Viewing 18 reply threads
  • Author
    Posts
    • #6384
      mwpeters75
      Keymaster

      Professor Frank has been exclusively making contributions to the Lectron.Info forum with many new circuits.  I felt that it was time for me to add one!

      For the 50th anniversary celebration of the Lectron System (1966 – 2016), new blocks were created by Gerd Kopperschmidt using my suggestion of creating an FM Stereo model.  Five new blocks (including #2488 – the block shown below) were subsequently created to demonstrate the FM Stereo technology.  Unfortunately, a new distinct model was never released due to the passing of Mr. Cahn Von Seelen on October 28th, 2016. He was the Lectron System product manager from 2001 to 2016.  A Tech Bulletin was written by Mr. Kopperschmidt however which featured numerous circuits using the new blocks.  A circuit that was absent from the Tech Bulletin was one which featured the use of two speakers.  The circuit below is my offering to fill that gap.

    • #6425
      LectronFan
      Participant

      Hello Michael,

      This seems like a great receiver and deserves certainly a place in the Lectron hall of fame !

      Does the tuner block also has a line output for sound manipulation ?

      Can it also be tuned with an external voltage ?

      Sad to hear that Mr Von Seelen can’t visit this website and forum.

      Lets honour him with your stereo FM radio !

      Greetings,

      Frank

      • This reply was modified 2 months ago by mwpeters75.
      • This reply was modified 2 months ago by mwpeters75. Reason: Changed font and size styling for easier reading
    • #6434
      mwpeters75
      Keymaster

      Hi Frank,

      There is a line output available.  Please see the referenced tech bulletin which is available through the link.

      There is a circuit in the tech bulletin which shows a Lectron System block LCD voltage display.  It allows you to ‘dial in’ the voltage to equate to a desired frequency. The table of these voltages is also in the tech bulletin.

      I hope that Mr. CvS would enjoy the site now.  He never said anything about the Lectron.Info version 1 site.

      We can honor both Mr. CvS and Mr. Kopperschmidt by acknowledging their leadership in bringing the 50th anniversary blocks to fruition.

      Best,
      Michael

    • #6456
      LectronFan
      Participant

      Hello Michael,

      I’ve checked the tech bulletin and the FM module offers quite a lot of possibilities !

      Hmm, I see lots of mods and new circuits around this module 😆

      On the train back home, I had an idea with the FM module 2486.

      Let’s build a FM radio with bass and treble control !

      So back home, I grabbed the Start and expansion set and build an active Baxandall tone control circuit.

      With the upper potentiometer we control the bass tones, the lower potentiometer the high tones.

      The circuit consists of a preamplifier, followed by an active Baxandall tone circuit. The speaker is connected to this circuit.

      The radio module 2486 is very well constructed, it has an amazingly selectivity and sound quality !

      The Lectron team did a marvelous job !

      Here a picture, circuit setup follows later !

      Many greetings,

      Frank

      FM Baxandall

      • This reply was modified 2 months ago by mwpeters75.
      • This reply was modified 2 months ago by mwpeters75.
    • #6457
      LectronFan
      Participant

      Hello Michael and dear readers,

      To honor Mr. CvS and Mr. Kopperschmidt for their realization and Mr. Michael Peters for his idea, I proudly present a FM radio with a Baxandall tone control.

      This active control amplifies or weakens the lower and higher tones. It makes a huge difference concerning sound quality.  This control circuit is often used in amplifiers.

      You can always use the DIN or CINCH connection block and use a mp3 player or similar as input (as seen in the 3-stage amplifier project).

      Thanks to the Lectron system, this circuit is build in no more then 2 minutes !

      Oh yes, I’ve changed the input capacitor C1 into 0,47µF to improve the bass response.

      Here is the diagram, try it out and be surprised !

      Many greetings

      Fm Baxandall

       

      • This reply was modified 2 months ago by mwpeters75.
      • This reply was modified 2 months ago by mwpeters75. Reason: Changed font and size styling for easier reading
    • #6461
      mwpeters75
      Keymaster

      Well done as always Professor Frank!  I did not know that you had some FM Stereo blocks!  Great idea to have tone controls.  May I suggest that you blend the L and R signals so that, while monophonic, you have both left and right music channels? 

      Best,
      M.

      • This reply was modified 2 months ago by mwpeters75.
    • #6486
      LectronFan
      Participant

      Hello Michael,

      Here we have the improved version (V2) of the same radio, L & R are mixed together.

      The input circuitry needed to be tweaked by adding R11 of 5,6K and the overall sound is  !

      Also a new resistor R12 of 220 Ω was added to the Baxandall circuit.

      Here is the diagram for you to enjoy !

      Greetings

      FM V2 Baxandall tone circuit

       

       

      • This reply was modified 2 months ago by mwpeters75.
      • This reply was modified 2 months ago by mwpeters75. Reason: Changed font and size styling for easier reading
    • #6487
      LectronFan
      Participant

      Hi all,

      I forgot to mention that I used a stereo in ear phone as FM antenna.

      Just plug it in the mini jack at the bottom of the FM module.

      Works as a charm !

      Greetings

      • This reply was modified 2 months ago by mwpeters75.
      • This reply was modified 2 months ago by mwpeters75. Reason: Changed font and size styling for easier reading
    • #6520
      mwpeters75
      Keymaster

      Thanks so much Professor Frank!  Excellent use tips as well.

      Best,
      M.

    • #6882
      Guenni75
      Moderator

      Hi,

      the sound control is a good idea – I will keep it in mind and realize when my work with a lot of other things is done.

      By the way: here is a short overview of the developing steps of the FM radio since 2014.

      • starting with my first proposal (above left) with loudspeakers, connected via contacts OR cable(s), built-in batteries.
      • my first prototype with veroboard for a 81×81 mm block (above right)
      • my first PCB based on this prototype (to the left), assembled (2. row left) with 3 color LED for all functions
      • nice idea: combination of Lectron block (loudspeaker) with Lectron Bastelsatz case (Radio + 2. loudspeaker,  middle)
      • several radio blocks (designed by G. Kopperschmidt and built by myself, last row)
      • my small version connected with 2 speakers (down right)

      Next photo shows my extension (with UAA170 and 16 miniature LEDs) and a real FM scale:

      …and another nice FM radio, based on a ready assembled PCB:

      No Lectron block but another FM radio…

      Now it is enough of FM radios for today – here as a proview a simple BC / SW radio receiver block (was my low cost jubilee proposal):

      Best,
      Guenther

       

      • #6885
        mwpeters75
        Keymaster

        Hi Guenther,

        Love the history here!  Thank you for this succinct exposition with the photos.  

        Best,
        Michael

    • #7228
      Guenni75
      Moderator

      I have a question reflecting the R-pot-values of the Baxandall / Shelving filter / (in common German: Kuhschwanz-Entzerrer): I have two tiny pots with 100 kΩ which I would like to use – how should the values of the corresponding C’s (and serial R’s) be chosen, if I build a special block with all the components inside? I have found a “Calculator” on a homepage but are not sure how to use the right basic values as an input… and my time to study all the theoretical background is strongly limited – sorry.

       

      Thanks in advance,

      Guenther

       

      • This reply was modified 1 month, 1 week ago by mwpeters75.
      • This reply was modified 1 month, 1 week ago by mwpeters75.
      • This reply was modified 1 month, 1 week ago by mwpeters75.
      • #7233
        mwpeters75
        Keymaster

        This one’s for you Frank!

        M.

    • #7260
      LectronFan
      Participant

      Hi Guenther,

      I would love to help you calculating the circuit. Could you provide me more details ?

      Are you going to use transistors or op amps for the tone control ?

      Does it need amplification or not ?

      greetings

      • This reply was modified 1 month, 1 week ago by mwpeters75.
      • This reply was modified 1 month, 1 week ago by mwpeters75.
    • #7342
      LectronFan
      Participant

      Hello Guenther,

      I really like the German name for this circuit 😛

      For the Lectron Baxandall proposed above, I used only the parts of the Basic and extension set, do I was a little bit bounded to the parts available. This is why I used a different circuit around the treble control. I made some measurements with a sweep oscillator and oscilloscope and it performs very well.

      Don’t forget that there’s a lot of volume loss. This is why I used a preamplifier first !

      Maybe you can try to build it first and compare it with the following proposed weblink.

      I found a website where a Baxandall circuit is proposed using 2 potentiometers of 100K.

      here is the link.

      Maybe this is the circuit you were looking for. It uses an opamp as active component.

      Using this circuit saves some time calculating it.

      I believe that any opamp will do fine here.

      I will try the circuit out tomorrow and publish my findings.

      Many greetings

      • This reply was modified 1 month, 1 week ago by mwpeters75.
      • This reply was modified 1 month, 1 week ago by mwpeters75. Reason: Changed font and size styling for easier reading
    • #7400
      Guenni75
      Moderator

      Hi Frank,

      Thank you for the link – very helpful indeed. In the past I built several amplifiers (even with tubes, like guitar amplifiers), but the values of the pots and the “strange” schematics I could not use for this actual project, because pot values up to 5MΩ very used – no chance for use with this small FM radio.

      I trashed all my collected schematics over the years, so now I have to search in the internet or look at commercial amplifiers – but there are usually so complex RC networks which are no base for a low cost Lectron version…

      The above named link brought me to another thought, because I have the LM1035 with complete stereo tone control and loudness feature (I like that and use it anywhere if available). But on the other hand it seems to shoot with a huge cannonball to kill a fly…

      The more simple circuit may work with a 741-like Opamp or 1/2 MC1458 – but is the lost amplification at the end (or output) strong enough to drive a speaker? Or has the input signal (FM radio) too much reduced to get no distortion? Questions over questions…

      But I will wait and see and have a looks at your results, thanks in advance!

      Best,

      Guenther

    • #7403
      LectronFan
      Participant

      Hi all,

      It seems like the circuit proposed on above link doesn’t perform well.

      So it’s time to grab our electronic parts and build it ourselves !

      For this, I’ve created a new Lectron block: the proto block !

      A small breadboard fits perfectly inside a 4×4 cube. I cut a rectangle hole in the white surface so the breadboard protrudes a little bit. Then I used acrylic stand offs to keep the breadboard steady. The self adhesive tape underneath keeps the breadboard at it’s place.

      I soldered some breadboard wires to the contact plates and used black for ground.

      This will make it easy to experiment with parts for making a permanent Lectron block.

      Here’s a closeup :

      Proto cube

      Now, for the tone control, I come up with this easy yet great working circuit, which fits perfectly on the Protobit.

      Here’s the schematic:

      Baxandall schematic

      A1 is a half of the popular LM1458 chip. It’s used here as a buffer/preamp. For my Lectron radio module it was not necessary to amplify the input signal. You may increase R2 if you want to.

      The tone control is slimmed version of the Baxandall I made with the Lectron cubes proposed above.

      I tuned the circuit with better values to achieve a sweet sound control.

      The bass potentiometer controls towards 350Hz, which greatly helps our tiny speaker.

      The treble potentiometer influences the signals above 5000 Hz.

      I used a sweep generator and a oscilloscope to visualize.

      Of course, you may experiment with these values, but please use good quality capacitors.

      C5 serves for suppressing HF oscillations.

      Just remember, the measurements are made with the improved speaker box as mentioned in this topic.

      When it was already sounding good, the Baxandall circuit helps to make it even better ! I enjoy some classical and jazz music playing while I write this topic 🙂

      The output of the Protobit (+/- 3V pp) is strong enough to drive a typical class A amplifier for the speaker via a volume potentiometer.

      Here’s a picture with the protobit of the circuit:

      FM Protobit Baxandall

      Many greetings

       

       

      • This reply was modified 1 month, 1 week ago by mwpeters75.
      • This reply was modified 1 month, 1 week ago by mwpeters75.
      • This reply was modified 1 month, 1 week ago by mwpeters75.
      • This reply was modified 1 month, 1 week ago by mwpeters75.
      • #7408
        mwpeters75
        Keymaster

        Hello Professor Frank!

        Once again you scintillate with a helpful adjunct to the Lectron System.

        Thank you for your efforts in continuing to advance the usefulness of the Lectron System development.

        Best,
        Michael

    • #7412
      Guenni75
      Moderator

      Hi Frank,

      that looks absolutely great – it will be my very next project!

      Even “tuned” speakers will not allow to reproduce J.S.Bach’s Toccata & Fugue in D-minor, BWV 565 in whole with 32″ pipe Principal & 16″ Trombone registers (LOL) – but it is a good way for enjoy any music with a better sound, thank you so much again!

      Best,

      Günther

    • #7479
      Guenni75
      Moderator

      Hi All,

      many thanks to Frank – here is my universal Lectron Tone Control block based on the schematic above, and works great! Easy creation, ease of use – that’s it what I like and what Lectron with it’s possibilities means for me, thanks again!

      Best,

      Günther

    • #7482
      LectronFan
      Participant

      Hi Günther,

      Your block is awesome !

      And what a very good looking cover !

      Did you draw this yourself ?

      Can you share the picture so we can print it out and make our own block ?
      I might however change the controls to normal potmeters as I don’t know how to find the small potmeters you have.

      Many greetings

    • #7483
      Guenni75
      Moderator

      Hi Frank,

      no problem – here is the cover:

      Glad that you like it. The cover is created with a PMVIEW (IBM OS/2 – which I use since about 30 years…), the symbols are from Wikipedia and other sources and via Cut&Paste placed on the cover. For schematics (circuit drawings) and text I may use PMDRAW – or (and for all MS WIN users) the free IRFANVIEW – which I use since more than 20 years, too. This program is a standard tool for all photo / draw problems and very comfortable. I don’t need the expensive and high-tech tools…

      In the above cover it may be better to change Treble and Bass because the diagram starts left with the deep/low frequencies…

      May first intension was to use Treble (Höhen / Diskant / Sopran are other used words in German) and Bass (Tiefen / Bässe / Sonor) but in that case there is a problem with the abbreviation to T and B! So I decided to use the music symbols like on many table radios in the 195x years.

      This block already exists in my Lectron Card File (at location 756 and can be used – like all blocks there) via snapshot to create an own one.

      Best,

      Günther

Viewing 18 reply threads
  • You must be logged in to reply to this topic.