Glass Ware Aikido Stereo 5687 PCB Bedienungsanleitung

Aikido Stereo 5687 PCB

USER GUIDE

Introduction

Overview

Schematics

Recommended Configurations

Tube Lists

Assembly Instructions

lass are

G W

AUDIO DESIGN

Dec 16 2011

DANGER!

This PCB holds a high-voltage power supply; thus, a real

—

and possibly—lethal shock hazard exists.

Ideally, a variac should be used to slowly power up the

regulator, as it is better to have a mis-

oriented electrolytic

capacitor or a mis-located re

sistor blow at low voltages,

rather than at high voltages. Remember that the danger

increases by the square of the voltage; for example, 200

volts is four times more dangerous than 100 volts

and 400

volts is sixteen times more dangerous.

Once the power supply is powered up

, be cautious at all

times. In fact,

even when the power supply is disconnected

or shut down, assume that power-supply

capacitors will have

retained their charge and, thus, can still shock

. If you are not

an experienced electrical practitioner, before

attaching the

transformer windings to the board,

have someone who is

well

-experienced in electronics review your work.

There are too few tube-

loving solder slingers left; we cannot

afford to lose any more.

AUDIO DESIGN

www.glass-ware.com

www.tubecad.com

sales@glass-ware.com

GlassWare

Warning!

This PCB contains a high-voltage power supply; thus, a real and lethal

shock hazard

exists. Once the power transformer

is attached, be cautious at all times. In fact, always

assume that the high voltage capacitors will have retained their charge e

ven after the

power supply has been

disconnected or shut down. If you are not an experienced

electrical practitioner, before applying the AC

voltage have someone who is

experienced review your work. There are too few tube-

loving solder slingers left; we

cannot afford to lose any more. Overview

Thank you for your purchase of the GlassWare Aikido 5687 All in One 9-

pin stereo

PCB. This FR-

4 PCB is extra thick, 0.094 inches (inserting and pulling tubes from their

sockets won’t bend or break this board), double-sided, with plated-through heavy

2oz

copper traces. In addition, the PCB is lovingly an d expensively

made in the USA. The

board is 7 by 6 inches, with five mounting holes, which helps

to prevent excessive PCB

bending while inserting and pulling tubes from their sockets.

Each PCB holds two Aikido line-

stage amplifiers; thus, one board is all that is needed

for stereo unbalanced use (or one board for one channel of balanced amplification).

including the necessary components for the heater and high volta

ge B+ power supplies

on the PCB, the5687 All in One board makes building a standard-

setting line stage

amplifier a breeze. This assembled board with a chassis, volume control, selector

switch, power transformer, and a fistful of RCA jacks is all that is needed.

PCB Features

B+ and Heater Power Supplies On the 5687 All in One board, two power su

pplies

reside, one for the high-voltage B+ for the tubes and a low-

voltage power supply for the

heaters. The high-voltage power supply uses an RC filter to smooth

away ripple, while

the low-voltage power supply uses an LDO

voltage regulator to provide a stable and

noise-

free voltage output. The power supplies require an external power transformer(s)

with two secondary windings, one for the B+ voltage and one for the heater

power

supply.

Redundant Solder Pads This board holds two sets of differently-

spaced solder pads

for each critical resistor, so that radial and axial resistors can easily be used (

radial

bulk-foil resistors and axial

film resistors, for example). In addition, most capacitor

locations find many redundant solder pads, so wildly differing-

sized coupling

capacitors can be placed neatly on the board, without excessively bending their leads.

Two Output-Stage Topologies The output stage can

be configured either as the classic

Aikido line amplifier or as an Aikido headphone amplifier. The 5687 is a robust

triode

that can deliver a lot of current at relatively low voltage

s, making it ideal for driving

headphones or other low-impedance loads.

Power-Supply-Decoupling Capacitors The 5687 All in One

PCB provides space for

two sets of capacitors to decouple both Aikido gain stages from the B+ connection and

each other. This arrangement allows a large-valued electrolytic capacitor and small

valued film capacitor to be used in parallel, while a series voltage-

dropping resistor

completes the RC filter.



GlassWare Audio Design

The

Aikido

amplifier delivers the sonic goods. It offers low distortion, low output

impedance, a great PSRR figure, and feedback- free amplification. The secret to it

superb performance— despite not using global feedback—

lies in its internal symmetry,

whic

h balances imperfections with imperfections. As a result, the Aikido circuit

works

at least a magnitude better than the equivalent SRPP or grounded-cathode amplifier.

Aikido Amplifier

B+

out

5687

Rgs

Introduction to the Aikido

Universal Topology

the schematic

above

, the

5687

triodes are

specified

as an

example only, as 300B

and 845 triodes could be used to make an Aikido amplifier.

The circuit does not rely on these triodes or any other specif

ic triodes to work

correctly. It’s the topology, not the tubes that make the Aikido special. (Far too m

any

believe that a different triode equals a different topology; it doesn't. Making this

mistake would be like thinking that the essential aspect of being a seeing-

eye dog

rested in being a Golden Lab.)

Low Distortion For example, the Aikido

circuit produces far less distortion than

comparable circuits by using the triode’s own nonlinearity against itself

. The triode is

not as linear as a resistor so,

ideally, it should not see a linear load, but a

corresponding, complementary, balancing non-

linear load. An analogy is found in

someone needing eye

glasses; if the eyes were perfect, then perfectly flat (perfectly

linear) lenses would

be needed, whereas imperfect eyes need counterbalancing lenses

(non-linear lenses) to see clearly. Now, loading a triode with the same triode—

under

the same cathode-to-plate voltage and idle current and with the same cathode resistor—

works well to flatten the transfer curve out of that triode.

PSRR The

Aikido circuit sidesteps power supply noise by incorporating the noise into

its normal operation. The improved PSRR advantage is important, for it greatly

unburdens the power-supply. With no tweaking or tube

selecting, you should easily be

able to get a -30dB PSRR figure (a conventional grounded-

cathode amplifier with the

same tubes and current draw yields only a -6dB PSRR); and

with some tweaking of

resistor R1’s value, -60dB—or more—is possible. Additionall

y, unless regulated power

supplies are used for the plate and heater, these critical voltages will vary as

the power

line’s voltage falls and climbs with your house’s and neighbors’ house’s use

, usually

throwing the supposedly fixed wall-voltage askew. Nev

ertheless, the Aikido amplifier

will still function flawlessly, as it tracks these voltage changes symmetrically.

Aikido 5687 Stereo All-In-One PCB

5687

56875687

GlassWare Audio Design 3

Age

Tolerant

Remember

, tubes are not yardsticks, being more like car tires

—

they

wear out. Just as a tire’s weight and diameter decrease over time, so does a

tube’s

conductance. In other words, a fresh 5687 is not the same as that same 5687

after

2,000 hours of use. But as long as the two triodes within the 5687

age in the same

way—which they are inclined to do—

the Aikido amplifier will always bias up

correctly, splitting the B+ voltage between the triodes.

No Negative Feedback Loop The Aikido topology d

oes not use any negative

feedback, other than the local degenerative feedback because of the unbypassed

cathode resistors in the input stage and the active load presented by the bottom

triode of the output stage. In fact, the Aikido topology makes use of f

eedforward

noise canceling at the output. Unlike negative feedback that has to

wait until

something goes wrong

before it can work to undo the damage, feedforward feedback

anticipates what will go wrong before it does. It is proactive, not reactive, to borr

the terms of pop-psychology.

The Aikido circuit eliminates power-supply noise from its

output, by

injecting the same amount of PS noise at the inputs of the top and bottom tube

s in

the two-tube cathode-follower circuit. Since both of these signals are

equal in

amplitude and phase, they cancel each other out, as each triode

sees an identical

increase in plate current—imagine two equally stron g men in a tug of war contest.

So,

shouldn’t resistors R1 and R2 share the same value, thereby also splitting the power

supply noise at 50%? No. If triode did not present a low plate resistance, then the

50% ratio would apply. Because of the low rp, the correct relationship between

resistors R1 and R2 is given by the following formula:

R1 = R2[(mu - 2)/(mu + 2)]

Low Output Impedance The

Aikido topology uses a modified cathode follower

circuit as the output stage. Cathode followers

are famous for providing low

distortion and low output impedances, but no voltage gain. This modified cathode

follower scrubs away the power-

supply noise from its output and provides a

complementarily non-

linear load for the top triode’s cathode. The top triode’s

capacitor resistor is in series with the output, so its resistance must be added to the

cathode follower output impedance. Had the output connection been

taken from the

top triode’s cathode, then the

output impedance would be slightly l ower, but the

symmetry would be broken and the PSRR enhancement would be lost.

Gain Calculating the gain from an Aikido amplifier is easy, as it roug

hly equals half

the mu of the input triode used. The gain from a simple grounded-

cathode amplifier

(with an un-bypassed cathode resistor) is

Gain = muRa/[Ra + (mu + 1)Rk + rp]

In the Aikido, the resistance presented by the top tube and its cathode r

esistor is

R' = (mu + 1)Rk + rp. So if you substitute R' for Ra in the above

equation and

simplify you get

Gain = mu[(mu + 1)Rk + rp ] / [(mu + 1)Rk + rp +(mu + 1)Rk + rp] = mu/2

Of course there is a slight loss though the Aikido’s modified-cathode-

follower output

stage

, whose gain usually falls between 0.93 to 0.98.

4Aikido 5687 Stereo All-In-One PCB

Heater Issues

The 5687 All in One PCB holds the heater's raw power supply and its DC

voltage

regulator. The regulator is an LD1085 low-

dropout adjustable voltage regulator. The

regulator can be set to an output voltage of 12V or 12.6V. The

advan tage of running a

slightly low heater voltage

(12Vdc) is that it extends tube life and can lower distortion a

tad. All the 5687 tube's heaters are placed in parallel, so a 6.3V or 25.2V heater

voltage

cannot be used. Be sure use jumpers J1 and J2.

-H

Filament Jumper Wire Schedule

C18

LD1085

Adj

InOut

Heater +

Heater -

C15

C14

R20

D8 C10D7C9

D10 C12D9C11

R21

{

C18

C13

C16

to B+ heater

bias voltage

s can be seen, the power supply can accept either

full

wave

bridge

ectifier circuit or

a full-wave-voltage-doubler-rectifier configuration. When used as a full-

wave bridge

rectifier circuit, the two power-supply filtering capacitors are placed in paralle

l by

orienting their positive leads to where the heatsink sits;

and the secondary attaches to

the two encircled AC pads. Configured as a voltage doubler, these capacitors

placed in

series by being rotated 90 degrees clockwise, so the positive leads point to the center

tap ("CT") pad at the bottom of the PCB; the secondary attaches to single "AC"

pad in

between capacitors C13 and C14 and AC pad number 2 that feeds rectifier D7

and

D9; and D8, D10, C10, C12 are left off the PCB. If used as a full-wave center-tap

circuit, the two power supply filtering capacitors are placed in parallel by orienting

their positive leads to where the heatsink sits;

and the secondary attaches to the two

encircled AC pads (1 & 2) and the secondary center-tap attaches to the CT pad

and

C11, C12, D9, and D10

removed

See the inside back cover for more information.

Filament Regulator

GlassWare Audio Design 5

The

heater’s PS

reference

bias

voltage to

target is

one quarter of the

plus

voltage

that the Aikido’s tubes use, not the initial raw B-plus

voltage at the high voltage

rectifiers. Alternatively, you might experiment with floating the heater power supply,

by “grounding” the heater power supply via only a 0.1µF film or ceramic capacitor

leaving resistors R19 and R18s off the board

. The capacitor will charge up through

the leakage current between heater and cathodes. Not only is this method cheap, it is

often quite effective in reducing hum with certain tubes.

Heater

Regulator 300k 1W

47k 1W

[L] B+

R18

R19

Final B+

Since one triode stands atop another, the heater

cathode voltage experienced differs

between triodes. The safest path is to reference the heater power supply to a voltage

equal to one fourth the B+ voltage; for example, 75V, when using a 300V power

supp

ly. The ¼ B+ voltage ensures that both top and bottom triodes see the same

magnitude of heater-to-

cathode voltage. The easiest way to set this voltage relationship

up is the following circuit:

Heater Voltage =

R21 =

R20 =

D7 - D10 =

D5, D6 =

C9, 10, 11, 12 =

C13, C14 =

C15, C16 =

C18 =

Regulator =

Vac Input =

12V 12.6V

1.07k 1.13k

124 124

MUR410G "

1N4007 "

0.1µF / 50V "

10kµF* "

1kµF / 16V "

1k-3900µF* "

LD1085, LT1085

12Vac or 12.6Vac @ 3.5A for or 12Vdc or 12.6Vdc

*Capacitor voltage must exceed 1.414 x Vac input voltage

Typical Part Values

Resistors

and

set the voltage regulator’s output voltage. The formula is

= 1.25(1 + R

/ R

)

Heater

Elements

[R] B+

R18

C17

6Aikido 5687 Stereo All-In-One PCB

R12

R10

R7 R11

C5C4

L-in

L-out

V1 V3

B+

R22

C23

Configuring the PCB as a Headphone Amplifier

The standard Aikido is a thoroughly single-

ended affair, nothing pulls while

something else pushes. Unfortunately, wonderful as single-

ended mode is sonically, it

cannot provide the larger voltage and current swings that a push-

pull output stage can.

Single-ended stages can only deliver up to the idle current into a load, whereas class-

push-pull stages can deliver up to twice the idle current into the load

. For a line stage,

such big voltage and current swings

are seldom required; headphones, on the other

hand, do demand a lot more power; really, a 32-

ohm load is brutally low impedance

for any tube to drive. Fortunately, the

PCB can be configured with an optimal White

cathode-follower stage, which will both ret

ain much of the Aikido’s great PSRR and

allow up to twice the idle current to be delivered into low-

impedance loads. All that is

required is to include resistor R22 and capacitor C23 and replace resistors R6 & R

with jumper wires.

Headphones require big current swings and little voltage swings, so we should lower

the B+ voltage and raise the idle current, say 160Vdc and 24mA for the output tube

(Rk = 47 ohms). A coupling capacitor of at least 30µF is required when driving 300

ohm headphones; 330µF for 32-ohm headphones. Capacitor C3

can be bypassed by

using a small film or PIO capacitor on bottom of the PCB.

In the optimal White cathode follower, the critical resistor is R22

. This resistor is used

to sense current flow variations through the top triode and to create an anti-

phase

signal that is relayed to the bottom triode's grid. In other words, it sets the

dynamic

current

balance between top and bottom tubes. A value that is too high or too low will

compromise performance. Finding the correct value for resistor R22 is easy:

R22 = (rp + 2Rload)/mu,

where rp equals the plate resistance and Rload

equals the load impedance. From a quick

inspection, we see that the lower the load impedance, the closer the formula comes to:

Ra = rp/mu. On the other hand, when the load impedanc

e is as much as 600 ohms

and the rp as low as

the 5687's 16

00 ohms, then the difference is fairly large.

GlassWare Audio Design 7

C1, C2 =

C3* =

C4* =

C5 =

C6* =

C7, C8 =

C23 =

0.01-0.33µF (optional) Same Same Same

0.1 - 4µF Film or PIO " " "

0.01 - 1µF Film or PIO " " "

270µF 200V 270µF 200V 150µF 400V 150µF 400V

0.1 - 1µF Film or PIO Same Same Same

220µF 200V 220µF 200V 47µF 450V 47µF 450V

None None None None

*Voltage rating must equal or exceed B+ voltage

*High-quality resistors essential in this position. All resistors 1/2W or higher

Typical Part Values

() Parentheses denote recommended values

Configuring the PCB as a Line Amplifier

The Aikido topology makes a

perfect line amplifier, as it offers low distortion, low

output impedance, and excellent power-supply noise rejection—

all without a global

feedback loop. The key points are to replace resistor

R22 with a jumper wire and leave

capacitor C23 off the PCB. The following

table list four recommended

configurations, but actually there are in infinite number of possible setups.

B+ Voltage =

AC Secondary =

AC Current =

Heater Voltage =

Heater Current =

R1,11 =

R2,5,8* =

R3,4* =

R6,7* =

R9 =

R10 =

R22 =

5687 & 5687 5687 & 5687 5687 & 5687 5687 & 5687

100V 150V 200V 250V

150 - 170Vac 230 - 250Vac 200 - 250Vac 115 - 120Vac

50mA 60mA 80mA 60mA

6.3V or 12.6V 6.3V or 12.6V 12.6V 6.3V or 12.6V

2A or 1A 2.5A or 1.25A 0.75A 1.5A or 0.75A

1M 1M 1M 1M

100 - 1k (300) Same Same Same

100 - 470 (300, 5.5mA) 300 - 1k (390, 7mA) 300 - 1k (390, 10mA) 300 - 1k (845, 7mA)

200 - 340 (150, 8mA) 200 - 470 (240, 10mA) 200 - 470 (300, 12mA) 300 - 1k (680, 10mA)

100k Same Same Same

78.7k 78.7k 78.7k 78.7k

Jumper Same Same Same

R12

R10

R7 R11

L-in

L-out

V1 V3

B+

R22

C23

Tubes =

8Aikido 5687 Stereo All-In-One PCB

5687

Specifications

Heater Voltage 6.3V & 12.6V

Heater Current 900mA & 450mA

Maximum Plate Voltage 330V

Maximum Plate Dissipation 4.2W

Maximum Cathode Current 65mA

Maximum Cathode-to-heater Voltage 100V

Amplification Factor 18.5

Transconductance 11.5mA/V

Plate Resistance 1600 Ohms

Grid-to-Plate Capacitance 0.75pF

RETMA 9H

Bottom View

Pin 1: Plate, triode 2

Pin 2: Grid, triode 2

Pin 3: Cathode, triode 2

Pin 4: Heater

Pin 5: Heater

Pin 6: Cathode, triode 1

Pin 7: Grid, triode 1

Pin 8: Heater center-tap

Pin 9: Plate, Triode 1

Inhaltsverzeichnis

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