Upgrade my 8000A where is a good place to start

[grahamfocal]

I have the upgrade bug, as am in the process of upgrading my CD player with a little (well a lot to be frank) help from Mooly.
I now feel that I might as well do the same to my Audiolab 8000A.
Had a look at some of the threads but nothing is conclusive.
I am looking for a good place to start, simple and not too expensive.
I am a newby to DIYing my stuff, but really loving the fact that you can improve the equipment that you have for very little money.
I know that the amp has a good following and places still offer upgrades, but they are expensive (as they obviously do them for you)
where is a good place to start?
Pre amp caps? power supply caps? opamps?

 

[Mooly]

One thing at once methinks

Circuit here,
Audiolab 8000A | Owners Manual, Service Manual, Schematics, Free Download | HiFi Engine

 

[grahamfocal]

One thing at once methinks

Circuit here,
Audiolab 8000A | Owners Manual, Service Manual, Schematics, Free Download | HiFi Engine

I agree, just looking at doing it in the next few months, preparation, and all that.
I dont want to mod the cd player too much, start small, as they say.
cheers for the link

 

[Mooly]

I'll have a look at the circuit but tbh I think all you can do is think of replacing old caps etc... you are not going to change the basic structure of character of the amp. Only the power amp shown here anyway.

So what's in the preamp as regards circuitry. Is it opamp based ? or all discrete.

 

[Mooly]

The TL072 opamp in the power amp by the way... that's not in the audio path. It's used as a DC servo and it's perfect for the job.

 

[Andy5112405]

No Op-Amps in the 8000A at all, it's all discrete transistors.

I've got the Circuit Diagrams if you need to see them.

 

[grahamfocal]

The TL072 opamp in the power amp by the way... that's not in the audio path. It's used as a DC servo and it's perfect for the job.

just read the same thing somewhere else, I suppose the one thing that I might do, not now, but in the future is build a power amp for it as a separate box, but not sure that I am that confident yet. It could do with a little more power to ease up the slight 'harshness' when turned up, bit more headroom.

 

[grahamfocal]

No Op-Amps in the 8000A at all, it's all discrete transistors.

I've got the Circuit Diagrams if you need to see them.

That would be great, thanks. just want to start small on me DIY quest, and in a few years, hopefully build my own, but small steps and all.

 

[Andy5112405]

Tell a lie, there is a dual TL072 in the Power Amp section.

 

[Mooly]

I used the same opamp in my MOSFET amp for the DC servo.

If you want to experiment with "different" amplifier topologies I would recommend building something like the John Linsley Hood 10/15 watt class A amp as it's easy to build, still sounds fantastic, and is AC coupled so you have no worries about destrying speakers if something went wrong. Only downside is the Class A = hot and it needs big heatsinks and power supply.

 

[grahamfocal]

I used the same opamp in my MOSFET amp for the DC servo.

If you want to experiment with "different" amplifier topologies I would recommend building something like the John Linsley Hood 10/15 watt class A amp as it's easy to build, still sounds fantastic, and is AC coupled so you have no worries about destrying speakers if something went wrong. Only downside is the Class A = hot and it needs big heatsinks and power supply.

that sounds like a good place to start....

 

[sreten]

Hi,

I've got a 8000A, there is not much you can do to "upgrade". I too notice
a slight "harshness" on occasion. I think the only way to approach that
is simming the biasing of the output stage and looking for something awry.

I've bypassed all electrolytics in the signal path, made a slight difference.

rgds,sreten.

 

[Mooly]

It is

It's a simple circuit, I'll find the links for it. It's good not just because of the Class A, but because it goes away from using a "differential" input stage like 98% of modern stuff. That means the distortion is even harmonic mainly, the right sort that's pleasing to the ear.

My amp is similar, but I used a MOSFET output stage using Lateral FET's rather than the more common HEXFETS as they are far more linear and were purpose designed for audio.
I run mine in class b (well ab) with just a small current so it runs cold.

 

[grahamfocal]

yea thinking I might go all out and build a power amp as Mooly suggested, might have to ask santa for it, where is a good place to get the details on that design (linsley hood)

 

[Mooly]

Here we go,

The Class-A Amplifier Site

don't be put off by the date... this is still an absolutely top flight performer.

 

[Mooly]

Figure 3 in the original articles... how simple is that ?

 

[Mooly]

I'm not an Ebayer but found this,
STEREO CLASS A 10W AUDIO POWER AMPLIFIER KIT! JLH 1969 - eBay (item 380167713304 end time Sep-08-10 06:26:21 PDT)

and if you research or search the DIY forums there are loads of threads on this classic amp.

The thing to keep in mind is to stick to the original concept... keep it simple. The original can be built using tag board as it's so simple. The main cost is the PSU and the heatsinks, but it's a wonderful amp to learn with and get a feel for what's possible.

The cost of the parts for the amp is minimal and there are loads of modern transistors that can be used, the originals are all obsolete now anyway.

 

[Mooly]

Plenty to be going on with I guess... there's nothing like building an amp for the first time and getting it all to work. The worst part is pulling it all together into something that looks good I find. Having a piece of wood on the floor with bit's screwed to is no good for the lounge. But ! it's a good way to learn.
Just be realistic... the JLH is easy to build... works brilliantly. Taking it to the next level and building it all into something domestically acceptable is something else... that's the bit I don't like.

Don't know how much you would want to spend on all this but if it's ultimately to replace the 8000A and be used as a main amp at home then you might want to look at more "complete" alternatives.

Have a look at Hugh Deans "AKSA" forum and adverts and products on here. Hughs a great contributer to DIY forum and sells and develops kits and ready built stuff.

 

[grahamfocal]

Plenty to be going on with I guess... there's nothing like building an amp for the first time and getting it all to work. The worst part is pulling it all together into something that looks good I find. Having a piece of wood on the floor with bit's screwed to is no good for the lounge. But ! it's a good way to learn.
Just be realistic... the JLH is easy to build... works brilliantly. Taking it to the next level and building it all into something domestically acceptable is something else... that's the bit I don't like.

Don't know how much you would want to spend on all this but if it's ultimately to replace the 8000A and be used as a main amp at home then you might want to look at more "complete" alternatives.

Have a look at Hugh Deans "AKSA" forum and adverts and products on here. Hughs a great contributer to DIY forum and sells and develops kits and ready built stuff.

well I think that you might be right, ultimately want to replace the 8000A with a more 'complete' design, going to check out Hugh Deans, for me, a kit might be a better start into it.

 

[Mooly]

OK... it's feeding time

I'll have a think too.