Separating the Pre and Power Sections on an Audiolab 8000A

Audiolab 8000A Integrated Amplifier
Audiolab

For anyone who might be interested most Audiolab 8000A amplifiers can be modified internally so that the pre and power sections of the amp can be run independently which is ideal for me as I have been looking to upgrade my main stereo amplifier but still want to use the Audiolab 8000A because it has such a good MC/MM phono section.

By separating the pre and power sections, I can feed the phono and other switchable inputs via one of the tape or video out phono sockets to another pre amp, and use the power amp section to amplify the centre speaker in my home cinema system.

So how easy is it to modify ? Well firstly most Audiolab amps already come with separate phono sockets for pre-out and power-in, so it is usually just a question of removing some links or swapping a couple of resistors.

The Audiolab 8000A has been revised a number of times so there are various circuit board layouts in existence but the principle remains the same. If you are unsure about doing this yourself but never the less want to modify your amp then the best advice is to contact the IAG service dept and arrange for them to carry out the modification.

If you feel up to the task yourself and are quite competent with a soldering iron then read on. I will point out at this stage that Hi-Fi Insight cannot be held responsible if anything does go wrong, the information below was supplied to me by IAG and I assume is correct, and my own modification was a doddle even though my board does not appear in the documentation supplied, but it was easy enough to work out what to do and this was later confirmed by IAG.

Model 203 - DIN

Remove R401/402 (2 x 1CR positioned at output of line amp.
Fit 2 x 33R and 2 x 560R as below.

Model 204 DIN

Model 207 PCB Issue 1 & 2

At SW5 remove links between points 6-4 and 5-3.
Fit links between 4—2 and 1-3.
Fit links across C701 and C702 or if any DC or sub-sonic signals might be fed to power amplifier fit 1.OuF/160V 10% polypropylene capacitors in place of links.

Model 207 PCB Issue 1 & 2

Model 207 PCB Issue 3

Remove links L701/L702.
Fit links L703/L704 or if any DC or sub-sonic signals might be fed to power amplifier fit 1.OuF/160V 10% polypropylene capacitors at C701/C702 in place of links.

Model 207 PCB Issue 3

PCB ISSUE 4 — Serial nos 89....

Remove R711/R712 (560R).
Fit R713/R714 (560R) — use good quality metal film resistors.
If any DC or sub-sonic signals might be fed to power amplifier fit C701/C702 (1.OuF/160V 10% polypropylene capacitor) in place of R713/R714.

PCB ISSUE 4 - Serial Pre-amp output muting

For amplifiers with Serial numbers 89 it is possible to fit a PCB mounted pre-amp output muting relay. If automatic pre-amp output muting is required fit RL2 (48V 2PCO relay) to PCB. Two wires are required to energise the coil. The two points marked RL2+ and RL2- (adjacent to the relay RL2) must be wired to the corresponding points marked RL2+ and RL2- adjacent to the main relay RL1.
Each time mains power is switched on the pre—amp outputs will be muted for approx. 8 seconds. When mains power is switched off the pre-amp outputs will mute. The pre—amp output will also mute while headphones are connected.

PCB ISSUE 5

Remove R979/R980 (560R), these should be labelled on the back of the PCB.
Fit R985/R986 (560R) — use good quality metal film resistors.
If any DC or sub-sonic signals might be fed to power amplifier fit C701/C702 (1.OuF/160V 10% polypropylene capacitor) in place of C985/C986.

A relay as specified below can also be used at RY2 located next to R979/R980.

Audiolab 8000A Mk 5

RL2/RY2 SPECIFICATION

Contacts: 2 pole change over (2PCO)
Coil: 48V DCI4000 ohms.
Case: DIL
Pin layout: as below.

RL2

Note: The pre-amp outputs of the 8000A are not muted at power_switch on/off. If you use the 8000A to drive another power amplifier, always switch the power amplifier on AFTER the 8000A, and always turn the power amplifier off BEFORE the 8000A power is switched off.

This entry was posted on Thursday February 9th, 2006 at 2:03 PM and is filed under Amplifiers, Tweaks. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response.

24 Responses to Separating the Pre and Power Sections on an Audiolab 8000A

Janusz a. szorc Says:
February 26th, 2006 at 6:15 PM

Hello,
I want to do the same. And my Audiolab ser. no. is 2073110234. Could you email me relevant photos of the modifications required? I'm no expert and I can't send my amp to IAG. jaszor@interia.pl
Thanx

Hi-fi insight Says:
February 27th, 2006 at 9:34 AM

Janusz,

The only information I have is on the site, you will need to check your board to find out which version you have.

Iain Says:
April 29th, 2006 at 2:26 PM

Do you know if I can use a 8000A & 8000P combination without doing any internal mods and if so how best to set the system up? I've had an 8000A for many years and have recently acquired and 8000P with the intention of linking them. Is it simply a case of using the preamp out and input/load jack plugs or is something else required?

Many thanks for any advice

Iain

Hi-fi insight Says:
May 2nd, 2006 at 8:36 AM

Iain,

The pre-out of the Audiolab 8000A is internally wired to the 8000A's power amp as well as outputting through the rear phonos so you would be in effect driving two amps which may effect impedience and performance. I would speak to IAG's technical helpdesk first for clarification but I would imagine it is best to separate the power and pre sections of the 8000A.

The details are :

IAG Service Center
Unit 4, St Margarets Way
Stukeley Meadows Industrial Estate
Huntingdon, Cambs
PE29 6EB
Phone: +44 (0) 1480 452561
Fax: +44 (0) 1480 413403
Email : tmahelpdesk@iaguk.co.uk
Website: www.audiolab.co.uk

Joe abdilla Says:
June 15th, 2006 at 10:05 AM

First of all 'Very Well Done' for a very interesting and informative site. It is great for tweakers!

Now, I've bought an Audiolab 8000A DIN version. As I don't have the service manual I need to know how each of the DIN sockets connects to other hi-fi separates (with RCA sockets).

Is anyone on hi-fi-insight in a position to provide a diagram showing these connections.

Also, what is the DIN socket marked 'MM Load' for? Isn't the phono preamp already set for a standard load (approx 47K Ohm)?

Many thanks for your help.

Hi-fi insight Says:
June 15th, 2006 at 10:17 AM

Joe,

Your best bet is to get in touch with IAG (details above) as we have never used the early DIN type Audiolabs.

Hi-Fi Insight

Neil holms Says:
June 19th, 2006 at 4:15 PM

With ref to Joe who enquired about "MM Load", the manual for my phono equipped 8000A (an '85 model) says:" The MM LOAD socket is wired in parallel with the PHONO MM input and allows the electrical load impedance to be optimised for different cartridges...."
Goes on to say a range of plug-in loads available from your dealer - then of course !

Leo Says:
September 7th, 2006 at 8:42 PM

Hello:
I'm from south america (argentina), we haven't official service, & i'have to repair ma 8000A. The serial number is: 207F000065. I really apreciate if can send me the manual service.
Best regards.
Leo.

Hi-fi insight Says:
September 8th, 2006 at 8:22 AM

Leo,

Sorry we don't have any service manuals. You're best bet is to emai IAG and see if they can supply a copy on .pdf or something.

Steve Says:
January 2nd, 2007 at 11:13 AM

What is your opinion of the 8000A as a headphone amp? I can get one used but I don't know if it's headphone section is up to snuff. It's either get the 8000A or buy a Heed CanAmp. Which in your opinion is better for headphones?

Hi-fi insight Says:
January 2nd, 2007 at 11:23 AM

Steve,

Good question. I guess it boils down to how important listening via headphones is to you. Like all pre-amps bolted on to an amplifier be it for phono or headphones, considering the amplifier cost around £450 new there is always going to be a cost constraint that affects performance somewhere.

The Audiolab 8000A has a surprisingly good moving coil phono section but i cannot comment on the headphone amp as I do not listen via headphones. If you are serious about headphone listening then treat yourself to a dedicated headphone amplifier. There are many good designs available, some are in kit form, some are valve based or some use very high quality Op amps such as the Burr Brown OPA627 which have a lovely warm valve sound. Either way they will give better sound quality than your average £400 amplifier.

Hope that helps

Sara Says:
January 2nd, 2007 at 2:58 PM

I have just bought a MF X-Can v2 to tide me over until my Heed Canamp arrives but I wondered if I could connect it to the Pre amp outs of the 8000A or should I stick to using one of the tape outs?

Also, is it safe to run the 8000A without any speakers connected? I can switch the speakers off on the front panel but I don't know if that is enough.

My 8000A has a fault where by the speakers (when connected!) thump and pop a few times and a clicking can be heard internally on the 8000A but once it is warmed up and as long as I don't switch it off and on again it is fine but currently I intend to use solely headphones as I have no room for speakers.

Thanks

Hi-fi insight Says:
January 2nd, 2007 at 3:14 PM

Sara,

The clicking you refer to sounds like the mute relay switching which can kick in if you overload the amp's input. Are the speakers a difficult load ? Is the clicking the same noise you hear when you first power the amp up.

I am not sure whether Audiolab 8000A's pre out is enabled by default. You may have to separate the power and pre's first.

No damage should come from not having the speakers connected.

Sara Says:
January 2nd, 2007 at 3:27 PM

Thanks for your reply, my speakers are 8ohm, rec amp power 50-200w and are pro studio monitors (passives obviously!) would they be difficult to drive?


Sara

Hi-fi insight Says:
January 2nd, 2007 at 3:28 PM

Sara,

Sounds fine to me. If there is no audible fault with the speakers then i would guess you either have a faulty relay or one some components in the Audiolab 8000A have developed a fault and the amp is not as stable as it should be.

IAG are company to contact, their details can be found further up the page.

Ami Says:
August 17th, 2008 at 10:41 PM

HELLO IAG Service Center / ADMINISTRATOR,

I AM FROM ISRAEL AND WOULD LIKE TO KNOW WHAT ARE THE DIFFRENCES BETWEEN ALL THE VERSIONS OF THE AUDIOLAB 8000A.
I AM PLANNING TO BUY ONE AND THIS WOULD BE A GREAT HELP FOR ME.

ANOTHER THING - I DODNT UNDERSTAND WHY PEOPLE WOULD WANT TO SEPERATE THE PRE AND POWER SECTION ON THIS AMP,
WHAT WILL IT GIVE THEM BY DOING THAT?
THANK YOU

Dave Says:
January 19th, 2009 at 7:42 PM

Hi,
I got on yesterday a not running 8000A .
I'm going to fix its burned channel, and have the power section schematic, but am not able to find out the preamp section schematic.
is there anyone having it?
I mean phono mm phono mc and line stage as well..
regards
Dave

Barry godfrey Says:
July 1st, 2009 at 12:08 PM

My 8000A stopped working a couple of months ago. It is with technician who is having problem with repair.. it works after repair but stops again after 3 or 4 on/offs. If left on - no problem!
Components are all suitable and meter readings are good.. any ideas where problem might lie?

Many thanks,

Barry

Joe abdilla Says:
March 3rd, 2010 at 8:46 PM

I came back to this thread and would like to ask you whether anyone has got the manaul for the Audiolab 8000A integrated (with DIN inputs).

Im still trying to figure out how to separate the pre and amp sections. Any info about these early 'Labs would be greatly appreciated.

Thanx

John Says:
May 17th, 2010 at 3:14 AM

can i use 4 ohms speakers for my Audiolab 8000A

Hef Says:
December 22nd, 2010 at 1:29 PM

you can use anything between 4 and 16 ohms load with a stock 8000a.
i'm interested in the headphone preamp specs if anyone knows anymore about them...

Hef Says:
December 22nd, 2010 at 1:40 PM

you can use anything between 4 and 16 ohms load if you only use one set of the outputs (i.e. switchd or non switched).
if you are gonna use both sets of outs you need to use a load of between 8 and 16 ohms.

for the guy who was asking about headphones and the headphone preamp section....
the manual states the following with regard to the headphopnes;

"Headphones
Output impeadance 330ohms. Suitable for headphones 8ohms to 2000ohms impeadance."

so there you go.

Audio rehab Says:
December 13th, 2012 at 7:11 PM

Hello,

I have a model 8000A issue 8 on the bench.

The customer wants the Pre/Power amp separation modification.

I see that there are no instructions for issue 8. Does this mean there is no need for the pre/power amp separation mod?

Thanks,

Andy critchlow Says:
August 18th, 2016 at 11:19 AM

Hi

I'm splitting the pre/power on my late 8000A PCB Issue 5, but am struggling to find the relays you recommend - any idea where I may source these?

Audio lab themselves int me to your site for this.

Many thanks.

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