X-DAC v3 mods (another one)

[puggie]

I have just bought an X-DAC V3, had a little listed (stock PSU wall wart) and it sounds pretty decent to my ears... but I believe from reading SandyK's threads there is more to come. I've had a little look under the hood and the assembly is somewhat hap hazard, caps at funky angles and the like. So my intention is to do some sound basic mods to this and not go crazy, I don't have a great listening room so frankly the point of diminishing returns will be met fairly soon. My plans are:

Build a PSU for it, 30-50VA transformer and a regulator/capacitance multiplier. Aiming for 17v rails.

Acoustically dampen the casing as I have some sound deadening.

Replace electrolytics as per the mods guide, I have a selection of Panasonic FCs and Rubycon ZLs, they are my go-to amp powersupply caps for car audio stuff.

remove the internal bridge rectifier and fit ultra fast diodes with snubbers elsewhere on the board

Replace the ceramics for Op-Amp PSU decoupling for decent film caps (Red boxy Wimas or do you have other recommendations?)

Replace the op-amps, I'm looking at the OPA1612 as I have some, Just need SOIC to DIL adapters, I may fit a decoupling cap directly across the pins under the SOIC adapter PCB, I have done this before to good effect. The jury is still out on this one, everyone has their preferences.


Further thoughts:
is there a nice drop-in replacement for the regulators on the heatsinks?

Has anyone considered the NDK NZ2520SDA Oscillators as a replacement for what is on there? I've read of the 'Vanguard' ultra low PPM gold plated oscillators being used, the NDK units seem to concentrate more on minimising phase distortion rather than just outright clock stability (although that isn't shabby either). They seem to be a new serious oscillator with Allo running them on a lot of stuff, and not stupid money. An adapter board may be required as they are SMD.


So any thoughts and suggestions? I'm going to start amassing components shortly and will update this thread with pics as I go. 

[puggie]

So my first thought. For the PSU I'm looking at one of these Chinese r-core transformers:

www.ebay.co.uk/itm/30W-15V-2-6V-2-R-core-audio-power-transformer-0V-115-230V/261591270397?epid=2132675153&hash=item3ce80e03fd:g:iEIAAOSwm8VUsqsk

taking the 15-0-15 to give me the 18v I want for the analogue side, and the two 0-6v taps to do clean and dirty 5v for the digital audio and control sides for the amp respectively. Rectify, regulate and feed these through the JLH ripple eater or similar capacitance multiplier circuit, something to clean them up a bit. the DIN socket will probably be changed for a 7pin XLR.


Anyone care to comment on my plans?

[puggie]

Is there a nice or established way to manually switch 'sources' between the optical and coax inputs. I could just run a dpdt switch to disconnect the input I'm not using at the time. But has anyone a more elegant solution. I just want a push button on the front to switch between inputs.

Thanks.

[nando]

Interesting. I have four optical cables which I often plug in and out of my x24k.
A switch would be handy.

[puggie]

Neoteck on Amazon do a decent cheap 3 or 4 toslink optical input one output box for about £15. It has an ir remote and single button on the front to cycle through the inputs. I just want to control the internal switching of the x-dac.

[puggie]

Well, made start:
Full recap with panasonic FCs and Rubycon ZL.
Nichicon ES on the non polars
All op amps swapped for OPA2134 with ceramic decoupling caps over the sockets
The rail caps are now 10uf, I wanted 2.2s really, but these were the closest in my box (and the ceramics are good for hf bypass).

Next step will be a dedicated psu as the rails are not symmetrical with the std setup due to the amount of positive rail going to the 5v and 3.3v regs. I may look at better regulators too, there is real estate by the digital input side I could mount something on.