Ambika Ladder Filter - Transistor, Diode and LED in works. Prototype OK

Here a Video with soundexamples:


More sounddemos coming soon on Soundcloud.

The LED ladder is pretty epic. :slight_smile:

Really really nice-this could supplant the 4P cards in my second Ambika…

cool !

Hi, it was only s small Demo, the filter can more, distortion mode on the diode ladder(jumper), you can de-sync the diff amp for distortions (Pot)…all Filter units TR,D,LED have a good bass response.
I will make a workaround for the LED LAdder > needs more resonance and than i start with the final PCB.


Well done, sir! :slight_smile:

great work!
I preferred the first version (I think it was transistor?) in the video because of not losing gain when increasing the resonance and the nice punch!
led sound also quite interesting but I don’t like to lose gain with increasing resonance


i working on loosing the gain (LED). And i have found a solution. Ok i have found it before the video.
There is a special crunch function ( a jumper) only for the diode Ladders >>Diode + LED.
This gives a more crunchy sound and moves the Gain up. But LED and DIODE are goodys.
In this Time , DIODE works fine without readjusting the pots. LED is a little more special.
I had to change one resistor in the feedback Path to become a higher resonance.
I think i will make three schematics but only two solder instructions. TR and diode needs only one Jumper. For the LED we need another resistor. Thats all.
If i have a little time i am working again on the LED Ladder and than i make a first proto-PCB.



Sounds like another jumper could select the feedback resistor. With some 4066 magic (would require firmware hacking) one could even make a software configurable ladder card.

Nice work, getting it going! I’m excited.

Hey, you can build only only one Ladder on one PCB. Not all three together . The PCB is too small , also for a 4066 . I must look that i don’t use too much jumpers. But i will see.
Otherwise you become an hedgehog (deutsch Igel) hihi.


Hmm, I had this idea of part sandwich, part putting what you have as a daughterboard a little bit off-board using as much SMT as possible. But, we’ll see when I get there.


Upps, error in the schematics. Thanks DMM.
Here Version V 1-7, both Transistor and Diode.
C 36 must be 100 nF and C 35 = 1 uF.( use C35/R48 only with the diode ladder) Have update it here in the schematics V 1-7.
PS @DMM, the DAC gives out the the real signal, not a PWM signal ! So you don’t need a filter circut behind the DAC.

@DMM I have look to my actual configuration for the Transitor Ladder. I have use for the Video a TR-Ladder with 4x 100 nF not
63 nF. Hmm, i must test it out which Caps gives the best sound . I have used for testing 47 nF, 68 nF 100 nF and 120 nF. For the Diode Ladder i use 47 nF.


I’m currently using the ladder filter in one of my Shruthis, mostly for bass. It sounds great, very thick. I’m not so sure it would be a good choice for polyphony 'though. It might be too thick.

Personally I like 4x 100nF in the ladder the most.
I’ll try to build a second voice this weekend to see how it sounds together. Need to have the calibration right first.

@piscione, I had thought the same thing. I’m not sure if its just my board or if they are all like this , but the resonance seems to be way overdriven. It could just be I have a misplaced resistor. I’d like it to be a bit more tame with high resonance. As it is it would be too much for poly. I need to spend a little time with the schemo. But, the bass that comes out is…babygotback.

That’s why I haven’t made any changes to mine, the bass is great!

Ok, here the latest Infos about the Ambika Ladder. First the schematics. I have change a little.
Latest Version is V 1.8.
To get both Ladders first to work, i am set the resonance with a the same resistor for both, ladder and transistor. It is R 42, 470 Ohm. This works on both ladders , on Diode Ladder it is the right value 470 Ohm. Than the resonancy begin in 60. For the transistor Ladder i think i had to increase the resistor a little, because the resonance is full coming on 40…42. @DMM i will test 370…420 Ohm, so that i become the full resonancy on 60…63 like on the Diode Ladder.
The LED Ladder needs 500 Ohm. up to…1 Kohm .I must test this at first.
Than i have draw a diagramm Testpoint adjustment.
If both testpoints have the same values, here 0.355 V, you see , that the frequence of the resonance in on the pos wave the same than on the neg wave. If you have , use an oszilloscope and look, than you have exact the same reso Freq on the pos and the neg Wave. This means the ladder diff amp works synchron. After adjustment with an oszilloscope or a Volt meter, take your ears and move the pot a little right and left.You will find a point that sounds very clear like a sin without a little overtones. This can’t measure an oszilloscope or a Volt meter. Adjsut it with your ears !

But, if you want to have a special sound, you can adjust the test point 2 >>> 50 mV less than Testpoint 1, means, TP 1 =0.355 V, TP2 = 0.305V. Than you become the same sound like on the shruthi Filter.
I have made a few testsounds and upp it on soundcloud.
Filter sweep synchron
Filter Sweep de-synchron:
Small Bass 1 osc symmetric :
Small Bass 1 osc unsymmetric:
The sounds are only for hear how the adjustment works. I have only use on oscillator, so don’t think the sound is thin. It is only for compare if your ladder sounds like my ladder.
PS, take the last schematics here !1


Hi Andre, looks great! Just one question-I’m curious why you decided to use a 78L05 to power the frequency cutoff trimmer-would a 3k resistor between the trimmer and the 8V rail, and a large cap in parallel with the trimmer achieve the same objective?

I guess it’s because the 8V rail is/might be wobbly. The regulator just plays the role of a cheap and rather inaccurate voltage reference (a LM4040 would do the same trick).