Ended Tube Amplifiers
Impressions by Francesco Pintavalle
Andrea Ciuffoli Single
ended amplifiers (published on Audio Design Guide) are the last creation
of this world renowned audio designer, in search of definitive sound for
its system. The technicalities are best described in the project pages,
nevetheless I would like to recall some of the important aspects of those
The topology chosen
for both of the devices resembled a bit the Sakuma style. It works in pure
A1 class, the power stage is coupled to the driver tube with a 1:2 transformer
- good decision but only for a null grid current setup - the bias is fixed
for the power stage (even if there was an automatic bias setup made for
testing purposes). The power supply is very very strong with a double L
filer fed by a couple of good GZ34.
The Listening test
has been performed in a rather small room, with a system setup ...
Tubes: 2x Rytheon 5842,
4x Svetlana 300B, 2x Mullard GZ34.
for all the magnetic devices.
Passive: Caddock resistors
everywhere, all caps are Elna Cerafine.
Transport source: CD
player Philips CD723
DAC: Andrea Ciuffoli
DAC 2.0 (see the project pages)
direct connection to the Power Amplifier
Speakers: 2 ways self
made with a TQWT low frequency unit with 20W75 Esotec Dynaudio driver (200mm)
and a HD14D34HR Audax dome tweeter (34mm). Crossover point @1550 Hz 20dB/dec
J.S. Bach: die Kunst
der Fuge, Experion XX, Astree
L. van Beethoven, 5th/7th/8th
Symphony, ..., ...
Pink Floyd, ..., ...
Tunnel of Love, ...
many CD by Fonè
1. PSE listening session
Due to the usage of
a fully transformer coupled system, the amplifier seems to disappear, especially
when set up with a fixed bias for the power tubes.
The Soundstage is
really impressive, stable, clean, open, wide. Instruments are perfectly
positioned in the acoustic scene. The depth of the musical event is really
stunning, as well as its elevation. I can 'see' the natural dimensions
for each instrument.
Power is more than
what can be required for a good level of pressure. In particular with complex
musical events, like orchestras, there are no compression effects at any
Low level details
2. SE listening session
Lower power has its
effects, considering that the loudspeakers userd for this test are 84dB
spl @2.83V it is not a problem!
The image is something
less stable than the PSE, but such an effect could be generated by the
usage at the power limit of the amplifier itself.