Welders progress

[Welder]

Right, let’s see if I can do this without making a complete balls up of it.
I don’t own a camera. I will borrow one shortly to update.
The majority of these pics were taken at the vinyl/CD to file transition point. There have been a few changes since, notably Dac and balanced cable/amp mods

This is me.
http://www.mediafire.com/imgbnc.php/5efe717a665b759d5d017108cb1a4f952g.jpg (http://www.mediafire.com/imageview.php?quickkey=8k30ah9mv6xah22&thumb=5)
This is Sunny my best mate.
http://www.mediafire.com/imgbnc.php/56e59214375a768b17be7ef6df29b04a2g.jpg (http://www.mediafire.com/imageview.php?quickkey=momimtzlz3m&thumb=5)
This is……oh way back in the 70’s.
http://www.mediafire.com/imgbnc.php/4fb77c3747c8308fdd5cd679cd3f9eb22g.jpg (http://www.mediafire.com/imageview.php?quickkey=nllhrz7wt8dl2cl&thumb=5)

Still with Exposure CD Player and recently moved in and still setting up.
http://www.mediafire.com/imgbnc.php/77858999a2c0b67ef4b02377d2d632502g.jpg (http://www.mediafire.com/imageview.php?quickkey=myzzymmt5yz&thumb=5)

http://www.mediafire.com/imgbnc.php/99323928b42f706471cf7a985958d0c42g.jpg (http://www.mediafire.com/imageview.php?quickkey=zxydlq7521s02cs&thumb=5)

http://www.mediafire.com/imgbnc.php/e374b7ad82f8fda433ed72af33aedd462g.jpg (http://www.mediafire.com/imageview.php?quickkey=5ag34gfvk7125k4&thumb=5)

http://www.mediafire.com/imgbnc.php/ef68d9a036b1550ca040b70e93835fa62g.jpg (http://www.mediafire.com/imageview.php?quickkey=urh4d7tjnvj5udn&thumb=5)

Last of the decks going on flea bay and my SME 3009 with Nagaoka mag alloy headshell. This turntable had been sat in a slate and oak surround which I do have a picture of but just cant find it atm.
http://www.mediafire.com/imgbnc.php/4475e36db0058906d5e813b9324caad22g.jpg (http://www.mediafire.com/imageview.php?quickkey=wre8n4kpgfq6w8h&thumb=5)

http://www.mediafire.com/imgbnc.php/8a207e35fa8d852a1a012f7cedc19b7e2g.jpg (http://www.mediafire.com/imageview.php?quickkey=odqc5ih08c3f1tt&thumb=5)

Finally no CD and my first step into file based audio with the excellent HRT 11.

http://www.mediafire.com/imgbnc.php/e417ce8dba34499fbbff5528d3576ae42g.jpg (http://www.mediafire.com/imageview.php?quickkey=9q388m9bfrhswls&thumb=5)

http://www.mediafire.com/imgbnc.php/a66eb4d32a6dbf3947e7eb8a29d47cd32g.jpg (http://www.mediafire.com/imageview.php?quickkey=mdbj88q1isvi4yy&thumb=5)

All the cables are hand made and so is the power conditioning box.

Quantum 102 pre and 207DA power on floor. Two more 207DA’s stuffed in my active experiment currently in someone else’s loft atm along with a couple of self built valve power amps which I must dig out and play with in the near future.
The Quantum pre and power is still a stunning combo, bags of grunt and control and I’m in the process of replacing the power amp supply caps and tweaking the pre. I may even replace the Exposure 25 RC with the Quantum stuff if I can get the cabling right which is all DIN and better S/N in the pre.

The Volts.
The obvious changes from the original is the replacement of the mid and hi drive units.
They were, Peerless MRF40 and Audax HD 100 D25
Now,
All the Volts have new suspension and the drive B250’s have new spiders as well.
The back of the cones are 1cm “ring doped” about an inch from the coils to help stiffen this area.

The PCB crossovers have been replaced. I used 10cm tufnol board and laid out a + and – rail in solid 1.5mm copper wire.
All the electrolytic caps have been replaced with ICL or Ampohm metalized poly’s and/or Auricaps.
I used a 1.5mm solid core and multi strand outer speaker wire for the internal wiring.
The resistors change about a bit depending on room and Dac but I use decent quality wire wounds throughout and tune using Speaker Work Shop and finally by ear.
The crossovers were at the time of these pictures mounted just behind the WBT terminals at the back.
Crossover at 406 Hz and 290 kHz

I’ve added two aluminum braces either side of the bass drivers that connect to the ABR and B250 at their mounting points at their top fixing points.
The box internals were lined with roofing felt the back of which was smeared with Dum Dum and then filled with lambs wool rolls.
The original cabs are ¾ “ HD chipboard.
I think I spent about £1000 on the drivers and mods. I did all the work myself.

They’re fairly efficient at 96db for 10 watts at 1 metre
Frequency response is 20 Hz to 20 kHz rolling off at the low end by about 1 db per Hz from the 48 Hz mark.
The ABR is tuned to 20 Hz
Polar response uniform around 32 degrees.

Oh arr, I also welded up the stands out of fence posts and partially filled them with sand.
At least there is one thing in the flat Sunny cant knock over.

The most recent change which isn’t shown in the pics is the rebuilt cabinets.
I shall try to get some pics up in the future.

The chair, well someone is bound to ask ……..
It is a car seat; recaro connoly leather which I adapted; it’s very comfortable.


Problems.
They need a much larger room than I have atm. They don’t really come alive until you feed them 15 watts.
They are most at home with anything that can loosely be described as popular music. They will do classical but much like their owner, they love a beat and a heavy helping of base.
However, even for chamber music they blow most commercially built units out of the water.
I’ve had some fun dragging them to a few dealers now to listen to the latest prospective bit of kit watching the dealer suspiciously eye up what are not very attractive and slightly battered black boxes only to hide his prize audition speakers a short time after the Volts fired up.
The weight
Positioning; the furthest I can get them from the rear wall is about 12” but I’m stuck with the side wall. To get the best out of these they need to be a couple of foot from any wall and 2.5 metres apart.

Even if I wanted too I couldn’t find anything to replace them that gets close to their performance at a price I could even dream about spending.

Stopping my three main Hi Fi conspirators from stealing them.


For some reason I still prefer FM radio for some stuff so the old NAD gets back into service.
Oh yes, please note the upgraded equipment rack with stainless steel floor spikes. Yep, it is/was a tea trolley. Sunny leant on the last table and it sort of fell apart.

My current place is far from ideal for Hi Fi and a few weeks ago I took the main bits round to a mate who has solid walls and floor in a well set up listening room. If there is an upgrade that makes a huge difference it’s the room your set up is in. I had almost forgotten just how good my kit sounds given the room to perform in.

Forgot the other source of noise.
http://www.mediafire.com/imgbnc.php/3cf9beee00db2decae44977b0c0f8ab02g.jpg (http://www.mediafire.com/imageview.php?quickkey=i5k0iv9ive59jgy&thumb=5)

[chris@panteg]

Interesting system , and a lot of work put into it , well done:)

[Rare Bird]

Nice i had Quantum 102 Pre/207DA Power amp/402 PSU..Later upgraded to 205's..Brilliant amps

[Welder]

Thanks for the comments Andre and Chris
Granted, it’s not big in the eye candy department but quite a lot of work and experimentation has gone into getting it to its current state.

I now have a dedicated socket for the laptop and Hi Fi. I hesitate to call it a dedicated mains supply which if done properly is separate from the household supply and earths to ground off the grid.
All the power cables are 1.5mm 2 core, mylar foil and copper braid screened. This can be done very cheaply if you avoid the audiophile products and build your own.
I recently built the Swampy filter Mike posted and incorporated it into my distribution box, hard wired using the above cable and round pin sockets. All the cables from distribution box to components, apart from the laptop supply which I am working on use the same cable with ferrites.

The Exposure amp has had the original toroidal transformer upgraded. I have also upgraded some of the board components, particularly on the output stage and board to inputs and output wiring upgraded. The XLR input mods are still in place but I have discovered that there is a bit more to balanced amp design than is immediately obvious.
The Exposure RC25 was imo one of the best integrated amps produced in that price range (around £1200)
It is extremely musical and involving with ample power to drive sensibly designed speakers, albeit at the expense of some finer detail at high frequencies and a slightly restricted soundstage if not carefully partnered. It seems to have bags of drive and enthusiasm without being in your face. John Farlow had a talent for amplification ;)

Similar upgrades have been made to the WAD headphone amp; a competent, valve based, simple design which has now I believe had a star grounding arrangement implemented, something I did at the initial build along with some cable routing changes. It’s a bit laid back, but easy to listen too with the 595’s. At the time of purchase it cost £200; now it’s closer to £500 with mostly cosmetic changes :eek:

I build my own cables. My current interconnects are semi balanced (apart from the XLR I built but no longer use)
I’ve tried a number of designs from the simple twin parallel wire arrangement as DNM to some fairly complicated mixes of wire diameters and arrangements shielded and unshielded.
My current interconnects use FT100 low loss coax as the starting point with the centre conductor removed and two of the channels in the dielectric very gently opened up (there are 5 air gaps in this dielectric so it’s not possible to get the wires exactly opposite) to take a twisted pair of differing diameter copper wire. I’ve tried various wires, silver. Copper with silver coating and I finally stuck with plain copper; one drawn from cat5E solid and the other a very fine multi strand. I get a friend to wind them on a lathe and then I impedance match them and feed them through the widened dielectric.
The main difficulty is opening the air gap in the dielectric to accept the wires and to get a half metre interconnect without splitting the air gap is a mission.
All joins are soldered and the unattached screen end is taken as close to the termination as possible and finally the joins are individually PTFE tape wrapped.
I’m about to try out some cables built using CTFC-T10 1028 which looks remarkably similar to the interconnects sold by Mark Grant bar the “vibration damping” outer sleeve :scratch:

I’ve also built various speaker cables but atm I’m using those shown in the pics.

The speakers have been an ongoing project for many years.
The most recent changes have been to the enclosures which increased in volume by 4.2 lites. The baffles have increased in thickness by 25 mm to 75mm, the outer edges sloped and rounded and the overall construction is a laminate of birch wood ply (inner) bitumen roofing felt (sandwich) and ¾ inch high density chipboard outer. The crossovers have been taken out of the enclosure and sited on the back of the speakers behind the high frequency units and the midrange had a 2db attenuation. I have also done a bit of capacitor swapping, mainly to smooth the higher frequencies and despite many speaker builders believing low pass filters are quite happy with electrolytics I’ve changed to Ampohm metalised polypropelene. Given I need 70 micro Farad at the lowest value the crossover has grown somewhat! :rolleyes:


The speaker build changes have made an improvement from what I can hear in the few trial listening sessions I’ve done. What has made a very noticeable improvement is repositioning the speakers. I now have them a foot away from the back wall and the left-hand speaker nine inches away from the side wall. Not only has this improved the soundstage, it has also placed the speaker’s midway over the floor joist which has helped with floor born vibration. It also seems I have knocked out what I assume was a standing wave problem in the midrange giving slightly clearer reproduction.

This is still WIP but I’ve tried the drive units out in the new enclosures and it all sounds promising. I may even veneer the sides. Unfortunately progress is slow. Decent enclosures are expensive to build in both time and money which I seem to have increasingly less of.

I’m also in the process of constructing some acoustic panels. I have enough material to construct around 8 square metres of ½ inch acoustic felt 2mm bitumen sheet and heavy weight carpet laminate which I have made and used before to good effect. The plan is to use 1 metre by 70cm panels behind the speakers and see where I go from there.

The tea trolly hi fi stand has also undergone a few mods. The stainless steel floor spikes are not fixed into steel lined rubber car suspension bushes let into the wooden legs. An extra strut has been added to improve the rigidity of the stand and the main shelf is now supported on a neoprene and Perspex undershelf (it sort of floats) with the granite slab still underneath the amp. Does it make any difference? I couldn’t honestly say but it was fun to make.

The struggle with persuading the laptop to give bit perfect unadulterated sound reproduction goes on. The main problems with my current Viao laptop are restricted RAM (1 Gig) and lack of processing power. It’s pretty quiet mechanically and has proven to be very reliable. I think the final answer will be a Touch if USB connectivity in and out becomes an option or a purpose built server which so far has produced the best “computer” audio I’ve heard.
While XP is fairly system un-intensive compared to Vista and Win7, Win7 or Linux seems to have the greatest potential for bit perfect sound and player flexibility currently.
I’m rather attached to foobar now and don’t really want the chore of finding my way around another player.

It would seem to me collect data from point A and send to point B should be the simplest task a computer can carry out. However, it seems this isn’t so; lots of audio management tiers want to get involved and trying to bypass them before the media player gets to piss about with the files is a nightmare :scratch:

A couple of things I think have improved the overall quality of playback in my system have been replacing the Belkin pro 0.5 metre USB lead with a 1.6 Belkin Gold and the addition of a 1 TB Hitatchi 3.5 mains powered remote hard drive.
It’s probably audio nervosa but if the USB lead change has actually made a difference I believe it has something to do with the extra length combined with the powered USB hub, but tbh I don’t know.
Initially I had some 50 Gigs of my “most listened to” music ripped with EAC using Accurate Rip to Flac on a hard drive partition on the laptop. I assume the improvement I believe I can hear may come from not having the hard drive spinning up in the laptop and possibly the extra processor power available to the stream.
I’m going to try out my galvanically isolated, regulated 5V USB power supply between the Dac and laptop again once the speaker changes are completed :mental:

The hardest change to come to terms with is facing up to the HRT Pro needing an amp that is designed for balanced audio to perform at its best. Despite being considerably cheaper particularly when the amp XLR mods and cable costs are taken into account the HRT Music Streamer 11+ sounds just as good to my ears. Fortunately the guy I sold the MS11+ to will has taken the Pro off my hands in a part exchange deal giving me back the 11+ and a bit of much needed cash so it hasn’t been a total disaster :steam:

I rather fancy revitalizing the Quantums. They Power Amp definitely need new power supply caps and new speaker output connections.
The Pre Amp also needs some attention to improve the Signal to Noise ratio and maximize its potential.
So far I’m considering the following changes.
Blue Alps volume pot
Bypassing the balance control
Upgrading the caps on the output
Signal leads replaced with screened leads
Making a new matching card to correctly match the Dacs output using the phono in option.

Like many here I suspect work is intermittent and financially times aren’t that great. It doesn’t look like things are likely to improve in the foreseeable future.
Thankfully I just have myself to finance these days.

One reads a lot about a systems ability to reproduce sound as if the musicians were in the room, detail, neutrality, soundstage etc, but the truth is what you get is what the engineer thinks is an acceptable mix and that often bears little resemblance to what the musicians played in the studio. Even live recordings are “played” with by the engineer prior to release.
For the recent past this has meant digital processing in the studio, upsampling, over sampling, effects added with all the artifacts and digital nasties audiophile’s strives to eliminate already present. This applies to modern vinyl just as it does to CD given most recording studios use digital rather than analogue equipment.
My conclusion, in the end there is no “right” or “better” sound in absolute terms, the best one can hope for is to reproduce accurately what is on the recording and that is not always the ideal sound for the listener.
The advantage with being a bit handy with a soldering iron and having a few electronic and acoustic measuring tools is with patience and relatively little money you can “tailor” your system to give a sound that you find of an acceptable quality and enjoyable to listen to in the environment you have at a relatively reasonable cost. Beats the hell out of spending thousands of pounds on new kit and having to believe it sounds better because you spent the money :lol:

[Reid Malenfant]

Now rest your weary fingers & joints after all that typing :lol:

Hi John, i just noticed something that i didn't spot on a previous look in ;) I see your speakers use 2 x 10", one on the front & the other on the back. Are they both being fed the same signal or are you rolling off the midrange to the rear bass driver (a little like a 2.5 way?). I guess this depends on where you midrange comes into play in all honesty ;)

I must say it's a great idea, it cancels out vibration induced into the enclosure as well as giving you a greater driver radiating area :eyebrows: Good job the Volts are designed to work in small enclosures, i commend you on the design.

[Rare Bird]

I rather fancy revitalizing the Quantums. They Power Amp definitely need new power supply caps and new speaker output connections.
The Pre Amp also needs some attention to improve the Signal to Noise ratio and maximize its potential.



A definate upgrade for the '102' pre would be to try source a '402' power supply so it's got it's own power source instead of taking it from the '207' they are hard to come by these days, their half width the same as the '102'..That was a huge improvement for me..

[Welder]

Hi Mark
I would love to be able to say I designed the speakers but it wouldn’t be true.
The original design is by David Lyth of Volt Loudspeakers, i've rebuilt them with minor design changes and his assistance.
The unit at the back isn’t a drive unit; it’s a ABR (auxiliary bass radiator)
However, the resonance canceling factor still applies and while it is a tuned unit (optimal radiation at a particular frequency, 20 Hz in this case) it does assist the front driver throughout its range.

The most dramtic impact so far has been the use a variety of makes of polypropylene caps to replace the original electrolytics; hardly surprising given they can operate at 50x the speed, have higher voltage tolerances and considerably lower leakage and ESR.
Some care was taken in choosing the replacement mid and hi range units (both matched). Scanspeak have long had a reputation for very high quality drive units.
They sound gorgeous to my ears and are brick wall filtered at the bottom end to prevent and sloppiness in the bass.
I have tried a double bass driver in another build but the crossover proved to be over complex for my design skills.

Andre.
Thanks for the tip. I had looked into a separate power supply for the Quantum’s. As you can imagine the 402 quantum marketed is virtually impossible to come by now.
Once I’ve sorted out the obvious I may just take the supply out of the 207, beef up the regulation and upgrade the transformer.
From what I can remember about the sound of the amps they had exceptional control and grunt. My opinion is while the topology of the pre amp is decent, the quality of the components could do with some improvement. Hopefully with the changes I outlined above

[Reid Malenfant]

Hi Mark
I would love to be able to say I designed the speakers but it wouldn’t be true.
The original design is by David Lyth of Volt Loudspeakers, i've rebuilt them with minor design changes and his assistance.
The unit at the back isn’t a drive unit; it’s a ABR (auxiliary bass radiator)
However, the resonance canceling factor still applies and while it is a tuned unit (optimal radiation at a particular frequency, 20 Hz in this case) it does assist the front driver throughout its range.

The most dramtic impact so far has been the use a variety of makes of polypropylene caps to replace the original electrolytics; hardly surprising given they can operate at 50x the speed, have higher voltage tolerances and considerably lower leakage and ESR.
Some care was taken in choosing the replacement mid and hi range units (both matched). Scanspeak have long had a reputation for very high quality drive units.
They sound gorgeous to my ears and are brick wall filtered at the bottom end to prevent and sloppiness in the bass.
I have tried a double bass driver in another build but the crossover proved to be over complex for my design skills.
:doh: I realised this before i decided to reply :eyebrows: A quick scan of your signature revealed the truth :o

I honestly don't know why this never occured to me as i was recently watching some Volt speakers with ABRs on fleabay, ah well, call it old age creeping up on me :) They still look very nice & purposeful...

I agree 100% with the capacitor replacement, you can't beat film caps for crossover duties & also a rather good idea to as you call it "brick wall filter" the bottom end, though this needs to be done carefully to avoid too much phase shift. As your enclosures are actually pretty big for the driver parameters i'd expect a gradual roll off of bass as it gets deeper, unless of course the filter used was a peaking second order high pass (12Db/octave) in which case you'd get a flatter response & the brick wall filtering with little phase shift.

I'm sure they sound great ;)

[Welder]

The Loudspeakers

I want to make a point here, cabinets are something you use for display purposes’ enclosures are something designed to contain a function. I build enclosures :)

My view of sealed box enclosures is the less they resonate the better they sound.
If you can achieve zero resonance then in theory all you hear is the drivers and the ideal box just supports them and supplies a volume of air for the driver to work against.

I had calculated that with the Scanspeak midrange and hi frequency driver replacement and the slightly stiffer than original Volt suspension surrounds roll replacement, a 4 litre increase in internal volume might improve the overall performance. I wanted to keep the exterior width dimensions, the reason being the speaker stands I built for these are designed to support the enclosure at the edges with a single central cross strut joining the two sides at the top. This design would seem to have the best chance of not transmitting any vibration into the stands because the support is at the point of highest material density.

The sides, back baffle, top and bottom were all constructed using 12mm birch marine ply as the internal layer, then a 2mm layer of Dum Dum, then a sheet of bitumen roofers felt, another 2mm layer of Dum Dum and finally 18mm High Density flooring grade chipboard.
Dum Dum has great damping properties and was originally used to seal and prevent panel vibration on Morris Minor Travelers, (Woodies or estates to our American readers)

Each enclosure panel was made by gluing a 38mm x 6mm hardwood strip to the outer edges of the pre cut Birchwood ply panels making what could be described as an edged tray. A uniform layer of Dum Dum was achieved by laying strips in the tray and repeated use of a rolling pin to get a uniform coverage to the correct depth. Next the bitumen sheet was placed in the tray and the next layer of Dum Dum applied. The bitumen sheet might seem unnecessary but unlike the ply or chipboard, Dum Dum sticks to it and prevents it from pulling up when rolling it flat. Finally the Chipboard panel is laid on top, glued where the edges contact the hardwood strips and a row of hardwood dowels are driven in reamed holes around the edge of the panel. Basically what you end up with is sealed frame filled with Dum Dum.
The bottom panel is slightly different being filled with a single layer of Dum Dum and a sheet of roofers lead.

The sides, top and base were assembled using glue, more dowels and staggered decking screw in pilot drilled, countersunk holes. The whole assembly was kept square using an internal cross frame and clamps while the glue set.

Next the rear baffle was rebated and hole cut. I cheated a bit here and having scraped out the Dum Dum filling to a depth of 10mm, cleaned the exposed surfaces to remove any Dum Dum traces; I filled the gap with wood filler. The hole was tapered by 5 degrees front to back and the internal hole edge sanded to a 5mm radius.

Two rectangular plywood braces with a central cross strut, with rounded inside edges were fitted, one just above the bass driver and ABR, central strut going from left to right and the other between the midrange and tweeter going back to front. A central vertical brace was also fitted, running from back to front on the box base cut to exert slight pressure on the back of each driver magnet and support it at the six o‘clock position. These were screwed and doweled in position.

I’ve had a salvaged badly stained and damaged solid beach worktop knocking around for a bit and I decided to use that for the front baffle, it’s 38mm thick and I just managed to get two 60mm X 34mm sections out of it.
http://www.wickes.co.uk/Solid-Dark-Beech-Worktop/invt/324593
Apparently a plumber has scorched the underside during fitting it, brought it back to supplier who then left it in the warehouse where it got run over by a forklift. I paid the warehouse man £30 to “liberate” it :eyebrows::lol:
I had this machined for me, holes and rebates. The front edges were given a 25mm radius to help prevent edge diffraction, the holes tapered to 5 degrees

At this point I fitted the ABR and bass driver to check that the magnets were indeed supported and touching the brace in the horizontal plane. After a bit of adjustment all seemed well and I got on with the interior.

I glued and stapled 6mm vehicle under carpet felt to all the internal surfaces slightly overlapping in the corners.
The section above the midrange driver brace was filled with loose rolled Monacor MDM3.
In the midrange section I cut MDM3 panels and used a contact spray adhesive on the panle edges to glue them to the felt at the back and sides and for the front I cut an over sized hole so as not to obstruct the air movement directly behind the midrange driver and glued that in place. I then wedged rolls of MDM3 in the edges creating a soft sided box around the driver.
I used glued eggcrate acoustic foam on the sides and base of the bass driver section and made similar MDM3 rolls as above for the edges leaving a fairly large open space for air to travel from the driver to the ABR.
Finally the front baffle was glued, doweled and screwed in place and any slight overlap at the outside edges was sanded flush.

The crossover is mounted in an aluminum box on the outside top rear of the enclosure.
The crossover box is surrounded by 50mm X 12mm hardwood (I think its oak) and I made a cover in the same wood all salvaged from an broken dinning table someone threw out that I liberated from a skip a while ago.
The crossover box and surround is the same width as the enclosure and the lid has a similar radius to the front baffle.
The base of the crossover box arrangement has six 12 holes drilled through it and the top edge of the lid has the same to aid the flow of air across the crossover components.
The WBT speaker terminals are mounted on the underside of the crossover box and cable entry into the enclosure is done by forcing the wires through a ferrule and then pulling the ferrule and cable together through a a set of pre drilled holes in the back baffle. This keeps the box airtight.
I made my own internal cables using braided solid and multi-strand Cat 6 PTFE coated OFC copper; six opposite direction braid sets 50/50 solid and muti strand mix covered in heat shrink. The cables are soldered directly to the drive units using high silver content solder. All the internal cables are the same length 50 cm and have enough slack to rotate a driver 180 degrees.
The tweeter and midrange are mounted on small rubber grommets set in a ring of Dum Dum and tightened with a torque driver so that the grommet deforms enough to hold the driver steady but not enough to transmit vibration to the front baffle; that’s the theory anyway. The Dum Dum squeezes around the outer edge of the driver face plate during the tightening process and gets trimmed off with a hobby knife. I clean the back off after assembling.
The bass driver and ABR are also sealed to the baffles with Dum Dum but no grommets and done up tight.

I achieve, approximately, the 4 litre increase in volume without major changes to the exterior dimensions, despite some extra internal bracing and felt. The enclosure is about 8cm deeper than it was and 10cm taller. Moving the crossovers to outside and the thicker baffles which pull the magnet further out have all added to the internal volume.

The finished enclosures are 62cm x 32 x 42. With the crossovers they weigh 72 kg each.
Atm the enclosures are painted in black satin Plasticoat.

I took my time building these. I fell in love with them when I first heard them some 30 years ago. They’ve outlasted a wife, a few lovers, countless moves, seen two kids grow up and my hair go grey :mental:
I did try once to estimate what they would cost to buy and in materials alone the figures got scary :eek:
They don’t look like much in the pictures above and they haven’t got any prettier. They sound awesome though.
I couldn’t have kept these going over the years without the help and advice of David Lyth of Volt Loudspeakers, Wilmslow Audio for sourcing drivers, and my mate Steve for letting me use his garage and woodwork tools.

If you’ve managed to read all this you may now understand why a wry smile spreads across my face when 12mm MDF cabinets covered in veneer are mentioned :doh:

[Welder]

USB power supply

Tell most audiophiles of my generation that a USB Dac with galvanic isolation and asynchronous transfer doesn’t transfer computer generated noise into the analogue stage and jitter is dependant on the Dac clock and has little to do with cables and computers they just don’t believe you :doh:

Now I know many audiophiles would rather look at pictures of racks of impressive looking boxes than read a lot of boring specifications so I have tried to keep the links relevant and hopefully informative ;)

File based audio and in particular USB power isn’t without its problems though and depending on the make of the computer and which type of USB implementation it has determines the amperage and voltage you will be able to draw for a particular device from a particular port.

http://en.wikipedia.org/wiki/Universal_Serial_Bus
http://www.pcug.org.au/boesen/USB/USB2.htm

My HRT Pro uses USB 1.1, draws 350mA and outputs 4.5VRMS and is asynchronous.
I’ve never been quite sure whether it’s the 100mA packet draw problem or the closeness of the Voltage to the max available for USB (5V nominal 4.75 to 5.25) but the fact is the HRT Pro Dac sounds noticeably better when powered from an independent USB hub and so imo does the HRT 11+ :scratch:

I read in a review of the HRT Pro (rather comical given the guy was assessing a pro audio fully balanced Dac linked to an amp that only had balanced connections and not a proper balanced audio circuit not to mention his problems with getting the computer to recognize the Dac :lol:)
http://www.6moons.com/audioreviews/hrt2/pro.html
(Don’t you just love Hi Fi reviewers)

However, it did set me off on a quest for a non computer based USB power supply.

I started off with a mains powered linear, but poorly regulated, wall wart USB hub.
This did give an improvement in sound from both the HRT11+ and Pro but the hubs voltage fluctuated from 3.4 V to 6.8V and barely managed 3.6mA! :eek:

It wasn’t quite as badly done as this
http://commons.wikimedia.org/wiki/File:USB_Hub_Internals.jpg :eek::eek:
I very much doubt this would supply 500mA and 5Volts to all the sockets should you plug in more than one peripheral.
What the above does show is in theory at least, the possibility exists to directly connect a 5V supply to an adapted cable or plug.

After some fairly extensive research I came across this and bought a full kit.
http://www.circuitsathome.com/products-page/usb-interfaces :mental:

There is also this,
http://diyparadise.com/shop/index.php?main_page=product_info&cPath=3&products_id=124
Unfortunately this (circuitsathome) has a mini switch mode regulator on the board and given my soon to be connected dedicated power supply, I don’t really want switch modes possibly feeding noise back into the dedicated line. There is a way to bypass the supply on the board
http://www.circuitsathome.com/mcu/usb/linear-power-supply-on-usb-isolator-board
This is more like it, but it still needs a wall wart and case although I can’t see why a better ac supply couldn’t be connected.

I assumed unlike a remote hard drive or an amp the current drawn by the HRT is going to be fairly constant. If I provide twice the required current available then all I need is a supply as close to 5V (USB has a + and – 10% tolerance) as I can make.
You could of course buy such a PS.
http://www.paulhynesdesign.com/page7.html
:eek:

This makes an interesting read.
http://www.dxing.info/equipment/wall_warts_bryant.dx
I could knock that up using a wall wart :eyebrows:

I also considered something like this
http://www.circuit-finder.com/categories/pc-related/usb-devices/726/usb-power-injector-for-external-hard-drives :doh:

If you can wait a while
http://www.twistedpearaudio.com/power/placid.aspx
which does look to be very good quality and very reasonably priced :)
(The Dac is bloody brilliant by the way)

This looked more like it :)
http://www.discovercircuits.com/DJ-Circuits/+5V%20Transformer.htm

I had a few schottky diodes. I also happened to have a 230V input 7 volt 1.2 amp output transformer salvaged from a valve amp. You could probably manage with a good quality 230V/6V and still get 5V out of the above circuit if you pick the regulator carefully. As with everything the better quality the components and the tighter they are toleranced the more chance you have of producing something to the desired specification.
I used Rubycon ZA caps for the 47uF values and Panasonics for the 10000uF which I already had. I used the regulator suggested in the text. I hard wired everything on a piece of tufnol board with the intention to improve my temporary heat sink arrangement once I had tested the project and picked an enclosure.

I didn’t really want yet more USB connectors in the data path so after a bit of careful surgery on the circuitsathome ADUM board I was left with what they sell as the Isolator only kit suitable for direct 5V input but without the USB connectors.
I decided to adapt a 1.8 metre Belkin Gold USB (dontcha just love Belkin, you wouldn’t want to be doing this with your Wireworld Starlight :ner:) and cut out the centre of the cable. For my arrangement, B plug end cut at 150mm and 500mm on the A plug end leaving an extra 50mm of shield at each. I then soldered D+, D- and power wires directly to the board and joined the shield and connected up the power supply using a single twisted pair of Cat6.

USB hub controllers are a bit fussy about the order things are plugged in (more info about this on ciruitsathome Faq) but as long as I plugged in a live B plug into the Dac the controller recognized the HRT and music was forthcoming.

Right, for you regular AoS readers I want you to bear something in mind here, my name is John, not…………………….:lolsign:
Ferkin marvelous, not quite night and day but definitely getting on for dawn and dusk ;)
I knew the HRT liked a more voltage and current than my laptop or PC seems to be able to feed it to really shine but I hadn’t expected such a noticeable improvement with the better quality power supply and ADUM chip combo given the already excellent noise rejection of all the HRT’s.
I’ve tried it with batteries and it didn’t sound quite as good.
I’ve tried using just a wall wart and that didn’t sound as good either.

These ADUM boards are excellent if you have a USB Dac that isn’t particularly well designed regarding noise rejection and a great many aren’t. Plus, you have the option of greatly improving the power supply off board.
I tried it out on a mates USB NOS Dac and had to wrestle the cable and PSU from him on his way out.

Okay, once I had got it all in a small enclosure (I used a bit of capped copper pipe covered in heat shrink in the end) connected the cable shield to the box and got ferules sticking out in three places it’s a pretty odd looking USB cable.
If you’re a terminal USB cable swapper you’re a bit stuffed on this one but if you bought a decent async Dac with an isolator in the first place you wouldn’t have to piss about with the cables anyway :ner: