Article: Further power supply modifications to the DiyParadise 'Monica2' DAC using Paul Hynes regulators and CCS.
Parts reviewed:
Paul Hynes Z1A regulator module: Cost 60 UK pounds.
Paul Hynes Z7805 voltage regulator: Cost: 30 UK pounds.
Paul Hynes CCS2, constant current source: Cost 16 UK pounds.

Review: Nick Whetstone - TNT UK
Reviewed: September 2008

The DiyParadise Monica2 articles are in danger of becoming a long-running serial! For those of you not familiar with the previous articles, you can find the original review here, the article on adding the Rudolf Broertjes' output stage here, and the article on modifying the DAC circuit here . In this article, we will look at taking the Monica2 just about as far as we can, with the addition of some very high quality parts for the power supply, for both the DAC section, and the output stage.

With the Monica2 now discontinued, and replaced by the Monica3, you may ask what is the point of spending time and money on the former. It's true the Monica3 is said to be an improvement on the Monica2 but the upgrades described below are relevant to the Monica3, or indeed, most DAC's that don't cost the price of a secondhand car. If you have enough interest in hi-fi to visit TNT-Audio, you probably know by now that the power supply is one of the most important parts of any piece of active hi-fi. It is the foundation on which the sound that comes out your speakers is based, and the better the power supply, the better the sound, assuming that the rest of the equipment is designed and built properly.

The upgrade items used for this review all come from Paul Hynes. They consist of a stand-alone high quality regulator module for the output stage, three 'drop-in' 5 volt shunt regulators for the DAC section, and a Constant Current Supply (CCS) to replace the LM317 on the DAC board that sets the current for the DAC chip supply.

I decided to start off with what was the easiest item to install, the Z1A regulator module, as it is a 'stand-alone' item. The output stage had previously been fed from a fairly typical regulated supply using an LM1084 regulator circuit built according to the application notes. I removed this circuit and replaced it with the Z1A module which supplied 21.5 volts. This was a fairly quick mod and I was able to have the Monica2 back in my system and playing music within about 30 minutes.

The sound improvement was immediately obvious. Better detail, more control of bass, darker background. In fact the music sounded better in just about every way. I didn't notice very much change over the first couple of days of use (as I had done wit the PH SR1-5 PSU for the SB3). But I decided not to proceed with the other upgrades until I had listened to Monica2 for at least a few days to get used to the 'new' sound. In fact I was so satisfied with the sound, it turned out to be a couple of weeks before I went on to the next stage of this upgrade.

The modifications to the DAC board were a little more complicated. But I would still rate the job reasonably straight forward for anybody who has good soldering skills. Apart from a soldering iron, I used some desoldering braid, a pair of small needle-nosed pliers, a small file, and a 0.6mm drill. The Monica2 PCB is double sided and I always find desoldering components from such a PCB more difficult than with a single-sided PCB. However, with care and patience, it isn't too difficult and the Monica2 PCB is robust enough to stand items being replaced a few times with care. The components to be replaced are shown here circled in yellow.

First off, I tackled the three 5 volt regulators. two came out quite easily but there always has to be one trouble-maker, and the third stubbornly refused to budge. But it was simply a matter of persistence, mopping up the solder with the braid until the 7805 became loose enough to remove. Then I carefully poked the 0.6mm drill through each hole to get rid of the last trace of solder.

Even then, I found that the legs of the PH Z7805 shunt regulators were too large to go in the holes. If you do this job don't be tempted to try and force them through or you will break the pads on the bottom of the PCB. I used a small file to carefully file down each leg of the Z7805's. Not much is needed, it is more a case of rounding the legs, and it didn't take too long.

As you can see from the picture, the Paul Hynes regulators are quite a bit larger than the standard types that they replace. Although they all went onto the comparatively compact PCB without much trouble, you should always check to see if you can physically fit an upgrade item like the Z7805 before you order them.

I decided to audition the new regulators before I installed the CCS. But I had a problem. The (added by me) winding on the toroidal transformer easily provided enough current for the DAC in standard form. But the addition of three shunt regulators drawing in excess of 120 mA each was too much for it. Looking around for a quick fix, I found an SMPS with a 12 volt output, and connected it up to the DAC. With the extra power of the SMPS, the music flowed. Once again, the difference in sound was immediately apparent. I felt that the tone was now slightly darker and the sound a little 'restricted', as though it was somehow too controlled. But that changed after a few hours of operation although I was still not sure if I liked the overall presentation. So I went ahead and replaced the LM317 with the Paul Hynes CCS. This was similar to replacing the regulators and was completed without any problems (the LM317 being in a TO-220 package with the same size legs as the PH CCS). So if your are replacing the T0-220 packaged regulators with the PH equivalents then you won't have to file down the legs (the 7805's on the Monica2 are the smaller package (TC-92) type with the thinner legs).

Adding the CCS was like adding the final piece of a jigsaw. That slightly 'closed in' sound disappeared to be replaced with music just gushed from the speakers. The sound now was controlled but producing a large sound stage, wide and deep. From memory, I would say that the sound stage extended just a bit wider of the speakers than it did before these power supply upgrades. The top end sparkled, the bottom end was powerful but tight and controlled. All in all, the Monica2 now sounded nothing like the standard item that I had first listened to a few years back. The TDA 1545 isn't my favourite DAC chip but I would be confident enough to put the modified Monica2 up against most other DAC's and know that it wouldn't disgrace itself. Perhaps the best indication of how good the Monica2 had become with these modifications was when I listened to my Scott Nixon DacKit which now sounded a bit 'muddy' in comparison.

Of course, there is always a caveat with these projects and in this case I know that many of you will raise your eyebrows at the cost of the Paul Hynes items compared to the original cost of the Monica2. It's always dangerous to generalise but I would hazard a guess that most DIYers, the type of person most likely to want to upgrade a piece of kit like the Monica2, and the sort who like to get a bargain, will therefore see the Paul Hynes items as 'expensive'. The non-DIYer because he has to buy stuff ready-built is far more used to spending more, and therefore wouldn't be so put off by the cost. But of course, the latter probably doesn't look at items like the PH regulators anyway, unless he knows of somebody who can fit them for him. So is it all worth it?

My experience of DACs, is that despite the advertising claims, despite some of the more over-enthusiastic reviews, there isn't a huge difference between most of them. It's not so much the DAC chip that is used, but how the circuit is designed and built, with probably the most critical part of the unit being the power supply. Just look at the more up-market DACs with their complex and exotic power supplies to see what I mean. There is no getting away from it, the signal that the DAC passes on to the rest of your system comprises a tiny and delicate signal generated from the data supplied, mixed with a comparatively large amount of power supply. You don't need to be called Einstein to realise that the bit added by the power supply has to be as 'clean' as possible in order not to pollute the original signal.

I see the PH bits appealing to people who have found a DAC with a signature that they like the sound off. They may have already tried several DACs and don't want to spend more money finding out that other DACs sound different, but not necessarily better. They would rather improve the DAC that they already own which it is most likely the Paul Hynes bits will do in no small way. And these days, for those not handy with a soldering iron, it is not too difficult to find somebody to carry out this sort of work (in fact you can ask Paul Hynes for a quote). So I say yes, if you like your DAC but feel that there is more to be got out of it, then using the Paul Hynes regulators etc is a sensible investment!

The problem for this reviewer is that in future I will be listening to equipment and wondering what it would sound like with a sprinkling of Paul Hynes components!

Paul Hynes has informed me that customers wishing to buy a set of regulators for either the Monica2, or Monica3 upgrade, will receive a 10% discount off the quoted prices. Please also be aware than the regulators used in the M3 are different to those used in the M2 (with different pin-outs) so remember to quote which model you are upgrading when ordering these regulators.