DIY UcD400HG Monoblocks that can do Stairway to Heaven

This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.

Have been a happy user of a pair of DIY Monoblocks built on UcD180AD for more than two years now. I had been planning a super souped up version using UcD400AD since a year or so but a hectic work schedule kept me from putting it together till now.

With Hypex announcing UcD400HGs and the HxR regulators earlier this year and the realisation that another year was about to pass by (like 'Time' in Dark Side of The Moon) set me into action and I completed this pair in October 07. It's been running in for well over six weeks now and seems to have settled in nicely.

The objective was to improve on my previous attempt and to provide a worthy enough platform to all the hard work put in by the Hypex engineers in the HG upgrade and the HxR regulators. A lot has already been written about the sound quality of these modules so I won't go into that. My system config should give you enough hints about my views on the pedigree of these babies. All I want to say is that High end amp manufacturers of this world should be really, really scared. Of course I will be sending Christmas Cards to the awesome folks at Hypex for making this possible ;)

I have also learnt a lot from many talented people on this forum especially those who have contributed to the UcD180 Hot rodding & 400 Q&A threads , so many thanks to you guys as well. If any of you ever pass by Singapore, please do get in touch and the beer will be on me :)

The specs and tweaks are as follows:


UcD400HG with HxR regs powered by UcD HG Supply and UcD soft start - soft start is not really needed but provides additional protection, reliable mains terminations and on/off, LED options etc).

- 42V, 330 VA EI Audio grade transformer custom built to my specs in Singapore
- All Aluminum casing, designed and fabricated to my specs in Singapore


- DC coupled signal input
- Auricap 0.68 output cap designed for Hypex
- Bybees in L & N legs of Mains input and Silver Bybees at signal inputs

( I know that some of you here don't like these - but I have had positive experiences. In the worst case, they perform no less than the hook up wire they replace ;) )

- ERS StillPoints EMI/RFI Sheets and Soundcoat damping sheets in critical
- Super Cryo fuses in Mains and in the HG Power Supply,
- Demagnetised Faston crimp connectors
- Silver nano contact enhancer for all Faston connections.
- Directly soldered joints on one end in the heavy current carrying wires
and crimped at the other end


- Cryoed Furutech IEC inlets
- Cryoed ACME Mains Silver fuse holder,
- Neutrik Silver XLR,
- Eichmann Speaker terminals

All wiring inside is Cardas 14/12 Gauge hook up wire, except for signal input which is solid core silver and Mains input, DC Sense which is 14 Gauge Silver plated copper with Teflon insulation. Solder used throughout is Cardas Quad eutectic.

Lastly, some pics:

Side View:
An externally hosted image should be here but it was not working when we last tested it.

Rear View:
An externally hosted image should be here but it was not working when we last tested it.

Internals - Top view:
An externally hosted image should be here but it was not working when we last tested it.

Internals - Front View:
An externally hosted image should be here but it was not working when we last tested it.

System View:
An externally hosted image should be here but it was not working when we last tested it.
Thanks glt. I didn't really have much complaints with the stock cap for the first 10 days or so - I was so bowled over by the sound quality improvements of the HG modules over the AD version :). The changes are not very major - the stock cap is pretty decent. I guess the biggest difference is in the air it imparts to musical presentation but that's just my subjective assessment - it's not possible to capture it on a scope.

From an electrical perspective Auricap is a closer match in tolerance to the new output coil (+- 5%) as opposed to the +-20% stock cap. From a physical layout perspective it's a bitch to install if one is trying to keep inductance loops to a minimum and keep it close to the ground plane - there is simply no space for it on the circuit board side after the HxR regs go in.
Kooka said:
Well done! Can you please tel me which one of the original smd caps is to be switched to the auricap you put? This is my layout of Ucd180 (modded with LM opamps and Nichicon Fine Gold caps, and I am going to give a similar layout to my new dual mono power amps with Ucd400s), so I am interested...

Thanks Kooka. The original cap in question is the output cap 680nf - its a film cap not an smd. A lot has been written about this output cap in the following thread

Its best if you read through it- I know it's a longish thread but is essential reading for anyone wanting to tweak their UcD modules.

You can e-mail me offline if you have specific questions or post in the Q&A thread.

All the best with your mod. :)
Disabled Account
Joined 2007

Nice amplifier. I think you went a little crazy with the gimmicks though. Most of those are likely to only hurt the wallet that paid for them, and can only benefit the wallets that sold them. That's fine as long as they do no harm to the sound or safety factor.

If someone paid for a carpet made from silver lined clouds, you'd certainly expect them to say they were walking on air.

In this case you have used one gimmick component that will actually give much worse performance and that is the 45$ auricap, which by the way, was not made for Hypex, you don't see them using it, do you.

Even the guy who works for Audience and had them make it does not use it in his own modules.

The modules used to use a cap of lower quality which the comments in the old threads reflect, that was a long time ago. The Panasonic cap was the upgrade to it, and they are worth leaving in place.

What you are actually hearing is not air, but an increase in high frequency noise brought about by several factors that mean a cheaper component from a worse process, and also the increased EMI you've produced by using it.

So for a $45 gimmick and increased noise, there is also the factor of reliability that you've put in question. You don't really think their process rivals that of Panasonic do you?

Also I doubt you can really say what a good match for the coil actually is.

While you have done these things, there are rather basic improvements to be had that could have gotten you far more and don't require gimmicks.

As long as you are happy with it it's fine, but people should think twice before doing the same.

Thanks for your comments - very poetic :)

Your comments about the Auricap are very very interesting and probably the first time that someone is openly commenting about them in the forums - I did read the Hotrodding and UcD400 Q&A threads end to end and most other forums but I guess yours is the first comment in detail about the effect of this cap on the Hypex module. Thanks a ton for that. It's really appreciated.

In the next few days, I will do some more careful listening and report back on the air vs HF distortion issue.

If what you say is true indeed then it's a shame that representatives from Auricap have gone about making such claims and the Webshop I purchased these from makes similar claims. I have written an e-mail to John M of Audience on this topic, I will report back if he replies to it.

I don't really have a view on the manufacturing process and quality of Panasonic vs Auricap (not my domain) but I have been a satisfied user of caps from both companies although in different applications. The Auricap .47uF/600V is special fav. of mine as is the FC electrolytic range from Panasonic.

My comment about matching of the coil and this cap is with respect to the specified tolerance which I assume to be correctly stated by the respective manufacturers.

You mentioned something about more basic improvements to be had without resorting to 'gimmicks' - could you please share those with me?


Amit and all,
I have been very busy designing new products for Audience and others so haven't kept up with the forum. This one I had to respond to however.
The reason I don't use the black Auricap and instead use our new part is purely a mechanical one. We had production problems with lead spacing that had absolutely nothing to do with the performance of the original UcD Auricap. This cap is superior in ESR and ESL so will significantly lower noise if the leads are kept very short by mounting it on the back as you did. The sound quality speaks for it's self!
Our new Auricap is more conventional and is produced to a lead spacing precision that allows it to be PC mounted given the proper pads. This new part is built to 1% tolerance and is a true precision part. I can personally vouch for the sonic performance.
Another point I feel necessary to make is that only once did we have a field failure of an Auricap. Our response was too recall and replace every single one from that batch. This was not cheap as it was a popular OEM part. This is the kind of quality and support you can expect from Audience.
Audience is a very high value manufacture and all prices are determined by a strict formula. You have to understand when you are dealing with small lots of exceptional quality custom products the price will reflect this fact.

Many thanks for you reply and for the insights on suitability of this cap with Hypex modules. Hopefully this 'caps' the jar of worms on the Auricap-Hypex debate once for all. More importantly, I hope this information will prove useful to other readers too.

A big meow from my cat to yours :)

Class D amplifiers involve electronic phenomena not understood by 99.9% of audio people and can be easily spoiled if they are modified with exotic components in the way it is routinely done with linear amplifiers, where almost no part is critical.

Those big film capacitors should never be used in any high frequency switching circuit. They don't act as capacitors above 100Khz.
Disabled Account
Joined 2007
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.