In the region of the most output in most music, the impedance will only be a fraction of an ohm over the DC resistance of the speakers.
If you try and drive two pair of these '8 ohm' speakers you will blow up the driver transistors in the Adcom. Certain Infinity models would do it with only one pair.
If you try and drive two pair of these '8 ohm' speakers you will blow up the driver transistors in the Adcom. Certain Infinity models would do it with only one pair.
Banned
Joined 2002
Must different amp then, because schematic shows 5 pairs.
Love it, i laughed so hard.!
Hi David,
Why all the yelling?
Anyway, I guess you didn't read the owners manual before messing around with the wires. Any chance of cut copper ends falling into the chassis?
You didn't mention what experience you have in electronic servicing, nor did you let us know what equipment you own or have access to. No way to assess your chances of success. Mind you, you don't sound like you have much experience from the looks of your post.
My first concern has to do with how you view what goes into a repair. There is far more going on than simply swapping parts, and that's if everything goes well.
Mechanically, you will need the proper thermal compound and an applicator. I like to use a #2 artists brush for this. You also need some fresh, clean mica insulators for each transistor and type. The mounting surface must be absolutely clean and free from dust. The new parts (or old ones) need to be snugged down evenly to approximately the correct torque.
Transistors, some should be matched for close gain. You must never mix old transistors with new ones, That is a critical point.
Did you take the time to read the other Adcom threads here? Almost everything you need to know will be contained in those threads. Don't go any further until you have read them.
One hint for you. Check the fuses in the holders across the rear panel. The lids accept a flat blade screwdriver, not a "Philips", or "star" screwdriver. If the blade isn't wide enough, you may wreck the cap. Be careful!
-Chris
Why all the yelling?
Anyway, I guess you didn't read the owners manual before messing around with the wires. Any chance of cut copper ends falling into the chassis?
You didn't mention what experience you have in electronic servicing, nor did you let us know what equipment you own or have access to. No way to assess your chances of success. Mind you, you don't sound like you have much experience from the looks of your post.
My first concern has to do with how you view what goes into a repair. There is far more going on than simply swapping parts, and that's if everything goes well.
Mechanically, you will need the proper thermal compound and an applicator. I like to use a #2 artists brush for this. You also need some fresh, clean mica insulators for each transistor and type. The mounting surface must be absolutely clean and free from dust. The new parts (or old ones) need to be snugged down evenly to approximately the correct torque.
Transistors, some should be matched for close gain. You must never mix old transistors with new ones, That is a critical point.
Did you take the time to read the other Adcom threads here? Almost everything you need to know will be contained in those threads. Don't go any further until you have read them.
One hint for you. Check the fuses in the holders across the rear panel. The lids accept a flat blade screwdriver, not a "Philips", or "star" screwdriver. If the blade isn't wide enough, you may wreck the cap. Be careful!
-Chris
No yelling just font size,,,, settle down.
I didn't touch them for fun! As you know amp designers think it's cool to put a pos and neg terminal right next to each other, I can promise you I'm NOT the first to have them touch because of this, but until they change it this will continue to happen. So to answer another question I am smart enough to check fuses and they don't always blow, I've seen this happen twice.
I've owned Adcom among many other brands for over 25 years, if that helps you know of my experience, but do not know a lot about electronics and have never worked on IC boards. I currently have a 585 blue boards, 750, 5500, 500, 555II, 555 of Adcom, and countless speakers many built by me.
I am somewhat interested in learning about doing some of this kind of work, (upgrading parts etc.) (I do not have leaky boards,,, yet) so this is what's driving my wanting to do a board upgrade but more over to fix the amp so I can use it for now.
You've given some good pointers Chris, but I'm going to need to find someone who's done one of these that could walk me thru it, I do have a PDF file sent to me by an Adcom person which discusses a revamp of a board with better caps etc. and it didn't look like it was to hard. He pretty much swapped parts (I can send you the PDF file, but it's to large for here) let me know.
I've searched the threads and haven't found anything useful, that's why I posted this and you're the only one who has really posted anything.
If I could find someone close I would have them do it, but haven't yet.
David
I didn't touch them for fun! As you know amp designers think it's cool to put a pos and neg terminal right next to each other, I can promise you I'm NOT the first to have them touch because of this, but until they change it this will continue to happen.
So to answer another question I am smart enough to check fuses and they don't always blow, I've seen this happen twice.I've owned Adcom among many other brands for over 25 years, if that helps you know of my experience, but do not know a lot about electronics and have never worked on IC boards. I currently have a 585 blue boards, 750, 5500, 500, 555II, 555 of Adcom, and countless speakers many built by me.
I am somewhat interested in learning about doing some of this kind of work, (upgrading parts etc.) (I do not have leaky boards,,, yet) so this is what's driving my wanting to do a board upgrade but more over to fix the amp so I can use it for now.
You've given some good pointers Chris, but I'm going to need to find someone who's done one of these that could walk me thru it, I do have a PDF file sent to me by an Adcom person which discusses a revamp of a board with better caps etc. and it didn't look like it was to hard. He pretty much swapped parts (I can send you the PDF file, but it's to large for here) let me know.
I've searched the threads and haven't found anything useful, that's why I posted this and you're the only one who has really posted anything.
If I could find someone close I would have them do it, but haven't yet.
David
Hi Docrw,
I would suggest that you check out the following thread to get an idea what you are about to undertake when trying to repair this amp.
http://www.diyaudio.com/forums/solid-state/157682-another-high-dc-adcom-gfa-555-a.html
Granted the above thread is for an Adcom GFA 555, not a 585, but there is A LOT of great troubleshooting information there. Also, understand that your 585 is a more complex amp (and more of a pain to work on) than the your 555.
I would suggest that you check out the following thread to get an idea what you are about to undertake when trying to repair this amp.
http://www.diyaudio.com/forums/solid-state/157682-another-high-dc-adcom-gfa-555-a.html
Granted the above thread is for an Adcom GFA 555, not a 585, but there is A LOT of great troubleshooting information there. Also, understand that your 585 is a more complex amp (and more of a pain to work on) than the your 555.
I hate to be a wet blanket, but ....
The Adcom 585 is a big amp with a big power supply, big rail voltages etc. If you don't know what you are doing, this is not the equipment to learn on.
If I have mis-judged your level of expertise, then I apologize. Otherwise, perhaps you should not take on more than an average person can handle.
The Adcom 585 is a big amp with a big power supply, big rail voltages etc. If you don't know what you are doing, this is not the equipment to learn on.
If I have mis-judged your level of expertise, then I apologize. Otherwise, perhaps you should not take on more than an average person can handle.
Hi David,
Well, I was authorized warranty for Adcom for some years. I've seen just about everything that can be done to these as can be done. The current staff at Adcom is totally different than the original staff. The company was sold and moved to a totally different State - so no one there really has a tight grip on the older amps. I would love to see what they sent you, could you email it to bhome at sympatico dot ca?
Adcom used good quality parts in all their equipment. The capacitor problem did not come about due to anything Adcom failed to do properly. This terrible situation affected many companies - like Nakamichi for example. I would be very cautious when considering any "upgrades" to the current parts. Especially avoid any part that is too large for the space alloted on the circuit board. This is extremely important.
Meaningful improvements in performance can be had, but not by swapping parts. To improve any of these amplifiers, there will be some hand matching of parts and possible minor circuit changes. Don't expect a night and day change though.
Capacitor problems occur on 585, 555II and possibly the 555 as well. I never did keep track of the affected models, but it's safe to assume anything produced in the same time periods should be affected. The board cleaning is an arduous process, beyond the normal quality of most audio service shops. What I am saying is that you do have boards with leakage problems, that is unless you've already had the work done to correct this.
Speaking of audio service shops, be aware that you should stay away from those places that perform modifications as part of their business model. These places typically read the internet and copy whatever the current fad is. Since these guys are not real technicians as one would be trained, their workmanship is often below standard. This is true even if they advertise superior workmanship. If they don't know any better, everything they touch is golden - right? Any suggestion to increase the size of the main filter caps (indeed, any capacitors) generally points to a person who doesn't really understand what they are doing.
I understand your desire to learn and work on your own products, however these amplifiers are too big to learn on. Any errors cause huge damage, simply due to the stored energy involved. If you really wish to learn about modifications, I'd highly recommend that you work on smaller, less powerful (and lower valued products). In this way you will really learn what changes have real effects, and the importance of making sure the circuit is working properly to start with.
Another really excellent way to learn first hand is to build an amplifier kit posted on this site. Amplifiers that sound good to begin with are a wise choice, something like a symasym, although there are some others that are just as good. Then you can build it and listen. Then change some parts and listen again.
Personally, I think doing upgrades this way only is risky and just plain silly. What you really need as a minimum is a distortion analyzer and an oscilloscope. A good DVM is something that is a basic requirement just to lift the lid and look inside. Cheap DVMs will not work, you will be measuring voltages in the mV for bias and offset. So the meter not only has to indicate to these levels, but it has to have acceptable accuracy as well. You will need a good audio signal source or oscillator in order to measure the distortion level changes with component changes. You absolutely require some instruments to keep yourself on the right track. I have yet to see modifications that sound better than original if the distortion is increased. It's also completely pointless to attempt changes to any amp that isn't running normally. Fix it first.
-Chris
Well, I was authorized warranty for Adcom for some years. I've seen just about everything that can be done to these as can be done. The current staff at Adcom is totally different than the original staff. The company was sold and moved to a totally different State - so no one there really has a tight grip on the older amps. I would love to see what they sent you, could you email it to bhome at sympatico dot ca?
Adcom used good quality parts in all their equipment. The capacitor problem did not come about due to anything Adcom failed to do properly. This terrible situation affected many companies - like Nakamichi for example. I would be very cautious when considering any "upgrades" to the current parts. Especially avoid any part that is too large for the space alloted on the circuit board. This is extremely important.
Meaningful improvements in performance can be had, but not by swapping parts. To improve any of these amplifiers, there will be some hand matching of parts and possible minor circuit changes. Don't expect a night and day change though.
Capacitor problems occur on 585, 555II and possibly the 555 as well. I never did keep track of the affected models, but it's safe to assume anything produced in the same time periods should be affected. The board cleaning is an arduous process, beyond the normal quality of most audio service shops. What I am saying is that you do have boards with leakage problems, that is unless you've already had the work done to correct this.
Speaking of audio service shops, be aware that you should stay away from those places that perform modifications as part of their business model. These places typically read the internet and copy whatever the current fad is. Since these guys are not real technicians as one would be trained, their workmanship is often below standard. This is true even if they advertise superior workmanship. If they don't know any better, everything they touch is golden - right? Any suggestion to increase the size of the main filter caps (indeed, any capacitors) generally points to a person who doesn't really understand what they are doing.
I understand your desire to learn and work on your own products, however these amplifiers are too big to learn on. Any errors cause huge damage, simply due to the stored energy involved. If you really wish to learn about modifications, I'd highly recommend that you work on smaller, less powerful (and lower valued products). In this way you will really learn what changes have real effects, and the importance of making sure the circuit is working properly to start with.
Another really excellent way to learn first hand is to build an amplifier kit posted on this site. Amplifiers that sound good to begin with are a wise choice, something like a symasym, although there are some others that are just as good. Then you can build it and listen. Then change some parts and listen again.
Personally, I think doing upgrades this way only is risky and just plain silly. What you really need as a minimum is a distortion analyzer and an oscilloscope. A good DVM is something that is a basic requirement just to lift the lid and look inside. Cheap DVMs will not work, you will be measuring voltages in the mV for bias and offset. So the meter not only has to indicate to these levels, but it has to have acceptable accuracy as well. You will need a good audio signal source or oscillator in order to measure the distortion level changes with component changes. You absolutely require some instruments to keep yourself on the right track. I have yet to see modifications that sound better than original if the distortion is increased. It's also completely pointless to attempt changes to any amp that isn't running normally. Fix it first.
-Chris
So, I have the chance to pick up an Adcom 555 or 555 mark 2. Which would you prefer and why? I would be driving a pair of b&w 801 series 1 speakers. 8 ohm. I dont need the most amazing thing ever, however, I am using this setup for mixing and tracking purposes. Are these units flawed? Im currently using a crown d150. How do they compare? Any help would be most appreciated! -G
Hello,
I'm new to this site and while I'm not an electronics wiz kid, at 56, I have along history of successfully building kits and soldering/desoldering and modding. I used to have the basic electronics bench instrumentation, can read a schematic, but when I got into med school in 1979, I spent much more time tending to repairing EKG's, EEGs Dynamaps, and pulse oximeters in the OR...I'm a retired anesthesiologist. Anyway, I have been an "audiophile" all of my life...yes, I got sucked into the Krell v. Levinson A/B wars-of-old and bought some serious Class A and other class amps in my day. I've also had ML CLSes, older Polks, and Thorens/Sonus/Grado blah blah blah..equipment. I've built Heathkits...damn old, David Hafler's DH-102, and learned alot from old friends who ran a shop in NJ that repaired primarily analogue equipment..amps, preamps, set up turntables & tonearms, cartridges, speakers and crossovers...Audio Research, Krell, Mark Levinson, Quatre, etc. I steer clear of digital electronics.
I have owned Krell MDA 500's which drove my Thiel CS5i towers (the latter which I still own).
At 56, testosterone has had its way with my inner ear's HF hair cells..so I'm less discriminatory now, but having owned the older GFA-555, I have to say that with beefier filter caps, it was more Krell-like (bass-wise) than the stock 555. That aside...
I sold the Krell KCD/KRC/KSP and both MDA-500s..after only 10 years, many of the caps dried out in the preamp...and a few in the amps...after all, with this equipment, my room A/C had to be on well into October in NJ...hastening the drying process...but I tired quickly of this unneccesary power wastage and the albatross that the high end is to your neck. The wife lost patience with the financial demands of "keeping up" so I just "let it go."
I moved to Scottsdale in '93 and it seems that ADCOM followed me! But a very disappointingly different ADCOM. Heck..they do NO will-call service (like David Hafler and Dalquist used to do years ago back east)...so either learn how to change out caps and beta match your output devices, etc., or pay a bundle on shipping and time and materials.
I want to drive my CS5is with bridged 555IIs (yes, I know...you halve the damping factor and increase the distortion, amongst other things). If I can get two working amps on Ebay or CL for a good price, is their anyone on this forum that just happens to have a schematic for the 555IIs? I have the SM sans schematics.
I think that given the nearly 15-years old that these caps are (Input driver PCB:C104 & 154,and C109 & 159, Left & Right output PCB C202 & 302, & C252 & 352 respectively,and of course the main PS Caps...C802,803,804 & 805... they should probably be changed out as a matter of course. I don't want a dried out or drying cap to result in dead super-expensive hand-matched Thiel drivers (that are no longer made). I don't like mucking around in a piece without the schematics though.
So with the many thousands of years of collective experience on this forum, what would you guys recommend in terms of cap brand and possibly size..(it appears to me that ADCOM took a few shortcuts with component quality), to afford the DIYer guidance in executing an event-less cap change-out? After the change-out, I would have a pro...like one of you guys, for a nominal fee...bench test the pieces to assure that DC offset/bias/other specs were in order..without paying an Ebay-defeating price on the whole job. Criticisms are always welcome....I can hear the critics now!
Sorry for such a long post...part of it was an intro as this is my first post here.
Coyotesx5
I'm new to this site and while I'm not an electronics wiz kid, at 56, I have along history of successfully building kits and soldering/desoldering and modding. I used to have the basic electronics bench instrumentation, can read a schematic, but when I got into med school in 1979, I spent much more time tending to repairing EKG's, EEGs Dynamaps, and pulse oximeters in the OR...I'm a retired anesthesiologist. Anyway, I have been an "audiophile" all of my life...yes, I got sucked into the Krell v. Levinson A/B wars-of-old and bought some serious Class A and other class amps in my day. I've also had ML CLSes, older Polks, and Thorens/Sonus/Grado blah blah blah..equipment. I've built Heathkits...damn old, David Hafler's DH-102, and learned alot from old friends who ran a shop in NJ that repaired primarily analogue equipment..amps, preamps, set up turntables & tonearms, cartridges, speakers and crossovers...Audio Research, Krell, Mark Levinson, Quatre, etc. I steer clear of digital electronics.
I have owned Krell MDA 500's which drove my Thiel CS5i towers (the latter which I still own).
At 56, testosterone has had its way with my inner ear's HF hair cells..so I'm less discriminatory now, but having owned the older GFA-555, I have to say that with beefier filter caps, it was more Krell-like (bass-wise) than the stock 555. That aside...
I sold the Krell KCD/KRC/KSP and both MDA-500s..after only 10 years, many of the caps dried out in the preamp...and a few in the amps...after all, with this equipment, my room A/C had to be on well into October in NJ...hastening the drying process...but I tired quickly of this unneccesary power wastage and the albatross that the high end is to your neck. The wife lost patience with the financial demands of "keeping up" so I just "let it go."
I moved to Scottsdale in '93 and it seems that ADCOM followed me! But a very disappointingly different ADCOM. Heck..they do NO will-call service (like David Hafler and Dalquist used to do years ago back east)...so either learn how to change out caps and beta match your output devices, etc., or pay a bundle on shipping and time and materials.
I want to drive my CS5is with bridged 555IIs (yes, I know...you halve the damping factor and increase the distortion, amongst other things). If I can get two working amps on Ebay or CL for a good price, is their anyone on this forum that just happens to have a schematic for the 555IIs? I have the SM sans schematics.
I think that given the nearly 15-years old that these caps are (Input driver PCB:C104 & 154,and C109 & 159, Left & Right output PCB C202 & 302, & C252 & 352 respectively,and of course the main PS Caps...C802,803,804 & 805... they should probably be changed out as a matter of course. I don't want a dried out or drying cap to result in dead super-expensive hand-matched Thiel drivers (that are no longer made). I don't like mucking around in a piece without the schematics though.
So with the many thousands of years of collective experience on this forum, what would you guys recommend in terms of cap brand and possibly size..(it appears to me that ADCOM took a few shortcuts with component quality), to afford the DIYer guidance in executing an event-less cap change-out? After the change-out, I would have a pro...like one of you guys, for a nominal fee...bench test the pieces to assure that DC offset/bias/other specs were in order..without paying an Ebay-defeating price on the whole job. Criticisms are always welcome....I can hear the critics now!
Sorry for such a long post...part of it was an intro as this is my first post here.
Coyotesx5
I think getting more is a great idea… 😉
Running 4, Two OG’s and two MKII’s, plus a 5 channel for surround. All 4 555’s are running bridged mono to the Snell A V reference speakers. One to the sub and one to the tower of each stereo channel.
It’s the first/only HiFi system I’ve ever played guitar at stage volume with that can hang. It sounds actually live. Like, you can play an actual tambourine in the room and it is indistinguishable from the track. The intensity it through the roof.
Running 4, Two OG’s and two MKII’s, plus a 5 channel for surround. All 4 555’s are running bridged mono to the Snell A V reference speakers. One to the sub and one to the tower of each stereo channel.
It’s the first/only HiFi system I’ve ever played guitar at stage volume with that can hang. It sounds actually live. Like, you can play an actual tambourine in the room and it is indistinguishable from the track. The intensity it through the roof.
Attachments
Nice! I always liked those. (Though my most vivid image of Adcom is actually white preamp which had yellowed from finger oils all around the buttons and on the volume knob, yuch). How do you feel that sound compared to your more recent designs? What are you trying to achieve differently?
These days I concentrate on simple Fet design, and spend as much attention on the character of the distortion as the quantity. You can pretty much follow the progress in the articles posted at www.firstwatt.com
