in the 80s and early 90s is the lateral mosfet stuff. They likely had a big design change when the mosfets were EOLd and the owner sold, the company moved south.

All Hitachi MOSFET gear from Napier. I met Peter Perreaux back in the day. I think he went off the rails and got into some weird chit at one point after Perreaux collapsed. Not sure.

I always liked the look of this early integrated of theirs:

1662513505593.png


1662513586613.png
 

Piere

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I had not browsed the Perreaux website in some years and wow what a change there has been. Brightly colored components but still in their typical high quality. Check out all the colors available in this integrated amp. (Downpage) Perhaps this is industry leading stuff and we will see colorful stuff in the future?

Due to the still large heatsinks it appears to me they still use their old Class-A/B Mosfet architecture. And why not? It was a landmark in the '80-ties and '90-ties. And sound wise to me it can still cope with most of the top amps today! Here a pin-up of the 3370 I restored recently:

IMG_3379_NCA.jpg


It was modified almost to death by some Audio Magician. When It arrived at my desk very large 4,7 uF 1000V Mundorf Silver foil caps, that merely belong to an audiophile speaker x-over, were strapped to the back as input capacitors. Very good hum catchers I know now! Also the feedback loop was modified and the poor thing cried (oscillated) out loud. Luckily all mosfets survived! You can still see the burned PCB under the zobel resistors at the top left. And if you ever touched the smell of burned epoxy PCB... The thing went firstly 2 weeks in quarantine for it. Top right the Hypex soft start.

After fondly restoration, the thing is now happily in service again. Here how it performs at 300W into 8 ohms:

3370 300W 8ohm.png


Mains hum looks a bit misleading dramatic here but it is about -108dB and distortion quite low. It's an order lower than specified in the manual.
 
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