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ST-70 & AB, ultimate ST-70 upgrade kit, auto bias 


ST-70 & AB, ultimate ST-70 upgrade kit, auto bias PC-3 driver - ECF82, 6GH8


Power driver + autobias for PP four triodes or pentodes

!! It will be on sale for a month !!

RIAA Phono Preamplifier for magnetic phono cartridge


3 Band Preamplifier - Double Bass, Bass, Treble


Driver for Dynaco ST-70 including module AB for autobias



Autonomous automatic control bias system ABF-Q without bias source


Auto bias module specially for amplifier DYNACO ST-70, ST-120

!! It will be on sale for a month !!


Auto bias module specially for amplifier DYNACO M125

!! It will be on sale for a month !!


Auto bias module ABS-Q+

!! It will be on sale for a month !!

Tube auto bias control 

Technology seamlessly integrated into the tube amp.
It will measure the current flowing through each power tube several times a second and will automatically make any necessary bias adjustment . This means the power tubes will always have an optimum bias over their entire lifespan . It will assure a consistent sound quality, trouble free usage and no need for any manual adjustments ever again. 

Replacing the power tubes is a breeze as well. Plug in a new batch of tubes, disconnect the input, turn the amp on and let it sit for 5 minutes. That’s it. No special tools or devices required. Spot on bias setting every time. 

Besides the obvious benefits of never having to worry about the bias, the same technology will also notify you if a tube is at the end of its lifespan and needs to be replaced. It will detect faults like a defective tube or problems with the bias voltage itself. If any of these errors threaten proper operation, the amplifier will go into protection mode to prevent any possible catastrophic damage.

Using tube amps just got a whole lot simpler.

Discover our latest solutions for output stages of tube amplifiers !

This website focuses on tube amplifier solution using modern elements. Special attention is paid to amplifiers output stages- their setting and control, output transformers, power supply units and another amplifier parts.

The information is based on many years of experience in construction and measuring of tube amplifiers, development of modules for tube stage control & quality output transformers . Comparisons of various connection types, measurement results and recommendations for the construction of modern tube amplifiers are all to be presented here.

You can easily equip your existing tube amplifier with fully analogous circuits that enable an effortless automatic bias control so that you can completely avoid repeated re-setting of output stages resulting from tubes aging and at the same time guarantee optimum conditions for the permanent operation of your tube amplifier.

  • Beautiful enjoyment of listening to music !
  • Silken bass, crystalline height !
  • Set your optimal bias for amplifier forever !

Fitting the module into your amplifier will have these benefits:

  • no need to constantly re-adjust tube operating points
  • significantly extended tube life
  • current regulation not influenced by the music signal
  • clear 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
  • optimum utilization of tube life
  • suitable for all types of output transformers (namely toroidal transformers 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 further re-adjustments. The module constantly creates optimum conditions for the output stage, independently of tube aging and consequent changes in their parameters.

Graf auto-bias

Coming soon:

We are going to focus on the construction of output transformers which may be the key to achieving perfect results utilizing only the currently available parts.

Serial production

Serial production

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