Cased Aussieamps nxV200 amp

Only missing the front panel and lid this Aussieamps nxV200 VFet stereo amplifier is complete. The four 10,000uf 100V caps can be seen "stuck" to the sides of the case. The led is ready for mounting on the front panel. In this image the amp is under test and a faint blue glow can be seen at the rear of the case. Surface mounted blue and yellow leds light-up when the amp is on. The heat sink and caps just fit in the case. The HS also acts as a magnetic shield between the amp modules and the big toriodal tranni. The rectifier module is on the left and is constructed from individual high current, high surge fast switch diodes. 0.01uf caps snub each diode. The power caps are snubbed with 0.1uf caps.

The internal signal and speaker wiring is intentionally kept very short because unshielded OFC speaker wire was used throughout for hook-up wire. The input gold plated RCA and gold plated speaker binding posts are mounted on the rear so amp modules and terminals are close to each other. The amp is dead quiet.

The sound is pristine and crystal clear. The modules are rated over 200W and after winding the volume up on my small bookshelf speakers I believe the specs. They can drive hard with no harsh overtones or strain. I made a pair of these stereo amps for bi-amping a 2-way speaker system.

Aussieamps nxV200 V-Fet 200W amp

These compact and powerful Aussieamps amp modules were bought by a DIYer to construct two stereo amps for bi-amping his large 2-way speakers. He approached me to design the power supplies, assemble and provide enclosures.

I modulised the construction by: mounting the amp modules on the heat sink, constructing the rectifier ccts. on a tag strip, assembling the speaker binding posts, AC captured cord, fuse, on/off switch and input jacks on back plate of the amp and mounting the transformer and large electrolytics caps (20,000uf per rail).

It took two days just to do the marking and drilling of the case and HS. And four days to assemble the first amp. The second amp only two days. Oxygen free copper wire was used for the hook-up and signal wires. Brass cones were mounted for the feet and the case is heavy gauge steel. See the image above.

Kit form Phono Preamp to top commercial product.

After revamping my TT and deciding I was going back into vinyl I required a phono preamp. I bought the Pro-ject SE (SS version). Coupled this with my new Grado wood bodied Sonata cartridge, I thought the sound was great. My TT is a Rega Planar3 with an RB300 arm. I changed many preamps and power amps over time but until the day I saw a kit form, OP amp based, phono preamp in the local electronics store I never changed that which was closest to the source.

The kit was $AU35. You required an AC supply and case but everything else was supplied (See image of the build below). With some variation to the kit I completed the project and now was interested to see (and hear) how it sounded. Immediately, from the first track of the first LP I was very impressed. The preamp was dead quiet, no hum hiss, just nothing. Music just flowed from the whole system. The sound appeared creamy and smooth and oozed from the speakers. When switching back to my Pro-ject I felt the sound was course and rough. The music sounded like it was being forced out, not rolling or flowing out. I cannot find one thing the Pro-ject does better than this inexpensive kit. The gain control is a bonus but without changing brd. level components various input capacitance and loads cannot be changed easily. The phono preamp is excellent.

Kit form Phono preamp

The construction for the preamp was reasonably easy once I found the right enclosure. Up to that point I tried a number of different boxes. What I was trying to do was find an enclosure which worked with all of the external connections for the kit mounted on the cct. brd. Once I removed them to mount them off-board things got better. The hard ABS plastic case fitted the cct. brd. easily and once lined with a Al and tar foil provided a good enclosure for the project (also see image above). The gain pot is mounted to the cct. brd. so mounting the brd. is critical to ensure the pot can extend out of the box. Insulated gold plated RCAs were used but probably not required in a plastic case. Non-insulated would have been OK.

Cct. brd. populating is easy from the kit except when fitting components for the various compensations. Though there is information for five different compensations there is only enough parts for one. The RIAA is the logical choice. Also if you install for other compensations you have to be able to access the cct. brd. to link them in.

An AC supply is used to bring energy to the device. +/- 12V regs. are mounted on the brd. and of course a diode assembly. A good size copper shield is mounted between sensitive ccts. and the power section. Some capacitors can be upgraded but others, due to their size cannot be. Often I used silver wire for signal line hook-up but in this case stuck with shielded wire. The preamp is exceptionally quiet and has a very smooth sound.

Fostex full range speakers

These compact 15L ported single driver boxes contain the Fostex FE167E 6" twin cone driver. Built to compliment a couple of 6T9 valve amps. No Xover is required and though the valve amps only provide 4.5W of power @ 94db efficient good listening levels can be obtained. For build notes see article below.

If you are not use to a single driver speaker system at first the sound appears quite different. The drivers do take some time to break in and the surrounds are extremely stiff when new. The frequency range is quoted 20hz to 20khz. Bass is good but is very dependent on the amp driving them. Voices 'tend to be a little forward but not unpleasantly so. Treble extension is good but you need to have the boxes pointed toward your listening position. Detail and sound stage is excellent when driven by my 6T9 valve amp. Sound stage especially can be broad and reasonably defined with an unusual ability to project instruments well beyond the distance the boxes are apart. When friends compare the Fostex with my standard two-way boxes they are generally very divided in opinions. For such a simple design they do sound very good. And no Xover distortion-bonus!

Fostex FE167E full range driver in ported enclosures

Hard to believe that after forty-something years of listening to hi-fi I finds myself back enjoying single driver twin cone full range speakers. Back then I bought a pair of 8" twin cone Kaltros to go with my very first Rotel based hi-fi system. Of course the 6" twin cone Fostex FE167E driver is far superior to the Kaltros but he Kaltros took an absolute pounding at the hands of Jimi Hendrix, Stones, Cream and a bunch of others. Not once did they whimper.

With the Fostex drivers comes two sets of box designs. A more complex one in which the top part of an integrated stand is part of the port loading and a simpler design 15L enclosure with a 50mm X 50mm reflex port. I built the simpler one. I really only built the speakers at alll because I needed an efficient speaker system to go with the two 6T9 valve amps I had just finished. At 94db efficient the 4.5W 6T9 amps drive these compact boxes with ease and at good volume levels.

The boxes were glued, nailed and clamped during drying. The internal back of the box is lined with dampening vinyl and all interior walls have a layer of Dacron. Grills were cut from the same thick 18mm particle board with black speaker cloth stretched over them. The grills are retained to the boxes with heavy duty Velcro. There is no Xover and OFC medium gauge speaker wire was used for hookup. For listening notes see article above.

Valve preamp in a Tea Box

I have built a number of audio devices in wood boxes. The timber box above is a Twinnings presentation Tea Box. This two stage valve preamp with remote PS performs beautifully partly due to the fact it is chock full of Cardas Golden Ratio caps and pure silver wire (see article below for more info.). In fact it performed so well, that on hearing it, a friend bought it on the spot. I had only had it a week. A switch mode 260V has PS has its own die-cast Al case. The lid was polished then clear coated. The base is black epoxy paint-quite attractive when paired with the Tea Box amp.

Though standard 12AX7(s) were used the preamp produced a very clean and natural tone across all music types. Classical music had a particularly enchanting and romantic feel from this preamp. When matched with a SS power amp, the full warmth and charm of valve pre-amplification could be enjoyed for many hours with boredom or fatigue. Distortion is usually an issues with valve gear but the levels for this preamp remain under 0.2%. It has a frequency extension to 180KHz! Great looking and great sounding.

Tea Box valve preamp with Cardas caps

My fascination for timber and electronics has lead to me assembling a valve preamp in a timber presentation Twinnings Tea Box. I like the idea of timbre helping to control cct. resonance and adding it's own signature to the over all sound. I also wanted to continue trying various coupling and input caps and for this build selected the excellent Cardas Golden Ratio caps.I did find their multi strands of fine leads difficult to work with if they were too long. But I was very pleased with the final sound. The box is lined with a tar and heavy Al foil layer for additional resonance control and RFI shielding. Computer stand-offs with rubber grommets fitted to them, support the brds. to further reduce cct. resonance.

You can see the cct. brds. above and rear terminal panel ready for installing in the drilled tea box. The timber is easy to work with in this box because it is a reconstituted wood and resin compound. So when drilling huge holes it does not splinter as other woods I have used. The valves are standard 12AX7(s) and other caps used are polypropylene types. All silver wire was used throughout, silver solder, Apls blue velvet attenuator and 4oz solid brass knob. The PS is remote in a metal enclosure. The amp is a two stage affair and over all gain is about 6db. Glorious sound.

SS preamp with Jupiter beeswax and paper caps

This is the third of these OP amp (OPA2134) based preamps I have built. One was sold to an audiophile in Denver. In this build I wanted to use the Jupiter beeswax, paper and foil caps. They are 1uf in capacity and very large in size and supposedly hand made caps. With four of these large caps (see image below) in the die cast case there is not a lot of room for much else. A lot of attention was payed to cct. resonance control (see below), quality components, component layout efficiency, flexibility of input device selection and overall looks.

A 4oz solid brass knob looks well against the thick epoxy red paint. The Alps blue velvet attenuator provides a smooth and very linear feel to level control and helps keep the overall noise level down. The sound of the preamp is extremely detailed with mids and highs given full range and very extended. Mids carry multiple textures with voice sounding very earthy, even gritty and raw from male performers. The bass is deep, textured and rich. The sound stage comes through wide and detailed. Instrument placement is point sharp with each instrument or group of instruments having their own space and time. The background is deep and black. This is the best sounding preamp I have ever built and I intended to build more equipment employing the Jupiter caps.

Beeswax and paper caps SS preamp

Most DIYers build audio gear because they have a need for a device or they just like to build equipment. I built this OP amp (OPA2134) based preamp because I liked the idea of using beeswax and paper caps. These are 1uf Jupiter caps and according to the advertising, are hand made. They ARE covered in beeswax that is for sure. I timber sub-floor was placed on computer stand-offs which themselves have rubber grommets around them. The rubber grommets and timber base are used to help control cct. resonance. The cct. boards, tiny in size, are also mounted on stand-offs and fitted with grommets. Only component leads are used to connect the individual components together on the brd. There are only three short straps on the cct. brd. and these are three earth straps made from silver wire. The Jupiters also have silver leads. Alps blue velvet attenuator and 4oz solid brass knob was used as much for decoration and smooth operation as for quiet running of the preamp.

20V DC is supplied to the preamp via a computer plug pack and a resistive voltage divider network provides +/- 10V to the brds. Each brd. has an individual power network with 2X 220uf low ESR caps. Power filtering and snubbing is provided also within the case. The preamp is two stage with gain and buffer and I used the Burr-Brown high performance chips on milled sockets. All solid pure silver wire is used for internal hook-up and WBT silver solder used also. A switch at the back allows selection between two input sources. The case is 2mm die-cast aluminum with two coats of epoxy enamel paint.

Cool looking SE 6T9 UL amp

The 6T9 tube has both a triode and a pentode in the one small compact glass envelope. The amp uses Spare Time Gizmo cct. brds. and is in SE UL mode. This is the second of the two amps I built. The first was on a Teflon $7 baking pan chassis. Edcor XSE15-8-5K OPTs are under the lid and help produce a frequency response from 20hz to 20khz (-3db points).

The sound stage produced is extremely wide and deep and when coupled with a pair of Fostex single driver 94db efficient speakers produces the most sumptuous music. Especially classical and voice. The paint used is Epoxy enamel and though the two coats take eight days to dry the finish is very tough.

The amp has no audible hum at 12" from the speakers and produces very sweet mids with excellent detail. At no time does the amp not sound musical and I would recommend the build to anyone wanting a very inexpensive and exceptional sounding amplifier.

SE 6T9 UL amp curcuit board

This Spare Time Gizmo cct. brd. only cost $AU16 and is double sided, screen printed and solder masked. I used it in both 6T9 amps. The components are quality without getting into exotica were available form my local electronics hobby shop. The coupling and input caps I increased to .22uf metallised polypropylene types and the final PS cap I doubled in capacity. Snubbing was added to the diodes and the PS caps. Edcor SE OPTs (XSE15-8-5K) were used and the UL tap wired to pin 10 of the valve sockets. The screen grid resistor left out. The power tranny is Hammond and I went slightly over-size. This is an excellent sounding amp and I would recommend it to any builder of audio gear wanting to try valve amp construction.

SE 6T9 UL amp on a teflon baking pan

This delightful little amp is incredibly musical though it only produces 4.5W of power. When coupled with some very efficient speakers (e.g. Fostex FE167E 6.5" drivers) more than sufficient audio levels are easily obtained. The sound stage is huge and particularly wide. This was the first of these amps I built. The second is also posted on this blog and was purchased by an iPod only user.

Portable high quality mini-recording setup

The setup seen above provides a portable recording facility with direct to digital facilities. The preamp (red lid) is the ESP two transistor low noise preamp and is simple to make and really is very low noise. No hiss or other audio artifacts can be heard at all in even quiet recordings. Mine was built over-size to allow a 12V battery pack to be included under the bonnet. Gain is limited though.

Low noise mic preamp

After purchasing a couple of Berhinger studio mics and valve preamps and doing some recordings of live choirs etc. I decided I wanted something more portable. I bought a Sony ECM-MS957 but required a portable preamp. This is the ESP low noise two transistor preamp. Though it is quite large it has a 12V battery supply and uses large 10uf polypropylene caps throughout. All silver wire and quality components were used. Two attenuators allow separate channel level control. I use a Cowon Audio6 mp3 player with a line input connection for recording direct to digital at 128kps. The whole mini-recording desk runs on batteries and even after four hours of recording barely effected battery level.