I recently purchased a used, nice condition Musical Fidelity A308 integrated amp. It works well and sounds great. I opened the top and I did notice what looks like significant modifications of the original factory capacitors throughout the unit. Below are hi res photos. Note the banks of caps sitting on wood blocks on top of the power transformers... and there seems to be replaced silver colored caps all over the main circuit board as well. The caps are not marked with branding, also no values can be seen. Below the pics of my unit are a link to an old for sale ad of a stock unit... the pics in it are not great but one can see the black original caps...
I am curious to know, if knowledgeable people here can tell me, what these modded caps are and any other thoughts or comments you might have. I will repeat, the amp is dead quiet and sounds great.
And FWIW - here is the link to photos of the innards of what should be a stock unit:
https://www.hifi4sale.net/t73965-musical-fidelity-a308-integrated-amplifiersold
I am curious to know, if knowledgeable people here can tell me, what these modded caps are and any other thoughts or comments you might have. I will repeat, the amp is dead quiet and sounds great.
And FWIW - here is the link to photos of the innards of what should be a stock unit:
https://www.hifi4sale.net/t73965-musical-fidelity-a308-integrated-amplifiersold
Obviously the previous owner has removed the 4 original snap in power supply caps and then added two banks (one for each channel) of what would be a higher value capacitance with all the caps wired in parallel, and hopefully better quality as well. I have no idea why they removed the capacitor covering foil, but I seem to remember a few years ago, there was a myth going around that electro caps "sounded" better with the outside plastic foil removed.
Hopefully the mod gives better bass control with more PSU capacitance.
Hopefully the mod gives better bass control with more PSU capacitance.
Hi. I think person ,who made these capacitor mods ,has not enough knowledge about currents flowing through capacitors . Even increase leaded capacitor leads length not a good idea , here we have long wires ... Capacitors must be close as much as possible to diode bridge , to allow high current pulses to charge them quickly . With long wires, capacitor added benefit is neutralized. Esr is higher , voltage drop on wires begin to dominate. Also wire prevents high current flowing from capacitors bank to amplifier, thus again ,no benefit. Ripple filtering also reduced . So incomplete mod i think.
they are glued to the top plates of the x-formers...
i am just curious to know if someone here who has been a diy-er for some time recognizes what kind of caps these are which have been installed in place of the oem ones...
You may measure their capacity ,by desoldering one of them and using proper capacity meter ... Also you can measure dimensions ,and try to look in mouser, digikey or another supplier catalogs to find similar capacitors ,with that capacity ,filter by dimensions ,determine possible voltage rating , then narrow possible variants . If someone has removed tube with labels ,probably it was reason to do so - maybe non-audio "brand " of capacitors ,or kinda like "i can mod your amp for money" and to "protect property" ,prevent choice discussions. Or to hide label how crappy those capacitors actually are . Actually , until some power , amplifier can sound ok with any type and capacity of capacitors , until PSRR of amplifier is enough to defend ripple and compensate distortions ,caused by voltage drop by load increase . But most effect is at higher power , or at short powerful peaks ,when capacitor bank supplying amplifier with power alone .Then every centimeter of wire can matter , depending on how much ohms load is ,and how long that power peak took ( bass in example ).
I would not have used oak..!
I'm wondering why the hacker didn't replace those 4 big caps. (Then, those added caps would at least bring down the ripple, despite the long leads.)
Is there a bottom cover to access the pcb's underside, or does the whole amp need disassembling to reach the underside?
You're welcome to bring it over for a debrief, as you're nearby us in Novato?
I'm wondering why the hacker didn't replace those 4 big caps. (Then, those added caps would at least bring down the ripple, despite the long leads.)
Is there a bottom cover to access the pcb's underside, or does the whole amp need disassembling to reach the underside?
You're welcome to bring it over for a debrief, as you're nearby us in Novato?
actually the amp was shipped cross country without incident
...and not sure which 4 big caps you are referring to, Andersonix -- seems like all original caps were removed and replaced with what we see
i was able to find the following youtube clip of what looks like this unit in stock form... towards the middle of clip are good shots of the original caps...
...and not sure which 4 big caps you are referring to, Andersonix -- seems like all original caps were removed and replaced with what we see
i was able to find the following youtube clip of what looks like this unit in stock form... towards the middle of clip are good shots of the original caps...
That's not the top plate but the high voltage insolation. They have basically made the amp very dangerous. Coupled with the METAL cap tin too. I hope the glue doesn't destroy the insulation or it will completely destroy the amp, anything connected to it and probably your house. That's a seriously dangerous mod. To correct or any hard impacts it will end up destroying the transformers and the amp.
Seems like this guy did a much better job!
https://rockgrotto.proboards.com/thread/11508/musical-fidelity-synthesis-amplifier-upgrades
Glue can lose its strength over time, those cap bands sit on top of transformer are for accident waiting to happen!
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