KT88 Bread Board amp with no driver stage.

This is the first bread board amp (said Be Bamp) under the retro-thermionic brand so it had to be a different to other BB amps and stand out. Also it was designed to be used with a high gain preamp because, in this model, there is no driver stage. It has been tested with the retro-thermionic Tea Box two stage valve preamplifier. Also all wiring is hidden under the board to give a clean neat look. To further enhance the look the two open OPTs are housed in a metal enclosure. The enclosure doubles as a mounting point for speaker and input terminals, all gold of course.

The driver stage has been removed to reduce the number of stages the music has to travel though before appearing at the speakers. This has resulted in an increase in transparency and detail. In future releases of the Be Bamp a version with the driver stage will be produced.

Though the wiring is hidden there is plenty of components above board. Also the high voltage (400V) rectifier is exposed so electrocution is possible both here and from other components. For a twist the HT standby switch, which must not by operated under one minute of warm-up time, is covered with a red rocket launcher cover. The board is Australian Pine and has been treated with Australian beeswax.

Main components are Hammond (over specified) power transformer and 10H Hammond, high current, choke. Edcor open OPTs are used. The Be Bamp will work with a number of different valves; 6V6GT, and EL34s being just two. A matched pair of JJ Blue Glass KT88s are shown in the image. The amp will produce about 5W if driven fully.

The retro-thermionic Fostex Back Loaded horns were used to evaluate the Be Bamp. Voice and all acoustic instruments display a very dimensional sound with voice sounding crisp and earthy with very controlled sibilance. The amp is absolutely hum, buzz and hiss free and is the quietest amp I have ever built. With a result of the deepest black back ground well know tracks sound new again and display extended fine grain detail.

On request retro-thermionic will provide this amp as a kit with rectifier module and power valve module assembled and tested. Ever part will be provided for the DIYer to assemble.

KT88 Bread Board amp with no driver stage.

The bread board amp (Be BAmp) is just as attractive from the rear as from the front. The enclosure which houses the OPTs is also used to mount the speaker binding posts and input RCAs which are all gold plated and the RCAs are insulated. The fuse and mains switch are also visible from the rear. Only the power transformer is connected to the mains earth.

Merlot

Merlot-entry level valve audio.

The build criteria for the Merlot valve amplifier was to construct a simple and excellent sounding valve amplifier from inexpensive parts. But this amplifier had to set an example of what can be expected from any valve amplifier.

Merlot's goal was to demonstrate to those listening to their first valve amplifier that, in a number of areas of quality audio, valve amplifiers can challenge, at a musical level, not only solid state amplifiers but inexpensive commercial designs. The design is single end (SE) and ultra linear (UL) with diode rectification.

Merlot uses two common valves: the 6N1P and KT88. The output valve can be replaced by a number of other valves: EL34, 5881, 6550, 6L6, 6V6 etc. I encourage "tube rolling". Feel free to replace the two output valves. Very different timbres and tonal balances can be obtained by tube rolling. This amplifier supports that practice.

If Merlot looks like this amplifier was hand built completely from scratch that is because it is. From the very solid Mirbeu timber base to hand assembled modules. There are no printed cct. brds. or commercially prepared modules Incorporated in construction. There is no additional wire used in the hand made modules, on component wires joined to other components. This is a technique I have used extensively here called component-2-component wiring. Fewer solder joints and less "hook-up" wire than point-to-point wiring. Individual modules are available.

retro-thermionic attempts to bring back some of the look and sound of early valve amplifiers. The use of heavy timbers, metal, large transformers and protruding valves is purposely done to produce a retro look and to reproduce music as it was meant to sound. Like music.

The sound of the Merlot is excellent mid-range tones, clean clear highs extending to 46khz and a balanced bass down to 35hz. Merlot's greatest strengths lay in its mid-range. Human voice and acoustic instruments are rended with great transparency, natural tone, real depth and immediacy. Output is 6.5W RMS per channel so efficient speakers are required.

This amplifier can be ordered and built with minor modifications should you require. Other models include: Cabernet and Shiraz which use more expensive parts but still the same retro look, more refind and detailed sound. These amplifiers will feature on this page.

Merlot - rear panel

The rear of the Merlot amplifier carries all connections. These include: two switchable RCA inputs, speaker binding posts which will take spades, banana plugs or captured wire, power cord outlet, fuse and on/off switch. The Merlot can be configured for 11oV. A standby switch is atop the the amplifier. This allows you to switch off the high tension but leave the heaters on for immediate listening, during short breaks. This saves power and stops cathode stripping by applying the HT after the tubes have warmed.

Merlot with JJ KT88 Blue Glass

A number of different power valves can be fitted to the Merlot. It is one of the great strengths of an open valve amplifier, that different tubes can be "rolled" for different tonal balances. In this instance a matched pair of JJ KT88 Blue Glass have been fitted. This has increased the low end weight and brought the mid-range forward slightly. Apart from the different tonality the Blue Glassed JJs look stunning. Many other valves and speciality tubes can be rolled into the one basic power amp. Have a favourite power tube which has the same pin outs and specs as a common KT88? Then roll it into a Merlot. Plug and play-your way!

Merlot - Black Top and Black Sable EL34

This is the first of the Merlot range I constructed. In this build all switches, controls and connections are on the top plate. The paint used is an epoxy enamul and forms a tough and textured finish. Modular design was developed in this first "proof of concept" build. Once again component-2-component construction was used in forming the modules.

This amplifier diplays all the mid-range fine grain clarity of the second build (above). A number of different valves can replace the EL34s used in this amplifier. Matched Black Sable EL34s are installed in the amplifier above.

Merlot - Black Top EL34

With the Merlot - Black Top build the valve sockets were recessed into the top plate.Therefore valves with large basses e.g. KT88 could not be installed. This issue has been corrected with the second build and now all bases sizes can be accommodated. Fortunately the amplifier sounded excellent with the EL34 Back Sables. This amplifier has also delivered excellent music with 6V6 Black Glass (original Australian made valves).