I did upgrade the two big PSU caps of my Audiolab 8000A replacing the 25year old Elna 10.000uf 50v with new Audio Grade quality caps Mundorf MLytic 15000uf 63v. Since the toroidal transformer is rated 230VA, adding 50% of extra capacitance with the Mundorf Mlytics, means proportionally higher current pulses to recharge, taking the transformer out of its designed envelope. Not a massive problem at low levels, they say, but when driven hard for long periods, the transformer WILL overheat.
As I need to change the transformer, (because it started to hum) do you suggest choosing a higher power rated transformer all the way or fit with original Talema transformer rating? Should it be 250VA perhaps? because I have no idea what the new transformer power rating should be in order to suit these new Mundorf Mlytic caps without overheating. Is there a way to calculate that?
As I need to change the transformer, (because it started to hum) do you suggest choosing a higher power rated transformer all the way or fit with original Talema transformer rating? Should it be 250VA perhaps? because I have no idea what the new transformer power rating should be in order to suit these new Mundorf Mlytic caps without overheating. Is there a way to calculate that?
It's unlikely that the new caps have resulted in much of an increase in peak current, refer section 5.3 in this Rod Elliott article:
Linear Power Supply Design
Perhaps there is another reason why the transformer started humming?
Linear Power Supply Design
Perhaps there is another reason why the transformer started humming?
I often wonder why the DIY enthusiast thinks they know more about engineering design than the designers ... still for torroid buzz, check the bolt is electrically isolated at one end or choose a stainless steel, non magnetic bolt.
Do we know how much hum the OP is hearing and is that really a problem? Does it hum with no signal or power output too? More hum if powering a dummy load etc? We need some facts rather than be left guessing what might be happening.
Thanks tikiroo, great reading, thanks.
JonSnell, I frankly am very ignorant in technical engineering. I wanted to do the upgrade because I think some of those engineers choices are made to suit a certain market price level and since there are many competitors in that level the Audiolab was situated, imho engineers made obvious economy choices. Do you think 25 year original ELNA caps are better than the Mundorf Mlytics? I don't think so.
Ian, main problem is not the humming but (I fear) the overheating of the transformer. That's why I didn't dwell on humming details (it's a classic mechanical low hum coming from the transformer, not very loud though. I have no led dimmers and it's the same even with speed controls on...)
JonSnell, I frankly am very ignorant in technical engineering. I wanted to do the upgrade because I think some of those engineers choices are made to suit a certain market price level and since there are many competitors in that level the Audiolab was situated, imho engineers made obvious economy choices. Do you think 25 year original ELNA caps are better than the Mundorf Mlytics? I don't think so.
Ian, main problem is not the humming but (I fear) the overheating of the transformer. That's why I didn't dwell on humming details (it's a classic mechanical low hum coming from the transformer, not very loud though. I have no led dimmers and it's the same even with speed controls on...)
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In engineering, good designs are balanced. Changing individual elements does not necessarily improve performance.
Does the hum come from the amplifier cabinet when the speakers are off? Replace the elastic silicone gasket under the transformer - it may have lost its properties.
Does the hum come from the amplifier cabinet when the speakers are off? Replace the elastic silicone gasket under the transformer - it may have lost its properties.
Better quality doesn't necessarily lead to an upgrade and is more likely to cause other issues, as you have.
Have you thought about adding some resistors in series? Defeating your object yet the object wasn't practical.
Have you thought about adding some resistors in series? Defeating your object yet the object wasn't practical.
OldDIY, the hum comes from the cabinet, no hum audible on speakers.
StewartH83, good point. I decided to change them based on many other people here that cry for better bass and improved sound after the replacement (some say after upgrade it "sounds like a new totally different better amp")
StewartH83, good point. I decided to change them based on many other people here that cry for better bass and improved sound after the replacement (some say after upgrade it "sounds like a new totally different better amp")
So its increased heat that's the problem now? This just doesn't make sense. The Audiolab amp is certainly hot running but I don't recall whether the transformer was any particular problem. If I suspected it, I would have the clamp type multimeter out and checking the primary and secondary winding currents to see what the matter was but I don't imagine many audio DIYs would have one in their toolkit.
There are other ways to check AC load current though.
There are other ways to check AC load current though.
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Recapping seems the trendy thing to do in this era yet I find DIY'ers create more issues than improvements.
I do believe recapping can improve older gear yet it has to be done right. Mundorf caps won't benefit much, if any, over Panasonic or Nichicon in that area. I'm not a hater of high-quality caps as I prefer Mundorf Supreme's through tweeter crossovers as that's where they have the most effect, outputs of DACs too.
I'd also be worried about the regulator on your unit as it run hot anyway. It has to drop down the voltage a lot which effectively increases heat the more it has to drop.
I do believe recapping can improve older gear yet it has to be done right. Mundorf caps won't benefit much, if any, over Panasonic or Nichicon in that area. I'm not a hater of high-quality caps as I prefer Mundorf Supreme's through tweeter crossovers as that's where they have the most effect, outputs of DACs too.
I'd also be worried about the regulator on your unit as it run hot anyway. It has to drop down the voltage a lot which effectively increases heat the more it has to drop.
i also agree that an extra 5000 uf can't be a problem .. (add that some capacitors have a tolerance of + 70% -20% instead of the standard +/- 20%) I usually use 30,000 uf on each rail for all my class AB amplifiers.
But I've seen "semi-dead" diode rectifiers (in older amplifiers they weren't very powerful)
Symptoms: transformer buzz and high power consumption from the mains...or blowed fuse on primary side.
Symptoms: transformer buzz and high power consumption from the mains...or blowed fuse on primary side.
Here's my reference though, nobody mentioning the toroidal overheating. Audiolab 8000A recap and mod
This (transformer getting hotter than usual) was told to me by a technician (I didn't verify myself) so I'm asking you if changing the capacitance rating will effectively increase significantly the transformer temperature.
Ian Finch, right, that's quite a warm blooded amp, I know.
osscar, thanks for sharing your experience.
This (transformer getting hotter than usual) was told to me by a technician (I didn't verify myself) so I'm asking you if changing the capacitance rating will effectively increase significantly the transformer temperature.
Ian Finch, right, that's quite a warm blooded amp, I know.
osscar, thanks for sharing your experience.
This amplifier is quite "thin" and sealed..Of course there will be a warm transformer which is normal. The question is how warm? what 45 degrees Celsius is nothing crazy ...
with cheap ebay Wattmeter you can measure power consumption..it will indicate whether there is a problem - increased bias current, ossciolation, etc
with cheap ebay Wattmeter you can measure power consumption..it will indicate whether there is a problem - increased bias current, ossciolation, etc
This “audio grade” capacitor malarkey always bamboozles me. I’m just a simple electronics engineer. What makes an electrolytic “audio grade”? Pretty sleeve? Big profit margin for distributors? No sleeve? Sounds like BS to me.
Eventually I can go back to a 10000 µF 63 Volt Mundorf Mlytic, they produce THAT ONE too and keep same 230VA rating for a new toroidal. When I checked back last year, the 10000 µF was rated 80V.
Suzyj, I think the same, pretty skeptical on those epithets. I just wanted to renew the main capacitors. Guess those 25 year old ones did their job already. Can't afford latest brand new audiolab amp but 2 new Mundorf caps, sure! So why not, it's just 40 euros more. Price of an LP to me.
Suzyj, I think the same, pretty skeptical on those epithets. I just wanted to renew the main capacitors. Guess those 25 year old ones did their job already. Can't afford latest brand new audiolab amp but 2 new Mundorf caps, sure! So why not, it's just 40 euros more. Price of an LP to me.
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today i listen to my Leach amp for 6 hours at a low background volume ... (idle power consumption around 60W) - 800VA transformer and 33 000uf capacitors (actually more because these are specified -10% + 75%) ... you can see the transformer heat. So without measurement it's all a guess.
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was the transformer running hot before replacing the caps?
Have you checked any voltages? Overvoltage can cause transformers to work harder
Have you checked any voltages? Overvoltage can cause transformers to work harder
osscar I want that thing! 😀
Stewart, not really. I'm just discussing in theory what a english audiolab tech said to me. I haven't checked temperature actually so can't say if it's overheating more that it generally did... As osscar says, maybe that's all a (techy) guess.
Stewart, not really. I'm just discussing in theory what a english audiolab tech said to me. I haven't checked temperature actually so can't say if it's overheating more that it generally did... As osscar says, maybe that's all a (techy) guess.