My amp , wharfedale 2050a is a good 20 odd years old and I am assuming it needs a recap?
I would like to change the Power supply bulk capacitors to BHC/Aerovox perhaps and the power stage local power supply caps to Rubycon ZL, for these would there be any benefit to using 10 x the old value?
It will also get a new volume pot then possibly the voltage gain stage re-engineered and bias will be reset, also some changes to NFB loop. I will do the caps and volume pot but I will leave the rest to someone who knows what they are doing.
Am I flogging a dead horse here? also, newbe question coming up but if I were to post detailed photos could someone show me where these caps are?
Advice on draining them would also be appreciated.
I would like to change the Power supply bulk capacitors to BHC/Aerovox perhaps and the power stage local power supply caps to Rubycon ZL, for these would there be any benefit to using 10 x the old value?
It will also get a new volume pot then possibly the voltage gain stage re-engineered and bias will be reset, also some changes to NFB loop. I will do the caps and volume pot but I will leave the rest to someone who knows what they are doing.
Am I flogging a dead horse here? also, newbe question coming up but if I were to post detailed photos could someone show me where these caps are?
Advice on draining them would also be appreciated.
You don't need to replace the volume pot. Just clean it with some contact cleaner or alcohol.
Using bigger smoothing caps is not going to change anything. If anything, it could cause problems (blown fuses, transformer damage, etc). And using Rubycon caps could get unnecessarily expensive. You won't hear a difference from cheaper caps, anyway.
I don't understand why you would like to do those other mods, if you do not know what you are doing. The amp was probably designed by a professional, and I don't think there's a lot of people out there who can make it that much better without making some very serious changes (and in that case you might as well start from scratch). 🙂
You can drain the caps by putting a low value resistor (I use 33 ohm / 5 watts) across its two terminals for a second or two.
Good luck!
Using bigger smoothing caps is not going to change anything. If anything, it could cause problems (blown fuses, transformer damage, etc). And using Rubycon caps could get unnecessarily expensive. You won't hear a difference from cheaper caps, anyway.
I don't understand why you would like to do those other mods, if you do not know what you are doing. The amp was probably designed by a professional, and I don't think there's a lot of people out there who can make it that much better without making some very serious changes (and in that case you might as well start from scratch). 🙂
You can drain the caps by putting a low value resistor (I use 33 ohm / 5 watts) across its two terminals for a second or two.
Good luck!
how do you know if the pot need to be replaced or not? do you know what's wrong with it?
caps in PSU do make a difference in sound (x10 is way to much but)
re adjust bias is a good thing for a 20+year old amp.
change the NFB will alter the destortion (MAY be a good thing)
Thanks guys, the volume pot is foobared, it drifts from channel to channel. Its an alps dual concentric pot and as these are hard if not impossible to find I am going to put an Alps blue rk27 pot in there instead , I will lose my balance control but hopefully , unless I am very unlucky both channels will be at the same volume.
A while back I read an e bay auction for a Ten Audio upgraded 2050a, I contacted the seller asking what exactly he does to the amps and got this reply.
I know there is some sales pitch in there but as my volume pot is going adrift anyway I thought why not do as much of this as I can. I have also read through this paper on gain.
http://www.diyaudio.com/forums/diyaudio-com-articles/186018-what-gain-structure.html
A while back I read an e bay auction for a Ten Audio upgraded 2050a, I contacted the seller asking what exactly he does to the amps and got this reply.
Wharfedale 2050A, A rarity+ TEN Audio upgrade, Warranty | eBay
I know there is some sales pitch in there but as my volume pot is going adrift anyway I thought why not do as much of this as I can. I have also read through this paper on gain.
http://www.diyaudio.com/forums/diyaudio-com-articles/186018-what-gain-structure.html
To be honest 10x the size would be significantly larger part. Where would he put them?
I think you'll be happy if you simply use modern capacitors of the same value. The Panasonic series are good, and readily available from CPC
I think you'll be happy if you simply use modern capacitors of the same value. The Panasonic series are good, and readily available from CPC
Thanks Jaycee, do you think reworking the gain , bias and NFB loop will make any difference to sound quality?
Here are some photos of the amp. The two big caps are numbered 9244 and 9245, does this mean they are paired in some way?
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Cap numbers are probably vendor part numbers. There is no such thing as matching caps.
About 10 years is when I consider caps. Even things like new main caps has to be approached with thought. Modern caps have much lower ESR and may stress the bridge and transformer. 2X you should be OK. 4X you are looking for trouble. I agree with most of what has been said, leave well enough alone unless you are going to dive in head first and learn about amps. I have been trying to do this myself, and it is very complicated. I happen to have a degree in electronics, so that should be a hint. Do you have proper tools to replace them? Do you have a scope to look at the rails, or a spectrum analyzer to see if you do lower the noise floor? (A Hexfred rectifier and caps lowered the noise floor and 60 Hz harmonics by 8 to 13 dB in my Hafler. It went from inaudible to still inaudible. )
What you should do is learn first is to set the bias. I can bet it is off. Do you have the manual and schematics? Proper meter?
If you want a better amp, BUY one. Much cheaper. Having a "pro" do mods that you read about in some forum ( like this one 😀) is costly and I would bet a pint not worth it. If you do decide to jump off the cliff, pick an amp you won't mind saying "drat" when you blow it up. Not that you will, just don't start on anything you care about. Be sure the one you start on you can get the parts for. It seems most of the decent transistors are no longer available, so when working on a 20 year old amp, it can be very frustrating finding suitable replacements. If you don't need it for a switching supply or cell tower, you just about can't get it.
About 10 years is when I consider caps. Even things like new main caps has to be approached with thought. Modern caps have much lower ESR and may stress the bridge and transformer. 2X you should be OK. 4X you are looking for trouble. I agree with most of what has been said, leave well enough alone unless you are going to dive in head first and learn about amps. I have been trying to do this myself, and it is very complicated. I happen to have a degree in electronics, so that should be a hint. Do you have proper tools to replace them? Do you have a scope to look at the rails, or a spectrum analyzer to see if you do lower the noise floor? (A Hexfred rectifier and caps lowered the noise floor and 60 Hz harmonics by 8 to 13 dB in my Hafler. It went from inaudible to still inaudible. )
What you should do is learn first is to set the bias. I can bet it is off. Do you have the manual and schematics? Proper meter?
If you want a better amp, BUY one. Much cheaper. Having a "pro" do mods that you read about in some forum ( like this one 😀) is costly and I would bet a pint not worth it. If you do decide to jump off the cliff, pick an amp you won't mind saying "drat" when you blow it up. Not that you will, just don't start on anything you care about. Be sure the one you start on you can get the parts for. It seems most of the decent transistors are no longer available, so when working on a 20 year old amp, it can be very frustrating finding suitable replacements. If you don't need it for a switching supply or cell tower, you just about can't get it.
Dont have the manual, no schematic, not very much info at all on this amp and I really havent got a clue about apms apart from the buttons on the front. The bias is something I have just been reading up on. Apparently measure the miliamps between the + & - post (see photo) for each channel with no speakers or source attached, use the trim pot (see photo) to get it to 5mv (when warm apparently).
I think you might be right there fella.
20 years for caps is not the end of the world. I would not overstimate progress in electrolytics . If the amp is quiet and not humming I'd not worry about it .Replace the pot and enjoy that amp or buy a new one.
It is humming, even with no source connected. The transformer is humming like a fridge and I can hear a humming from the speakers right from across the room.
I know this may or may not be the caps so is there anyway to test this?
I know this may or may not be the caps so is there anyway to test this?
I've just replaced all the old Rhode electrolytic caps in my 92 Krell KSP 7b, swapped them all out for new Pana FM's. Zero difference.
Other than to check and re-adjust bias to its suggested level (handily written on the pcb), no.
The two big caps are the main power supply capacitors. The numbers are manufacture date codes. Looking at the age of all of the caps in there, and the fact that a lot of them are near heatsinks, i'd definitely replace.
Hm, it also looks like there are two F&T capacitors, round and dark browny-red, in the power amp circuit (visible in the first picture, near the right-hand black switch cable). If they are what I think they are, replace them.
Thank you, are these the fellas?
An externally hosted image should be here but it was not working when we last tested it.
The amp in the tenaudio advert has different caps in there, i'm not sure if ten audio had already modded the amp before taking the photo as the two big caps have not been changed. That could be a later model of the amp as it also has a gold headphone output plug socket, mine is black plastic.
On closer inspesaction there are a few more differences, caps in the power amp by the big heatsink for example.
Above is Tenaudio's amp.
Mine.
Above is Tenaudio's amp.
Mine.
An externally hosted image should be here but it was not working when we last tested it.
If you don't mind a less than tidy layout, I'd suggest you ADD in an RC after the existing rC you have, to make an rC1RC2 supply.
The r= transformer and wiring resistance.
C1=existing 10mF .
R=0r1 2W
C2= 22mF
This will improve the hum attenuation being fed to the amplifier.
It will also give you GOOD new caps in the final stage of the PSU.
It stiffens up the supply showing lower impedance particularly at lower frequencies.
1992 and twisted pairs everywhere (well, almost).
Old simple technologies still work well.
The r= transformer and wiring resistance.
C1=existing 10mF .
R=0r1 2W
C2= 22mF
This will improve the hum attenuation being fed to the amplifier.
It will also give you GOOD new caps in the final stage of the PSU.
It stiffens up the supply showing lower impedance particularly at lower frequencies.
1992 and twisted pairs everywhere (well, almost).
Old simple technologies still work well.
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