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Mr C Durandal from Germany his favorite EL 84 and 2A3 Single Ended Amplifier

Durandal's in Germany

please visit Durandal's Main Site in Germany


Mr C Durandal from Germany and his EL 84 Single Ended Amplifier
and around his system .if would like to see picture full size here
and his comments are next:

After having build this amp, so here they are:

Talking about sound is a controversial topic. Reading HIFI reviews
may get oneself lost in the confines of others subjectiveness and
others interests. One has to learn to hear and judge by himself if
you want to get somewhere. You are the judge. Free yourself from any
preconceptions and get out for the hunt!

One of the best and cheapest ways to get on the right track is to
embark in a D.I.Y. project and I think this EL84SE is a very
rewarding enterprise.
Don_t mind the 4W rating, this amp will fill your listening room
with refined sound provided your speakers are up to it. When I
first listened to it I had the original CYRUS 780s from Mission with
89dB sensitivity and they performed excellently and loud enough
to get the neighbours interested.
This amp will rock, swing and play classic or jazz to the listeners

One thing about this amp that puzzels me still is the effect of the
so called stopper diodes. One connects +B to the output transformer
and the other supplies the screen grid after some filtering.
If you build this amp try replacing them with a piece of wire and
compare the difference.
Do one at a time, they have different effects and to my taste very
positive ones, specially the grid connection.

Also the feedback employed here is not ususal and I think it is a
key detail responsible for the sweet and yet dynamic sound character
of this amp.

This capacitor at the EL84s cathode has a great influence on the sound.
I found this out per chance as I did not have the specified MUSE or
Cerafine. I tried several capacitors and settled with a 220uF/100V SXE
series from UNITED CHEMI-CON.
Also Sanyo OSCONs where at hand and found them to be also good.
Unfortunately I have never tried the MUSE or Cerafine.

Be sure to wire this part of the circuit correctly.
Which lead of the OPT connects to ground and which to the capacitor
is crucial. If wired the wrong way around you build a powerfull oscilator.

There is another difference my version has compared to the original
schematic, the output transformers. In my amp I use TAMURA F-475, they
where there when I needed some OPTs and fitted the spec.
Don_t save money here unless you have enough to spend it twice;
once for the wrong and once for the right ones. They don_t have to
be TAMURA though.

This amplifier connected to a good source and decent speakers
will carry the listener away. A most enjoyable sound experience.

Carlos Durandal

Mr Carlos Durandal
from Germany on 12nd May 2008

I just saw the picture on your web site, looks good!

Very hot in Bavaria today. A little rain would be good.
Today was holiday in Germany.

Tamura with 2A3 Single Ended Amplifier on 20 Oct 2008

:Durandal 2A3 Single Ended Amplifier
:Inside of Amplifier

circuit 2A3 SE by Carlos Durandal
Push botton to see picture

picture up load on 22nd Feb 2009 for inside of 2A3 SE
and Circuit Diagram is next on 29er Oct 2008

Ayer he pensado mucho en ud. porque ayer tarde finalize mi amplificador
2A3EH SE con TAMURA, 6AQ8EH en SRPP y 5U4GB. Cuando realizaba las ultimas
medidas antes de poner los parlantes de prueba mis manos estaban temblando...

Aunque los filamentos 2A3 y 6AQ8 funcionan con corriente alterna
no hay hum a menos que pegue el oido al altavoz (!!!) y aún asi es muy poco!
Parlante tiene 90dB de sensibilidad (B&W 703).

El que mi primer DHT funcione sin más problema, enseguida ha sido también
una gran alegria.

Cuando lo conecté a mi equipo (9 de la tarde) mi mujer dice que suena tan claro.
Es muy transparente y sutil, es lo mejor que he oido.

Estuve escuchando musica hasta 12:30. Fue dificil para mi ir a dormir :-)

later I got a letter from him in Germany.he said......

lately I have been thinking of you, the reason being that my new 2A3 SE
amplifier project came to a happy end. My hands were trembling when I was about to
switch it on hooked to a dummy load. I was very exited and amazed because all seemed
to work well the first time. I measured some voltages and then hooked it to a pair of
test speakers (single driver horns) and a portable CD player that I use for preliminary tests
in my workshop. The music sounded very promising in this setup. It was already very detailed
and delicate and the hum was so low I could not believe it since all heaters run on AC.
I took the amp to the living room and hooked it up to my system. I was very tense and
was rewarded with clarity and smoothness of sound, very delicate. I think is the best amp I have build.
The first comment from my wife was "how clear!".
It was around 21:00 when I started and I found it hard to get to sleep at 00:30.
The tubes were 5U4GB, 6AQ8 and 2A3 all from EH.
I have made some changes since -out of curiosity- and tried ECC83 from JJ and 2A3 from Sovtek.
The change to ECC83 brought an improvement and the cathode bypass used in the 6AQ8 circuit could
also be removed. The Sovtek has a warmer touch than the EH, to me it has more soul, so I left the Sovtek in.
I am very happy I embarked on this project.
Many thanks for your advises an encouragement. It will take a long time before I build another amp.


PS: I decided to use fixed bias to reduce the heat under the hood of the wooden chassis and to keep
the electrolytics cooler. The bias of the 2A3 lies at 52mA with 250V plate voltage ref. to GND.

Note: Driver is 6N2P and coupling capasitor is VitaQ East-One Japan.
He said "Tiene m_s vida y profundidad. Pienso que el nuevo condensador
que ud. me envio es extremadamente bueno para el sonido.
Estoy encantado."on 22nd Feb 2009 in germany.

Mr Carlos Durandal
from Germany on 7th Nov 2008
if you would like to know moremailmeask to him

And his Main system are:

The CD player is a ROTEL,
The CD player is Philips CD830,

The Record player(turn table) a LUXMAN,

The Speakers are B&W 703

His Project on 2009 from Germany

next is experiment of pre-amplifier

Test pre

built in Pre Tubes into CDP

Built in Pre Valve into CDP


Proto Type his 6N3P Pre-amplifier

6N3P SRPP Pre Amplifier

pre-proto tipo 2009

Ref: Lukaz Fikus lampiz and Materials Tufnol Sheet


circuit diagram and some picture

The "Preamplifier" story:

The "Preamplifier" story:

Having experimented with different OPAMPs in the output stage of different CDP and
in view of the results, the idea of building a tube output stage haunted me for a long time.
Several reasons kept me from doing it, mainly lack of time,
knowledge and space inside the CDP.

Several web sides deal with this, but it was the Lampizator site from
Mr. L. Fikus that provided the definitive trigger. An SRPP circuit directly after
the DAC? No anti alias filter!!! ???I was very skeptical but very curious.

A CD-ROM drive was at hand that could be sacrificed for a test:

After some effort to find the DAC output and figure out what type it was
(current or voltage output), it turned out to be TOSHIBA
IC with a 24bit DeltaSigma DAC with voltage outputs inside.

Great! My 2A3SE amp has SRPP input stage so all that needed to be done to test
the Lampizator idea was to connect the CD-ROM to the DAC via suitable capacitors.

After I did this and listened -DAC output was generous enough to drive the SRPP input stage
(6N2P)- I was impressed and confused. This CD ROM drive with all its HF inside,
running from a switched power supply and no anti aliasing was sounding
better to my ears than the Rotel!?

I could find no peace and went a long way until I ended up with a Philips
CDP830 converted to non oversampling and 6N1P SRPP tubes fitted in Lampizator


The best CDP so far to call my own. Then the Rotel had to be saved and this "preamplifier"
came to the rescue. It is based on the Lampizator schematic. Only I found 6N3P to sound
most pleasing in my setup. on 21st Apr 2009

6P7S single ended amplifier under experiment

6P7S single

More Power from 6P7S,
El amplificador esta en marcha desde casi una hora y parece que el sonido se hace mas
6P7S is family of 807,1625 and 6L6GC.
6P7S Spec from OLD Radio QRZ?

The 6P7S SE amp is just a tested for this newly adquired output valves. Originally
it was an EL84SE with Tamura's OPTs. I had taken the OPTs for the 2A3 SE amp and
had fitted some small cheap OPTs to keep it alive.
The new OPTs are far from the Tamura but still give a very nice sound.

I though that with very little effort modifying the amp the 6P7S could be
tested for basic function on it: 270 ohms cathode resistor and 10 more volts on +B
that were possible.

The new tubes have octal bases so an adapter was needed.

The tubes operation point settled at 250V/50mA and the grid voltage to -15V.
About 12W total dissipated power. The 6P7S can do 20W I read.
In pentode mode the sound was good but not quite. Changed to triode mode using 200
ohms between the plate and screen grid and the sound became smooth and sweet.
I like it so much I am thinking of building a proper chassis for it.

6P7S Single Ended Durandal Amplifier may 2009 germany

6P7S SE Durandal Amplifier may 2009 germany


Circuit diagram and comments for 6P7S SE D.I.Y

my line

Hand Made High End Amplifier early 2009

near own city

Near Durandal home town on Apr 2009

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"Durandal Dreams" since on 10th May 2008 last up date on 19er March 2012
K  Mizushima a part of Single Ended Amplifier D.I.Y