I recently picked up, in great condition, an Adcom 5500 thinking i would use the chassis and power supply to house an Aleph J clone I've been wanting to build. The chassis has plenty of heat-sink and all the connections I would want. But in my haste i neglected to check the power supply schematic... I was seduced by the gleaming pics of BEER CAN SIZE CAPS! 60 Volts DC is way too much for the Aleph J.
1. Is it possible to replace the transformer with a lower voltage transformer, maybe even two (one for each channel) and use the existing PSU circuitry?
2. I was planning on selling the power amp boards on Ebay, should I sell off the complete power supply and build my own? (it'll be difficult parting with 4 18,000uF Capacitors!)
3. Build speakers that will handle the 200 watts per channel and enjoy the Adcom 5500 in it original glory?
It's worth mentioning option three might not pass the partner test as I am just completing, quite slowly, some very reasonable sized diy bookshelf speakers to replace some old Sansui sp200's that a driver went on.
I have very good electronics building and modification skills but circuit design is a bit over my head currently. Any help is greatly appreciated!
1. Is it possible to replace the transformer with a lower voltage transformer, maybe even two (one for each channel) and use the existing PSU circuitry?
2. I was planning on selling the power amp boards on Ebay, should I sell off the complete power supply and build my own? (it'll be difficult parting with 4 18,000uF Capacitors!)
3. Build speakers that will handle the 200 watts per channel and enjoy the Adcom 5500 in it original glory?
It's worth mentioning option three might not pass the partner test as I am just completing, quite slowly, some very reasonable sized diy bookshelf speakers to replace some old Sansui sp200's that a driver went on.
I have very good electronics building and modification skills but circuit design is a bit over my head currently. Any help is greatly appreciated!
Attachments
If your transformer is also tapped for 240V and you run that at 120V,
then you can think in terms of 30V rails. This is close to the maximum
rating of the Jfets, though, so if you want to drop the voltage a bit with
an RC filter, that would give you 2 benefits.
Looks like your transformer has the dual primary coils....
then you can think in terms of 30V rails. This is close to the maximum
rating of the Jfets, though, so if you want to drop the voltage a bit with
an RC filter, that would give you 2 benefits.
Looks like your transformer has the dual primary coils....
Holy Smokes! Nelson Pass himself is the first response to my inquiry! And with such a great suggestion, Thanks Nelson!
I was under the impression that you designed this amp..?
Then Zen Mod jumps in WOW! ZM i am 10 pages into babelfish j and most of it's over my head. Can a 50 WPC version of this be built? and are pc boards still availible?
I was under the impression that you designed this amp..?
Then Zen Mod jumps in WOW! ZM i am 10 pages into babelfish j and most of it's over my head. Can a 50 WPC version of this be built? and are pc boards still availible?
sky is the limit , with Aleph topology
pcbs are not a problem
though - reconsider what other Greedy Boyz are saying - maybe is best to sell Adcom as is , and then invest in new hardware
@Levistubby and Gadult my plan is to build "NEW" Aleph J boards into the Adcom 5500 hardware. A chassis and the connectors alone cost nearly double what I picked up the Adcom for. Plus someone will be able to purchase some very reasonably priced boards to restore their once beloved 5500. I'm not sure how his is a shame since two people will now be enjoying music they love. Keeping the 5500 is a stretch for me since I'm looking to build an amp, or two maybe twenty, and really want to stay in the 25 to 50 WPC range. Frankly, the only reason I'm looking to keep the power supply is that it just looks so solidly built that I'd like to try out re-using it. Should the PS prove disappointing, oh well it'll just be another project!
it sez power consumption 1400W , which means xformer is good for at least 1K2
if you run two 115Vac primaries in series , on 115Vac mains (as Pa advised) , xformer could bring half power of said 1K2 , so aroundish 600W
say that you're good up to 150W of heat per side (maybe with little Babysitter help) , and that xformer can cover that
so , you're in bracket of 50W Aleph
though , 4pcs of 18mF ......... that's on sissy side , you'll need more for intended Iq
if you run two 115Vac primaries in series , on 115Vac mains (as Pa advised) , xformer could bring half power of said 1K2 , so aroundish 600W
say that you're good up to 150W of heat per side (maybe with little Babysitter help) , and that xformer can cover that
so , you're in bracket of 50W Aleph
though , 4pcs of 18mF ......... that's on sissy side , you'll need more for intended Iq
@Jeffreyjuice
Your story reminded on my DIYaudio journey a decade ago, when i purchased aragon2004 because i was on limited budget but i didn't nt want to be cheap. the review was good, mint condition, never been opened, trafo is huge with 4caps 19mF which i thought if i did not like it, I could use the chassis for my gainclone build.
But later i decided to keep my aragon2004, then started to build my gainclone from scratch chassis. Since i had put my hobby on this audio, I started to buy the parts slowly month by month. That's the beauty of diy, you dont have to spend lump sum money at front.
Now I have built many and I had never sold any of my build because each of them have spesific story of collecting parts and different construction ideas. the longest build was my dac, it took 3years.
AlephJ was also my first class a build, started by buying the pcb from the store then you can slowly collect each parts.
Your story reminded on my DIYaudio journey a decade ago, when i purchased aragon2004 because i was on limited budget but i didn't nt want to be cheap. the review was good, mint condition, never been opened, trafo is huge with 4caps 19mF which i thought if i did not like it, I could use the chassis for my gainclone build.
But later i decided to keep my aragon2004, then started to build my gainclone from scratch chassis. Since i had put my hobby on this audio, I started to buy the parts slowly month by month. That's the beauty of diy, you dont have to spend lump sum money at front.
Now I have built many and I had never sold any of my build because each of them have spesific story of collecting parts and different construction ideas. the longest build was my dac, it took 3years.
AlephJ was also my first class a build, started by buying the pcb from the store then you can slowly collect each parts.
Jeffrey, I agree with what some others have said.
Technically, sure you can transplant something else in there.
If it were my amp (it's yours, so do as you please
), and it were functioning well - I'd leave it whole. Heck, maybe you want to run a sub or something later.
Also, I find it's useful to keep some decent commercial stuff around, just to see how my DIY stuff is doing. Most times, I honestly like the way my builds sound over the commercial stuff most others use. Keeps me going.
Technically, sure you can transplant something else in there.
If it were my amp (it's yours, so do as you please
), and it were functioning well - I'd leave it whole. Heck, maybe you want to run a sub or something later.Also, I find it's useful to keep some decent commercial stuff around, just to see how my DIY stuff is doing. Most times, I honestly like the way my builds sound over the commercial stuff most others use. Keeps me going.
May be two more options available:
1) modify your Adcom to run in class A only, it has papa's signature after all and I am sure it can be done.
2) Buy another Adcom in non-working condition to build your aleph, it will have all necessary parts and power supply, and keep this one for other use, they are good sounding amps.
1) modify your Adcom to run in class A only, it has papa's signature after all and I am sure it can be done.
2) Buy another Adcom in non-working condition to build your aleph, it will have all necessary parts and power supply, and keep this one for other use, they are good sounding amps.
adcom gfa 5500 to pure class A
This is an old thread but I'm wondering if anyone has moved on the gfa5500 to class A conversion . If so any details ? I have one sitting around as well , want a first watt 15-25/channel but don't have the budget for it right now. If the conversion is straight forward and yields good results I would head that way .
Driving Tekton Lores thus really don't want a lot of power. I find the Lores sound better with lower watt amps than with the 5500.
I also have a Amber series 70 I would consider the same procedure . Maybe the Amber would be better for this ??
This is an old thread but I'm wondering if anyone has moved on the gfa5500 to class A conversion . If so any details ? I have one sitting around as well , want a first watt 15-25/channel but don't have the budget for it right now. If the conversion is straight forward and yields good results I would head that way .
Driving Tekton Lores thus really don't want a lot of power. I find the Lores sound better with lower watt amps than with the 5500.
I also have a Amber series 70 I would consider the same procedure . Maybe the Amber would be better for this ??
Thank you for the response Nelson . The issue I have is my listening room is my living room and while the Adcom does sound good with the Lores , it drives them to high volumes so easily it lacks much in lower end . I know the 5500 delivers big in low end because I drive a pair of AAD2001 monitors with it , they sound amazing together. I drive the Lores with a vintage L480 luxman and/or Amber 70 , both sound very good with the Lores . I'm guessing a smallish single ended class A would be better. Pass and First Watt are the game in that department.
I see 200 watts on their website. This would agree with the Eminence B102 spec sheet, assuming that this is the actual driver they are using in the Lore. Just sayin'.
Can't imagine someone pushing that much power thru those speakers in a domestic setting.
jeff
Last edited: