Baxendall tone control circuit

jacky April 20, 2010 38 Comments

Description.
This simple tone control circuit is designed based on the famous Baxendall tone control circuitry. The circuit given here can give a maximum cut or boost of around 12 dB at 10 KHz (treble) and 50Hz (bass). Also, both bass and treble can be independently adjusted.
Transistor Q1 (BC109) and its associated components (R1, R2 and R3) form an emitter follower which is the input stage. The voltage gain of this input stage is around 1 and it has an input impedance of around 225K ohms. The output of the input stage is coupled to the passive Baxendall circuitry using the capacitor C1. POT R7 can be used to adjust the bass and POT R10 can be used to adjust the treble. Transistor Q2 and associated components (R11, R12 and R13) forms the final output stage which gives an overall voltage gain of three to the system.
Circuit diagram.

baxendall tone control circuit

Notes.

  • Assemble the circuit on a good quality PCB.
  • The circuit can be powered from 12V DC.
  • POT R7 can be used to adjust the bass while R10 can be used to adjust the treble.
Comments
  • Aiza Basquina
    December 18, 2014

    Try this 300W Hi-Fi mosfet amplifier http://adf.ly/vNFeo the is superb.

  • Pascual
    October 16, 2014

    Sir can i use S9014 in my place BC109C not available?

  • p robertson
    May 5, 2014

    why no mention of a volume or level control?

  • February 22, 2014

    I quite like this diagram. However, I twill be my first experience of building a tone controller. My work/interest has been to build musical instruments, and, especially, on the basis of traditional prototypes. So, as I use them on stage, and if professional musical performance, I have found myself a way to amplify them, and now I need better control of the sound, allowing me to manipulate the tones.
    I am looking forward to this controller, as I am starting to build one now. Is there another advice you would give to entrants in the areas of sound electronics or acoustic engineering?

    Regards
    Luka

  • yl kasun udayanga
    July 25, 2013

    diagram ok

  • Prudencio G. Peritos Jr.
    July 12, 2012

    Sir,,, this is me again to ask you regarding the PIN OUT of BC109C
    transistor…thanx

  • seetharaman
    October 31, 2011

    Hi Tanker use the values shown in the following circuit
    http://www.circuitstoday.com/passive-tone-control-circuit

  • Tanker
    October 31, 2011

    Hi.
    If I would use 100K pots, how will that affect the sound?
    What should I change, if I want to use 100K pots?

  • July 20, 2011

    sir
    I went to an electronics hardware man, yes u were right. I made a mistake in connecting the E & B of the main transistors. Sir is there a way to know the EBC configuration of transistors using digital multimeter .Small transistors can be tested using that hole in the side but sir what about big transistors ??

  • seetharaman
    July 16, 2011

    Hi Rahul may be your bias diode polarity is wrong hence the output transistor might have blown. check the C,B& E connection of each transistor whether they are connected in the right way. check the entire wiring. if you can get help from a nearby electronics hardware man, please do not hesitate.

  • July 16, 2011

    Sir
    The 100 watt woofer circuit is not working. I have used 2n5296 instead of 2N5294,0.33 ohms 2watt instead of 5 watt .
    sir i have made the power supply with two 12 0 12 transformer, made it 24 0 24. when I tested it wit 24 0 24 the speaker burnt off after switching the supply for 2 to 3 min. there was only a humming sound no clear output. the speaker I used for testing the circuit was 4 ohms 5 watt speaker. can u please suggest me something ?…..

  • seetharaman
    July 14, 2011

    Hi Rahul 549C is BC549C is a plastic TO92 version of BC109 metal TO18 version. Refer Philips datasheet.
    http://www.datasheetcatalog.org/datasheet/philips/BC549_550_3.pdf

  • July 13, 2011

    sir
    I could’t understand .Is 549C a transistor? can U explain me a bit?

  • seetharaman
    July 13, 2011

    Hi Rahul with some samples of BC547 i had problem with 549C it is ok. you can try fixing a 47PF capacitor between collector and base of Q2. this should solve your problem.

  • July 13, 2011

    sir
    I have checked the tone circuit with other amplifier’s the noise is due to the tone not because of the motional feedback amplifier. When ever the circuit is switch on it sounds like untuned radio (when the song is not played).The noise reduces when the song is played but a part of it is still there. specially in high frequency notes of the songs. Is because of the transistor BC 547

  • seetharaman
    July 10, 2011

    Hi Rahul the isolating capacitor, which will block DC flow from one stage to next stage. only the AC signal (Audio) alone will be transferred to the next stage. For motional feed back amplifier you require at least 40volts DC below this voltage it will give distortion. For tone control it is sufficient 560K is OK. now try to improve the supply voltage to amplifier you will get best out of it.

  • July 9, 2011

    sir
    Your motional feedback amplifier is a beauty along with the tone control. my tone control worked along with your modifications but sir the out put is not that clear .A little noise is still there.
    I have used 12V transformer for both the circuit’s with an dc output of around 16v .I have used 0.47 mfd 63V in series with supply and 560K instead of 820k for the tone control circuit.sir what do you mean by an isolating capacitor as stated in 6 July reply…

  • seetharaman
    July 9, 2011

    Hi Rahul mail me your requirement i will reply with diagram at seethasub@hotmail.com

  • July 8, 2011

    sir
    I could not understand how to use two 12 0 12 transformer to make it 24 0 24. can you explain me it in detail or give me a circuit diagram of it…

  • seetharaman
    July 8, 2011

    Hi Rahul you can use voltage doubler in the secondary that will make 24 0 24. but the current will get halved. You have to double the value of filter capacitor. If you have 12 0 12 say 5amps rating(120VA) then you can make it 24 0 24 at 2.5 amps the same VA rating. or you can use two transformers using full 24 volts from each transformer. primary paralleled and secondary in series in phase.

  • July 8, 2011

    sir
    how to convert 12 0 12 into 25 0 25 . in my place I won’t even get a 24 0 24 transformer…..

  • seetharaman
    July 8, 2011

    Hi Rahul for sub woofer amplifier you equire both positive and negative supply. Minimum is +25 0 -25 volts for the circuit to function. The first stage differential circuit will not function with such a low voltage.

  • July 8, 2011

    thanks sir
    sir I have even made the 100 watt sub woofer but I am not getting the out put..
    the components i have used are
    2N 5296 instead of 2N5294 R14 & R15 of 2 watt instead of 5 watt C1 2.2 uf instead of .22 uf .sir a baarrrrr sound is heard as output . sir I have powred it using a 12 volt 2 amp transformer instead of 35 volts transformer due to unavailability . is it because of the 2N5296 transformer????? i have used a mp3 player as input…

  • seetharaman
    July 7, 2011

    Hi Rahul if you are using BC547 instead BC149C / BC109C you will get less hfe hence you have to change the bias for Q2 transistor. supply polarity need not be reversed. with supply reverse it will act only as an attenuator since there is no active component. Reduce R11 to 820K and R13 to 1K.

  • July 7, 2011

    Thanks a lot for your reply sir….
    sir i have used bc547 instead of bc107c. sir i get an out put only when the power polarity is reversed.but my bass & treble pot’s are not working properly.
    I have used it as an pre amplifier for you motional feed back amplifier .wow…it sound’s really good..

  • seetharaman
    July 6, 2011

    Hi Rahul Q1 is the input (wrongly shown as audio out – it is audio in)device you connect your signal source through an isolating capacitor 0.22uF(ipod, walkman, Mp3 player etc). connect output from C7 to any power amplifier of any power.

  • July 5, 2011

    hi
    can any one suggest me how to connect the circuit to an amplifier . I have assembled the circuit but i dont know how to connect it….

  • Seetharaman
    April 9, 2011

    Hi PJ it is better to use the circuit for what it is designed for. to suit our requirements we have to carryout the modifications ourselves.

  • pj
    April 9, 2011

    i see.. i ask seetharah about a 35 v transformer he said that i just replace r14 to 12k..

  • pj
    April 7, 2011

    what transistor would i replace bc109? and is it ok if i use 50k pot? and the voltages of the capacitor if i use 35 v transformer. sorry just a beginner student.. its a project.

    • admin
      April 8, 2011

      you can use BC546 or PN2222 in place of BC109

    • admin
      April 8, 2011

      The circuit requires 12V for operation and there is no scope for a 35V transformer in this circuit. Electrolytic capacitors can be rated 15V. 50K POT is fine.

  • Seetharaman
    April 4, 2011

    Yes that is all you have to do. wish you happy hearing and enjoy.

  • pj
    April 4, 2011

    ahh. is that the only resistor that i would change? so that it would work?

  • Seetharaman
    April 2, 2011

    Hi Pj You can use a 35volt transformer will give you 50volt DC approx. this circuit requires around 3mA @ 12 volts. To drop 50 volt you have to increase the value of R14 to 12K.

  • pj
    April 1, 2011

    hi seetharaman what if i use a 35 volts transformer in this circuit? is it possible? thanks

  • Seetharaman
    February 15, 2011

    Hi Jacob This being a passive tone control there will be an attenuation of sound, Q2 should take care of increasing the level suitably.
    First interchange C6 polarity(+ should go to base of Q2)
    Increase R3 to 4.7K
    Reduce R12 to 5.6K
    Add 100uF in series with 220 ohms resistance in parallel with Q2 emitter resistance R13 – 2.2K.

  • Jacob
    September 20, 2010

    hello seetharamn i have used this tone control for 100watt amplifier a izzzzzzz noise is coming from this circuit and also volume is getting decreased a little and at maximum sound quality is not good

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