Audiolab 8000A fault in power amp side - HELP! - diyAudio
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Old 24th April 2006, 06:12 PM   #1
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Question Audiolab 8000A fault in power amp side - HELP!

I just wanted some help / advice regarding a 8000a amp I own, it would be really appreciated!

So my Audiolab 8000A...
After a bang against the back of the unit several of the plastic RCA unbalanced input holders broke. I had to replace several a number of inputs (tape 1,2, video, cd & tuner) which I ordered from you and did some light soldering. All the inputs seemed to work fine after this.

It has been working fine acting as an integrated amp for several months, with only a slight fault on the left channel where by it would take a minute or two longer than the right channel to warm up and produce sound, & maybe with a crackle to begin with until it was fully warmed up.

However (and here comes my problem), recently I purchased a Meridian 501 pre-amplifier as I thought that the Audiolab 8000A was able to act as a power amp (through the phono-inputs marked 'power amp in' at the rear of the unit), and since connecting the pre-amp to the 8000a I get no sound coming from my speakers.


I have checked my pre-amp and source stage and they seem to be working fine and producing an output OK so I suspect it is a problem with the amp.

Is there any thing I can do to check & work out what exactly is the problem. I have also heard that it is possible to separate the pre & power functions of the amp by removing resistors R979/980 and putting them in R985/986.

My PCB issue is 51539.109
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Old 24th April 2006, 06:20 PM   #2
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carribey,
Do I understand it correctly that you didn't use the 8000 power amp stage till now.

/Hugo
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Old 24th April 2006, 07:58 PM   #3
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Yes that's right Hugo, I just bought my pre-amp today!
John
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Old 24th April 2006, 08:05 PM   #4
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Well, I still don't get it. You used the 8000 as a preamp only and now you want to use the power section as well. What did you power your speakers with until now?
Anyway, the power amp seems to be broken. Do you have a schematic you can share?

/Hugo
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Old 24th April 2006, 08:38 PM   #5
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sorry maybe I've been a bit confusing.

Previously to today I just used the Audiolab 8000A as an integrated amp - it works fine as this; I plug all my phono inputs in (CD, Phono, Tuner etc.) and my speaker cables come out of the back of it.

The 8000A model is an unusal Integrated amp in the fact that is can be used as either a full integrated amp or Pre-Amp or a Power Amp: There are aditional RCA unbalanced connectors on the rear for "Preamp out" and "Power Amp In".

Today I connected all my sources the Meridian 501 Pre Amp and then made a connection from this to the "power Amp in" on the Audiolab 8000A - to which I was greeted with silence from my speakers. I know there is a schematic or a picture of the layout of the board in one of these posts. I will find it now and attach it in a separate post.

With thanks,
John
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Old 24th April 2006, 08:44 PM   #6
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John,
Now I understand.
If the 8000 plays fine as is, e.g. with the pre and power section connected at the back, I'd say the Meridian is faulty.

Connect a CD player to the Power amp in and play a few notes of a very silent intro of a known piece of music. I'm sure you understand why not to insert an AC-DC intro into the power amp.

/Hugo
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Old 24th April 2006, 09:24 PM   #7
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Here is a schematic diagram for the 8000A, but I'm not sure which Mk it is though.

I just tried putting a source straight into the power amp connectors: I used an old MiniDisc player as there as there is a level control on it. Sadly not a sound came out of the speakers even with the direct connection.

Do you have any other suggestions?

John
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Old 24th April 2006, 09:35 PM   #8
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I can't seem to get it to attache properly so I have posted the link to where it is on this site.

Schematic for Audiolab 8000a

cheers,
John
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Old 24th April 2006, 09:51 PM   #9
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If the phono sockets are normal sockets I can't think of anything that might cause this problem.
Honestly, don't ask me what abnormal sockets would look like.
If your speakers can take it, insert a small screwdriver into the phono socket and listen if you hear hum. Or use an old speaker if you are not sure. If the speaker(s) hum, I have no idea why the power amp works with his proper preamp and not with an external source connected.

/Hugo
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Old 24th April 2006, 10:13 PM   #10
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I changed my speakers and stuck an old set on and rather hesitantly stuck a small screw driver into the phono socket that says 'power amp in'.
Not even a buzz sadly.

Quite a mystery why sound comes from the amp when in integrated mode, but when run as a power amp nothing. The only thing I can think of at the moment is that the physical connection between the 'power amp in' is badly soldered to the circuit board. But on inspection it looks fine, and even with the worst soldering I would at least expect some crackling rather than the dead silence I am getting from it at the moment.

It will be curious if any other ideas come up as what might be the problem. I am going to have a word with IAG tomorrow, but no doubt they will just say "send it back to us" with their 65 an hour labour costs plus whatever other charges they will make.

John
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