Adcom 5802 VS dual 565's

eeagle

BIZILL wrote: »

it's gonna be a very long week. anyone know if the 5802 has the 'thump' upon power-up? i just want to know what to expect beforehand.

I have never experienced a "thump" upon power-up.

You will enjoy this amp as well as the 1.2TLs....SDAs in general never cease to amaze. I have occassionlly tripped the 5802 built-in thermal protect after lengthy high level passages, but never when the wife is home

You will not need to tie the neg terminals together on the 5802 for the SDA 1C's, CRS +'s, or 1.2TL's [according to DarqueKnight testing].

BIZILL

eeagle, holy hell man. i can't fathom tripping a 5802 because even driving the tl's with my friggin' 125 wpc RECEIVER it plays so loud and clean that i wonder how much i even need an amp at all. you must listen at monstrous levels. you must have something against the dead sleeping.:eek:

also, whether or not i truely need to tie the grounds together, i wouldn't think it'd hurt to do so as much as i feel it'd hurt NOT to if needed???

and btw, nice setup you got there.:) i'm glad my thread could bring you out of hiding to say hello.:)

ben62670

eeagle wrote: »

You will not need to tie the neg terminals together on the 5802 for the SDA 1C's, CRS +'s, or 1.2TL's [according to DarqueKnight testing].

Please disregard this statement.
Tie them together;)

heiney9

eeagle wrote: »

You will not need to tie the neg terminals together on the 5802 for the SDA 1C's, CRS +'s, or 1.2TL's [according to DarqueKnight testing].

Please explain your statement. Why just these models? All SDA's need a common ground amp. Where is the DK testing info? Can you provide a link or a reference.

The DIY audio link I provided is valid. Chris (Anatech) the gracious person who answered my question is a 20 year veteran tech who did warranty work for Adcom, Carver, Nakamichi, etc. So he is the expert and he explained WHY this needed to be done.

Let's all get on the same page here so we aren't confusing people.

Anxious to hear your reply.

Thanks

H9

heiney9

eeagle wrote: »

I have never experienced a "thump" upon power-up.

This is correct. Going back through my notes the 5802 has an inrush limiting circuit to gets rid of the "thump" at turn on.

H9

BIZILL

heiney9 wrote: »

This is correct. Going back through my notes the 5802 has an inrush limiting circuit to gets rid of the "thump" at turn on.

H9

very nice.:) and yes, i am planning on grounding the negs.:)

eeagle

heiney9 wrote: »

Please explain your statement. Why just these models? All SDA's need a common ground amp. Where is the DK testing info? Can you provide a link or a reference.

H9

From an "old thread" over in Vintage Speakers Titled: SDA SRS's and the Adcom 5802...

03-09-2005, 01:03 AM DarqueKnight message #14

DarqueKnight

eeagle wrote: »

You will not need to tie the neg terminals together on the 5802 for the SDA 1C's, CRS +'s, or 1.2TL's [according to DarqueKnight testing].

heiney9 wrote: »

Please explain your statement. Why just these models? All SDA's need a common ground amp. Where is the DK testing info? Can you provide a link or a reference.

Eeagle is referring to this thread: SDA SRS's and the Adcom 5802

The Adcom 5000 series MOSFET amplifiers are not common ground designs, but the resistance between the negative outputs was low enough that it didn't "upset" my SDA CRS+'s, SDA 1C's, and SDA 1.2TL's.

Similar to jcmccorm's measurement of 20 ohms between the negative output terminals of his GFA-5802 (post #1 of the thread above), I measured 18 ohms between the negative output terminals of my GFA-5802.

I have five GFA-5500's and the resistance between their negative output terminals ranged from 8 to 14 ohms.

The resistance between the negative output terminals of my GFA-5400 was 0.08 ohms.

I found that I could use any of my Adcom 5000 series amps with my pin/blade design SDA CRS+'s, SDA 1C's, and SDA 1.2TL's with no problems. [See post #14 of the thread above.]

If I tried to use any of my Adcom 5000 series amps with my blade/blade design SDA 1B's or SDA SRS's, I would get the loud howling sound signifying a shout circuit condition at the amp's terminals. [See post #13 of the thread above.]

I would still recommend strapping the negative terminals together even if you are using an Adcom 5000 series amp with one of the pin/blade SDA's. The interconnects or speaker cables used might cause a short circuit condition. [See post #8 of the thread above.]

SDA's are weird.

BIZILL

yeah, i saw that thread myself the other day. but yes, i'll still opt to tie the negs together for the sake of safety.

heiney9

Thanks eeagle and Dk for clarification. My personal POV has always been to tie the terminals together on 5xxx series Adcoms.

H9

BIZILL

the ebay auction just closed at $965 shipped for the 5802 i was watching. good thing i got mine for only $750. i just saved myself $215. so now i don't think i'll worry about a buncha screws that i can replace for free.

xoaphexox

I know this is an old thread but I was in a similar situation recently- I purchased a GFA-5802 for my 1.2tl speakers. I tied the negatives together with a piece of monster cable and two banana plugs.

My GFA-5802 definitely does thump when I turn it on, but it's not terribly loud. Loud enough to notice, however. Is that an issue? If so, what would a likely culprit be? Does this amp have a DC offset pot (I'm assuming not)?

DarqueKnight

DC in the output can cause a turn on thump. The GFA-5802 does have a DC offset adjustment.

Connect a millivoltmeter across the speaker output terminals and adjust DC offset pot R179 on the input board for 0mV (+/- 5mV).

xoaphexox

Hey, that's great news! I will definitely check it out! I would have thought this was one of those 'fancy' self adjusting amps because I only saw one set of pots on the circuit boards - turns out I didn't even notice the input boards. I was using a penlight to look through the top of the amp...

Thanks again, I will get this checked out.

xoaphexox

Unfortunately one channel has an offset of 150mV and cannot be changed via the pot. The other channel was -5mV and was easily dialed down to 0mV.

So, I assume this amp has a fault in the one channel.

Do you know a place I could get a (free) service manual or schematic - or any ideas of what the issue may be?

Thanks much

heiney9

check diyaudio.com

Lots of repair info on that site

H9

cnh

Would love to hear a 5802. At this point the only Adcoms above the 555 that I've heard are the 565 mono-blocks at a mini/local Polkfest. And, frankly, the 565s had "better" synergy with most of the bookies we were listening to than amps several times their price!

They made some fairly high end amps sound like A$$ when paired with some speakers. It seemed that a couple of the Higher end amps were too "damned" particular. In my book, that's not something I want to have to mess around with (running through a dozen or so speakers before I can get one to play nice, let's say, with a Conrad Johnson, etc.? Good Luck!

The 565s seemed "solid" and did well with a LOT of different speakers!

cnh

heiney9

I have always said, IMO, Adcom is hard to beat. Many talk down at Adcoms and I have found mating with the right pre-amp really helps. I don't think the Adcom pre's of that era are a good match for the amps. The 565's are stellar amps and 5802 is the cream of the crop too. Many times here I've been tempted to pull the trigger on a 535 or 545 for old time sake and run it again for awhile in either rig.

H9

DarqueKnight

xoaphexox wrote: »

Do you know a place I could get a (free) service manual or schematic - or any ideas of what the issue may be?

Adcom used to send free schematics and would answer general troubleshooting questions. I don't know if they do that now. It's worth giving them a call. At the very least you would get the name of the closest service center.

xoaphexox

The good news is that I think I just figured out what the issue is. I swapped the input boards between channels and the DC offset issue switched channels as well, so now I know the issue is in the input board. There is a 39V zener diode on the bad board that looks shot - so I am going to order a 39V zener and hope this will fix the issue. I'll report back with the results. If all else fails, Adcomparts.com sells replacement boards for $60, so I can always go that route.

Thanks for the responses!

FTGV

xoaphexox wrote: »

.

Do you know a place I could get a (free) service manual or schematic ...

Heres the schem. for input board ,output section and power supply.You'll need to create an account before downloading. http://www.hifi-manuals.com/Download/Adcom/GFA-5802-schematic

xoaphexox

Thanks FTGV, downloaded it and that's what helped me figure out the zener I need to replace. I took resistance measurements of the surrounding parts and they were the same between boards so I'm thinking (hoping) that this zener is the only bad part. I admit even with the high DC offset in one channel it sounds amazing to me. The only reason I went searching for an issue was the 'thud' I heard at power on - I thought for sure an amp this expensive wouldn't behave like that...

xoaphexox

Well the new zener did not fix the problem. At least one of the hand matched FETs are blown as well, so instead of buying a bunch of them and gain matching them myself I decided to just buy a NOS replacement input board from AdcomParts.com. It should be here today.

xoaphexox

The new input board is in and 0mV offset dialed. This thing sounds amazing. No regrets with the purchase. I will be selling my old power amp because this one is here to stay! Thanks for the suggestions and guidance.