Oh, and, the stock caps, after being removed, were simply two pins that branched off into four. I just had no idea! Should have taken the old ones off earlier, and I would have known.
Seems a strange way to do things, but, the original wire is solid core, which could have something to do with it? Also, I noticed the solid core wire wasn't soldered to the poles of the caps. Just extremely tightly wrapped around. When I put it all back together, I shortened those ends and soldered it to the Nichicon pins (which were MUCH shorter than the stock ones), and I also left some length for the black wires as a shunt.
All works well. Would it be worth it to upgrade the RCA jacks on the amp? I wouldn't be changing the wire on the pre amp, as it is hard wired, but I wonder if this would add anything. So far, I am enjoying the sounds!
Seems a strange way to do things, but, the original wire is solid core, which could have something to do with it? Also, I noticed the solid core wire wasn't soldered to the poles of the caps. Just extremely tightly wrapped around. When I put it all back together, I shortened those ends and soldered it to the Nichicon pins (which were MUCH shorter than the stock ones), and I also left some length for the black wires as a shunt.
All works well. Would it be worth it to upgrade the RCA jacks on the amp? I wouldn't be changing the wire on the pre amp, as it is hard wired, but I wonder if this would add anything. So far, I am enjoying the sounds!
That's great 🙂 Pleased it al went well.
Wire wrapping done correctly (proper tools) is as good as a soldered joint. The wire physically cuts into the terminal its so tightly done.
Unless the sockets are badly corroded I don't think you will gain much real benefit tbh in replacing them. No risk of shock either, the rails collapse quickly once turned off. Officially I think voltages over about 30 volts can be classed as a shock hazard if you grabbed hold the right (wrong 😀) way. You would need wet hands and to grab hold across the supply with each hand though for it to be a risk. It is good practice to always work with just one hand when delving into powered up equipment though.
Wire wrapping done correctly (proper tools) is as good as a soldered joint. The wire physically cuts into the terminal its so tightly done.
Unless the sockets are badly corroded I don't think you will gain much real benefit tbh in replacing them. No risk of shock either, the rails collapse quickly once turned off. Officially I think voltages over about 30 volts can be classed as a shock hazard if you grabbed hold the right (wrong 😀) way. You would need wet hands and to grab hold across the supply with each hand though for it to be a risk. It is good practice to always work with just one hand when delving into powered up equipment though.
This is great to know, Mooly. Yeah the connectors on it are the silver colored ones, with some corrosion, but work perfectly fine. I cleaned around them with contact cleaner as well, but thought shiny gold ones would be nice haha. I also thought of upgrading the wiring in the amp stage because of the solid core stuff, probably not the best? Anyway, just something fun to do and to squeeze the absolute most out of it.
I guess another question would be what about the transistors? Worth replacing? Maybe upgrade opamps in the pre? I've heard there are several options...
I guess another question would be what about the transistors? Worth replacing? Maybe upgrade opamps in the pre? I've heard there are several options...
Opamps, maybe... Depends on the type fitted. Some early devices were one offs and used non standard pin outs. Transistors are probably a definite no because again, they are early devices and the circuit relies somewhat on their characteristics to perform correctly. The output devices are an obsolete package too and so new replacements would need new holes drilling and new insulating kits. Doable if it had to be done but a bit ambitious otherwise. The circuit would need slight reworking with different component values in some locations.
edit... I was going off the picture in post #12 when mentioning obsolete package.
edit... I was going off the picture in post #12 when mentioning obsolete package.
Ahh yes, this makes sense. Probably ambitious for the greenhorn such as myself. They appear to be working fine as is. I will likely be recapping the remainder of my pre amp, ad the opamps I would replace would be the two in the pre amp, as this would probably influence the sound elsewhere down the chain. I heard the pre was more of the weak link, and that the amp is relatively good quality. There was a forum elsewhere that mentioned other possibilities for opamps. Again, he had changed some values for caps as well, which I don't feel comfortable doing, as I'm not sure what benefits that would provide me.
At least, with new caps, I shouldn't have toooo much to worry about. Some values I couldn't find like 1uf 50v. Found several bi polar ones, which I don't think are suitable? But, I was hoping to stick with Nichicon fine gold for the pre amp stage. Also didn't want to buy in bulk or spend tooooo much on these caps as, once again, it will likely only have subtle differences. But, in any event, I am happy with what I've done so far. Now if I could get my VU meters working......
At least, with new caps, I shouldn't have toooo much to worry about. Some values I couldn't find like 1uf 50v. Found several bi polar ones, which I don't think are suitable? But, I was hoping to stick with Nichicon fine gold for the pre amp stage. Also didn't want to buy in bulk or spend tooooo much on these caps as, once again, it will likely only have subtle differences. But, in any event, I am happy with what I've done so far. Now if I could get my VU meters working......
If you tell us what the opamps are we can take a look and see. VU meter, are they not working at all ? I imagine they are 'passive' in operation and as such probably pretty insensitive i.e. you have to turn it up pretty loud to get some movement from them.
You shouldn't need to change any cap values... there is a lot of myth and mystique over that kind of thing... occasionally there can be reasons for doing so but generally you are best sticking with the original design values.
You shouldn't need to change any cap values... there is a lot of myth and mystique over that kind of thing... occasionally there can be reasons for doing so but generally you are best sticking with the original design values.
I will have to get back to you about the opamps as I don't have the documentation in front of me. The VU meters have a sensitivity switch as well, which I've used to no avail. Also, there are pots in the circuit for biasing? Schematic says +/- 10mv. I assumed this was for the output originally, but a friend tells me he thinks its for the VU meters. I tried tweaking while listening to music, but no sound change, and no movement on the VU. I've seen other amps like mine that look to have a different piece above the VU meters, which i do not have? I'm not sure what its for, and mine doesn't appear to be missing anything...
Don't touch any pots for biasing, otherwise you might be going down the replacement transistor route for real. 10mv sounds like the volt drop across one of the emitter resistors of the output transistors and is the indirect way the current is measured.
I would have to see the circuit for the VU meters to see how it operates but if it has a sensitivity switch then they just might be 'active'. As long as the actual meters are OK it should be an easy fix. You can test the meters (amp off) just by connecting your DVM on diode range across them. They should shoot to the end of the scale 😀
I would have to see the circuit for the VU meters to see how it operates but if it has a sensitivity switch then they just might be 'active'. As long as the actual meters are OK it should be an easy fix. You can test the meters (amp off) just by connecting your DVM on diode range across them. They should shoot to the end of the scale 😀
The OPAMPs are JRC4558... Someone has used a NJM2068 as a drop in with good results, I'm told. But, I don't know if this is accurate. Some people have also told me about replacing ceramic caps with film ones to reduce noise? Would this be accurate?
What is better? Eletro or Poly caps? Some people have said to replace some lytics with poly ones...
What is better? Eletro or Poly caps? Some people have said to replace some lytics with poly ones...
The 4558 opamps would be an ideal candidate for an upgrade, one that would bring real audible gains. There are a couple of points to be aware of...
1/ Although opamps draw only a tiny current with the 4558 drawing somewhere in the region of a couple of milliamps, the replacements (depending on what you choose) often draw a bit more, perhaps 12 milliamps. That's peanuts but if the supply is a simple zener regulated one then you might need to change a couple of resistors to allow for the higher draw.
2/ Stability. Dropping a high performance opamp into a circuit designed for something of much lower performance can sometimes cause stability issues. This is very unlikely in an application like this but worth mentioning so you are aware.
This is what can go wrong... this is an opamp used in a CD player output stage,
http://www.diyaudio.com/forums/anal...u-have-checked-see-its-stable-havent-you.html
3/ Recommended replacements. The humble TL072 would almost certainly be a drop in replacement guaranteed to work. This has a similar current draw and is a good performer sonically (don't believe all you read about it). The NE5532 would be another 'obvious' choice but this draws more current. Even better is the LM4562 which is the 5532's successor and my current recommend pretty much across the board. The OPA2604 is another, and this is possibly the most coloured sounding, but in a good way and well worth trying. Like the others, it was designed first and foremost for audio and in the right setup can be a stunning performer.
I would suggest fitting sockets and then you can try a few. The TL072 costs peanuts and is pretty much a guaranteed drop in replacement which would get you started.
I would caution the use of the TL0 and the OPA devices in a phono stage simply because being FET devices they are less suited to really low noise operation at the impedances they would see (the 5532 and 4562 are the ones to use for that duty)
Leave the diodes, you won't make any gains there. That said it could be worth adding a snubber across the transformer secondary. That is just a 4.7 ohm resistor or thereabouts in series with a 0.1uf/250 vac rated poly cap such as a Class X or Y suppression type.
There should be no ceramics in the audio path but if (and I don't think there will be) there are then poly ones would be better. Electrolytics get a bad press but used correctly they are transparent to audio. I would just replace what is there with new alternatives. Another problem with replacing electros with poly is the physical size of them and getting them to fit neatly. I wouldn't go there...
1/ Although opamps draw only a tiny current with the 4558 drawing somewhere in the region of a couple of milliamps, the replacements (depending on what you choose) often draw a bit more, perhaps 12 milliamps. That's peanuts but if the supply is a simple zener regulated one then you might need to change a couple of resistors to allow for the higher draw.
2/ Stability. Dropping a high performance opamp into a circuit designed for something of much lower performance can sometimes cause stability issues. This is very unlikely in an application like this but worth mentioning so you are aware.
This is what can go wrong... this is an opamp used in a CD player output stage,
http://www.diyaudio.com/forums/anal...u-have-checked-see-its-stable-havent-you.html
3/ Recommended replacements. The humble TL072 would almost certainly be a drop in replacement guaranteed to work. This has a similar current draw and is a good performer sonically (don't believe all you read about it). The NE5532 would be another 'obvious' choice but this draws more current. Even better is the LM4562 which is the 5532's successor and my current recommend pretty much across the board. The OPA2604 is another, and this is possibly the most coloured sounding, but in a good way and well worth trying. Like the others, it was designed first and foremost for audio and in the right setup can be a stunning performer.
I would suggest fitting sockets and then you can try a few. The TL072 costs peanuts and is pretty much a guaranteed drop in replacement which would get you started.
I would caution the use of the TL0 and the OPA devices in a phono stage simply because being FET devices they are less suited to really low noise operation at the impedances they would see (the 5532 and 4562 are the ones to use for that duty)
Leave the diodes, you won't make any gains there. That said it could be worth adding a snubber across the transformer secondary. That is just a 4.7 ohm resistor or thereabouts in series with a 0.1uf/250 vac rated poly cap such as a Class X or Y suppression type.
There should be no ceramics in the audio path but if (and I don't think there will be) there are then poly ones would be better. Electrolytics get a bad press but used correctly they are transparent to audio. I would just replace what is there with new alternatives. Another problem with replacing electros with poly is the physical size of them and getting them to fit neatly. I wouldn't go there...
This is all excellent information Mooly. I really appreciate your help here lately. I am going to replace the other caps I ordered in the phono board and power supply, hopefully to clean up the sound a bit. I'm probably going to stick with the stock op amps for the moment. There are only two in there. But, I will consider something you are talking about. I like good bass tone, and clean crisp highs. So far, I am getting that. The bass is more controlled, not as boomy.
I am using an Audio Technica cartridge at the moment, and a really small pair of Mission standmount speakers. These replaced a old pair of vintage Hitachi that were big and boomy, but the tiny bookshelves that have replaced them actually have more bass. Who'd have thought going from a 8" woofer to a 5" driver would increase bass? Just quality of the speaker, I suppose.
Would it be worth upgrading the caps in my speaker crossover? Only had the speakers a few months, so I probably won't, but just a thought...
I am using an Audio Technica cartridge at the moment, and a really small pair of Mission standmount speakers. These replaced a old pair of vintage Hitachi that were big and boomy, but the tiny bookshelves that have replaced them actually have more bass. Who'd have thought going from a 8" woofer to a 5" driver would increase bass? Just quality of the speaker, I suppose.
Would it be worth upgrading the caps in my speaker crossover? Only had the speakers a few months, so I probably won't, but just a thought...
Out of all the mods you can make, replacing those 4558's would be top of list... honestly. Put some sockets in and try the TL072 🙂 And if one opamp is in the phono stage then try a 5532 for that and compare it to the TL072. You won't harm anything... just try it !
Changing opamps won't alter the amount of bass or treble or anything like that, what it will do is alter the 'distortion spectrum' produced, and that has a massive impact on the subjective quality.
I'd leave the Mission speakers alone tbh. No comparison with those to old Hitachi's. The Missions may well be more inefficient needing more drive for the same level of sound... the price of getting more from a smaller box.
Changing opamps won't alter the amount of bass or treble or anything like that, what it will do is alter the 'distortion spectrum' produced, and that has a massive impact on the subjective quality.
I'd leave the Mission speakers alone tbh. No comparison with those to old Hitachi's. The Missions may well be more inefficient needing more drive for the same level of sound... the price of getting more from a smaller box.
I may just try it. I think I will order some, and just try soldering them directly for the time being. Unless I can find a socket somewhere, I will likely only mod it once. Looking for a laid back sound, but don't want to mess with values of caps... Will look for the ones you mentioned.
Just ordered some 5332s and TL072s from the net. I think the 5332 were TI brand, and listed as low noise. Ordered from the US, isntead of china, partially because of shipping, partially because of asian knockoffs that I've read about. Paid a little more, but hopefully they are decent...
Also, I am noticing less heat from the power amp... Is this the new capacitors working more efficiently? Causing less stress on the transistors?
Changing caps shouldn't (wouldn't) have changed any of the DC conditions. You are probably just super aware of things with working on it all.
The 5532 is recognised as an industry standard and found in most professional gear (recording studio consoles etc). Its often said that any recorded music you own will have passed through perhaps dozens or more of these. The TL072 is, well, you decide when you listen to it 😀
Sockets are a great option for the IC's and should be available anywhere for peanuts. For the actual desoldering of the IC's try solder braid and a large hot tip on the iron. They should come out cleanly in seconds. Use some ISO (isopropyl alchohol or meths) on a cotton bud to clean up any old flux from the print.
Solder braid,
http://www.diyaudio.com/forums/parts/127924-working-smd-how-do-without-specialised-tools.html
The 5532 is recognised as an industry standard and found in most professional gear (recording studio consoles etc). Its often said that any recorded music you own will have passed through perhaps dozens or more of these. The TL072 is, well, you decide when you listen to it 😀
Sockets are a great option for the IC's and should be available anywhere for peanuts. For the actual desoldering of the IC's try solder braid and a large hot tip on the iron. They should come out cleanly in seconds. Use some ISO (isopropyl alchohol or meths) on a cotton bud to clean up any old flux from the print.
Solder braid,
http://www.diyaudio.com/forums/parts/127924-working-smd-how-do-without-specialised-tools.html
This is true Mooly. All the opamps I've seen have been cheap, as have the sockets. Can't wait for everything to arrive. I've seen some other ones with D at the end? (Low Noise?) should I have taken these into consideration when ordering? lol
D suffix for NXP and TI branded parts, normally means SOIC-D, or tiny surface mount types. If you are reading from a Mouser or Digi-key catalogue, it will surely tell you what the package type is and all relevant variations. The data sheet with illustrations can be downloaded as a PDF to check. You are looking for standard DIP-8 size parts as you already have but different manufacturers often have their own distinct codes to identify the physically different versions.
Needless to say, you will not get any improved version with that suffix - just a lot of grief for not checking the catalog properly and no easy way to adapt the tiny bits when they arrive.
If you are going to change opamps, only resolder once by fitting a socket (I prefer a low profile type) as Mooly suggests because it is all too easy to detach the tiny pads with repeated soldering. When that happens, it often leads down the slippery slope to the end of your amplifier.
Replaced the phono path opamp. Little differences. Maybe sharper sound. Still breaking in, not sure how long that will take. I should give it a few hours, but can't imagine much of a break in period for opamps. I first had some issues, I think two pins were bridged with my poor soldering skills and having a metal rod underneath the board in the way made it a little difficult to see. But, once I fixed that it was fine.
May complete the other opamp this weekend when I have more time...
May complete the other opamp this weekend when I have more time...
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