sales@effectrode.com

  • About Us
  • Knowledge Base
    • Tubes
    • Binson Echorec
    • History
    • Pedals
    • Quality
    • Techie Tone
  • News
  • Press
  • FAQ
  • Vacancies
  • My Account
  • Login
logo
  • Store
  • Stockists
  • Artists
  • Contact
  • | Newsletter
  • Store
    • Accessories
    • Pedals
    • Vacuum Tubes
  • Knowledge Base
  • Stockists
  • Artists
  • Contact
  • FAQ
  • About
  • News
  • Press
  • Newsletter
  • 0

    Shopping cart

    0
    Cart is Empty

Blackbird Bias Settings

  1. HomeKnowledge BaseBlackbird Bias Settings

Blackbird Bias Settings

Biasing

The new model of the Blackbird tube preamp is fitted with a ‘PRE-EMPHASIS’ (previously labelled ‘PRESENCE’)  toggle switch on the rear panel. This replaces the ‘BIAS’ switch on the older model. Both models feature an internal ‘BIAS’ trim-pot which allows full control over biasing of the first gain stage of the drive channel. The brief article below explains how make the adjustment.

bias
Internal biasing trimpot

The internal trim-pot allows the resistance value of the cathode bias resistor of first tube stage in the drive channel to be decreased or increased. The dual triode tube in the middle position is the input stage and second gain stage of the drive channel. A trim-pot adjustment tool or precision screwdriver can be utilised to adjust the trim-pot. Rotating the trim-pot clockwise increases the bias voltage, ‘hot’ biasing the tube stage and rotating anti-clockwise ‘cold’ biases the tube altering the voltage gain, sensitivity and linearity of the first gain stage. In laymans terms this affects the biting point and ‘feel’ of the drive channel, that is, how it responds to playing dynamics. For a more detailed explanation of this check out the article Guitar Preamp Tone Explained

According to the RCA Receiving Tube Manual—the same book Leo Fender used when he designed his amplifiers in the early 1950s—each tube type needs to be biased so that it’s operating in the middle of its linear region. The book contains charts with values for bias resistors used in resistance coupled amplifier test circuits—the same type of circuitry as used in tube preamps. These circuits utilise a test 100KΩ anode resistor and the cathode bias resistor is chosen to set the anode current for different types of tubes according to the table below.

Tube TypemµResistor (Ω)
12AX71001K8
5751701K6
12AT7603K
12AY7451K6
12AU7204K7
6189202K7

A digital voltmeter can be used to confirm the resistance of the bias resistor is technically correct for the first gain stage, however the ‘BIAS’ trim pot is really there for guitarists who wish to experiment with moving the bias point up (‘Hot’ biasing) or down (‘Cold’ biasing) to achieve more non linearity to affect the character of the Blackbird’s drive channel. Note: when measuring resistance of the cathode resistor make sure the pedal is disconnected from the power outlet. Place test probes between ground and wiper of the trim-pot.

blackbird_bias_trimpot_adjustment_640px
A digital voltmeter being used to confirm the resistance of the cathode bias resistor.

Bias resistance can be adjusted from about 10KΩ (cold bias – trimpot fully anti-clockwise) to 0Ω (hot bias – pot fully clockwise). Note: you cannot damage a preamp tube by hot biasing it.

In This Section

  • A Little Vibe History
  • Blackbird Bias Settings
  • Blackbird Sample Settings
  • Blackbird Sounds
  • Blackbird Switching Options
  • Blue Bottle Sounds
  • Custom Work
  • Delta-Trem Sounds
  • Delta-Trem Tremolo-Panner In-depth
  • Everything You Need To Know About Playing And Recording With The ‘Blackbird’ Vacuum Tube Preamp
  • Fire Bottle Sounds
  • Fuzz Pedal Placement
  • How to Use a Guitar Buffer Pedal
  • Mercury Fuzz Sounds
  • PC-2A Compressor In-depth
  • PC-2A Sounds
  • PC-2A Supplemental
  • Phaseomatic In-depth
  • Phaseomatic Sounds
  • Story Behind the Tube Drive
  • Swapping Tubes in the Blackbird
  • The Dream Machine: the Echorec 3°
  • The Effectrode Blackbird: A study in tube rolling
  • Tube Drive Sounds
  • Tube-Vibe Expression Pedal Options
  • Tube-Vibe Sounds
  • Vibe Pedal Placement
logo
+44 (0) 1782 372210 sales@effectrode.com
facebook instagram twitter pinterest rss soundcloud
Newsletter

Useful Links

  • Shipping Policy
  • Refund Policy
  • WEEE Policy
  • Privacy Policy
  • Warranty Policy
  • Register Your Pedal

Instagram

The Phaseomatic Deluxe™ is unique phaser pedal t The Phaseomatic Deluxe™ is unique phaser pedal that utilises vacuum tubes and photocells to create rich, lush vibrato and swirling phase-chorused effects with amazing presence and clarity.
 
#effectrode #phaseomatic #phaser #phaserpedal #pedaloftheday #tubeeffects #guitarpedals #guitarfx #effectspedals #guitar #pedalboard #guitareffects  #guitargear #guitarist #knowyourtone #guitarpedal #stompbox #guitarplayer #geartalk #fxpedals #guitars #electricguitar #pedalboards #guitare #guitarra #chitarra
These two audio tools do essentially the same job These two audio tools do essentially the same job—compress (level out the dynamics) your guitar signal using class-A vacuum tube electronics and photocells. However, the Leveling Amplifier has a few extra bells and whistles up it's sleeves. It was primarily designed following requests from sound engineers and musicians for a four knob version of our PC-2A photo-optical tube compressor to include 'attack' and 'knee' knobs. We took this on board but, being engineers, we also added several other really cool features including balanced transformer isolated output, gain pad, tube boost, dynamic equaliser and parallel tube input stage (4 triode tube gain stages in parallel) for hyper-quiet operation.#effectrode #PC-2A #compressor #compressorpedal #levelingamplifier #tubeeffects #guitarpedals #guitarfx #effectspedals #guitar #pedalboard #guitareffects  #guitargear #guitarist #knowyourtone #guitarpedal #stompbox #guitarplayer #geartalk #fxpedals #guitars #electricguitar #pedalboards #guitare #guitarra #chitarra
The Best of 2020!   #effectrode #tubevibe #blackb The Best of 2020!
 
#effectrode #tubevibe #blackbirdpreamp #tubedrive #levelingamp #phaseomatic #deltatrem #compressor #pc2a #overdrive #univibe #phaser #tremolo #guitar #guitarpedals #guitarfx #effectspedals #guitareffects  #guitargear #guitarist #guitarpedal #guitarplayer #geartalk #fxpedals #guitars #electricguitar #pedalboards #guitare #guitarra #chitarra
© 2020 EFFECTRODE THERMIONIC