Hello

[Learnincurve]

Hi,

I just joined the forum as I'm trying to gain as much knowledge as my limited understanding of electronics will digest. I have a few projects up my sleeve so will probably be posting all sorts of stupid questions. Please bear with me!

Summer 2013 saw what was intended to be a simple home-improvement project. I'd always wanted a subwoofer and my eyes were getting too weak to read the text on our 32" TV. So were my wife's and both were getting tired of the daily conversation that went something like:

"What does that say?"

"I don't know. I can't read it either!"

... but my wife refused to have big speaker cabinets and ugly flat panels littering our siting room, so I unwittingly promised that I could build everything into a bench, hiding the sub there and making the TV disappear into it when we weren't watching it. The project has snowballed. the bench is more or less finished (6 months late), but spin-off projects for multi-channel amps, decoder/preamp improvements, ELF shaping for the sub and other upgrades all round promise to keep me busy on this for a long time yet.

The first project will be to build a 3 channel front amp that is good enough for HiFi 2 / 2.1 music (mostly classical), while also powering the centre for films. It will be based on two Net-Audio Quad 405-III boards for the front pair and a heavily modified 405-II for the centre. I've worked out that I can just fit everything I need (including 3 330VA toroids into a custom-built cabinet that will fit into some space I set aside in the bench, but I need some help with the design. My first post here will be regarding the best mods for the 405-II. Stay tuned!

[keiths]

Hi Maruius and welcome to AoS

This sounds an interesting project - we'd all love to see some photographs when it is finished (or, better still, of it progressing...)

Hope you enjoy the forum.

[The Grand Wazoo]

Hi Maruius and welcome to AoS from me too.
It sounds like you've got a lot on your plate there! What does the rest of your system consist of?

[Learnincurve]

Hi again and thanks for both of your replies. I tried to reply to this just now (spent about an hour doing it) and my session timed out (AAAAARGH!!) Don't have time now but will try again later.

[Learnincurve]

Trying again :-)

I will post photos as soon as I can take some. Most of the hard work is now hidden, but the project has taken me almost all my spare (and not so spare) time since early summer and involved partially demolishing the outer cellar wall, large holes in the floor, countless hours of carpentry, veneering, electrical rewiring, some electronics (most of that still to come), pulling apart a perfectly good computer and splitting it between cellar and bench (with internal cable challenges) and routing many metres of A/V, power, computer bus and other cables to different parts of the project. Amazingly it all works.


I'm almost embarrassed to admit to the rest of my system in these forums. I'm not an audiophile. Both I and my wife are trained classical musicians although I now work with completely different things.
Like many classical musicians, I for one was quite happy if I could hear a performance I liked under clicks, pops, hum, hiss and distortion. We're both over 50 now and I can't hear anything over 12KHz anyway. My wife is even worse having sat in front of trumpets and cymbals for most of her working life.

Having said all that I do notice when the instruments appear in the right place or I can hear something resembling a human voice rather than an unnatural, edgy, metallic sound.

First some history:

About 15 years ago I found a pair of QUAD 405-II's on ebay. The seller thought they might be quads and said that Abbey road studios had thrown them out. They had been taken out of their original cases and the boards had been mounted in some special enclosures that fitted into mixer desks. The Quad transformers had been replaced with some very nice toroidals and the boards had already been modified to bring them more or less up to quad's 12565 iss. 7 release.

I modded them up top Bernd Ludwig's 1999 revision. One set kept the original rca dumpers, while the other got Bernd's full double TO-3 treatment to allow them to play nicely into lower impedence loads.

I threw out my old Bell and Howell (If I remember correctly) speakers and bought a pair of System Audio SA520AV's

A friend had been given some church speakers and didn't know what to do with them. They were wired very wierdly to give them an impedence of a few KOhms if I remember, but I found I could easily rewire them to 8R and they disappeared nicely into the back corners of my room, so I had the brilliant idea of building a surround system out of bits and pieces. I also got hooked on MythTV (a linux HTPC project) so a surround system made sense.

My tired Qaud 303 (overhauled around 1990) was retired to drive the back pair. The new SA fronts were given one of the 405's and I found a Klipsch decoder to feed the whole thing as a quasi-surround 4.0 system. The Klipsch actually sounded terrible but we ignored that ;-).

I've been meaning to upgrade the sound ever since but other duties kept it sufficiently low on the list of priorities that it never happened.

Everything changed this spring when I was finally allowed to add a sub to supplement the musical, but light-on-bass SA's/ our middle-aged eyes could no longer see text on the TV screen and the Klipsch started to die all around the same time.

The current state:

Speakers:

Front pair are System Audio SA520AV's mounted vertically. I'll add some home-made, heavy sand-filled boxes under these as stands and bond the speakers firmly to the stands. Probably re-veneering them with South American rosewood as the whole setup should look good as well as sounding decent.

Centre is a System Audio Mantra 10 AV mounted in the middle of the bench directly in front of the slot which the TV descends into when it's not in use. The challenge was to keep the back port open without risking damage to the TV, so I ended up modifying the cabinet to recess the binding posts. The back port now opens into a spacious, well damped chamber that the TV leaves behind when it is raised. In taking the speaker apart I found that it was quite loosely put together, so I ended up reinforcing the joints and making sure it was properly caulked-up. I've probably rendered it completly un-overhaulable in the process but hope that won't be necessary. I also veneered the front panel in South American rosewood to go with the rest of my "dashboard".

LFE is a Dali Suite 1.2 sub. which I bought second-hand. I chose it because it's a sealed, 12" design which just fits in the space I have available and it plays musically, giving nice, tight bass down to 29Hz @-3dB. It's on the light side for film, but we don't listen at particularly high volume and it just fills out the sound of the SA's for music so they don't sound so light. I have a Marchand Electronics WM8 which I have assembled and which will provide low frequency extension down to 20Hz. I'll have to guess the setup as there are no Thiele-Small parameters available for the Dali. If at some pointv the Dali feels too light, I might mod it with beefier driver and amp.

Back pair are the aforementioned church speakers. They're a load of rubbish, but are only used for film effects fopr which they are good enough. I might swap the drivers for something better or upgrade them to something like System Audio Talent, but they do disappear into the room better than any "real" loudspeakers would, so the wife probably wouldn't accept anything more visble.

Power Amps:

Front pair currently still driven by my one of my Quad/Ludwig 405-II's. This will shortly be replaced by the new 3-channel Net-Audio/Quad front amp.

Centre temporarily connected to a NAD C270 which is very in the way. Will be retired as soon as the 3-channel is done.

LFE is active

Rear pair driven by my Quad 303. It's badly in need of a new overhaul and I have the kit but will wait until I have mounted power-switching relays so I don't dry up the new electrolytics too fast.

Pre-amp:

The weakest link of the system. I'm a cheap skate, I admit it. But if I were going to throw money at challenges I probably wouldn't have anything like as much fun.

The trouble is that the system is supposed to do everything from multi-channel encoded film soundtracks to real 2 channel music. Obvioulsy that isn't going to work.

Currently I have a cheap, Chinese processor/DAC/Preamp. HiFi360 HF-D1B. There are reasons for this madness:

1. It does everything out of the box, so changing between sources and speaker configs is just a point and click of the Harmony remote.
2. It uses many discrete components of reasonable quality with space around them - making it moddable
3. The decoder chips are reasonably good quality
4. It already sounds far better than the Klipsch it replaces: Better imaging, less metallic sound, clearer and music sounds continuous rather than patched together from 1.5 second pieces.

When I get a chance I'd like to:
A) see what can be improved by modding. I can already think of:
*Upgrading the power supply, possibly providing separate supplies for analog, digital and clock sources
*Upgrading the electrolytics, and signal path caps in general, bypassing where necessary
*Rolling the op amps (currently NE5532's and making sure they don't oscillate (I think they do at the moment as cutting the power gives a "WheeeeeeeeeeeeePOP!")
*Replacing the crystals with stable clock sources

OR

B) accepting that it will never be more than a surround decoder and adding a proper DAC/preamp to the system. There are challenges to combining WAF with audio benefit, but it's probably easier than solution A (though maybe not quite so much fun)


Sources:
Denon DVD-1940 DCD/CD-player
MythTV media centre


A record deck and standalone flac player might be nice at some point.


Interconnects:

Multimedia content is routed through HDMI to TV (LG 50LA667V) then toslink to decoder. This is due to A/V sync.
Audio only content through S/PDIF coax from PC and CD

That's all for now.

[pjdowns]

Hi Marius and welcome to the forum