Arcam Alpha mods

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What... ?

Instead you got oak vat matured silver mica of very close tolerance

.....which worked very well ...ask Walter....he liked them

I do love my old caps from Russia. The 1u KBG PIOs are particularly sweet to my ear. The Teflons brought out some crystal clear high end. Just starting to play with the Silver Mica.

At the other end of the spectrum these OSCON SEPCs are magic around the digital. I think its time to stock up on a few more. I put them everywhere in my Sony and it came into the same ball park as the ARCAM.

Martin, thanks for the orientation info. I might try chiping in an OSCON as a comparison. I just have 130u which is a lot more than you and Andrew recommend. I have them everywhere else replacing the original 100u caps.
 
Walter that's a compliment - thanks - but I'm not a ' Martin Clark ' believe me.
He's one of those guys whose crumbs you grab where you have a 2 second think about what he just said and then you apply it - like the 10uf Oscon tip.
Martin - put your hands over your ears please:eek:

I'll tackle most things but I'm not a calculator, scope owner or an Ohms law expert at all - I just steal away at everyones good results - not ashamed. I've learned the hard way with everything but it's because of this site.

Seems there is another DEM trick that I missed by a mile today too - like I put the zener in the wrong place ?.......but why does it work so well ?
I'll be making some changes in the morning - do the test again and advise asap

Have valve buffer almost ready to try too - could all happen at once tomorrow.
Splitting the input grounds and routing to the new star .
Both pin 9's now grounded too. I reckon I'll have cracked it all by tomorrow evening

Andrew
 
If the rail to the -15v doesn't have a little bit of RC decoupling ahead of the -15v reg, add some. 10ohms and a 10-100uF is enough. It will clear-up noise that otherwise passes right through regs

Even if it's an op-amp based super-reg ie. S Power? I'm making a list of several tweeks to do at once today and wondering about this one.

I'm going to feed the -5V S Power directly from -24V and install the silver mica and a cap from -5 to -15V. I'll probably have to put those two caps underneath the audio board.

Simon
 
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RC on -15v

The Alpha board has LC right before the -15v consumer. L201 followed by C224,5. It is less than a cm. In my case I put OSCON SEPC 130u at C224 and left the stock film bypass. Just before the Reg is a CRC consisting of 3600uf BG STD and BG N. I think my issue remains to replace the LM337 reg with something discrete. I know your super reg worked well, but its too$$ for my setup. I'm looking at ECDesigns for inspiration.
 
You can make these super regs DIY, but making them neatly / compact is perhaps another matter. Sometimes old Audiocom units appear cheaply on Ebay too.

I removed the inductor and film bypass as they were in the way of the new elco. My SEPCs are all 6.3V-rated so I had to use a Rubycon ZA, probably a 220u/35V, which also has outstanding specs. TBH I thought the film cap was a bit pointless without it being nearer and when it's mated to an already-good elco.
 
Final implementation as attached.

Just running unit now - too early to say.
Works great though - more later
 

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That's it - no more or a while now - it's all done on the tweaked board and is installed - I did the Oscon tweak across -5 and -15 too.

It's been running quite a few hours now and have had a good listen.
Smooth and more detailed - period.
The attack speed has improved quite markedly
Background details are part of the ' whole ' in a way that were not last night or before - room acoustic has moved another step and Piano pedal movement is now easy to hear - who whats to hear that ?
Actually - I do ;)

Simon, you've commented in the past about the sound of drums being amazing in your system - well, it's just an opinion but I think you are going to get a bit more of that :)

It's just tremendous and the whole thing could get a bit better once it all settles down too plus the valve stage could be an addition soon.
I quietened it down quite a bit this afternoon by fiddling round with a few grounds as per your suggestions - not perfect yet but I'm on a roll here:cool:.
So far as what it does musically is concerned it's lovely so I'm going to push on with it until I can silence it completely.

Looking forward to seeing your progress next

Andrew
 

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Thanks Andrew, sound great

I look forward to following your lead.

Can you point me to the thread where you picked this up? I would like to savour this for a while. I'm going to order parts in a few days and will add this to the delivery. What part did you chose for the diode?
 
Simon - yes, even with superregs a bit of RC ahead of them can help.

Do keep the R value fairly small though, up to say 10ohms works well. Active regulators can go unstable or perform worse when fed from high supply impedance; this is why 3-pin reg datasheets always show a small cap on the input to a reg - it is always a good idea. If manufacturers could guarantee stability with out, I'm sure they wouldn't mention it!
 
Thanks Andrew, sound great

I look forward to following your lead.

Can you point me to the thread where you picked this up? I would like to savour this for a while. I'm going to order parts in a few days and will add this to the delivery. What part did you chose for the diode?

Thanks Walter -

IN 5711 - little zener types - about 40 cents each in your money !!
Love this type of mod - least money / biggest grin factor :D
 
Forgot - I picked the thread up in ' building the Ultimate NOS DAC ' where ecdesigns and Thorsten Loesch contribute and there's links and stuff to other
threads I'm sure.
If I could learn how to attach threads to this one I might be able to make it a bit simpler for you !!

I'll have a go but don't hold your breath !!

Andrew
 
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