Flesh And Blood The Reichert 300B
Article By Herb Reichert
The light from the
streetlights mixes with the glow of the bright emitters in my listening
room. Nyiregyhazi plays Liszt in front of me and my skin seems electric
but I am completely relaxed. I let out my breath and my pulse is near
flatline. Audio can really be good to us... if we let it. This is why we
must seek to create and explore the frontiers of audio. This is why many
of you build your own audio equipment.
I started building and designing my own
audio because I am a 'gearhead' by nature, not because I thought I could
do better than the pros. However, one day I took the negative feedback
out of an amplifier I had built and my whole body went limp. Big
symphonies by Mahler began to expand and breathe. A strong sense of
voluptuousness replaced a feeling of tension and hardness. Average and
poorly recorded program began to become part of my midnight repertoire.
I concluded I was on to something important. I realized that there must
be more design decisions, big ones, like this one with the feedback,
that impact the basic character of my system. This is the point at which
I became "high fever". I now had a sense of what was possible.
I began to engineer with a purpose.
Over the last decade, I looked carefully at each part of the audio
amplifier design process. My first rule was: take nothing for granted
and keep an open mind. This attitude steered me down many wrong roads;
like the six months I spent chasing A/C balance in push-pull amps or
looking at pentode driver stages. Big dead ends!
On the other hand, looking into every detail of the single-ended,
directly-heated triode amplifier has netted results beyond my wildest
dreams. The whole world of high-end audio is changing and believe me, it
is the result of the work you and I and our friends are doing in our
homes. We are experiencing a 'new dawn' in audio, but this new dawn is
only the beginning and there is much new work to do. So, I want
you to take this design as a beginning and build on it. Apply your own
audio ethics and benchmarks.
From the letters and phone calls I receive, I know that many of you
believe that if you can get a schematic for a great amp, then go out and
buy what you think are some great parts, and put it all together
carefully, then you will end up with a great amp. Sorry, it just doesn't
work that way. You might get a good amp by this method, if you
are lucky and inspired, but to get a great amp you must suffer.
Whenever I build a BAD amp, and I have built quite a few, J.C. always
says, "Welcome to the next level." It is the failures and the
mistakes that get you to the other side of the mountain. Each failure
makes more clear what you do not want. Each success enlarges your vision
of what is possible. The process of building is to wire your mind, to
focus your sights on that point on the horizon where greatness lays.
I know the Reichert 300B-SE amp doesn't look like an unusual or original
design. But, on the test bench, this amplifier design sets very high
standards for bandwidth, rise time, and distortion. My main design goals
were vividness, body, color, and dramatic contrast. I want a vibrant,
breathy, gripping sort of presentation. I am an artist, a painter in the
painterly, romantic tradition. I want my hi-fi to paint with strong,
What I don't want is distant, thin, or mechanical sound. Lots of flesh
and blood. Lots of drama and empathy and lots of Technicolor and
Panavision; this is what I was after when I designed this amp. Each
design decision was a trial and error attempt to get to this end. Please
understand, this is not a 'part of the month' design. Each parts choice
has a personal evolution, all yin/yanged to my taste. If you change ANY
part, it is your amplifier design, not mine.
Amplifiers are engineered from the output terminals backward. The
amp/speaker interface is everything and one's focus must always be on
the 'black & red'. Amplifiers are always designed for a particular
speaker or speakers and any amp designer who says differently is trying
to sell you something he doesn't own. How the amplifier behaves into the
chosen speaker load is the first point to consider when making all major
engineering decisions. This amplifier was created to power Altec VOTs,
Edgarhorns, WE-755As, and Altec 601As. I have also discovered that it
works very well with LS3/5As, AR-M1s, Lowther PM-6s, and Audio Note
Model 2s & 3s. I used a circa 1946 Altec VOT system to do the
initial design work. Final touches were done with the Onken/Edgar system
and Audio Note Model 2 & 3 speakers.
Output transformers are the cornerstones of any tube amplifier design.
Since 1980, I have tried outputs from UTC, ACRO, Peerless, Dynaco,
Fisher, Partridge, Western Electric, Chicago, Hammond, Magnequest, RCA,
Audio Note, and God only knows...? I prefer the Tango to any other. I
distributed Tango in the U.S. until 1993. Maybe that's why I began this
design with the Tango XE-60-5S single-ended output. I do not care how
"romantic" you want to be, you must have speed and bandwidth.
An amplifier that is slew limited or unstable outside of its passband
will never have good tone character.
I believe the ultrasonic and infrasonic behavior of a SE amp must be
carefully examined. Excessive phase shift or ringing in these regions
will surely sabotage the amplifier's potential for greatness. If the
output transformer rotates phase more than 40 degrees below 100 Hz, the
amp will sound slow and the bass will seem to lag behind, lacking
"tunefulness". Bass transients will sound dull. Likewise, if
there is ringing in the ultrasonic region, the amp will sound hard and
The proper selection of core material, core size, aspect ratio, and
winding technique is far more critical in SE designs. Poor choices lead
to soft, lazy, unrefined sounding amplifiers. The Tango line is unique
in that it is the product of two decades of continual development.
World-wide, there are thousands of SE amps with Tango outputs. The Tango
XE-60-5S measured 18-80 kHz, -2dB in this amp. This is at 7 watts!
Remember, I do not sell these transformers anymore. I just still love
I chose the WE 300B tube after living with amps built around the 6B4G,
2A3, 50, 45, 801A, and the 10Y. 10Ys push/pull are still my personal
favorite, but even the VOTs like more than 3 watts. Of the available
triodes, the 300B plays the most records with the greatest ease and the
most refinement. It is voluptuous and elegant. Also, it is the ONLY tube
I am aware of with perfect sample to sample consistency. The Western
Electric 300B is always quiet and it will last forever. There is a
hypnotic quality to the 300B sound that draws me into the performance
like no other type of amplifier.
Operating points are next on the design agenda. My best friend and tube
maven, J.C. Morrison, has already written the book on this subject: run
your triodes hot! With pentodes, I like low plate voltages and high
current. With triodes I like high plate voltages AND high current. I run
the WE 300B at 425VDC on the plate and 80mA standing current. I want
deep class A1. I want to tickle the center of the B/H curve and swing
very little current across the power supply. Symmetrical clipping and
fast graceful recovery are a combination of power tube operating point,
driver stage design and power supply engineering. These three elements
work in concert and must be designed together with a clear sonic goal in
mind. The amplifier's ability to drive speaker loads with ease and
refinement will be seriously handicapped if we make a bad decision here.
I chose the 6SN7 cascade after examining the distortion spectrum and
sonic character of the SRPP, transformer coupling (Tango NC-16 and
NC-14), 5687 anode follower, the mu-follower, and several variations on
direct coupling. With the R-C coupled 6SN7 and 500VDC raw supply the amp
'locks' into class A1 with a minimum of A2 voltage. The 12K plate load
on the driver stage gives me the rise time and low odd-order distortion
product I wanted. Don't laugh, but I only like the GE 6SN7GTB in this
position. You must use GTBs to get the required plate dissipation and
the GE version sounds best to me. The first stage is R-C coupled to the
driver stage to hold the output tube grid swing to max even with poorly
matched tube sections or aging tubes. Direct-coupled designs seem to
change their sound over time even though their minimum phase character
is highly appealing. In this design, the time constants have been very
carefully considered, so don't go changing any resistor or capacitor
The power supply is everything in these little amps and it also seems to
be the area where designers agree the least. All the SE 300B amps I have
heard sound very different from each other. Some sound more mechanical
than the worst solid state designs. The reason, I expect, is wildly
different ideas on power supply design. First rule of triode amp design:
Solid state rectifiers = mechanical sound. You don't think so? Then you
haven't really compared. I promise you, IF there is only ONE thing I
have learned in ten years of amp design, it is this first rule. A lot of
time went into selecting the rectifier tube for this design. Normally, I
use the WE 274A/B, but this amp sounded best with the RCA-5R4GY.
The pi-filter is the heart of this amplifier. If this amp sounds better
than others, it is probably due to the choke/cap selection on the
pi-filter. I don't like to waste a lot of energy charging and
discharging caps. I want a narrow torque curve - high rev supply. Low
impedance and minimum storage gives fast recovery and fine texture to
the sound. Remember, most amps under 2000 watts are running at or near
overload. Let's make them sound unstressed at overload. Then the music
will sound unmechanical. The power transformer should be rated at least
500mA at 800VCT. An even higher current rating is better (I use 750mA)
because I want a small value bleeder resistor at the end of the filter.
I like to bleed at least 25%% of the total standing current. This
stabilizes and regulates the supply. With the small Black Gate caps, the
heavy bleed appears to enhance the clipping characteristic.
We want 480 to 500 volts across the output of the pi filter. The choke
should have a DCR of less than 300 ohms. I aim for 10-20 Ohms DCR! This
is a big chunk of iron, but it is a very important part of the design.
The number of Henrys is less important than the DCR rating. Two to ten
Henrys is fine. We are looking for a B+ that is fast and linear, but
loosely and naturally regulated. Remember, the reservoir and decoupling
capacitors are part of their respective stage's transfer function. This
means that they are just as important as the tubes in determining the
linearity and character of the amplifier.
For caps there are a few choices. I have tried all the usual stuff: WE
oil and paper, photoflash, polypropylene, etc. The Black Gates (47uf at
500vdc x 2) are now my first choice, but only if you play music every
day. These are electron-transfer/electro-static and must be kept
charged. They take a full 24 hours to recharge when left to discharge.
These are not electrolytics. They work more like an electrostatic
speaker. There is no electrolyte or electrochemical delay. These caps
are super wideband, linear, non-resonant, and quiet. The Cerefine are
almost as good. They use a ceramic powder instead of pure carbon like
the Black Gates. This ceramic powder allows for a quicker charge up
time. Both caps behave very gracefully under A/C conditions. Do not use
polypropylene. If you do, this is your amp design, not mine.
I am not going to get into the parts philosophy thing except to tell you
I have tried everything I could lay my hands on. My ideas change daily
so here are today's recommendations. No Teflon. No silver plated wire.
No MIT multi-caps. No metal film or metal oxide resistors. No
polypropylene caps. No Vitamin Qs. No Solen. No REL caps. No Holcos. No
metal oxides. No Vishays. No SCR. No MKP-1845s. No solid state diodes.
No solid state current sources. No silicon anything. If you use this
stuff, you know who's amp design it is NOT.
Please use Allen-Bradley resistors in the plate circuits. Paralleled
resistors, in plate circuits, are quieter and sweeter sounding. Use
Audio Note Tantalum resistors in the cathode and grid circuits. On the
cathodes of the 300Bs use Caddock 50 watt MP 850s. You can use Caddock
MG or MX in the plate circuits if you are a noise freak, but I think the
A/Bs sound more relaxed and showcase the wood and brass tones on
orchestral music. I have only three recommendations for coupling
capacitors and they are all Audio Note. Due to my affiliation with Audio
Note you probably won't take my coupling cap recommendation too
seriously, but that's OK. You lose! If you want even a chance of
catching my Ongaku sonically you must use Audio Note silver foil paper
in oil coupling capacitors. If you can't afford these use AN copper foil
paper and oil capacitors. There simply are no other choices.
Wire is a separate issue. Wire is a system thing. After twelve years of
building amps, I only know two things for sure:
1) Use tube rectifiers
2) You can never have too much silver in
the signal path.
Go without food or clothes, but buy lots
of records and wire your hi-fi in silver. Audio Note or Kimber silver
wire are my first choices for internal wiring of this amp. If you can't
afford this stuff, just use Carol PVC hook up wire. Nothing is worse
than silver-plated copper. Stay away from all Teflon coated wire if you
are looking for relaxed natural sound. Believe me the Carol PVC stuff is
good for everything in your system from the tonearm to the speaker. If
you can't afford silver, and you trust me, try it.
In fact, if you want to build this amp on a budget, try this... you can
still say it is my design. Use the Tango XE-20S or the Audio Note
outputs. Use the Carol PVC wire, the AN Paper and Oil Caps (Regular
type), Allen-Bradley resistors, and Sprague or Mallory power supply and
bypass caps. You will lose some of the refinement but none of the
If you make substitutions with parts try to avoid plastic, especially
hard plastic. Think voluptuous and colorful. Oh yeah, even if you are on
a budget, try to use a copper chassis, 2% to 4% silver solder, and high
quality ceramic tube sockets.
Please, try to wire the circuit just as given on the drawing, observing
the ground points of the cathodes and the PS capacitors. Do not buss the
power supply caps. The pi-filter and the 300B cathode resistor should be
grounded at the same point. Likewise the 6SN7 cathode resistors, the
driver stage bypass condenser and the decoupling capacitors should all
go to the same point.
All of this design talk may be for naught. You see, I believe most
deeply that the real magic ingredient in any amp design is the wu of the
designer. This wu flows from the designer's hands during construction
and raises the effort above the common and imperfect. Therefore it might
be best if you design your own amplifier, for your own speaker, based on
what you already know and what you think of my ideas. My philosophy
rests on the romantic and the expressive. Drama and contrast with the
grace and poise of a bullfighter are my audio system goals.
This circuit and these parts choices were developed inside the world of my
hi-fi to my taste! If you want an exceptional music reproduction system
in your home you must first develop your internal reference for natural
sound. Then you must outline your aesthetic and make a series of design
decisions that reflect that aesthetic. But remember, you won't be happy
if you acquire your aesthetic from reviews and audio pundits. You must
discover your own. Trial and error is tedious and it takes a long time
to become a wizard, but I am sure you will look good in the wizard's
Click here to view the schematic.