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Modified HDX-1000

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I have been searching for a way to upgrade or modify the sound of my HDX-1000 for some time now.


Although the HDX can play .wav and .flac up to 24/192 the sound can be better. It’s not bad especially for the money, but it could be better. Comparing playback of hdtracks titles via the HDX with the same titled burned in dvd-audio with dvd-solo and played with my Rotel dvd-audio player.... my Rotel dvd player is better. However, I find myself returning to the HDX time and time again, because of its simple and powerful interface. Nothing beats being able to crash on the couch, select from a bunch of albums and titles and play music for hours!


First, I researched an external re-clock for the HDX via a spdif connection from Empirical Audio and the well-respected Steve Nugent. The unit is simple and straightforward with no mod. Steve is very cool and was very informative and offered to help in any way. I had to pass though, because the unit was out of my price range.


Second, I researched an internal re-clock. The internal re-clock was very interesting, but not very compatible with the HDX. My understanding is we would fix the jitter at the clock only to reintroduce it at another point. It seems the clock goes up to 96khz and then it feeds a chip for the hi-res stuff. Go figure, you fix one and the other one burns you.


I then researched a few shops and the more I looked the more all roads lead to Reference Audio Mods. Kyle is very cool for taking on a very new project and dealing with mod happy me. After some e-mails and a phone conversation, we agree that the basis of the mod would be a power supply upgrade with a battery. Clean power!


These are the specific details:

1. New 12v gel type battery.

2. No power charger as I am going to use a solar panel with charge monitor to keep from over charging the battery.

3. Rubycon capacitor bank to lower impedance.

4. Stock umbilical cord. I wanted the upgrade to connect to the stock 12vdc input. I will upgrade the wires and hardware later.

5. Rubycon decoupling capacitor on main board.

6. I also opted to have Kyle pre wire i2s outputs for a future dac project and another idea I have up my sleeve. These are topics for another day though.


You should also know that Kyle proposed other upgrades, but the ones selected were a compromise I agreed to in order to reach a price point. I don’t really want to discuss the cost except to say it’s very reasonable for expert help.


I also want to say thanks to John Kenny from the NMT forum for his electrical help and advise.


So the upgrades are underway and I should have the unit back this week….


Comments please!



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  • 3 weeks later...

Team, sorry for the delay. I wanted to be sure what I was hearing and had my audio buddy here for the tests. I trust him completely for this task as he has more experience than I due with this sort of stuff.


First some final details on the mod to the HDX:

1. New 12v AGM drycell battery from Odessey model #pc925. It’s about half the size of a small car battery.

2. Home car 12v charger for now.

3. Rubycon capacitor bank to lower impedance.

4. Modified stock umbilical cord into stock 12vdc input. I will upgrade the wires and hardware later.

Rubycon decoupling capacitor wired on the main board with positive lead to the back of the switch and the negative lead to a typical ground.

6. i2s was not done.


The set up:

Rotel cd/dvd-audio player rdv-1092 with analog striaght wire Rhapsody interconnects to a Rotel processor rsp-1069 with Striaght Wire Rhapsody interconnects to a Rotel rmb-1075 amp. The analog input of the processor was set to bypass and only acts as a pre-amp. Power is from dedicated outlet with three #10s fed from the electrical panel at the house entrance. Rotel line conditioner for all digital units and the amp direct to the outlet with Striaght Blue Thunder power cord. Bi-wired series 602 version 3 B&W speakers with Straight Wire Symphony cables. HDX (with and without mod) with Straight Wire SPDIF rca interconnect. The HDX has a 16/44.1 dac and we decided not to test it.


The test:

First, I played the cd version of Kent Poons Jazz Prologue III title #3 in the dvd player and my audio buddy said...ok that is nice. Then, I played a dvd-audio version of Kent Poons Jazz Prologue III title #3(original 24/192 aiff converted to 24/192 dvd-audio with dvd-solo) in the dvd player and he said...ok wow very nice. The dvd-audio would be our reference point. I then played the stock HDX and he said nothing new and sounds the same as last time....bad. Now, I plugged the battery into the stock HDX and I could see he became more interested. He said, yeah I can hear an improvement and it sounds much better. This was a 35 to 40 percent improvement. Now we swapped the stock for the mod HDX with the battery. He said slightly better, but not as much of an upgrade as I expected. We also checked the mod to make sure it was wired correctly and it was. At this point, we decided to just compare full mod HDX with the dvd-player. We listen to a few things back and forth and at the end of the day the dvd player always sounded more alive, more sound stage. My buddy said that the instruments sounded like real instruments and not as much with the HDX. He said that the HDX was flat.

The mod HDX is pretty good and simple to use, but its like we are listening to many years of Rotel experience and refinement on the other hand. The Rotel has more soul.



From best to worse the Rotel dvd-audio player then the mod HDX and battery then stock HDX with battery and then stock HDX with stock power supply. Adding the battery to the stock HDX gave a reasonable improvement over the stock power supply. However, even with these upgrades the Rotel dvd-audio player is just that much better. The Rotel dvd-audio player is really good and the sound stage is beautiful and the instruments sound really nice. The mod HDX and battery is good, but still flat compared.


In my opinion a stock HDX would be good for everyday use and adding the battery would be cheap and easy upgrade. The capacitor bank could be an optional upgrade and they don't actually don't have to be inside the unit. The capacitor bank can be a DIY project for sent to a Pro like Kyle at Reference Audio Mods. If you want to impress and due critical listening then something else is needed.


Additional tests done at the request of a friend:

Same song from Jazz Prologue III title #3 in 24/192 dvd-audio vs 24/192 wav. Its basically a Marcia Seebaran singing a guitar and a base. First she is up then the guitar and then the base. I compared dvd-a in analog then dvd-a with hdmi and then the HDX with hdmi. The dvd player is better both time. Let me explain. I would guess that 98% of people would say they are the same. However, after listening to it a lot and learning from my buddy I start to see what is going on. That is not to say it’s easy for me, because I guess I never really have been listening. Her voice on the HDX sounds a bit less natural and free. With the dvd you really feel like its her and through the HDX a very slight bit like through a can or slightly metallic sound. The guitar on the dvd is very crisp and natural and on the HDX it seems to have a glare around it. The base on the dvd you can here the strike the tone and the vibration that follows on the HDX you hear the tone but less of the rest.



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Have you considered that the limiting factor in your system maybe the DACs in the Rotel processor - I had the previous generation to your Rotel and while it was good, was easily beaten by a MF X-DAC v8 (approx £800). Spending lots on a better interface into the processor will only get you small improvements (IMO) may be an upgade to a better DAC may be money better spent than things like Lynx cards (unless you're planning to use Analogue out of the card).






...in my opinion / experience...

While I agree "Everything may matter" working out what actually affects the sound is a trickier thing.

And I agree "Trust your ears" but equally don't allow them to fool you - trust them with a bit of skepticism.

keep your mind open... But mind your brain doesn't fall out.

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In this case I am pretty sure that the limiting factor is the HDX. We squeezed as much as is practical out of it. The processor while really intended for surround and all that is actually pretty darn good. The HDMI and SPDIF out of the dvd player into the processor also sound very good. However, in conversation with Rotel they informed me that the dvd-audio is a better DAC than the processor. For this reason and some tests I have the dvd as analog into the processor in bypass mode.


Also, I am considering the Lynx L22 (as you may know) and yes also as analog into the processor in bypass mode.


Team, it would interesting to see how the HDX fairs up against the Mac Mini as source.


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