Step-Up Transformer Project

I had upgraded my cartridge on my Rega Planar3 by replace my cheap shure with a Grado wood body Platinum Reference. But even through a Project SE phono amp and a valve preamp the signal level was low. The Grado cartridge is a MM variety and I knew K & K Audio had a MC tranni kit. On an enquiry to them they provided me with a MM tranni kit. The Lundahl LL1550 amorphous trannies and cct. brds were configured for my cartridge and fitted in the wood box the cartridge came in.

Silver wire and WBT silver solder was used throughout. Sticky bitumen coated thick aluminium strip was used to shield the wood case and vinyl speaker dampening glued to the inner lid. The trannies were Velcroed to the inner lid and low profile felt feet added to the bottom. The sound is just as pure and now just a little louder. The trannies also provides some dampening back to the cartridge and the cartridge accurately loaded.

Headphone amp cct. brd

The large input caps block the other components from view but you can see how small this whole amp is. Smaller input caps could have been used but I wanted to use locally available metal film polypropylene caps. The original cct. uses .22uf but on a friend's suggestion I use .47uf. Even the power caps (330uf low ESR) fit on the brd. It could not be more compact if you tried.

Computer style adhesive stand-offs with rubber grommets provide easy and removable mounting. The inside of the box is lined with sticky bitumen coated aluminium thick foil. The amp is dead quiet when listening so all the trouble I went to to shield the cct. from RFI etc. was successful. A very satisfying and easy project. And no big PSs or high voltage to scare off the novice. In timber or tin this project was very successful.

The Wooden Cased headphone amp

Inspired by the the headphone amp on diyaudioprojects and after purchasing a wood body Grado phono cartridge, I decided to make my headphone amp in an old Essential oils cedar box. Grado also make a wooden cased headphone amp but a friend said he tested the CMoy styled amp against the wooden boxed Grado and believed his to be better sounding. The owner of the Grado headphone amp agreed!

I never intended this headphone amp to be portable. Though the amp weighs very little it is bulky. All connections are at the back. An aluminum strip at the back of the amp holds all the connectors and the on/off switch. Large holes had to be drilled to take the body of the connectors and drilling the soft cedar was difficult without causing damage. Movable compartments inside the box allowed my to have separate battery and amp cct. brd. areas with two spots for spare 9V batteries. Aluminum and bitumen adhesive (flashing) strips line the whole inside of the box and speaker dampening vinyl also lines the lid.

Cotton coated pure silver (.4mm) wire is used in the signal path. Over size power caps (330uf low ESR) and polypropylene input caps (.47uf) were mounted on the tiny cct. brd. with all the other components. I wanted the passive parts as close as possible to the OP amp chip the OPA2134PA. The chip was socketed with a gold pin socket. The cct. brd. was mounted on plastic stand-offs encircled with rubber grommets (resonance reducing). Two 9V batteries and a voltage divider network provide the +/- 9 volts for the chip.

The test set-up was a portable CD player with a line-out, new Grado SR80 phones and my home made Cotton ConneX cables. Bass was a bit muddied and there was a nasaliness in female vocals. A NAD C542 replaced the portable player and things got a whole lot better! I'm usually a speaker freak when it comes to listening to music. But two hours latter I was still glued to the lounge in a world of my own listening "up-close-and-personal" to both live and studio recordings. How would I describe the amp - "GREAT"!

Synergy Chip Amp

The Synergy Amp is by far the best sounding amp I have ever built. Taking the concept of using inexpensive baking dishes for chassis one step further I grabbed the heaviest cast aluminum (3mm thick) Teflon coated baking pan I could find and torqued it down to a super thick timber chopping board. Using the principals of a mass-loaded amp the active amplifying components almost become a minor consideration. Now chassis and active components move-as-one, pure Synergy. The amplifying "bits" are a minimalist chip amp (LM3875) bolted to the underneath of the chassis under the heat sink.

This 26lb retro looking monster is dead, dead quiet with no signal. When played it delivers big time. Punchy, clear and a massive sound stage. The sound does not appear to emulate from the speakers but leaps from the wall behind and to the sides on the speakers.

The big caps are 10,000uf 100V electrolytics, the plastic rapper is pealed off and a red coat is sprayed on. These are by-passed by 10uf polypropylene and .1uf green caps. The 10uf caps for better mid-range transparency. 160VA toroidal tranny powers up the 50W RMS pc amp and a well snubbed rec. bridge provides clean power. The massive heat sink on top helps with cooling but also adds some extra weight directly above the chips. Pure silver wire is used for the sig. path and OFC use for the power wiring. Extra heavy copper wire connects the speaker binding posts to the amp output pins.

There is NO cct. brds,. at all in this amp. It is all point-to-point wiring. The passive compenent s are woven into the chip. The chassis is torqued down to the chopping board by two ¼” bolts, spring washers and wing nut. An RFI filter cleans up the 240V power and aluminum and pitchmen flashing covers the internals surface of the board to provide additional shielding and more resonance deadening. The amp plays extremely well and was in-expensive to build. It has now replaced my monoblocks as my main amp. Check-out the full write-up on diyaudioprojects.

Under the chassis of the Synergy amp.

The Synergy breaks all the rules by making the chassis far more important than the active components. As you can see no cct. brds, all point-to-point wiring, minimalist chip amp construction now turns the sound focus to the chassis. This concept was born in the original Gaincard amp. Low component count, a big quiet PS, short feed-back path solid chassis and quality parts. Where my Gainclone varies strongly is in large line capacitors. Usually Gainclones have small 1500uf line caps. This amp features 10,000uf caps! Another stunning quality of this amp is the stereo imaging. Is extended and multi-layered. A very revealing amplifier.

DIY afternoon with the MAC

From my first meeting with the Melbourne Audio Club I got into one of the break-out group meetings. This one was held at a member's house and it was to show off his new Millennia amp. This is a solid state discrete component power amp capable of 120W. All equipment here is DIY except for the unusual speakers which have also been modified. A BBQ and some drinks stated the afternoon but soon the gear was warmed up and the music started. All music is played from hard drive and controlled from within iTunes and operated from the owners comfy chair. There is way too much very specialised gear here to go into but basically from media center to valve preamp and then the millennia power amp. The sound was excellent and all who attend commented on the beautiful balance of components. The builder hadb an exceptional eye for detail. The Millennia was a work or art both aesthetically and auditory.

Jean Hiraga-symmetry and Croatian Circuit boards.

Jean Hiraga designed and built an number of symmetric amplifiers which were renowned for purity of sound and natural tone. I love the design philosophy of an amplifier which not only says it is symmetrical but looks symmetrical in circuit and build. These circuit boards I ordered from Croatia and are extremely well made, you guessed it, symmetrical in appearance as well as layout. Jean did state that the boards should not be solder masked and these are. I can only imagine the difference in tone and performance. The mask remains.

What you see in this image is the assembled circuit boards and their related heat sinks (HS). The HS(s) will form a part of the case by employing some heavy aluminium panels, self tapping screws and isolation feet (you must check back to see this). This ensures vibration and resonance issues are controlled. The power supply will be assembled around 60,000uf of filtering, ultra fast diodes, PS snubbing and EMI and RFI reduced, high current deliverable power. The quietness and beauty of this 8 watt audio amplifier lays not in multi-stage, multi-feedback enhanced "more stages are best" design but in its simplicity, ability to deliver and balance of design. Not to mention NO signal caps AT ALL! Not even line caps on the circuit board. Want to find inner musical peace:- Jean Hiraga

Finally this amp is complete and sounding excellent see the new images above. See the retro-thermionic blog for more details.

Columbia and Spice Engines

We have seen audio amplifiers move from valves to transistors. Of course the next step on is to place many transistors on a single substrate. Yes the integrated amplifier or monolith is born. Not integrated in the normal way we think of amplifiers with preamp, attenuators, selection switches, tone controls and power amps all combined under the one lid. But integrated depletion layers and resistors on a tiny slab of silicon. Less than 1" square and weighing but a few grams some of these chips can put out 100s of watts. My axe of choice when it comes to chip amps is the LM3875. My nanoo and mono blocks use the same chip and the amp modules shown here are what I base all my chip construction on. See the next Blog for more detail about these powerfull little amps or visit diyaudioprojects.

Spice Engines (LM3875 with 2000uf of low ESR line cap) are used in my mono blocks. In the nanoo the same chip was used with 5,600uf caps which form a Columbia Engine (bigger caps-the one pictured uses 10,000uf line caps). I have currently built Spice Engines with 1000uf low ESR line caps for a special project yet to be completed. Why the small and large caps? Simple, the smaller the cap the better the mid range especially with low ESR caps. You may lose heavy bass or extreme dynamics at high volumes with this design though. So I build different engines for different amp uses and styles. If you constantly played loud hard rock with difficult speaker loads-the Columbia Engines would be for you. Quiet jazz or simple jazz or classical trios or a lot of acoustic content with vocals-Spice Engines.

I always use the same chip amp PS. This has not varied to date. Usually UF diodes are employed but the one pictured used a diode bridge. As you can see from the photo the amp modules are very easy to construct and build into a full system. See the next Blog for more information. As noted below I will build these amp modules for $90 each.

Columbia Engines - Chip amp modules-LM3875.

What no printed cct. brd? With such a small component count (only three resistors) and the opportunity to do a little point-to-point wiring, why go any other way. These Columbia Engines (LM3875 chip amp modules with large line caps) lend themselves perfectly to this type of "get-your-hands-dirty" construction. With the ability to deliver an easy 56W RMS pc @ as low as .06% THD, these small, powerful and excellent sounding chip amps can be the centre of any high-end amplifier construction. The Gaincard from 47 Labs is based on a similar chip.

This is a view from the bottom and from here you can see the line cap (10,000uf) snubbers (.1uf polies). Also obvious is direct wiring to the the amp module with no clamp-down or plug connectors. Every connection is direct soldered. All wiring is heavy duty. Earth is a perfect "star" configuration. I use the component leads as part of the cct. Less than 1" of additional heavy duty copper connecting wire is used on the cct. brds. and this is an all one piece wire which is also the Ve- PS wire and part of the fuse assembly. The rest of the "hook-up" wire is the component leads themselves. No hook-up wire, no printed cct.

Resistors share the same mounting hole as the chip leads and are rapped around the chip leads, with one other connection if required and silver soldered all together. No tracks, no additional hook-up wire no added signal path length. The feed-back resistor is also mounted in the chip lead holes resulting in a feed back path the total length of the .5 W metal film resistors itself. And with the whole chip less than an 1" long, and this is the amplifier complete, you can only guess how fast these chips are. With excellent PSRRR and SPiKe these chip are very tough and dead quiet. Don't want to build your own - I can supply for $90 each (minimum of two) including in-line fuse housings and fuses. Why not build your own. Here's how: diyaudioprojects

MAC - Melbourne Audio Club - second oldest in the WORLD!

I had been looking for the MAC for some time but for whatever reason could not find it via the Internet. My Canadian friend Gio (see his diyaudioprojects site) lead me to a local site which sells cotton insulation. From a link on that site I found the MAC site. And believe it or not they were meeting that night. You can "try before you buy" so I went along. They had two very nice pairs of Canton, German made, speakers powered by Hugh Dean's Aksa Lifeforce 100 W transistor amp and a pair of 50 W valve mono blocks (under the table). The CD player was a Marantz SACD unit and all preamped through Hugh's GK1 valve preamps (valves ECC189).

The Group meets on the third Wednesday of each month and they have also break-out groups of:- Pop, Opera, Classical, DIY etc. Plus restaurant nights. And they have been doing this for 33 years to-date. I'm off to their Hi-Fi feast night where (amongst others) Halcro will be displaying their incredible goods. I also snuck into a DIY group to be convened in early June at a members house.

Good carefully chosen music was played across combinations of amps and speakers. For my money the best sound was from the Karat (silver outside speakers) and Hugh's Lifeforce tranny amp. The speakers are voiced very accurately and for me probably a little forward. The other speakers, Ergo (brown ones), were too boomy on bassy tracks with the bass also a little muddy. The Ergo(s) didn't really shine until classical was passed through them. Great night.

From No-Fi to Hi-Fi

So how good can 12 litre $AU60 speakers sound. If you say "like rubbish", you would be close. When I first listened to these Dick Smith Electronics (DSE) small bookshelf speakers I new I was in for a challenge to get them to sound even half reasonable. I was also certain they were really only being let down by one component. The tweeter was an insult to the words "design and manufacture". The tweeter had to go first and foremost. The Xover wasn't much better.

Now for the good points. They look good though in simple black. Not like $10K speakers but appeared well made from a low density particle board. The woofer/mids are small but the bass is well extended (comparatively) and as long as they are not driven hard, appear well balanced though a little inefficient. They come with GOLD speaker binding posts and have a bass port.

Firstly I replaced the tweeter with a $AU19 mylar, ferro-cooled, shielded variety, with phase plug. Instant improvement. The Xover (what there was of it) was replaced with a high wattage 12db roll-off, air cored chokes with upgraded metal film polypropylene speaker caps. The terminal plate was upgraded but the original gold binding posts were recycled. Heavy copper speaker wire was used for internal hook-ups and lots off additional dacron was used to line and dampen the boxes.

Hi-Fi came to No-Fi speakers. In my system the tweeters were to dominating over balancing the small woofer. A -6db reduction in the tweeter volume with non-inductive 5W resistors (maintaining 8 ohms impedance) was implemented. Now you're listen! The bass port had a restrictive grate. This was cut-away and the opening smoothed out with a file.

I absolutely love these speakers. These are the only speakers I use in my current system. Yes, the bass is not ball shaking deep. They are small woofers, it ain't "gunna" happen. BUT the bass that is there is weighty, precise, clean, controlled, tonal, room filling and thoroughly enjoyable. I do have them out from the wall a good way and they sit atop heavy duty stands. BUT the sound stage from such a small box is razor sharp. Each instrument is clinically defined, sits in it's own space and time. The two boxes are 2.5m apart and if you walk toward the center of the speakers the sound stage leaps out and grabs you. It is not imaginary. I have tested this with a number of armature listeners and I always get a startled reaction.

So you CAN morph cheap speakers into good speakers. The thin timber walls do flap a bit. They ARE light weight. The bass could be more extended. Yes, I know all their short comings but $60k speakers have short comings too. What really appeals to me about these diminutive bookshelves is their accuracy, sheer speed, chiseled sound stage, clear crisp mids, beautiful highs and cute looks. For a total cost of $AU200 these babies speak with a razor tongue. If I purchased them from a store for $600 I would deem then good value. But the real value for me comes with the knowledge that I made them what they are. Should you feel the urge to own these precise little speakers, I can produce a pair for you for $400.

Silver Highway Interconnects for $AU60

Since my first quality CD player I have used high-end interconnects. My first pair was Transparents 200 which I was sold with my NAD C542. Then a second set of Transparents and finally Nordost Blue Heavens. The last lot cost me $AU300. I had been using silver wire as hook-up wire for some time in amplifiers and wondered if I could turn bare, pure silver (99.99%), wire into quality interconnects. What you see above is the result and the answer is a definite "YES"

"How do you make them"? It has to one of the easiest and most satisfying projects I have done.

1. Cut your silver wire into six 1 meter lengths or as long as you wish to make them.
2. Clean and polish the silver wire - I used Silvo cleaner but make sure you polish it off. From now on do not let the bare silver wire touch your skin-you will contaminate it.
3. Cut thin heat shrink tube to length about 2 cm shorter than the wire. Use the thinnest heat shrink you can. Three different colours. I used White for the drain, Blue for ground and Red for active. Shrink it with a proper heat gun working evenly from the center out. Don't over heat it. NO hair dryers it is too uneven.
4. Bring the wires together and tight twist 5 cm from the end for about 3 cm. This is just to hold the wires in place.
5. Place some protective spaghetti over the bare wire at the twisted end and lightly clamp and secure the end. After platting remove the spaghetti.
   
6. From the secured end plat or braid the three wires firmly. At about 8 cm from the free end twist the wires for 3 cm to hold it all together. See this site for design info: - Black Art
   
7. Free the clamped end and feed the platted trio into firm fitting heat shrink of either black (or blue) for left channel or red (or white) for right channel and shrink it back leave the last 3 cm at each end uncovered. Again work from the center out.
8. Slid two same colour and same thickness 5 cm lengths of heat shrink onto the trio and the connector covers so when you solder the connectors on you can screw the covers up.
9. Trim the bare ends and solder to your connectors. USE SILVER SOLDER AND USE GOLD PLATED CONNECTORS. The gold connectors are not expensive and look great. Mine have red or black rings designating right or left channel.
   
10. On the source end (you decide which that is) solder your drain but DO NOT solder the drain at the termination end. My drain was white so I only solder the white wire at the source end. Cut the drain wire at the destination end. Connect the two other wires as normal.
11. Now slide up the 5 cm of additional heat shrink you fitted earlier. Cover the internal tags of the connectors. But it up hard to the screw part of the connector but do not cover the screw part.
12. Shrink back the additional strips these should poke well out from the end to add a little strength to the cable ends and cover the internal solder tags.
13. Screw up your covers. Rap some electrical tape on the termination end about 5 cm back and clamp on a ferrite choke. Use the tape to get the choke to bite in and hold without over pressuring the platted wire. No under pressure-you will alter the cables performance. The chokes help reduce RFI into the amps. The drain leaks it back to the source.
    
14. Plug the choked end into your termination in my case the power amp. The other end should go to your source for me that is my valve preamp.
    
15. Plug and play. Do not over bend the cables and no hard kinks. Once more you will alter the cables performance with small radius bends or hard kinks. Worse you could short the cable. They bend OK but keep moves and changes to a minimum.

"So how do they sound"? The first thing I notice was a huge lift in detail and sound stage. A dramatic refinement of mids and extended clearer highs. I have made a 1 meter pair (from preamp to power amp) and a 1/2 meter pair (CD player to preamp, pictured above). I think they beat my Nordost cables hands-down and a fraction of the price. If you do not want to make your own but simply MUST HAVE a pair of SILVER HIGHWAYS I will prepare a 1 meter pair for $AU120 plus postage. Check out Gio's diyaudioprojects for more info.

Under the bonnet of my latest tube preamp

The gold RCAs look stunning against the mat-black diecast case. This shot is electronic pornography. But the whole project was a juggling act trying to get all the parts in a compact case. I must have placed the cct. brds. in this case fifty times trying to squeeze everything in the right place before locking them down. They sit on adhesive computer mounting posts each fitted with rubber grommets to reduce resonance. This allow a construction with no nut heads in the top or bottom. You would not using adhesive stand-offs with heavier parts.

The large Sprague caps were mounted on the bottom of the brds. and then laid over to allow the lid (bottom) on. The SMPS is shielded from the other brds. to reduce induction into the preamp brds. There are dual inputs which are switched and an on/off switch at the front with a trendy blue led. Though a difficult project, due to cramming parts into a case, the results are worth the effort.

Valve preamp III

This the third of these 12AX7 based preamps I have built. And each time they do not get any easier. This is the first I have constructed with the valves protruding. To do this you must mount all the bigger components on the bottom of the cct. brd. The smaller resistors have no problem fitting on the front side. The Sprague "orange drop" audio caps I use are huge so not only do you have to place them on the bottom of the board but you have to lay them over. In future Blogs I will show the inside of the compact die cast case and you will see how cramped it is.

There is a lot which makes this preamp special:- Pure silver (.7mm) hook-up wire for all sig. connections, snubbed amp and PS board, dampened stand-offs and dampened die-cast case, heavy brass isolation feet, RF choke of plug pack lead, gold plated isolated RCA connectors, Golden Dragon 12AX7s and valve rings. Speaker plastic/rubber dampening material is glued to the inside of the case which adds weight and helps control resonance in the case and ccts. A shield was also erected between the PS and amp brds. With the SMPS and two amp modules in the case there was little room left.

I have been pleased with all of these kits I have built but especially this one. It looks and sounds sensational! They sound so sweet and add a nice rich harmonically textured sound to dryer amps. I would not use it with my valve power amps but with my chip amps (LM2875 see other Blogs) and ZCA (Zero Component Amplifier-single MOSFet per channel) sound stage and total music depth are enhanced dramatically. They are a cheap Jaycar (Australia) kit which has now been discontinued. With a little help from some friends (much better parts and construction TLC) they do magic-relay magic.

nanoo and PS

With only the desire to build something small, being motivated by the Patek, the nanoo was designed. It is based on the LM3875 amp-on-a-chip (chip amp). See the other nanoo blogs for a full description of the amp. I generally use heavy glass plate on thick silicon feet to isolate all my equipment or thick Italian marble. These isolation plates will appear in future blogs so call back. I have changed the solid brass feet seen here to one at the front two at the back. Also I have removed the adjustable part, lowering the amp by a center meter or two.

The idea is the PS can be hidden and the amp only is visible. Possible good if you are space challenged e.g. a flat dweller. The nanoo has the ability to deliver over 100W RMS so small it maybe be put weak it isn't. Most of the cooling is through the case which measures 119 X 94 X 34 mm. From this image you can see the working end. Everything just fits at the rear and the inputs are at the front to keep the output and the input well seperate. Twin attenuators allow volume control and reduces Xtalk. The case is alive. By this I mean the paint is like a thick powder which never curs. Small and powerful and with a great sound-who could want more?

Chip amp PS

Not much in here! The beauty of the chip amps is there top PSRRR. The amps run very quiet with no distinguishable noise from a meter back and only a slight hum/buzz with the ear against the speaker. I always use a power filter and you can see this at the back where the 240V power lead connects. I only ever use white power cords because they sound the best (just joking).

The multi-colour umbilical cord is fixed at this end but plugs into the amp (nanoo or mono block) using a RS232 socket. At the destination ens of the power card U place a ferrite choke. So any stray RF generated in the PS or traveling through the PS is choked-off before entering the amp. And of course any RF generated in the amp is stop at the power lead.

4.7uf polies do the pre-filter power clean-up job. In this PS I used a rec. bridge but in others (mono blocks) I used UF diodes. Small caps (.01uf) should be used to snubb the diodes/rec. bridge. 160VA toroidal trannis 25-0-25V @3.2A are used. If you are a bit anal about using a combination of 4.7uf polies and 2,000uf low ESR line caps put a couple of 10,000uf electrolytics across the supplier just after the diodes. Snubb the big caps with .1uf green caps. Try my combo first with the rest of your system. You can always add the bigger power caps later them later.

I use a 10A simple power switch. The amp, going hard, would only pull about about 2A so the switch and whole PS are well rated. In the mono blocks I fused both power rails with 2A inline fuses. I am yet to blow a fuse.

I'm not big on leds so I put .1uf cap across them to keep them quiet and run them about 1/8th brightness. Heavily twist your wires inside the case particularly any AC carrying wires. The heavy die-cast case keeps PS noise low and I earth the cases to keep any RFI out.

Inside the nanoo

I mentioned in another Blog that the nanoo was cramped and hard to work on. This image says it all. Also from the angle you can see the business end of the nanoo. The speaker terminals are are gold plated but inexpensive. And you can see the Rs232 male connector on the back. I use two of the pins to carry common ground in and two others for + and - volts. These chips use a dual supply. Notice how the chips are hard up against the case sides. You must have silicon insulation from the case.

Mini-pots were used and the cct. brd. had to be cut to get them to in. I like to use heavy copper wire for connection to the speaker terminals, you can see that here. As with this style of chip amp only three resistors are required. These I pass in through the same holes as the chip pins on the cct. brd. The signal path including the chip and speaker terminal connections is very short. The pure silver wire on the inputs is covered with a thin spaghetti. Two large bolts come through the centre of the brd. with spacers and with the secured chips hold the internals very securely.

As I have stated in the other Blog entry I wanted the nanoo to be small. I wouldn't attempt this for your first project. But have a go at chip amps in a larger case before attempting something so compact. In other Blogs I will be describing how I make my "engines". Spice engines are designed for mid-range finesse using small (2000uf) low ESR line caps. Columbia engines are designed for big bass, rock music style and employ 10,000uf line caps. I keep the PS the same for all and use only 4.7uf polies and UF diodes to provide the dual voltage. Lookout for the PS Blog next.

LM3875 nanoo

The nanoo is a compact (read small) amp using two LM3875 chip amps for full stereo delivery. I included two attenuators to help keep Xtalk down and to allow balancing between speakers. Also for the looks. I intended this amp to look like some small audio creature and I think I succeeded. Though diminutive in size at can be played quite loud. Because cooling is provided mainly by the sides of the case, with the larger heart sink on top only assisting with cooling, if you play it too hard the over-temp control cuts in and cuts the sound. If you play a cool jazz CD though it you can play it quite loud. It can deliver 100W bursts.

The PS is separate and is joined to the nanoo via a power umbilical cord. The PS employs an internal toroidal tranni, UF diodes and two 4.7uf polys for filtering. The connectors are RS232 male and female plugs. The line caps in the nanoo are 5,600uf quality electrolytics. There are no coupling caps - input or output.

The sound is clear, good bass, mids and treble but the mono blocks are a couple of classes better. Working in tiny spaces is frustrating and it took over an hour of fiddling to get all the parts in the nanoo and the chips snugly bolted to the sides of the case. Point-to-point wiring was used and silver wire on the input. Follow this link for more info:- diyaudioprojects

LM3875 mono blocks

The LM3875 is an "amp-on-a-chip" which can deliver 56W RMS. The first amp I built with these chips is this one. The other amp, using this chip, is my nanoo (like iPod nano) see my other Blog for this. These have a big clear sound and when combined with my valve amp is my axe of choice these days and is used for about 90% of my listening. UF diodes and 4.7uf ploies provide the prefiltering. The line caps (main power caps) are 2 X 1000 uf (4,000uf in total) low ESR electrolytics.

The sound stage is broad and deep with instruments well defined. They deliver good power and are fast and crystal clear. The distortion levels of the chip are extremely low. I would recommend these chips to anyone wishing to build a high quality reasonably powered amp. The mono blocks help create the excellent sound stage which still astounds me when listening to new material.

Inside the valve preamp

Once more you can see I used the Sprague orange drops. The cct. brds. are snubbed and rubber grommet mounted, including the PS. Pure silver wire is used to connect the signal path to the brds. In my third unit I am also using silver wire and silver solder in a heavy die-cast case. This is the insides of one I built for a friend who commissioned me to make him one after hearing mine which was just bare cct. brds. at that stage. His has two inputs but for some reason I didn't include that in mine.

The black material is speaker box dampening and is made from plastic and rubber with barium in it to make it extra heavy and dead. I put this everywhere I can to get all resonance and vibration out of the cases and brds. The bottom is totally covered in this material. The SM PS is in it's own box and shielded from the preamp brds. The amp is very quiet and I use mine to drive my LM3875 based mono blocks. A great balance of valve warmth and sonics and the clean loud power of the chips. Follow the link for more info:- http://www.diyaudioprojects.com/Tubes/12AX7_Preamp/index.htm

12AX7 Tube preamp

This tube preamp came as a Australian kit (now discontinued). It comes complete (no case) with PS. The PS is a switch mode type. You get to wind your own transformer. There is only 93 turns in total so it is not too hard. The PS does not effect the quality of the audio.

The Cd player is the NAD C542 which has been replaced by an Onkyo 7555. The cables are Transparents which have been replaced by my own Silver Highways which will appear as a separate Blog

It was my intention to keep the front panel blank apart from the blue led. On-Off switch and all connections are at the back. Foolishly I only install one set of inputs. In the third one of these I am building I will have two switchable inputs. Also the valves will be exposed. The inside will be very similar to this one. See the other Blog of the preamp to view the brd. layout. Also follow the link for more about this great preamp:- diyaudioprojects

The Cased K-12M

This is a cased version of the K-12M. I used an inexpensive instrument case and inverted it. So the lid is the base, with air vents, and the bottom becomes the top. I kept the standard OPTs which are quite small and easy to mount in the case. This amp and one other, similar to the one above, have been sold. Both the other owners are extremely pleased. I have kept the one above and use it all the time. Follow this link for more about this amp:- diyaudioprojects