Auto Bias Modul for DYNACO ST70 ST120

Description

Output Tube Bias Control System.
Auto Bias for DYNACO ST70 ST120
ABS Module Features:
Automatic dynamic bias control module for triode and pentode output stages or push-pull (PP) amplifiers with isolation transformer (universal modul)
Designed for
class A, AB, or B
amplifiers.
The module dynamically controls automatic bias settings to maintain a strict symmetry of currents through both tube branches in the output stage, and to completely avoid flow of DC current through the output transformer, all with minimum requirements on anode current in the tubes. The DC saturates the output transformer which results in increased distortion of low-frequency sounds.
Bias control is realized by maintaining a constant bias on output tube grids, independently on the level of the driving signal.
The module may be supplied by the voltage for tube heating (6.3V or 12V AC) in the amplifier.
Automatic dynamic bias control module for 4 tubes
Benefits:
No need to constantly re-adjust tube operating points
Significantly extended tube life
Current regulation not influenced by music signal
Undistorted sound for a great listening experience
Significant increase in signal clarity – extreme reduction of hum and noise level of the amplifier
Improved bass transmission
No maintenance or additional setup needed
Optimum utilization of tube life
Suitable for all types of output transformers (especially toroidal ones which require automatic control)
Safe operation due to minimized danger of runaway tube current – even when the amplifier is left unattended
Universal use: suitable for all connection types
Fully analogous control: the module has
no digital elements
The modules are suitable for all amplifier types (classes A, AB, or B), as well as single-acting amplifiers with A-class tubes connected in parallel.
Their use is strongly recommended in existing amplifiers with fixed bias of output tube control grids, as aging of the tubes causes the need for a constant re-adjustment of their operating points.
The connection secures an absolute symmetry of anode currents through both branches of primary winding of the output transformer. This way, saturation of the the output transformer core with DC current with subsequent signal distortion and dearease in available power is reliably avoided.
Furthermore, tube operating points need no additional re-adjustments. The module constantly creates optimum conditions for the output stage, independently of tube aging and consequent changes in their parameters.
Do you want to pre-set the modules? If so, what will it be value of cathode current?
Need help getting involved?
If so, send a amplifier circuit diagram.
We will draw the circuit diagram of the module connection into the circuit diagram.