Hi, I have an Aleph 30 from about 2004 that exhibits weak and distorted bass; midrange and treble seem fine. I've measured the rail voltages, bias currents and output offsets and all seem fine. Although physically, everything looks fine, I'm suspecting the 16+ year old power supply caps. Does that seem reasonable, or is there something else I should be taking a closer look at?
exhibits on same speakers, having proper bass in past?
yes, it is expectable after 16 years that elcos are sorta compromised, but really depending on hours spent in On state
but, still needing confirmation with some test or simple logic
yes, it is expectable after 16 years that elcos are sorta compromised, but really depending on hours spent in On state
but, still needing confirmation with some test or simple logic
Yes, the bass certainly used to be significantly better. It's seen quite a lot of usage in the past, but recently came out of storage.
Give it a couple of weeks more of regular use. If it does not improve,
the power supply electrolytics may need replacement.
the power supply electrolytics may need replacement.
It's been several weeks already. I pulled one of the caps off the board and it measures 8750 uF (nominal 10,000 uF), so a little low, but still within 20%. Assuming the rest of them measure about the same, that doesn't seem too serious a loss. So, I'm at a bit of a loss right now,
Could have higher than normal ESR. Also there's C103, which is 220uF, 35V.
However, if you mainly listen to LPs, maybe the colder winter ambient temperature
is stiffening up the stylus. If so, can you try another source?
However, if you mainly listen to LPs, maybe the colder winter ambient temperature
is stiffening up the stylus. If so, can you try another source?
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Actually, the source is digital. And I’m not hearing the issue with a 17 watt mini-Aleph or a Hafler 9180. So I’m pretty confident something is amiss with the Aleph 30. You bring up an interesting point re: ESR. I’m not sure how to determine if that’s the issue.
If you have built any other amps or have a PSU with new caps, perhaps a test with a different PSU could give you some confirmation.
Another suggestion - disconnect one channel (from + and - rails at least) and see if the reduced load changes the response for the channel still connected.
Another suggestion - disconnect one channel (from + and - rails at least) and see if the reduced load changes the response for the channel still connected.
value, if not really way outa specs, is not what's most important
as Boyz already pointed - ESR is what's in play there
anyway , as good new caps are not costing arm and leg, just replace them with new ones
Be sure to get 35V parts, and a low ESR, longer life rating, and higher temp are better.
Just make sure the diameter will fit.
Just make sure the diameter will fit.
Indeed. Not many options at this form factor (25mm OD, 10mm snap in). The originals were 50V, but I've selected some CDE 381LX 12mF @35V, 3000hrs @105C: https://www.mouser.com/ProductDetail/598-81LX123M035J052.
That 50mm length has usefully lower ESR than the 40mm cap at the same uF/voltage.
Those should last a long time.
Those should last a long time.
