Advertisement
Table of Contents
THÖRESS
F2a11 Integrated Amplifier
=============================
"F2a11 Integrated"
................................................................
I N S T R U C T I O N
M A N U A L
Thank you for purchasing the THÖRESS F2a11 Integrated Amplifier!
Our all-tube Integrated utilizes the famous F2a11 vacuum tube in single-ended
triode operation mode for an output power of up to 6 watts into a 4, 8 or 16 ohm
load. Notably, the F2a11 Integrated can also be employed as a stereophonic power
amplifier (in combination with a line or full function preamplifier) in which case the
volume control knobs of the amplifier serve as input attenuators to match the gain
of the line device to the efficiency of the loudspeaker.
The amplifier provides 3 line level inputs (2x3 RCA jacks) of equal gain status
selectable via rotary switch on the rear panel. High-grade continuously variable
potentiometers are employed for separate (manual) volume control of the channels.
The output transformers (OPT) are made in house to the highest possible standards
and allow for precise matching of a 4, 8 or 16 ohm loudspeaker load to the power
tube by way of jumpers soldered to the secondary terminals.
Please read the following explanations and instructions carefully to get the most out
of your F2a11 Integrated Amplifier!
TUBES
The power tubes are biased automatically (via voltage drop over a cathode resistor).
An obvious design choice (and very reliable setting of grid bias) in view of the
comparatively low grid bias voltage required for the F2a11 tube (thanks to its high
mutual conductance). The ideal (average) F2a11 tube draws an anode current of
Ia=73mA when it is exposed to an anode voltage of Ua=380V and a control grid bias
voltage of Ug1=(-)16V (in triode operation mode, screen grid connected to the
anode). Representing an excellent quiescent point for single-ended operation which
we have chosen for the F2a11 power tube in our amplifier. Corresponding to an
anode dissipation (Pa=28W=380Vx0.073mA) well below the permissible design
maximum of 35W,
Advertisement
Table of Contents
Subscribe to Our Youtube Channel
Related Manuals for THÖRESS F2a11
Summary of Contents for THÖRESS F2a11
- Page 1 An obvious design choice (and very reliable setting of grid bias) in view of the comparatively low grid bias voltage required for the F2a11 tube (thanks to its high mutual conductance). The ideal (average) F2a11 tube draws an anode current of...
- Page 2 (Ua, Ug1, Ia, Pa) = (380V, (-)16V, 73mA, 28.5W). Automatic grid bias is applied for the F2a11 power tube. The grid bias voltage cannot be trimmed to adjust the idle current of the power tube! Allowing for a tight 7% tolerance in anode current under the given voltage conditions (380V, (-)16V) , only F2a11 tubes with Ia values in the rage 68mA=73mA-5ma ...
- Page 3 It is not advisable to use a 4 ohm loudspeaker on the 8-ohm or 16 ohm load pattern of the OPT! It is not advisable to use a 8 ohm loudspeaker on the 16-ohm load pattern of the OPT! SETUP To setup the F2a11 Integrated Amplifier switch off all components of the system and proceed as follows.
- Page 4 Always make sure that the volume controls are in zero position before powering on the F2a11 Integrated! Never switch a program source on or off while the F2a11 Integrated is powered on! 11. Activate the desired program source with the input selector and listen to music.
- Page 5 Always switch on the preamplifier and the program sources first and then switch on the F2a11 amplifier, observing a delay of at least 30 seconds! Never switch the preamplifier or a program source on or off while the F2a11 Amplifier is powered on! 12.
- Page 6 13. Let the volume controls of the F2a11 Amplifier rest in the positions determined in step 14 and from now on use the volume control knob on the preamplifier for loudness control as long as input STER is switched active.
Need help?
Do you have a question about the F2a11 and is the answer not in the manual?
Questions and answers