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Post by indiehouse on Jan 14, 2016 11:32:29 GMT -6
Fellas - I'm about to try and repair, then mod, my Superbeast and PCM4222. I could use some help. Thought I'd start a thread so we could document this in hopes that there may be others who would benefit from this archival of knowledge. First, the problem. The Superbeast generates a pretty healthy level of what I would call white noise (high pitch hiss), with one side being slightly worse than the other. Since I know Ross has had issues with his op amps overheating, I'm guessing that I've got a bad AD4898. I'm going to focus on the Superbeast repair first. If I can get through that, then I'd like to explore a couple of mod options. Here is a gut shot:  I'm assuming that the AD4898's are the one's with the hillbilly heatsinks siliconed to the top?  Here are two more hiding under another PCB board.  Here is what I will be using to replace them, based on advice from tonycamphd    Also, the above pic looks like copper wire. I have some conduit left over from a studio build. Can I just strip some out from that? I'm not sure what gauge it is. Does it make a huge difference? I think it's just standard house wire. So, first things first. How the heck do I get the old AD4898's out of there? Do they just pop out or something? Or are they soldered in?  |
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Post by tonycamphd on Jan 14, 2016 11:50:28 GMT -6
ok, yes copper wire is great, it carries heat as fast as anything you can solder, the black BD(brown dog) adapter he used is a fail, there is no thermal pad on them to solder too, the green adapter boards i used DO have the thermal pad, and the copper is overkill cooling protection for the hot running 4898's, also the silicone that RM used is another misinformed fail on his part, silicone is an excellent heat blocker/resistor, he would have had to use a thermal conducting adhesive to make that work properly, so he just made it harder for those chips to cool. It looks like the BD adapters are push in, so you should be able to just carefully pry them out. the double sided pin adapters that I suggested are not the same size on both sides, so make sure you orient them properly. did you get the green adapter boards with heat pad? I'd rewire the whole thing with shielded cable, i'd also drill small venting holes in the case above the regulators, and possibly upgrade the regulators. dandeurloo jimwilliams could def make better suggestions than I beyond this. good luck with this mang. |
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Post by indiehouse on Jan 14, 2016 12:41:40 GMT -6
ok, yes copper wire is great, it carries heat as fast as anything you can solder, the black BD(brown dog) adapter he used is a fail, there is no thermal pad on them to solder too, the green adapter boards i used DO have the thermal pad, and the copper is overkill cooling protection for the hot running 4898's, also the silicone that RM used is another misinformed fail on his part, silicone is an excellent heat blocker/resistor, he would have had to use a thermal conducting adhesive to make that work properly, so he just made it harder for those chips to cool. It looks like the BD adapters are push in, so you should be able to just carefully pry them out. the double sided pin adapters that I suggested are not the same size on both sides, so make sure you orient them properly. did you get the green adapter boards with heat pad? I'd rewire the whole thing with shielded cable, i'd also drill small venting holes in the case above the regulators, and possibly upgrade the regulators. dandeurloo jimwilliams could def make better suggestions than I beyond this. good luck with this mang. Hey Tony, I did get the green pcb's. I'm definitely up for upgrading the regulators if I had some guidance there. Also, are you suggesting replacing every wire with shielded cable? |
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Post by tonycamphd on Jan 14, 2016 12:47:55 GMT -6
ok, yes copper wire is great, it carries heat as fast as anything you can solder, the black BD(brown dog) adapter he used is a fail, there is no thermal pad on them to solder too, the green adapter boards i used DO have the thermal pad, and the copper is overkill cooling protection for the hot running 4898's, also the silicone that RM used is another misinformed fail on his part, silicone is an excellent heat blocker/resistor, he would have had to use a thermal conducting adhesive to make that work properly, so he just made it harder for those chips to cool. It looks like the BD adapters are push in, so you should be able to just carefully pry them out. the double sided pin adapters that I suggested are not the same size on both sides, so make sure you orient them properly. did you get the green adapter boards with heat pad? I'd rewire the whole thing with shielded cable, i'd also drill small venting holes in the case above the regulators, and possibly upgrade the regulators. dandeurloo jimwilliams could def make better suggestions than I beyond this. good luck with this mang. Hey Tony, I did get the green pcb's. I'm definitely up for upgrading the regulators if I had some guidance there. Also, are you suggesting replacing every wire with shielded cable? I'm going to do it in all my rigs, there is a lot of sensitive stuff in there, and why worry when I can take an hour and fix it up? Jim or Dan can probably set you straight on the regulators, in fact, i think jim mentioned exactly the regulators he used in his SB2 mod, i don't think the PSU differs to what's in the SB original, not positive though.... I should mention that I think your rig is going to take a major step up when it's working as it should, RM improved on the design in the SB2, he just blew it by using the 49710's in place of the 4898's , the 4898's are no doubter better to my ears, it blows my mind that Ross can be so smart in some ways, and completely miss the boat on others that are directly related  |
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Post by indiehouse on Jan 14, 2016 13:19:34 GMT -6
Hey Tony, I did get the green pcb's. I'm definitely up for upgrading the regulators if I had some guidance there. Also, are you suggesting replacing every wire with shielded cable? I'm going to do it in all my rigs, there is a lot of sensitive stuff in there, and why worry when I can take an hour and fix it up? Jim or Dan can probably set you straight on the regulators, in fact, i think jim mentioned exactly the regulators he used in his SB2 mod, i don't think the PSU differs to what's in the SB original, not positive though.... I should mention that I think your rig is going to take a major step up when it's working as it should, RM improved on the design in the SB2, he just blew it by using the 49710's in place of the 4898's , the 4898's are no doubter better to my ears, it blows my mind that Ross can be so smart in some ways, and completely miss the boat on others that are directly related Do I need to ground all of these shields at one or both ends? |
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Post by svart on Jan 14, 2016 13:45:15 GMT -6
I could offer a lot of suggestions, but since Tony didn't mention my name, I can't.  |
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Post by indiehouse on Jan 14, 2016 13:53:27 GMT -6
I could offer a lot of suggestions, but since Tony didn't mention my name, I can't. Actually, you were one of the dudes I was hoping to see here. |
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Post by tonycamphd on Jan 14, 2016 14:32:43 GMT -6
I could offer a lot of suggestions, but since Tony didn't mention my name, I can't. haha, since when do you need my permission? i suggested dan and jim because they've both modded RM boxes, but if you have some suggestions of course it'd be great to hear em! |
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Post by indiehouse on Jan 14, 2016 19:41:00 GMT -6
Do the AD4898's have an orientation, or does it matter in which direction they're installed?
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Post by dandeurloo on Jan 14, 2016 20:02:19 GMT -6
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Post by svart on Jan 14, 2016 21:20:53 GMT -6
I could offer a lot of suggestions, but since Tony didn't mention my name, I can't. haha, since when do you need my permission? i suggested dan and jim because they've both modded RM boxes, but if you have some suggestions of course it'd be great to hear em! LOL, just messin' with ya dude. It's all good. |
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Post by indiehouse on Jan 14, 2016 21:37:13 GMT -6
ok, yes copper wire is great, it carries heat as fast as anything you can solder, the black BD(brown dog) adapter he used is a fail, there is no thermal pad on them to solder too, the green adapter boards i used DO have the thermal pad, and the copper is overkill cooling protection for the hot running 4898's, also the silicone that RM used is another misinformed fail on his part, silicone is an excellent heat blocker/resistor, he would have had to use a thermal conducting adhesive to make that work properly, so he just made it harder for those chips to cool. It looks like the BD adapters are push in, so you should be able to just carefully pry them out. the double sided pin adapters that I suggested are not the same size on both sides, so make sure you orient them properly. did you get the green adapter boards with heat pad? I'd rewire the whole thing with shielded cable, i'd also drill small venting holes in the case above the regulators, and possibly upgrade the regulators. dandeurloo jimwilliams could def make better suggestions than I beyond this. good luck with this mang. Man, I think these AD4898's are soldered in. Nothing is giving any kind of budge. I've got the pcb board out and gave a good go at it. Urgh. Looks like I'm gonna have to desolder these guys. Also, he's got silicone shoved up underneath all of these op amps, and it's just turned to sludge. Nasty. There is all kind of metal shavings, crud and dirt in this. The board is covered in solder rosin. It's definitely not a clean build. |
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Post by svart on Jan 14, 2016 21:42:46 GMT -6
Do the AD4898's have an orientation, or does it matter in which direction they're installed? Absolutely. If you look closely at the part, you'll see a dot/indentation by a pin at a corner. That denotes pin #1. I can't tell by the pics if the adapters have a marking for pin #1 though. Ok, first piece of information on the AD4898.. The bottom "paddle" that is used for heatsinking MUST be connected to V- or left floating. Do not ground it. The part works best if this is connected to V- though. I use these parts for both the ADC and DAC, and on the DAC I use them for both the I/V conversion, and the filtering. These parts dissipate around 1-2W each during usage, about 250mW during idle, and around 5W when the output is shorted. They can get HOT. Without airflow or heatsinking to the chassis, the interior of the box will get warm as an oven.. As RM found out the hard way, it is not possible to run these without heatsinking them or else they die. When they die, they don't output, and they'll likely get very hot or hold down the power supply rails. I don't think hissy sound is a symptom of a dead opamp. Hissy is usually a symptom of the sampling system being set incorrectly. Having the ADC set to a sample rate that is lower than the one the DAW is set to, will result in hiss. Generally you'll get more hiss in the right side when this happens too. |
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Post by tonycamphd on Jan 14, 2016 21:55:04 GMT -6
ok, yes copper wire is great, it carries heat as fast as anything you can solder, the black BD(brown dog) adapter he used is a fail, there is no thermal pad on them to solder too, the green adapter boards i used DO have the thermal pad, and the copper is overkill cooling protection for the hot running 4898's, also the silicone that RM used is another misinformed fail on his part, silicone is an excellent heat blocker/resistor, he would have had to use a thermal conducting adhesive to make that work properly, so he just made it harder for those chips to cool. It looks like the BD adapters are push in, so you should be able to just carefully pry them out. the double sided pin adapters that I suggested are not the same size on both sides, so make sure you orient them properly. did you get the green adapter boards with heat pad? I'd rewire the whole thing with shielded cable, i'd also drill small venting holes in the case above the regulators, and possibly upgrade the regulators. dandeurloo jimwilliams could def make better suggestions than I beyond this. good luck with this mang. Man, I think these AD4898's are soldered in. Nothing is giving any kind of budge. I've got the pcb board out and gave a good go at it. Urgh. Looks like I'm gonna have to desolder these guys. Also, he's got silicone shoved up underneath all of these op amps, and it's just turned to sludge. Nasty. There is all kind of metal shavings, crud and dirt in this. The board is covered in solder rosin. It's definitely not a clean build. pictures please |
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Deleted
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Post by Deleted on Jan 14, 2016 22:11:27 GMT -6
Hm, still possible it is the opamps. Transistors and opamps really can "wear out" due to age and usage. Considering these opamps are extremely high performance opamps running very hot under insufficient cooling it might be this is the case here, they might have aged a lot faster. Worn out transistors and opamps hiss.
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Deleted
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Post by Deleted on Jan 14, 2016 22:24:31 GMT -6
I.e. opamps are not always dying a sudden death. They can also die slowly, getting hissy more and more.
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Post by svart on Jan 14, 2016 22:29:43 GMT -6
I.e. opamps are not always dying a sudden death. They can also die slowly, getting hissy more and more. Lets just say I broke a few AD4898 during the R/D of my converter.. All of them died suddenly. |
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Post by Deleted on Jan 14, 2016 22:35:08 GMT -6
Okayyy. Hehe, i can only refer to very old standard opamp gear that suffered from the slow death hiss, cured by opamp change... nothing like these modern miniature case thermonuclear transistor ovens.  So the source of the hiss might well be somewhere else, but interesting to know how they die.  |
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Post by indiehouse on Jan 15, 2016 11:28:49 GMT -6
Do the AD4898's have an orientation, or does it matter in which direction they're installed? Absolutely. If you look closely at the part, you'll see a dot/indentation by a pin at a corner. That denotes pin #1. I can't tell by the pics if the adapters have a marking for pin #1 though. Ok, first piece of information on the AD4898.. The bottom "paddle" that is used for heatsinking MUST be connected to V- or left floating. Do not ground it. The part works best if this is connected to V- though. I use these parts for both the ADC and DAC, and on the DAC I use them for both the I/V conversion, and the filtering. These parts dissipate around 1-2W each during usage, about 250mW during idle, and around 5W when the output is shorted. They can get HOT. Without airflow or heatsinking to the chassis, the interior of the box will get warm as an oven.. As RM found out the hard way, it is not possible to run these without heatsinking them or else they die. When they die, they don't output, and they'll likely get very hot or hold down the power supply rails. I don't think hissy sound is a symptom of a dead opamp. Hissy is usually a symptom of the sampling system being set incorrectly. Having the ADC set to a sample rate that is lower than the one the DAW is set to, will result in hiss. Generally you'll get more hiss in the right side when this happens too. Yes, this describes pretty much what I'm hearing. Though, I think addressing the heat issues and swapping in new parts is still valuable. |
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Post by indiehouse on Jan 15, 2016 11:30:53 GMT -6
Man, I think these AD4898's are soldered in. Nothing is giving any kind of budge. I've got the pcb board out and gave a good go at it. Urgh. Looks like I'm gonna have to desolder these guys. Also, he's got silicone shoved up underneath all of these op amps, and it's just turned to sludge. Nasty. There is all kind of metal shavings, crud and dirt in this. The board is covered in solder rosin. It's definitely not a clean build. pictures please Sure. This is what I'm seeing.    |
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Post by jimwilliams on Jan 15, 2016 11:37:39 GMT -6
You will need a nice desoldering tool to get those soldered adaptors out cleanly without pulling plated-through holes out with them. Finding the source of the hiss may be a problem with a scope, the clock noise will wash that out.
You have the older pcb version than my Super Beast II. Mine is all SOIC, you have through-hole parts. I would install Milli-Max 8 pin machined IC sockets and then test with LME49710/20's. Solder the ADA SOIC replacement chips to a Brown Dog adaptor. Then they can be swapped. Once tested, glue on a 14 pin heat sink from Mouser or mini SOIC heat sink from Newark with Locktite thermal adhesive.
While in there, consider swapping the 1/8 watt metal film resistors to Dale CMF50 metal film, those make a huge difference. Also swap the 2200 pf I/V stage mylar feedback cap with a WIMA FKP-2 poly film cap.
I replaced the wallwort 1/2 wave psu with an on-board torriod full wave design. That eliminated all the background noise. The overheated linear regulators were removed and mounted to the rear panel with additional heat sinks, they run cool now. I used a grounded AC connector and connected ground to chassis at one point. The S/PFIF jack grounds were floated from the chassis by using Canare 75 ohm RCA connectors for impedance matching.
It's very quiet and sounds great.
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Post by indiehouse on Jan 15, 2016 12:00:08 GMT -6
You will need a nice desoldering tool to get those soldered adaptors out cleanly without pulling plated-through holes out with them. Finding the source of the hiss may be a problem with a scope, the clock noise will wash that out. You have the older pcb version than my Super Beast II. Mine is all SOIC, you have through-hole parts. I would install Milli-Max 8 pin machined IC sockets and then test with LME49710/20's. Solder the ADA SOIC replacement chips to a Brown Dog adaptor. Then they can be swapped. Once tested, glue on a 14 pin heat sink from Mouser or mini SOIC heat sink from Newark with Locktite thermal adhesive. While in there, consider swapping the 1/8 watt metal film resistors to Dale CMF50 metal film, those make a huge difference. Also swap the 2200 pf I/V stage mylar feedback cap with a WIMA FKP-2 poly film cap. I replaced the wallwort 1/2 wave psu with an on-board torriod full wave design. That eliminated all the background noise. The overheated linear regulators were removed and mounted to the rear panel with additional heat sinks, they run cool now. I used a grounded AC connector and connected ground to chassis at one point. The S/PFIF jack grounds were floated from the chassis by using Canare 75 ohm RCA connectors for impedance matching. It's very quiet and sounds great. Thank you for this great info, Jim! I'd like to plead with you one more time to let me send you my units. I have 2 of them, a Superbeast I and a Superbeast II. I'm kinda flying by the seat of my pants here. I'm afraid I'm getting close to the edge of my capabilities, and to get both of my DAC's on the bench of someone who knows exactly what they're doing (and will take these to another level) is worth money to me. I'm begging ya, man! |
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Post by rocinante on Jan 17, 2016 19:53:17 GMT -6
Buddy you are in capable hands here. Lets say you lift a trace; then you get some wire and make a new one. You're getting a blo by blow with numerous skilled techs guiding you. It doesn't get any better. Really. You bought the ticket; take the ride.
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druu
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Post by druu on Jan 19, 2016 8:02:53 GMT -6
I have a super beast mk1 sitting on the shelf in the garage with a bad left channel and I also suspect the opamps. It was replaced with a working unit but I was told to keep the unit. This thread is egging me on to try and repair it also. |
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Post by Deleted on Jan 22, 2016 16:15:04 GMT -6
Excellent idea.... :-)
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