Extreme X-DAC v3 mods by sandyK

[Deleted]

XTRFProf
Yes,DAC 5V, (analogue) Digital 5V and 3.3V i.e. 3 VRs
SandyK

[XTRProf]

sandyk said:

XTRFProf
Yes,DAC 5V, (analogue) Digital 5V and 3.3V i.e. 3 VRs
SandyK

Ah, yes, I saw it now after opening the dac again today to check and to order some Schottky diodes for the bridge rectifiers and tracing the supply rails. The 3 VRs are 2 7805 for the 5Vs and 7M33, I think, for the 3.3V. Now eagerly awaiting the schottky diodes to see whether this will improve sound further. I'm doing things one stage at a time and with time so as to be able to catch the improvements. Or else catch no balls literally. ;D

[Deleted]

Turbo charging the X-DAC V3.

This major improvement complements the modifications already presented, but it doesn't even involve opening up the X-DAC V3 !
Many DIYers will be aware that fitting Super Regulators in place of existing standard regulators can often result in major SQ gains. In this case, a JLH PSU module with it's current limiter bypassed , is connected directly to the output of the Dual Regulated PSUs Voltage Regulators. The result is a very quiet, very low impedance output , that virtually eliminates interaction between the various sections of the DAC, and allows the existing regulators to give a very clean supply to their various sections.
The result is a large, further improvement in soundstage and overall sound quality. I believe that the ultra stable supply to the clock section is another reason for the improvements too.

The attached photo, is of the new outboard PSU, but will not be the final version physically, as this was an experimental version, thrown together , and without a mains input IEC socket etc.
On the JLH PCB, the current limiter transistors have been removed, and the inputs from the Voltage Regulators, strapped to the output supply tracks.
On the Voltage Regulator PCB, I have replaced the 5W 100 ohm resistor with a link,and also replaced the 7805 regulator, which is unused in this instance, with a 7812 Voltage Regulator. This just gives me the flexibility of fitting a socket at the rear of the case for providing a regulated 12V supply for other projects. Currently it is supplying voltage for the front panel LED, which has a series 4.7K ohm resistor under the LEDs heatshrink. It isn't necessary to even fit any of the components associated with this regulator.
SandyK

Some Specifications from the original John Linsley Hood design, as published originally in E.T.I. (Electronics Today International ,date of publication not known)

The design generates the equivalent of approximately .5 FARAD capacitance. The original design, which used 2 x 2,200uF capacitors in parallel, has an Impedance of <.02 ohm to past 150KHZ. This version using 4 x 1,000uF capacitors in parallel, should have even wider bandwidth. JLHs own bench PSU had a noise and ripple output of 300uV measured over the range 20HZ to 20KHZ.
The original JLH version reduced this to 4uV

[Deleted]

Additional.

The PSU shown is readily adaptable to other voltages, and other uses. As the JLH PSU Add on module is not voltage specific, it can also be used with other equipment that may benefit from a very high quality PSU, up to .5 Amps or a little more. The voltage regulators shown could be, for example, set to + and -12V, or even up to + and -24V,or perhaps + and -5V if required, by changing a single resistor value (in most cases) in each of the regulator's circuits. How to work the values out is given on the National Semiconductor website. e.g. the .pdf for LM117 (LM317) and LM137(LM337) If used with regulators set to give + and -24V, the transformer voltage would need to be increased to 20-0-20V.
The JLH section can also mate directly with the non adjustable voltage regulators of the 78xx and 79xx types.
Each half of the JLH can be used alone if required, for the required PSU voltage of the desired polarity.

SandyK

[holland]

Question, for clarification. To remove the current limiter, you use a wirelink instead of the transistor, and you remove the diodes and change the resistor to 1K8? Or do you remove Q6, D2, D3, and R11?

Thanks!

[Deleted]

holland
You may need to use 2 small links to bypass the transistor and it's emitter resistor with Allan's mini PCB . R11 ,R12, the diodes, and Q6 are not fitted for this particular application
To fit this PCB, the 1.5uF 63V capacitors must have 5mm lead spacing.We used 1.5uF because the 2.2uF types with 5mm lead spacing don't appear to be readily available locally.
The 4x 1,000uF 10V capacitors are replaced by 2 x 2,200uF capacitors with Allan's mini PCB for space considerations.
Alex

[holland]

thanks sandyk. I don't have that PCB, but I'll wire it on a breadboard to do some testing when I have time.

Is there a PDF or something to print out for etching? I presume a single layer is fine.

[Deleted]

holland
I will email you a copy of Allan 's (pagan) mini JLH PCB design shortly. It is a single layer PCB.
SandyK

[Deleted]

The 4x 1,000uF 10V capacitors are replaced by 2 x 2,200uF capacitors with Allan's mini PCB for space considerations.

In the majority of applications, the JLH may sound better, if the
4 x 1,000uF 10V low ESR capacitors per voltage rail are replaced
by 2 x 2,200uF 10V (or 16V) low ESR types. The specified
4 x 1,000uF types could also be replaced by ordinary 1,000uF electrolytic capacitors. The original JLHs that have been used for many years, used ordinary 1,000uF 10V electrolytic capacitors, but recently , the only ones readily available locally in those values and voltage rating have been low ESR types.
SandyK

P.S. The Suntan low ESR 2,200uF 10V electrolytics (Jaycar CAT. NO. RE6300) have since been found to be an excellent choice with JLHs in general.- updated 16/9/2008

[Deleted]

Just came across the web pages of Burson opamps. A customer on there had used their devices in an X-dac. Are these something special as they seem quite expensive.
www.partsconnexion.com/Index/burson.php

[Deleted]

juke

Perhaps Sol may care to answer this ? Sol uses a Burson in the output of his X-DAC V3.
However, a Burson will perform much better if supplied by a well regulated power supply.
A standard X-DAC V3 has no voltatge regulation for the output stages.
SandyK

[Deleted]

Thanks SandyK, lets see if Sol comes in, I'm curious about it. I've found your original thread on the X-Dac upgrade, and the warnings! When you say the PCB tracks are fine, are they 'worse' than the X-Can? I'd like to do it next but wouldn't like to totally wreck it. I'm OK with soldering, just no knowledge of electronics, as you know.
Juke

[maabx]

sandyk,

Could you possibly describe how I would go about using batteries in place of the external supply in your mod? I can do the bridge rectifier/cap mods, but how would I wire the DIN connector? Also, what is the reason for the cap change from 2,200uF to 100uF? I assume those are the smoothing caps(?) With a battery supply would I bypass the smoothing caps?

Thanks in advance for any help you can provide.

Mike

[Deleted]

Mike
I don't think it is really feasible to do what you are suggesting. The X-DAC V3 uses dual supplies of up to + and - 17.5 volts after rectifying the A.C. from the wallwart with it's centre tapped 24VAC. Even a couple of 12v SLA batteries would be too low a voltage. You would need a minimum of + and - 15V from batteries capable of supplying .5A for realistic periods of time.The change to 100uF was to enable lower loading on the voltage regulators,which benefits sound quality. The JLH was added at a later date. The other filter capacitors are best left as they are, as Musical Fidelity appears to have optimised sound quality using those values.

SandyK

[maabx]

SandyK,

Not even with a pair of 18v 22ah SLA batteries. There is no way? I would still like to give it a try. But I am not that skilled in electronics and I would need help on how to make the connections.

Mike

[Deleted]

Mike
Yes, you could use a pair of 18V 22ah batteries with the modifications given.
You would need to make sure with a DMM on the ohms scale, that you have correct polarity before applying power. The 2 18V batteries would be connected in series, so that you have a total of 36V. The connection between the 2 batteries becomes the 0Volts (E) line, and is connected to the centre pin of the 3 pin DIN plug. Attached is from the original thread.
Alex

STAGE 2. Remove the circular bridge rectifier near the front panel and connect 2 wire links straight across where the bridge rectifier was previously.
Double check with a Digital Volt Meter that the +VE marking for the bridge rectifier on the X-DAC PCB , will connect to the +VE supply from the DIN plug when inserted.
The -VE supply from the DIN plug should also connect to the X-DAC PCB's -VE marking via the other fitted link

P.S. You could also use 2 x 12V 7AH SLA batteries this way, but you would have to omit the 78L12 and 79L12 added regulators, as well as use perhaps another OPA2134 in place of the AD8066, which would have it's ratings exceeded with freshly charged SLA batteries.

[maabx]

SandyK,

Thanks for the info. I assume the battery arrangement would be like the second image below? Would I need to bypass the smoothing capacitors?



Mike

[Deleted]

Mike
Connect the batteries as in the diagram ,and it would work fine without any further changes. TBH, I would be surprised if there is much improvement over an outboard dual regulator + JLH, but I can understand your reluctance to attempt building such a supply.
BTW, the 18V batteries would work without any internal changes to the X-DAC V3, with performance better than the supplied wallwart.You wouldn't even have to worry about getting the supply polarity correct, as long as the point where the batteries are joined connects to the centre pin of the 3 pin DIN plug at the X-DAC end.
Alex

[maabx]

"BTW, the 18V batteries would work without any internal changes to the X-DAC V3, with performance better than the supplied wallwart.You wouldn't even have to worry about getting the supply polarity correct, as long as the point where the batteries are joined connects to the centre pin of the 3 pin DIN plug at the X-DAC end."

Alex,

Are you saying I do not even need to remove the bridge rectifier?

Thanks, Mike

[Deleted]

Mike
YES, the bridge rectifier will steer the incoming + and - supplies in the correct direction, so you don't even need to take the cover off the X-DAC V3 if you don't wish to go further.
In fact, with 18V batteries, DO NOT go further. You are getting too close for comfort to opamp rating limits as it is, by using 18V batteries.
Personally, I wouldn't use 18V batteries, as a freshly charged 18V battery's voltage will be quite a bit higher.
Alex

[maabx]

Thank you very much Alex.

Further, it seems that it matters not which side of the DIN gets +12v or the -12v, as the bridge rectifier should flow the current in the proper direction also.

Mike

[Deleted]

Mike
You are correct, but it would be better to remove the bridge rectifier in this case, taking care to get polarity correct as previously discussed, due to the already lower than optimum voltage.
Alex

[maabx]

OK it's finished. It is powering an X-LPSv8. There are 12 D cells per side. The batteries are fresh and measure 19v and -19v per side, between 10 and 11 amps. The wall wart supply measures 13.5v and -13.5v per side and between 4 and 5 amps.

I've listened to it for about an hour and it sounds good. I haven't done any comparison with the wall wart yet.

Thanks again Alex for your assistance.

[Deleted]

maabx
Wow, you are keen !
Please let us all know how it compares to powering from the supplied wallwart.
Alex

[maabx]

Alex,

I'll report back. It probably won't be until next week sometime, as I am leaving town for a few days.

Thanks, Mike