Model ABS-Qi+
The model ABS-Qi+ auto bias module is designed to optimize the bias for four triode or pentode output tubes in Push-Push (PP) or Parallel-Push-Pull (PPP) amplifiers that DO NOT have their own negative bias supply circuit.
Suitable for class A, AB, or B tube amplifiers.
The ABS-Qi+ dynamically controls the bias in four tubes.
The module automatically optimizes the bias settings and maintains a strict symmetry of currents through both tube branches in the output stage. It will also stop any DC current flowing through the output transformers, all with the minimum of current loading on the anode of a tube. 
DC current saturates an output transformer which results in increased low frequency distortions.
The bias level is kept at the preset value irrespective of the input signal.
This module is completely autonomous as it has its own bias and 6.3VAC power supplies.
The ABS-Qi+ will operate with the filament supply in your amp reference to ground, such as a center tap, since it comes with it own power transformer!
- PCB dimensions are 100mm x 80mm x 25mm high / 4" x 3.15" x 1" high
- completely autonomous, comes with its own bias and operating supplies!
Price for one ABS-Qi+ module: US$100.00       in stock
Shipping of $11.00 for the lower 48 will be added when you click on the PayPal button.
For shipping outside the lower 48, please contact us first, thank you.
NOTE: Hardware such as spacers and screws to mount the module is NOT included.
For Canadian customers, please use the '+ for Canada' option in the 'Add to Cart' menu for additional shipping cost, thank you.
ABS-Qi+ options: