[Koan]

Sorry for my noob ness.  Have one exiting Adcom gfa 555.  Hasn’t been run in 15 or 20 years.  WhAt should I look for or replace pre-emptively.  Might consider another to bi-amp a pair of Vandersteen 2Ci s.   Would appreciate info on a pre amp that can tie to a computer or has a built in drive for mp3 s.  Have a GTP 500 II pre amp now, I read these were not as good as the GFP line.  Just getting back into this and would appreciate some input.  Thanks

[stonedeaf]

I am on my fourth GFA-555 - couple of things worth checking out :
1.) Check DC offset - this isn't a perfect indication of overall health -but it's a pretty good indication and most importantly - these amps have no sophisticated protection circuits - if the amp is putting out too much DC - it will all go into your speakers.
2.) IMHO - the original Nelson Pass designed GFA-555 sounds way better than any of the subsequent II or SE models.
3.) Assuming you get low DC offset measurements -spend your money on a pre-amp or sources - the Brits are right - the source makes more difference than the rest of the system put together - mostly because GIGO is really a rule.
But be happy you've got a GFA-555 -they are something special.

[Phil A]

Welcome!  Many moons back I had one and then a bunch of years I got another via a trade as I needed something of shallow depth.  No longer have it but a great amp for the money

[ArthurDent]

Greetings & Welcome to AC Koan   

[FullRangeMan]

Usually the first parts to go in a transistor amp are the capacitors. I would run it in low volume to test and listening for noises.
A tube preamp will embellish the sound of a big transistor amp.

[stonedeaf]

I only tested the large power supply filter caps in mine ( all purchased OLD over the last  five or six years) - none of them were bad or needed replacement - despite their age. The II series and definitely the great GFA-565 mono amps used capacitors that failed pretty routinely - replacing these PS caps would make sense. I at times ran double GFA-555 in a bi-amp system -but a single unit has enough grunt for the vast majority of the speakers ever made.

[Koan]

Wow
Thank you to everyone!  I have a decent Fluke mm - a 189 I think.  Again sorry for the noobness, what test points do I use to measure dc offset..., speaker terminals or under the cover?   Can I measure capacitance of the big caps while in circuit....will visual inspection usually show any issues.  What kind of numbers am I looking for??

I heard the GTP 500 Ii pre amp is not the greatest, and is susceptible to a variable capacitor failing in the tuner section.  Haven't hooked mine up yet... long story.  First wife didn't like the way the Vandersteens looked in the living room.  Fast forward... second wife thinks they are cool!!!

I am also trying to figure a good way to play off a 20 or 30 gig library of mp3 files, and of course need a turntable...was thinking pro-Ject or Music hall...

Thank you for the warm welcome and helping me get back up to speed

Should I consider  a tube pre amp?   Maybe a gfp series Adcom?

[FullRangeMan]

For a tube preamp consider PrimaLuna, Mystere and these two hand made Canadian builders:
https://hollowstate.netfirms.com/index.html#Preamplifiers
Scrool the page:
http://www.classicvalve.ca/products.html
There are lots more brands in US and China.

[Koan]

I think I am starting to get it.. thinking about vertical biamping with another gfa-555 .. can anyone suggest a good source to pick up another gfa-555 (original. Not a MkII). Thanks

[FullRangeMan]

I think I am starting to get it.. thinking about vertical biamping with another gfa-555 .. can anyone suggest a good source to pick up another gfa-555 (original. Not a MkII). Thanks

Stay away these monsters.
In a small room a good FR driver mainly Alnico magnet will fill your room with harmonics, in this case a small under 10W tube amp is suffice.
Read Dr.Gizmo talk:
http://www.meta-gizmo.org/Tri/index-1.html