Arcam Alpha 5 CDP upgrades

This evening I successfully implemented the RC filtering on the data lines with the values suggested (1K and 5.6pF).

The previous problem I had was just a dry joint. The tiny 1206 SMD caps have tinned ends which are really easy to overheat if you aren't very careful.

I'm listening to it now and wow it sounds good! That's a great little mod Martin, thanks for sharing. :)

I also took the opportunity to rethink the power lines to the clock PSU and SAA7220 PSU. I've now tapped into the 230vac from the underside of the main PCB, after the ceramic disc cap the following inductor and also after the PCB mounted fuse so everything is fused from one main fuse now. Having everything arranged this way is much neater. I upped the fuse slightly from 160mA to 250mA to take into account the extra inrush current on switch on which it will have to deal with.
 
mjp200581 said:
I also took the opportunity to rethink the power lines to the clock PSU and SAA7220 PSU. I've now tapped into the 230vac from the underside of the main PCB, after the ceramic disc cap the following inductor and also after the PCB mounted fuse....
Click to expand...

I had to reverse this change as it had a detrimental impact on the sound.

But look what the postman brought me this morning!



My other Taiwanese made chip is the best sounding of all the chips which I have auditioned so far. I hope this one is just as good.
 
Despite being quite for a while this thread isn't dead quite yet. Actually I've been busy doing quite a bit of tweaking recently but I want to wait until I've done plenty of listening before posting with my thoughts.

I'd like to refer you back to post #51 regarding the decoupling arrangement for the SAA7220:

>100uF electro and a 47nF ceramic cap paralleled to ground. Should I just leave these in place?

Yes, the ESR of the electrolytic will help 'damp' the supply.

[I didn't know there is a ground plan under the 7220 in the Alpha 5. If I had - as a more invasive mod personally I'd probably choose to use a surface-mount ceramic cap between the +5v pin (on the bottom left in you pic) and that ground plane, as close as poss (scratch off the green mask and solder to the copper below). I'd then whip out the existing 47nF ceramic cap in parallel with the 100uF electrolytic. ]

After a bit of reading up on the subject I'm interested to know if a surface mount X7R ceramic mounted on the underside of the PCB directly from the +5v pin to the ground plane would be a good arrangement here and better than the Oscon? Something like 1uF or higher?
 
Over the past few months I've been trying an assortment of different electrolytic capacitors in various positions on the DAC board and I've found there to be surprisingly noticeable differences.

The positions which I been experimenting with are:
  • The electrolytic decoupling caps by the TDA1541A for the +5v, -5v and -15v supplies (C219, C221,C225)
  • The two power supply electrolytics for the Op amps C8, C108)
  • C210 and C214 which downstream of the voltage regs and ultimately feed the op amps.
As standard C210 and C214 are 22uF and the rest are 100uF Rubycon YK. Initially I was using 220uF 16v Rubycon ZLH in all of these positions as that's what was supplied with the NET Audio upgrade kit.

The parts I have been trialling are Panasonic FC 470uF, Elna Cerafine 220uF and Elna Silmic II 100uF and 220uF.

I'll not bore you with the full tedious details, so here's a summary of my listening impressions:

Panasonic FC: I found these to have a crisper and more dynamic/powerful sound than the Rubycon ZLH when used for the TDA1541A power supply pins. However I found them ultimately too bright and harsh when used in over-abundance. I did however find the FC excellent on the +5v pin of the DAC (C219).

Rubycon ZLH: Good all-rounder without a particularly strong character of any sort but can be bettered.

Elna Cerafine: Very dark and cold sounding (in a good way). Superb in the low frequencies! I ultimately found these just a bit too dark and 'Hi Fi' for my liking.

Elna Silmic II: Very smooth and well balanced. Better bass than the ZLH and only marginally behind the Cerafine in this respect. I found these to absolutely magic for the op amp supplies!! (C8, C108, C210 and C214) but I did not like them on the +5v pin of the DAC where they sounded very dull.

For now I've settled on Panasonic FC for the +5v pin of the DAC and Silmic II for the -5v and -15v pins and also for the op amp supplies.
I certainly recommend trying Silmics at C8, C108, C210 and C214.

I'm very tempted to try some Sanyo Oscon SP for the TDA1541A power pins. I understand that the very low ESR of these caps can cause problematic oscillations with the voltage regs, however there is a 3R3 resistor in series before the +5v pin and a small 33uH inductor in series before the -15 pin (which has a measured resistance of 1.6 Ohm) so I think there is enough 'damping' on these supplies to make the Oscons safe to use. Perhaps Martin can comment on this?

I've got 15uF, 47uF and 180uF to play with in my parts pile.
 
Thanks for the reply Matt but I think I've hit the sweet spot with my current set up, although I admit I've never actually tried Black Gates.

Since writing my last post I added and extra 100uF Silmic directly under Z204 (-5v reg) from the output pin to ground. It sounds so good now I daren't change anything!
 
mjp200581 said:
Thanks for the reply Matt but I think I've hit the sweet spot with my current set up, although I admit I've never actually tried Black Gates.

Since writing my last post I added and extra 100uF Silmic directly under Z204 (-5v reg) from the output pin to ground. It sounds so good now I daren't change anything!
Click to expand...

Hi:
Many congratulations for your work around Arcam Alpha CD5, and many thanks to share your knowledge.

I have something to challange you: try this DEM implementation. For me it works better than a silver mica capacitar between 120 - 470pf.

Have fun!
 

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BTW, if you want to run NOS you dont need the NetAudio board. Just 3 wires linked as shown in the first pic.

Have fun!
 
Thanks for sharing. Is that DEM circuit implementation from a Grundig Fine Arts?

I've moved onto a couple of Sony CD players now so I'm no longer working on the Arcam.
 
mjp200581 said:
Thanks for sharing. Is that DEM circuit implementation from a Grundig Fine Arts?

I've moved onto a couple of Sony CD players now so I'm no longer working on the Arcam.
Click to expand...

Yes! Indeed! We can find it at Grundig FA. I have implemented it in a couple of CD players, TDA1541A based, with great sucess!

I also have some Sony players (two CDP-227ESD and one CDP-337ESD). Nice sounding machines, very powerfull and clean, but I have them stored because I do not like to hear the oversampling (and it´s not simple put them running NOS).

BTW here some pics about my Arcam Alpa 5 board.


Have fun!

DSC_6243.JPG
DSC_6247.JPG
 
quote:
I also have some Sony players (two CDP-227ESD and one CDP-337ESD). Nice sounding machines, very powerfull and clean, but I have them stored because I do not like to hear the oversampling (and it´s not simple put them running NOS).

I know those Sony's have two parallel dac's, and wires/mess can make it look hard on website you probably visited, but this is what it looks like on single dac Sony pcb (easier?):
nos sony.JPG
 

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