hello. Does anyone have the schematic for an audio preamplifier with baxandall tone control?
Last edited:
You'd be pretty hard pressed to find a schematic of an audio preamp without a Baxandall tone control. They do exist, but not common.
An option if you're not set on a Baxandall type tone control, is John Broskie's diy single-knob passive 'Tilt' type tone control, ala' Quad. It uses a single three-position switch, rather than two potentiometers. Pros and cons to each type of control.
https://www.tubecad.com/2015/06/blog0326.htm
https://glass-ware.stores.yahoo.net/tonecontrols.html
https://www.tubecad.com/2015/06/blog0326.htm
https://glass-ware.stores.yahoo.net/tonecontrols.html
Last edited:
can i connect the baxandal circuit suggested by member artosalo to the grid of a 6v6 tube for example with appropriate resister and pot or do i need a another tube buffer or inverter
Baxandall tone and volume circuits requires a lot of gain as its a negative feedback circuit - typically they are used with opamps, but a high gain pentode stage might be used for example. It is an inherently active circuit.
That's indeed what Baxandall himself used in 1952, see page 404 of
https://www.worldradiohistory.com/UK/Wireless-World/50s/Wireless-World-1952-10.pdf
One possible problem is that the volume control is up at the front which means the circuit noise is passed in full to the next stage (your power amp). How noisy such a stage is I don't know but it would not be done that way today with solid state gear. The output impedance looks very high (and variable) too.
The tone network is also just a passive stage which means it has some serious attenuation to it (it can only cut bass and treble, not boost) but by taking a cut of both as 'flat' it operates as boost and cut... if that makes sense. That is why it needs the high gain stage up front.
Some of the values look odd, why are CE1 L and R different?
The tone network is also just a passive stage which means it has some serious attenuation to it (it can only cut bass and treble, not boost) but by taking a cut of both as 'flat' it operates as boost and cut... if that makes sense. That is why it needs the high gain stage up front.
Some of the values look odd, why are CE1 L and R different?
this baxandal was proposed by artosalo, is this a good diagram ? can i connect to a amplifier without other stage ?. what book can guide me to understand input impedence,reverse polarity etc without heavy tecknical stuff. i have morgan jones book .my goal is to build a small preamp with baxandal, input selector, point to point construction and understand the theory of the preamp. next step is building low watt amp i have read wiring procedure , part selection ,coupling cap, resistor type etc , disposition of the parts on chassis ,magnetic field i have read pete millet guitar stuff . do you have reading or schematic suggestions
This is inteded for line level, not for signal levels of 10...20 Vrms, which may be required for driving the output tubes directly. I recommend to omit 6N6P cathode follower and take the signal from volume potentiometer to a common cathode voltage amplifying stage.
After this there is sufficent signal level for driving an output tube.
After this there is sufficent signal level for driving an output tube.
That is an active Baxandall type control. The volume pot is correctly located after the first stages and so noise is minimised. Output impedance is 'low' and constant because the output is taken from cathode follower. Input impedance is..... well certainly 'high'. About 120k with the balance pot centred?
I built that one too. I also built a tube version from one of the RCA Tube Manuals.