Hi all,
Doing some work on my Pioneer A400, started with reservoir and coupling caps making a nice improvement. Replaced a load of other electrolytics as recommended on another forum which seemed to make bugger all audible difference probably because they’re not in the signal path.
Next job was to replace all the signal path resistors with metal films. So far I’ve done half which seem to have made it sound a little more detailed.
The other half are 1/4 watt fusible carbon types so I don’t want to touch them, they are all measuring spot on. Would a 1/4 watt metal film be considered an acceptable replacement to get the rest of the signal path done or safer sticking with the fusibles?
Secondly - there are a lot of ceramics outside of the signal path, swapping these for films isn’t likely to make a difference is it?
Thanks 🙂
Doing some work on my Pioneer A400, started with reservoir and coupling caps making a nice improvement. Replaced a load of other electrolytics as recommended on another forum which seemed to make bugger all audible difference probably because they’re not in the signal path.
Next job was to replace all the signal path resistors with metal films. So far I’ve done half which seem to have made it sound a little more detailed.
The other half are 1/4 watt fusible carbon types so I don’t want to touch them, they are all measuring spot on. Would a 1/4 watt metal film be considered an acceptable replacement to get the rest of the signal path done or safer sticking with the fusibles?
Secondly - there are a lot of ceramics outside of the signal path, swapping these for films isn’t likely to make a difference is it?
Thanks 🙂
I would leave the fusibles if they measure good. Likewise the ceramics, they will do a better job at decoupling high frequencies compared to film capacitors.
Do they need to be fusible for safety? If not metal film will be less noisy and distorty in the places in the signal path where that matters. Most resistors in an amp are not critical though, mainly feedback paths that matter.
Ceramics it depends - if they are NP0/C0G then they are essentially perfect anyway, if they are just decoupling is doesn't matter. If there's the wrong sort of ceramic in the signal path that will show up in the measured distortion very obviously, as they are less linear than almost any other component!
Changing the electrolytics has added decades of longevity in all probability, it was worth it!
Ceramics it depends - if they are NP0/C0G then they are essentially perfect anyway, if they are just decoupling is doesn't matter. If there's the wrong sort of ceramic in the signal path that will show up in the measured distortion very obviously, as they are less linear than almost any other component!
Changing the electrolytics has added decades of longevity in all probability, it was worth it!
Thanks for the replies guys - yes the fusibles do all measure spot on. The service manual specifies them for safety (the fusibles I haven’t done in the signal path) in terms of protecting other components I guess. I’m just wondering whether changing the ones directly in the signal path would be a safe thing to do or if I should just leave the fusibles as they are. They’re 1/4 watt types I can’t seem to be able to source from anywhere.
There aren’t any ceramics in the signal path but a couple in the feedback path I haven’t done as well as a couple of resistors - the electrolytics have all been done there. You’re right about the electrolyrics - who knows how much longer the ~30 year old originals had in them 🙂
There aren’t any ceramics in the signal path but a couple in the feedback path I haven’t done as well as a couple of resistors - the electrolytics have all been done there. You’re right about the electrolyrics - who knows how much longer the ~30 year old originals had in them 🙂
I've left the fusible resistors as is - just been listening. Really starting to open up now I think things are starting to burn in (both the CDP and amp are full of new caps).
If I was to upgrade components in the feedback paths - this might be a bit of a long shot but I'd be extremely appreciative if someone could advise - could someone please advise which components to focus on here? My electronics knowledge doesn't stretch to choosing the important components here! Pioneer A400 integrated amplifier - Service Manual Free Download
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Hi ! very interesting point ... i have always thought the same.
May i ask your brand and model resistor of choice for the signal/feedback path ?
Thanks a lot, gino
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