6SN7 remote driver stage for the Be Bamp

Having the flexibility to change driver stages allows many different types of valves to use with the Be Bamp KT120 power section. The original 6N1P drivers stage can easily be unplugged and other suitable drivers stages plugged in. The power amp does not have to be turned off but the amp is placed in stand-by.

This stage is based on the 6SN7 twin triode valve. It is an extremely popular valve used by audio craftsman. The valve sits atop and a small metal enclosure. The base is sprayed with an epoxy enamel paint and the finish is hammered copper. Once again Russian military paper, foil and oil inter-stage and low ESR capacitors are used.

There is no hook-up wire or PCBs. used and once more component-2-component wiring is employed. The driver stage is compact and attractive and brings a whole new sound scape to the Be Bamp.

Be Bamp with KT120 Tung-Sol tubes

The KT88 Be Bamp is an excellent sounding amp and if taken no further would satisfy most audiophiles. But the Be Bamp with KT120 valves, replacing the KT88s, just takes excellence to a new level.

In previous iterations of the Be Bamp improvements were made to bass response and over all musical weight. Now with the replacement of the KT88s with the over-size KT120s so much more of the music is presented to the listener. Mid range and bass have lifted and the treble has received extra air.

Now bass is extended and controlled, mids are crisper, brighter and better defined and treble just a hint airier. Power has increased in the amp and though efficient speakers and still required to obtain voluminous listening levels, greater musical weight is heard right across the audio spectrum.

Classical, Opera, Jazz and other genera are brought into the listening area with greater presence than previously felt. Emotion from each track, weather CD of vinyl, is embraced with greater immediacy. Detail is better etched into the sound stage and the sound stage deeper than before. Simply a better audio amplifier from retro-thermionic.

Remote driver stage for Bread Board amplifier

To increase the volume level of the Bread Board amp (Be Bamp), else where on this bLog, a driver stage was built. This is the original cct. used in the Merlot amps with some components upgraded. The is no volume control or input cap and pure silver wire used in the signal path.

The Be Bamp can deliver full volume to the point of clipping. Well short of clipping a high volume level can be obtained with large 91db sensitive 3-way tower speakers. The over-all sound of the system, which also combines a two stage valve preamp, is extremely musical. The sound is very transparent with good bass extension and weight, broad well imaged sound stage and natural tones of voice and instruments.

With the driver stage being remote other driver stages can be matched to the power stage and share the power supply. This provides another level of experimentation and flexibility with the over-all system.

Remote driver stage for Bread Board amplifier

Because the Bread Board amplifier (Be Bamp) performed so well, though at low volumes, a driver stage was built for it. This stage is remote from the rest of the amplifier and is joined to the amp by interconnects. A multi-pin, high grade, plug and socket connect the 400V HT+ and the 6.3V filament voltage to the driver stage. This single stage front-end has been constructed in a Twinings Tea Box to match the two stage valve preamp else where on this bLog. Having the driver stage remote allows the trial of different driver stages while sharing the power stage and the and a common power supply.

The same drive stage as in the Merlot amp was used. This employs a 6N1P Russian tube. Parts of the original schematic were upgraded and Russian military paper, foil and oil caps were used for inter-stage connection. There is no volume pot or input capacitor. Low ESR grade caps were used where possible and pure silver wire used in the signal path. Construction is all component-2-component with no PCB or any other cct. brd. The timber Tea box is bitumanised Al foil lined.

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.