Wednesday, May 10, 2017

Mimic-833MC




Yet another phono preamp but this time a dedicated MC preamp only. This one also uses the LM833 all bipolar chip. One reason is I like the sound of this chip over the OPA2134 and also it had the lowest noise audible through my high efficiency speakers. This build uses MKT and NP caps which are know for there accuracy and stability of capacitance. These features are essential in a phono stage.

Only two 9V batteries would fit in this tight enclosure. I wanted to get back to my epoxy enamel painted enclosure being cast Al. It looks extra sexy in real life. WBT silver solder and fine silver plated hook-up wire is use throughout. No shielded wire is used. The cct. brd. is a prototype brd. and not a PCB. The differential PS is built onboard. A mix of Vishay and other metal film resistors are used and a machined chip socket. Heavy duty gold plated RCAs on the rear and battery test point at the front.

Sound is solid and balanced. Imaging appears good and instrument separation is obvious. Happy with the sound which is based on a very pedestrian OPAMP but as stated above I like the sound of the chip and it was the quietest in this situation.








Tuesday, February 14, 2017

"retro-4040" - Chip amplifier



















This amp was started years ago but originally didn't work as expected. Two chip amp Jaycar kits have replaced the amp modules and the heat sink and PS have been beefed up. NOW IT WORKS at long last.
 
40W RMS into 8ohms with the normal chip amp protection all built in. Also power filter and 160VAC tranni. 10A rec. bridge (snubbed) and 2X8,000uf filter caps. Sounding clean, linear and uncluttered and bloody great bass - OMG! Nice WAF too.


Wednesday, February 1, 2017

"Silver Supreme" - 6L6 SE UL amp in a wooden box






























Yet another 6L6 SE UL power amp in a gift wine box. This time the blond box has been stained and lacquered. Two layers of staining and three coats of lacquer provide a deep rich looking finish. The component quality has been raised for this build and the power supply (with external tranni box) substantially beefed-up. Why another similar amp - because they just sound so very good.

The external transformer box houses two 160VAC transformers and connects to the amp via a male and female XLR connection. One for the 12VAC for the tube filaments and the other for the 250VAC HT voltage. Internally there is a two stage rectifier and filter network with over 800uf of storage capacitance. Rectification is via a 1A rectifier bridge which produces over 400VDC. This is limited and filtered to 295VDC for the HT for the 6L6s. This is further limited and filtered to 280VDC for the 12AT7. Tube compliment is the same as the first amp - matched JJ 6L6s and Psvane top-of-the range 12AT7 "T" series MKIIs. These tubes and this combination of tubes produces an extremely accurate and tonally rich sound for just a simple two stage amp.

Mundorf MCap Supreme Silver and Oil caps are used for the inter-stage and Edcor 15W OPT UL trannies for the output. Resistors used are both metal film and carbon film. By-pass (Ck) caps are low ESR and NP types. All hookup wire is Cat5 solid core with no shielded wire and WBT silver solder is used in the audio path. All filtering and by-pass caps are snubbed by 0.1uf poly caps. Earthing wire and filament wire is all 10A rated and the amp is hum and noise free. There are no problems producing 40Hz with rock solid bass and mid-range. Voice is earthy and detailed music has excellent rhythm and flow. An astounding 3W, two stage amp.


Sunday, January 15, 2017

6L6 SE UL power amp in a wine bottle box

















This JJ 6L6 and 12AT7 top-of-range Psvane tubed power amp has been constructed in (and on) a $9 gift wine box. The box has been finely sanded beeswaxed twice. There is an external 12V transformer and another inside to step-up the HT voltage. Resistors are metal film and inter-stage caps are Solen.

The amps sound is solid, grounded and well rounded. Only a few watts but plays more than loud enough through my 99db efficient 15" Beyma concentric 170ltr speakers.