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-   -   Audiolab 8000A recap and mod (http://www.diyaudio.com/forums/solid-state/206333-audiolab-8000a-recap-mod.html)

Fulci 9th February 2012 10:58 AM

Audiolab 8000A recap and mod
 
Hello everyone!


I am thinking of recapping my Audiolab 8000A, series C, as it is already 20 years old. It still performs nicely, but sometimes I feel there's something missing, and I guess I take so much more out of this amplifier...

I can't find any good schematics for this amp, only for the Power section.

So, I am thinking of performing the following mods. I'd like if you could kindly give an opinion on these tasks and tell what else could I change, and if has anyone performed any mods on an Audiolab like this one.


1. Replace the 10.000uf 50v Elna PSU caps for new ones. I will be using 10.000uf 63v, but can't decide wether to get KENDEIL K05 or MUNDORF MLytics AG. Has anyone compared these or can give an opinion on which should be better?
Since it fits, can I use 15.000uf and would I get any improvement on this? Does anyone are the Kendeil selling on ebay coming from Cyprus or Italy trustworthy?
Will I need to reset the bias when doing this?

2. Replace all the Elna Starget and RE2 in the Pre (and Power) sections with ELNA SILMIC II (or NICHICON MUSE - again, what do you recommend here? Looking for PRaT and definition, don't mind a little coloring)
What is the difference between the Stargets and the RE2 and why did they differentiate these?

3. Bypass the PSU caps with a film MKP1837. I think there is already a bypass cap here, though I can't see which one, or it's value. If there isn't any, will I get any improvement placing these?

4. Should I change the EVOX MMK caps, in the pre section (or is it tone control?) with better ones, polypropylene, or are these great and should be let alone? What do you recommend as a better cap to use here? WIMA MKP10? ROE MKP? XICON MPP? EVOX SMR? Also, can I use a much higher Vdc when replacing? The original are all 63V, can I use 250V or even 630V if I can't find any smaller as long as it fits?

5. Replace the 22pF Polystyrene caps (transparent, tiny) in the tone control section for Silver Micas. Any idea of anything better to try here as well? Some film caps maybe?

6. Change the blue film caps (EVOX PFR, I think)? There are a lot of these, so lots of work. If it's not significant, I won't bother. Are these any good, or is there better to think of?

7. Change internal wiring, maybe. What do you recommend to place here? I might try speaker cable maybe, like Van Damme or Sommer, or maybe 0.6mm 5N or 6N silver wire?

8. Place new RCA plugs with silver wire and remove the ones unused. The original are cheap plastic, a few have already fallen off.


So, sorry for such a long post and thank you all in advanced for all the help you can give. I am looking to have a bit more PRaT and musicality out of this amp, but also warmth and better depth, definition and separation. I am aware that this amplifier was originally a bit sterile, even though warm, but I can make this happen.

I will post pictures of the internals later if needed.

Kei 9th February 2012 11:10 AM

I replaced the 10,000uF 50V elna psu caps in my luxman with mundorf Mlytic AG 15,000uF and the difference was remarkable. (though i doubt it had much to do with the replacements being mundorf, just that they were new)

The 2 compared.
http://i1142.photobucket.com/albums/...PSU_Filter.jpg

I used mainly nichicon KZ and FG for my signal path with a single pair of the silmic II used in the phonostage. I couldn't hear a big difference between the replacements and the originals. It was slight, but it was most likely down to a pair of knackered originals. I even tried some film caps in place of the electrolytics which made zero audible difference. I'd leave the polystyrene alone as they should be fine. I was changing out all the mylar caps for polyproylene and polystyrene and the ceramics for silver mica and again no audible difference whatsoever. Same story for swapping carbon film out for metal film resistors. The biggest differences were the PSU caps, changing the RIAA opamp and changing all of the electrolytic caps for new.

marce 9th February 2012 11:11 AM

I'd replace the cr***y RCA plugs, mine all fell of eventually, as to the rest I cant comment, did replace my main PSU caps, cant say I noticed any difference in sound, it did seem to sound different initialy, but I think that was just expectation, and possibly 17 years of daily use on the old ones.
Oh I did mod it so it could work as a pre/power, got the details from Audiolab before Tag bought them.
Amp still going strong though, its been a good workhorse over the years and driven everything I have thrown at them let down by the RCA's.

carlmart 9th February 2012 04:58 PM

Fulci,


I had a look at the 8000A schematic I could find, at HiFi Engine, so I'm not sure if it's your version.

There's also a a service manual there, corresponding to 8000A model 207, but from what I remember from an original SM I had, the 8000A preamp is still the same. It's the weak link of that project, as it has a single supply, when it should be using a dual supply.

So IMHO the preamp should be completely bypassed, or at least just leave the selector switch, volume and balance pots. MM/MC, line amp and (most of all) tone stages should be bypassed. I wonder if that is already provided on the 8000A.

About the upgradings, it will all depend on how much money you want to spend or how much you want to work.

Areas that might be improved:

1) Power amp. All film caps should be upgraded to polystyrene or polypropylene. Don't touch the caps that are already that. Silver mica is not better than polystyrene, so don't bother. Resistors should be 1% MF at least, but if possible upgrade those resistors on the NFB: 2K7 and 100. GEt the best you can get for them, like Caddock or something.

2) Power supply. It might be worth it to separate the supplies in two: L & R. From the bridge and further on. That would require some separation surgery on the pcb itself, but it might bring a few benefits. I don't see anything that could prevent from doing that mod. Twenty years old electrolytic capacitors should be upgraded indeed, if possible.

3) Line preamp. If you are keeping the line amp, at least bypass the tone-control stage. Apparently that is already provided on the amp, so replace the two large caps (4.7uF and 10uF) with film types, polypropylene if possible.

4) Volume & balance pots. What brand are them? If they are Alps or Noble keep them. If they are not, the volume pot might be interesting replacing it with an Alps Blue or even a 21-pos dual pot you can find on eBay. For the balance pot it may be trickier. I don't use balance pots, so it's not something I care much for.

5) Supply caps. Mundorf, Elna or Siemens/Epcos are my favourites. Up to 22.000uF/50v should do if you use a bridge. Don't exceed that. Bypassing them might be a good idea, adding 100uF, 10uF, 1uF, 0.1uF and .01uF types, but try them one by one and listen to the results, starting with .01uF. Some brands benefit from bypassing, some don't.

6) Wire. Replace the internal wiring with silver-plated teflon twisted pairs, gauge #23 or #24. Pure silver could do, or even oxygen free copper. But use thin solid types, firmly twisted.

7) Connectors. They should all be replaced with copper/bronze gold-plated types. All RCAs and speaker terminals. Also replace the cables you will be using for good connector types.

That should improve the sound quite a bit.

Fulci 9th February 2012 06:31 PM

Thank you all for all your replies.

E obrigado CarlMart pela excelente resposta, tão extensa e precisa.

Well, regarding your post:

1. I can replace all the MMK mylar caps for polyprop. Which one do you recommend best? WIMA MKP10? ROE VISHAY MKP? XICON MPP? EVOX SMR?

2. This should be a little tricky, I'm a total newb, so don't know how to proceed with this. I will get help from a friend though, so I'll look in to the future. Didn't want to mess with the PCB though. But the e-caps can be replaced first.

3. There is a button to bypass tone controls in the 8000A. Not sure if it's enough though.
I'll replace the 4.7uf and 10uf caps with film caps? Any MKP enough or boutique caps, like mundorf or better? Might get expensive though... You are talking about the 4x4.7uf and 2x10uf caps in the pre-amp, right? If I use Mundorf mCap, it'll be around €25 for all 6...

4. I can't see if the volume pot is any good. It's just a black box, can't find the brand or make or model. An alps blue cost €15, so no big worries here, if it's really worth it.

5. Will use either those Mundorf or Kendeils. I'll get 15.000uf 63v maybe. Can't seem to find Siemens easily, at least cheap ones.
I'll have to check what is that film cap under the two large PSU caps, if it's a bypass. I will try adding another bypass later too, just to test. Another €20 here...

7. Already have the speaker posts here to do it, just need some time and patience. The RCA will change later, only the ones that will be used eventually, and remove the others. Neutriks, I guess. My cables are all made with Neutrik too, NYS352G, and quite happy with them...


This will all be made in several phases and for a long time. I will post all the changes with pictures as I perform them. I want to spend as little as possible, way under €100, preferably.

Kei 9th February 2012 07:31 PM

Really don't think its worthwhile as the differences are (if there actually are any) so small its not worth the expense. I spent over £200 in parts for upgrading my luxman and the only difference i could hear came from a grand total of about 5 parts which set me back about £50. The rest was simply overkill as i'd hit diminishing returns by then. I swapped out electrolytics for film (which was supposed to net a big change vs mylar to styrol/PP, yet i could not hear any difference. Maybe it was me, maybe not.) I tested the amp in between changes to ensure i hadn't managed to break it which gave me a good opportunity to test the differences between each change.

Just to show you, this was before on the RIAA with 3.3uF nichicon fine gold caps.
http://i1142.photobucket.com/albums/...RIAA_Recap.jpg

After with panasonic ECWF polypropylene, and also takman metal film resistors. I put the fine gold caps back in. (no audible difference and they didn't look as daft)
http://i1142.photobucket.com/albums/...RIAA_Prog2.jpg

If you want to spend a bit on upgrading, do the electrolytic caps only as these are the only place you are likely to find a benefit. Also try the extra decoupling aswell as i believe that this also yielded a small improvement albeit inaudible but measurable. Wima, epcos, vishay or panasonic are fine for this job. (i've used wima mkp, vishay 1837, and epcos mkp. I chose mine based on size so that they actually fit)

Fulci 9th February 2012 08:13 PM

Hi Kei, thank you for your reply!

My guess is the Luxman was already such a great amplifier, there was not much where to better it. I will upgrade only the corresponding to those £50 you spend that was worthy. I am not going to spend much more on this. Will change to Naim somewhere in the future (unless these mods make it surprisingly so good that I won't need to, but I just love those chrome bumper boxes from Naim).

Also, since it will be made in several stages, it won't hurt the wallet much. Only problem is it'll become more expensive in count of post expenses.

First mod, PSU caps (€25), maybe try the bypass too. Second, all the other relevant electrolytic caps (€30). Later, all the 28 MMK to MKP (€15 for Wima MKP or Evox SMR). And later on try replacing some electrolytics for film (€20). The rest, the RCA and speaker post, the rewiring, etc will be done as time allows it(€25-30).

Kei 9th February 2012 08:33 PM

TBH, this is not a particularly high end luxman (only an L-220). It does sound pretty good to me, the audible differences i got were:

1. Less background hiss/noise partly with the new electrolytics and partly the extra decoupling.

2. A lot more low end from the new psu caps. I found myself needing to have loudness in or the bass tone control up slightly before. I don't need to now, and with them its excessive).

3.The new opamp in the RIAA took the harshness off the HF and greatly reduced sibilance. I reckon most audiophiles would say that my system is not "transparent enough" fro me to be able to detect the differences. The biggest difference of all will probably be a change of speakers, their position or the room.

In any case, i'm keeping the spare components from this upgrade and putting what i can into a DIY power amp project.

carlmart 9th February 2012 11:26 PM

Hi Kei,

If I'm not wrong it was me who suggested several parts upgrades in your Luxman.

Then I'm sorry you were not satisfied with the results.

All those things I suggested, some separately some together, were applied on other amps, including a Luxman.

You do need good speakers to feel differences, and by that I don't necessarily mean improvements. And good speakers do not necessarily mean expensive ones either.

If I recall I also suggested to completely bypass the tone control and lots of switches between the line amp and the power amp stage. That is something which proved very effective on the very first amp of mine that I modified, which did have tone controls and all that.

At least I'm glad the RIAA upgrades improved things a little.

Cheers

lanchile 10th February 2012 02:30 AM

Mundorf Audio grade caps for power supply are excellent. I did mine and also I upgraded the input caps with Sonicaps in my diy amp and there was a big improvement. ;)


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