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Aragon 4004 converted to MK.ll and maybe other mods

So.... I'm back after some rough weeks with C19, and no work performed at all while my head didn't function:(. Didn't go that well, and the aftermath were quite hard... But back to the thread and ready:
The 4x36.000uf Kemet's arrives Thursday for install. Listening to the amp as built so far, I still think it sounds a bit more dark and not so straight forward as a modded Acurus A250. I know it's a matter of taste, but a/b testing between my Acurus and the almost fully restored/rebuild 4004, I do tend to think that the mids in the 4004 lacks a little behind although it's now converted to mk.ll.
Any experience out there what to expect soundwise? Is the 4004 more dark (laid-back!??!) in the music reproduction? At lower levels is do outforme my Acurus should be mentioned.

The BIAS is 10mV and stable at 60°C when the amp is pushed really hard.

I'm not seeing to explore more expensive parts btw. Just a sound profile

Best regards
 
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Clarence regarding the Kemet 36.000uf is minimal. It's maximum 0.15" (4mm) from ecap to PCB. Also the clamp for the ecap near the power switch deserves some attention before installation. Be careful to measure before drilling new holes in the button of the chassis. Also the old mounting studs from the old clambs must be removed, for the new Kemet's to fit
IMG_20220322_205619.jpg IMG_20220322_205628.jpg
 
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Perfect fit:D
IMG_20220322_211825.jpg IMG_20220322_211833.jpg

Only problem no is that I'm missing a suitable inrush current limiter after switching to the higher uF at the PSU.
I have a bunch of AMETHERM SL22 2R018 (2ohm/18A), but feel the need for the bigger SL32 2R025 (2ohm/25A) before power up with 144.000uF on tab.
 
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Regarding the PSU, I think the 4x36.000uf is the limit without a soft start..(??) The lights in my house flickers quite dramatic for half a second when the amp is switched on! My Acurus does the same'ish, but this Aragon really draws some current from the wall when powering up!:)
 
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Just a small update... We agreed (the owner and I) to skip the Roderstein 2.2uf bypasses on the PSU, and replace with 2.7uf ClarifyCap ESA and four 56K bleeders for some security and discharge.
We hope to give the 4004 just a little more bite to the mid/high section soundwise with the new caps. From previous projects I often chose 2.7uf to the 36.000uf Kemet's, it seams to be a good match... Definitely a better choice then the smaller 1uf witch can make a quite sharp topend with the Kemet e.caps chosen, to my ears that is...

The stock 8amp fuses seams to be pushed to the limit with the bigger 4x36.000uf PSU, and so far one internal fuse has blown at power up. The amp works fine BTW, so inrush seams to be the deal-breaker... The inrush-limiter is 2ohm 25A and has worked flawlessly so far up to 110.000uf in my own amp without the needs of a soft start.....
At one point I managed to make the 10A (I have to call an electrician on this matter to get 13A ;) ) fuse at my home electronic installation pop at power up.
I switched to another wallplug where 13A at tab were available, no problems afterwards. The two internal 8amp fuses is changed to 10amp fastblow-types to see if this is enough to ensure future power up without fuzz afterwards :)
IMG_20220510_222132.jpg
 
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Hi @KNielsen, thanks for the detailed post and pictures. I have a 4004 on the way (mk 1 I believe, no mk II badge shown in the pictures) and will be restoring it.

Do you happen to have the parts list you used for reference? Also how did the change to ClarityCaps impact the sound?
 
per5at said:
Hi @KNielsen, thanks for the detailed post and pictures. I have a 4004 on the way (mk 1 I believe, no mk II badge shown in the pictures) and will be restoring it.

Do you happen to have the parts list you used for reference? Also how did the change to ClarityCaps impact the sound?
Click to expand...
It's an early build, so can't remember the sound when adding the ESA. In general today, I wouldn't do this mod with added caps to the main PSU on top of the big e.caps. Instead focus more on the decoupling caps right at the rails, and buy these caps in a decent quality. Nichicon KZN or similar e.caps with a Panasonic ECWF(a) filmcap on parallel would be my choice in the rails.
Regarding partslist I just followed the Mk.ll upgrade schematic, I think it's attached in this thread or I'll find it to you.

Best regards
 
KNielsen said:
It's an early build, so can't remember the sound when adding the ESA. In general today, I wouldn't do this mod with added caps to the main PSU on top of the big e.caps. Instead focus more on the decoupling caps right at the rails, and buy these caps in a decent quality. Nichicon KZN or similar e.caps with a Panasonic ECWF(a) filmcap on parallel would be my choice in the rails.
Regarding partslist I just followed the Mk.ll upgrade schematic, I think it's attached in this thread or I'll find it to you.

Best regards
Click to expand...
Thanks for the reply and guidance on the capacitors. I’ll use the attached list for guidance and post any questions here once i get underway. All the best, thanks again!
 
Upgrading the electrolytic and film bypass capacitors on the DC rails and adding inrush current protection, like a CL-150 thermistor to handle the power supply will tame it.
 
Interesting thread…

Nice looking 2002, @dapbmw
Owned a ‘76 same lime green color, that car got me a lot of tickets, drew more attention than any red car I ever owned.
Lots of Alpina updates and I replaced the motor with a factory longblock, sure wish I still owned it.
:jump:

Happy Listening all
 
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