5500 is a whole different beastie. Can you say MOSFETs? I knew you could. There's some good related discussion in one of the designs on Nelson's site. Maybe it's the A75 amp I'm thinking of? 
My brain's getting foggy again.
By they way, Adcom sells service manuals that have schematics in them. Great for study. Gotta' have something fun to read when I'm old(er) and crotchety.
mlloyd1
My brain's getting foggy again.By they way, Adcom sells service manuals that have schematics in them. Great for study. Gotta' have something fun to read when I'm old(er) and crotchety.
mlloyd1
Chad said:
The GFA585 looks just like the 565, just half the number of outputs.
" I ran my 555II bridged @ 1ohm "
You're very lucky, mine have much heavier drivers and two 105CFM fans and the transformer cuts out when driving less than 8 ohms in mono.
What did you do about the fuses? The stock fuses will open up at 50W into 1 ohm.
" I ran my 555II bridged @ 1ohm "
You're very lucky, mine have much heavier drivers and two 105CFM fans and the transformer cuts out when driving less than 8 ohms in mono.
What did you do about the fuses? The stock fuses will open up at 50W into 1 ohm.
--" I ran my 555II bridged @ 1ohm "
--You're very lucky, mine have much heavier drivers and two
--105CFM fans and the transformer cuts out when driving less
--than 8 ohms in mono.
--What did you do about the fuses? The stock fuses will open up
--at 50W into 1 ohm.
At 1 ohm, it was only driving tweeters, hardly any current draw.
I had an additional fuse at 3/4 amp to protect all the ribbons.
I didn't change the stock fuses. Recently I'm doing some listening tests with my Lambda 15" woofer, 4 ohm. The amplifier fins start
heating up after a long while but it works. I push it to mild
clipping. I've also connected another 8ohm midrange in parallel with the 15 when doing 200hz - 2.5khz tests.
So not all 555II can do this? I have the Voodo model ? heh
This is an Ebay amp, I don't know if the previous owner(s) did any mods, but looking inside it seems stock.
--You're very lucky, mine have much heavier drivers and two
--105CFM fans and the transformer cuts out when driving less
--than 8 ohms in mono.
--What did you do about the fuses? The stock fuses will open up
--at 50W into 1 ohm.
At 1 ohm, it was only driving tweeters, hardly any current draw.
I had an additional fuse at 3/4 amp to protect all the ribbons.
I didn't change the stock fuses. Recently I'm doing some listening tests with my Lambda 15" woofer, 4 ohm. The amplifier fins start
heating up after a long while but it works. I push it to mild
clipping. I've also connected another 8ohm midrange in parallel with the 15 when doing 200hz - 2.5khz tests.
So not all 555II can do this? I have the Voodo model ? heh
This is an Ebay amp, I don't know if the previous owner(s) did any mods, but looking inside it seems stock.
The 555Mk.II was similar to the Pass designed 555 except for the drivers. In the Mk.II Adcom used beefier drivers i.e. 2sb817/2sd1047. These were 130 watt/ 140v devices. Also they used a 33 ohm resistance across the driver emitters. The heatsinks were much more substantial than the original and construction overall much better.
The 585 and 565 were similar to each other but radically different topologies that the 535/545/555's.
They still used the Toshiba outputs but changed the drivers to 2sc3907/2sa1516 (???) pair which was a 180v device...
I always liked my 555's with lessor NFB than stock. Instead of the 22k NFB resistance, i used 30 or 33kohm and got a sweeter sounding amp..
The 585 and 565 were similar to each other but radically different topologies that the 535/545/555's.
They still used the Toshiba outputs but changed the drivers to 2sc3907/2sa1516 (???) pair which was a 180v device...
I always liked my 555's with lessor NFB than stock. Instead of the 22k NFB resistance, i used 30 or 33kohm and got a sweeter sounding amp..
I am also a proud owner of this thingy.
Bought it on a fleemarket with top cover missing and fuse holders missing.
Seems for some reason that the preowner did not like the fuses
It was dead and I bought the new expensive japanese transistors.
Changed them and it worked, oh yes !
Very nice amp
Just the problem was I could not get hands on new US fuse holders, so I did what the preowner did
No risk - no fun !
After a while when the amp was on, I pulled one cinch plug - and - boom the amp blew and the speaker blew and everything blew.
Bought new transistors and put in only 1 per bank, works.
Until now I had no time to complete the work.
One thing is for sure: This amp is no toy and needs fuses
Bought it on a fleemarket with top cover missing and fuse holders missing.
Seems for some reason that the preowner did not like the fuses
It was dead and I bought the new expensive japanese transistors.
Changed them and it worked, oh yes !
Very nice amp
Just the problem was I could not get hands on new US fuse holders, so I did what the preowner did
No risk - no fun !
After a while when the amp was on, I pulled one cinch plug - and - boom the amp blew and the speaker blew and everything blew.
Bought new transistors and put in only 1 per bank, works.
Until now I had no time to complete the work.
One thing is for sure: This amp is no toy and needs fuses
Hi kennyd,
Those models came out much later. They are mosfet and sounded okay.
The larger amps might work with Kappa 9's (silly speaker!). It really depends on how hard you drive them. It is possible to blown them up, but Adcom amps will generally put up with some abuse.
I have no idea what was going on in the Infinity design lab. Why would anyone design a speaker that stresses most amps? You want the speaker to sound good, but you've designed them to be hard to drive. Senseless.
-Chris
Those models came out much later. They are mosfet and sounded okay.
The larger amps might work with Kappa 9's (silly speaker!). It really depends on how hard you drive them. It is possible to blown them up, but Adcom amps will generally put up with some abuse.
I have no idea what was going on in the Infinity design lab. Why would anyone design a speaker that stresses most amps? You want the speaker to sound good, but you've designed them to be hard to drive. Senseless.
-Chris
DJK help with modifing the GFA-585 amp
DJK have you modifed the GFA-585 amp before? I've owned several Adcom amps and was considering something better but believe I could make my trusty 585 everything an Audiophile would want without spending the kids college money. Is this something you or another person on DIY could help me with?
David
DJK have you modifed the GFA-585 amp before? I've owned several Adcom amps and was considering something better but believe I could make my trusty 585 everything an Audiophile would want without spending the kids college money. Is this something you or another person on DIY could help me with?
David
djk said:
