The Leak Stereo 20
This amplifier should be from the year 1959. The factory print inside is very difficult to read.
According to other Leak enthusiasts on the "H. J. Leak & Co Ltd" Yahoo group, the first public Stereo 20 was offered for sale autumn 1958.
The amplifier was bought by the author on a flea market at Frederiksberg, Copenhagen in 1992 for 47 Euro.
A Leak stereo 20 is sold today for approx. 350-450 Euro depending on condition.
Website for HiFi people who like "DIY" & hi-fi equipment
In 1986 I built my first tube preamplifier called Röh-1 based on a presentation made by the German hifi magazine Elrad. The power supply of this tube amplifier was constructed with a “passive” high-voltage supply, where the voltage was reduced by simple CR links consisting of a capacitor followed by a resistor. 7 pieces of 47 volt zeners set the high voltage to 329VDC. Elrad’s design sounded excellent and the success brought me to this DIY construction from 1987 which was called “The Aurora”. This construction had originated via a circuit from Luxman called A-1033. Luxman A-1033 was an integrated amplifier launched as a DIY Kit in the USA, where the preamplifier was particularly interesting. People from The Audio Amateur, TAA, took this preamplifier circuit out as the basis for a complete preamplifier with only one switch, volume and balance control. I built this Lux kit preamplifier which included parts of the Marantz 7 topology, still with four 7025, two for the riaa and two for the line stage.
The Aurora sounds fantastic and I have never regretted building this preamplifier.
The Aurora my first attempt at designing a tube preamplifier.
Note the two 100R wirewound resistors and the 47K/220K voltage divider that elevates heater voltage
In 1996 everything was done by hand which meant that print layouts and drawings were created as pencil drawings exactly as was the case with the German Röh-1. The jpg shown is an update of the drawing, but the layout is identical to the original drawing from 1996 just with a new date. The difference is that all voltages and current are noted on the updated drawing made in 2025.
Above is the basic diagram of Aurora's phono and line amplifier which should be followed exactly as indicated. Note the added grid resistors at high level.
A special part is the high voltage power supply that I received for the Röh-1. It is an exact copy of the same supply based on four BUX85 Motorola transistors which deliver a completely stable voltage of 270VDC for the high level and 260VDC for the riaa amplifier. The transistor supply has some of the credit for the stability of the entire amplifier.
The above very stable power supply for "The Aurora" with Motorola BUX85 (TIP50 can be used).ripple less than 0.1 mVAC ...in the diagram with R5 as 233K8 + R4 as 95K2 = 329VDC Out
In the Aurora the voltage for the high level amp is 270VDC and 260VDC for the riaa amp
The complete preamplifier mounted with NOS ECC83 Miniwatt in the line stage and NOS Q-VEES 7025 in the riaa amplifier . Note RG178 B/U cable wiring.
The updated handmade pcb from 1996 with minor modifications. Starting with an updated hand-drawn diagram of The Aurora where small "inaccuracies" from 1996 have been corrected.
Four new ceramic sockets, reinforced circuit boards around the glow supply, a 7812 that could not regulate sufficiently on the approximately 14VDC that was available, was changed to a raw approximately 14VDC supply with 109mVAC ripple.
The 14VDC was smoothed out to < 3.4mVAC ripple via serial MOX and wirewound resistors, and on the recommendation of Mr. Vorhis, with approximately 40,000uF...in addition, the heater supply was elevated 47V above chassis ground. New 105 degree quality capacitors, new high frequency connection cables, etc....
A simple front with green on-off switch, switch for CD, Tuner and Phono including
LED indication and Tape monitor switch plus Volume and Balance control
A simple way to clean oxidated brass
To clean brass or polished brass, the following method can be used:
the ingredients
1. Water, 2. Flour, 3. Vinegar, 4. A teaspoon of citric acid, 5. A teaspoon of salt. Stir the 5 parts shown to form a thin paste and apply to the brass surface for a few minutes. Wipe off the paste, rinse and dry.
You can achieve the same result by applying Heinz tomato ketchup to the brass surface after a few hours....if you can live with the smell :-)
After cleaning, it is recommended to “seal” the brass surface with “Black Bison” antique wax to delay oxidation.
Had a free secondary of 4,5VAC ...so a voltage doubler for the 12VDC and fan runs smooth
On the right find the record player screen-ground
Tubeamp.dk under construction
Vintage HiFi & DIY
B&O ~ NAD ~ LC-Audio The End mk.I / II / III
Leak Stereo 20 ~ Michaelson & Austin ~ Dynaco
Marantz ~ Sansui
As a shield against radiation I made the metal foil shown which has an electrical connection to ground....and it works. I have the well-known shields for noval tubes, but it is not necessary in this construction, where there is no hint of 50-60 Hertz hum
As mentioned, approximately 40,000uF has been used to smooth the heater voltage and two serial "bleeder" MOX resistors which together reduced the ripple to less than < 3.4 mVAC, while the heater ground is elevated 47VDC above main ground.
"The End"
beginning of a amplifier success 1989
see index
The End mk.3.1 circuit modified by the author and
showed with permission of the owner
LC-Audio Technology
Back in the 1980s, L.C. AUDIO TECHNOLOGY ApS was established by Lars Clausen in Denmark. The vision was a stable power output amplifier without global feedback. The first version was named "The End" mk.1. The differential input stage was quickly redesigned from approx. 10K Ohm in input impedance to approx. 20K Ohm, a value that did not affect the signal from tube preamplifiers with an output impedance of 1K to the same extent. "The End" mk.II was created. The year was 1989.
No SMD components
"The End mk. 4a" modified layout with standard transistors
checked and working. Very stable amplifier without global feedback and use of
T1 & T2 ~ Toshiba 120V, 2SA970/2SC2240 super sound.
The End mk. 4a
The End mk. 4a
The two "The End" amplifiers shown on the left are both version mk.II
Two out of 17 amplifiers made according to "The End mk. II" circuit. The modification "The End 4a" and +-35,0VDC shown from the chinese supply......voltage limits seems to be approx. between +- 48~56VDC as far as the best sonic sound is concerned ....100kHz straight and no spikes....
After "The End" mk.II came version 3.1 where the input transistors were delivered as SMD components. All transistors in both the voltage amplifier, output stage and the current generators themselves should be measured for amplification. It is the emitter resistors themselves of 0.22R that determine the damping factor. The amplifier should have suitably large heat sinks as the amplifier balances thermally.
To avoid SMD components and be able to build "The End" mk.3.1... I changed the input stage to version mk.II, at the same time the output transistors were changed to Sanken ring emitter types 2SC3263/2SA1294. Since it was no longer version 3.1 the "new" amplifier was given the number "4a". "The End" mk. 4a is easy to adjust and shows no hint of instability. The complete design shown above.
In my collection "The End" mk.4a is one of the best transistor amplifiers around 100 Watts I have listened to.
