AVE MOD V2

This circuit is the first one I experimented with. After modifying a few video devices, I wanted to work on a little standalone glitch circuit, this is where the search for video schematic started.

I started taking interest in electronic with audio, so I was quite used to find information about guitar pedals, synthesizers, studio gear, but there’s much less about analog video on the internet.
However I found this circuit traced by Philip Baljeu (who recently did the Castle modules serie, distributed by LZX) from an Archer Video Enhancer/Sound Mixer and posted on the electro-music forum.

 

Here’s the result after a few prototypes, it adds 5 potentiometer, 4 switches and audioreactivity so the circuit can react with an external audio signal.

The circuit is PAL/NTSC compatible, it’s powered by either a 9V battery or a 9V DC power supply and works best with a CRT TV.
Circuit boards, kits and assembled circuits are now available through the store of the website.
Link to the dedicated forum

Tools needed:

– Soldering iron
– Solder
– Desoldering braid
– Multimeter
– Wire cutter

– 9V battery or 9V power supply (center positive, 100mA or more, the circuits draw around 50mA)
– Circuit board (included in kit)
– Components (included in kit)

ValueDesignationQtyNotesReference in kit
RESISTORS
10R 5%R111
24R 5%R131
75R 5%R11
220R 5%R101
330R 5%R4 R62
510R 5%R121
1K 5%R11'1
680R 5%R5 R72
5.6K 5%R3 R8 R93
8.2K 5%R1'1Higher resistance, less sensitivity to sound input
10K 5%R3' R5' R7' R9' R10' R12' R13'7
18K 5%R21
22K 5%R2', R4'2
68K 5%R6' R8'2
Photoresistor 650nm radialLDR1a Vactrol like VTL5C3 should work too, or you can try different LED/photoresistor coupleTayda/Waitrony - KE-10720
CAPACITORS
Electrolytic
1uFC2'1Max rating: 16V or more / higher capacitance, slower enveloppe response
2.2uFC1'1Max rating: 16V or more
10uFC121Max rating: 16V or more
47uFC1 C32Max rating: 16V or more
100uFC8 C4'2Max rating: 16V or more
220uFC51Max rating: 16V or more
Film/Ceramic
1nFC2 C62Ceramic/Film
10nFC7 C9 C113Ceramic/Film
100nFC3'1Ceramic
100nFC101Ceramic/Film
330nFC131Ceramic/Film
C4 omitted
SEMICONDUCTORS
Integrated Circuit
TL074U11
Transistors
2N3904Q1 Q3 Q1'3
2N3906Q21
Diodes
1N4148D1 D1' D2'3
LEDD3'1
HARDWARE
Potentiometers
10kB potentiometer PCB mount 6mm d-shaftVR1 VR3 VR43Bourns - PTV09A-4025F-B103
100kB potentiometer PCB mount 6mm d-shaftVR1'1Bourns - PTV09A-4025F-B104
100kB potentiometer PCB mount center detent 6mm d-shaftVR2 VR52Bourns - PTV09A-4225F-B104
Switches
SPDT switch ON - ONSW1 SW2 SW3 SW44
SPDT switch ON - OFF - ONSW1'1E-Switch - 100SP3T1B1M1QEH
Connectors
RCA connectorJ2 J32CUI - RCJ-024
Power connector 5.1mm x 2.1mmJ11Kobiconn - 163-7620E-E
9V Battery clipJ41
Jack PJ301BMJ1'1PJB301BM / Erthenvar

The build goes in 3 parts:

1. Enhancer
2. Modifications
3. Audio

Circuit board revisions:

– V1: no marking on the board, build during Fubar 2017 workshop, error with D1 (see 3.Audio bis)
– V2: audio circuit added, D1 corrected, error -> R13 replace R12 and R14 replace R13. (see 1.Enhancer)
– V2.1: R12/R13 corrected, 9V battery pads added.
– V2.2: VR1, R12 and R13 value have been changed for better enhancement range (no more sync loss when enhancement knob is all the way down). Capacitors values in the modification part have been changed, D2 has been added for a different effect. R1′ value has been lowered for better reactivity to audio. BOM and build guide for this version are  in the Documentation section.


The first part is the enhancer, it’s important to be sure that it works well before getting to the modifications.

A. RESISTORS:

R1: 75R (Purple, Green, Black)
R2: 18K (Brown, Grey, Orange)
R3: 5.6K (Green Blue, Red)
R4: 330R (Orange, Orange, Brown)
R5: 680R (Blue, Grey, Brown)
R6: 330R (Orange, Orange, Brown)
R7: 680R (Blue, Grey, Brown)
R8: 5.6K (Green, Blue, Red)
R9: 5.6K (Green, Blue, Red)
R10: 220R (Red, Red, Brown)
R11: 10R (Brown, Black, Black)
R12: 510R (Green, Brown, Brown)
R13: 24R (Red, Yellow, Black)

Be carful with R11 et R11′  that are close to each other, the components with a ” ‘ ” are for the audio part.

 

Error on V2 pcb: R12 and R13 have been respectively replaced by R13 and R14 so R13: 510R / R14: 24R. Corrected in V2.1.

R12 and R13 have been added to lower VR1’s value from 10k to around 500ohm like in the original circuit. If you use other pots than pcb mount ones, you should be able to find 500 ohm ones quite easily, in this case you don’t need R12/R13.
The value i choose give a bit more than 500 ohm, so the circuit enhance a bit more than with the original value.

It’s also possbile to use only one resistor by puttin it like on the picture on the left. With 470 ohm, it’s bit to low and 560 ohm is a bit too high, but it works anyway.

 

 

 


B. CAPACITORS:

 

C1: 47uF/16V* electrolytic
C2:  1nF ceramic/film
C3: 47uF/16V* electrolytic
C5: 220uF/16V* electrolytic

*This value is the maximum voltage the capacitor can handle. I choose 16V but any higher value should work (25/35/50V).

(C4 has been omitted from the original circuit, so it’s not present on the board).

Electrolytic capacitors (C1, C3, C5) are polarized, mind the orientation. The longer lead should go to the (+) marked on the board.

C2 (film or ceramic) is not polarized so you can put it either way.

 

 

 

 

 

 

To keep space for the enclosure, it’s better to bend the capacitors leads like this.

 

 

 

 

 

 

 

Note that C1 is moved a bit up to access to the two “LDR” pads, it will be useful for part 3.

 

 

 

 

 

 


C. SEMICONDUCTORS:

 

 

D1: 1N4148

The diode is polarized, the black band on the diode must be on the same line as the white line on the pcb.

Q1: 2N3904
Q2: 2N3906
Q3: 2N3904

 

 

 

 

 

 

 

The flat side of the transistor must be on the same side as the straight line on the pcb footprint.

The original circuit uses 2SC945/2SA733, I also tested with 2N5088/2N5087 and BC558/BC557 and the result looks quite the same.

However, if you want to use 2SC945/2SA733 or BC558/BC557, you’ll need to swap the leads cause the footprints on the pcb are for 2N3904/2N3906, it also work with 2N5088/2N5087.

 

 

 

 


D. HARDWARE:

J1: Power connector
J2: RCA connector
J3: RCA connector
J4: Battery connector (no pads on V2 pcb)

VR1: 10k potentiometer linear

S4: SPDT switch ON – ON

Don’t forget that there’s 2 type of switches in the kit, 4x SPDT ON-ON and 1x SPDT ON-OFF-ON (it has a middle position).

For S4 and the RCA connectors, best is to solder a leg first, check if the component is straight, if not, heat the already soldered leg and move it to fit it properly. Then solder the other legs. It’s important if you want to fit it in an enclosure.

 

 

 

 

 

 

The kit include a 9V battery clip to 5.1mm x 2.1mm connector, but a battery clip can be soldered under the power connector  like this. (V2.1 boards adds pads, so you can solder the battery clip directly on those pads)

Be careful to not use the 9V battery and a power supply at the same time!

If you want to use different connectors/switches/potentiometers from the one in the BOM/kit, you just need to wire them to the board.

 

 

 

 

 

 

When this part is done, the circuit looks like this. Now we can test the enhancer:

1. Plug the power supply.

2. Plug a video source (VHS/DVD player, video game console…) on the RCA input (J2), plug a monitor (CRT or LCD) to the RCA output (J3).

3. Check that S4 is up (like on the picture), it’s the ON/OFF switch.

4. Turn VR1 to the max, and check that the monitor gives a bright picture, when turning VR1 down, the picture should be less and less bright until losing sync near the minimum. If that’s the case, the enhancer part works! Mind to unplug the battery/PSU before starting the second part.


A. CAPACITORS:

 

 

C6: 1nF ceramic/film (1n or 102)
C7:  10nF ceramic/film (10n or 103)
C8: 100uF/16V* electrolytic
C9: 10nF ceramic/film (10n or 103)
C10: 100nF ceramic/film (100n or 104)
C11: 10nF ceramic/film (10n or 103)
C12: 10uF/16V* electrolytic
C13: 330nF ceramic/film (330n or 334)

*This value is the maximum voltage the capacitor can handle. I choose 16V but any higher value should work (25/35/50V).

Orientation of the 2 electrolytic capacitors isn’t an issue here cause it works the same either way. Bend them like we did in the previous part.

 

 

 

 

Those capacitors values can be altered to modify the effects. You can try different values at different places, it can be interesting to use a socket to make the swapping easier (for testing only, sockets doesn’t provide a connection as good a solder joint) or you can add capacitor in parallel of another (mind that the 2 capacitors value will be summed). The kit include some extra components to experiment with.

C6: VR2  max. S1 down
C7: VR2  max. S1 up
C8: VR2 min. S2 down
C9: VR2 min. S2 up
C10: VR3 max. S3 up
C11: VR3 max. S3 down
C12: VR5 max.
C13: VR5 min.

C6 value can be lowered, the effect will be less intense, nice colors around 470pF, and a value under 220pF doesn’t do anything. The effect get more intense when the value goes up. Same for C7

C8 value can be lowered and it looks like the effect on S1 (C6/C7), a higher value may change the colors. A good mod for this one is adding a small signal diode (like 1N4148) in parallel with C8, with the cathode of the diode pointing on the (+) side of C8 and changing C11 value to 1uF.

C9 value can be lowered and the blurry/hazy effect will be less pronounce. A higher value result in a more intense effect, with a bit more color, but it loose colors around 47nF.

C11 value starts to get interesting around 4.7nF, a higher value intensify the effect, no more colors when value is higher than 1uF.

C12 blur the signal a bit from 100nF to 0.47uF, then no more blur and less colors, but works nice with other effects.

I tested all of this on a PAL setup, so the results might change a bit in NTSC, so experiment with different value to see what you get 🙂


 

B. HARDWARE:

VR2: 100k potentiometer linear center identified
VR3: 10k potentiometerlinear
VR4: 10k potentiometer linear
VR5: 100k potentiometer linear center identified

Potentiometer value and curve isn’t that important. In this part of the circuit, they works as attenuators for the different feedback path, so it explains why it only react near the maximum, a bit like a switch but with a tiny range of action. I’m thinking about a solution to use the full range of the potentiometers, it would require to use an op-amp for each feedback path, an OTA would be even better for CV control, but the PCB would have to be modified and specific video op-amp/OTA (with a wide enough bandwidth) are not really cheap. Transistor as a VCA, will try and report here.

VR2 and VR5 are center identified cause they are at 0 (no effect) when centered, there is 2 different effects at their minimum and maximum. A potentiometer without identified center will work the same.

When every capacitors and potentiometers are at the right place, we can test the modifications:

1. Plug the PSU/9V battery, source at the input, monitor at the output.

2. S4 is up and VR1 at max, VR2 is centered, VR3/VR4 at minimum, and VR5 centered.

 

3. Turn VR2 to max, The picture should be affected. By switching S1, the effect should change.

3. Turn VR2 to minimum, the picture should be affected. By switching S2, the effect should change.

4. Put VR2 back to the center. Turn VR3 to max, the picture should be affected. By switching  S3, the effect should change.

5. Put VR3 back to minimum. Turn VR4 to max, the picture should be affected.

6.Put VR4 back to minimum. Turn VR5 to min, the picture should be affected, turn it to max, the picture should be affected differently.

If everything works, you can go to part 3 (don’t forget to unplug the circuit before working on it 😉 ).

 


The audio part is based on an enveloppe follower by Robert Iodice published in Electronotes #86, it’s pretty similar to the Polyfusion 2044 in the design. Here, op-amps have been biaised to work with an unipolar power supply. The enveloppe follower circuit goes into an inverter, then a LED driver to drive the LED and finally a photoresistor. The photoresistor makes the gain of the video circuit vary according to the enveloppe of the audio at the input, so it will react best with percussives sounds.

A. RESISTORS:
R1′: 8.2k

R2′: 22k
R3′: 10k
R4′: 22k
R5′: 10k
R6′: 68k
R7′: 10k
R8′: 68k
R9′: 10k
R10′: 10k
R11′: 1k
R12′: 10k
R13′: 10k

The value of the input resistor, R1′, can be lowered in the case the audio input is too low, and if the input is too high you can put an higher value. 8.2K works pretty well with the different audio sources i used. Original value was 20k.

 

D3′:  LED 5mm
LDR: photoresistor

In the kit, the LED and photoresistor are already coupled together.

D3′ and LDR makes an opto-isolator. It’s possible to make one by using a LED, a photoresistor and heatshrink.

 

 

 

 

 

Be careful to D3′ orientation’, the cathode (flat side,smaller leg) goes to the square pad on the pcb. The photoresistor (LDR) isn’t polarized.

 

 

 

 

 


Now, connect LDR1 to the pad just under and LDR2 to the pad just under. You can use components legs as a wire to connect the 2 points.

Those 2 points are where the LDR connects to the enhancer. This configuration(LDR1 connected to 9V and LDR2 connected to R7) works pretty well. If you want to experiment, dessolder thos 2 jumpers and put 2 longer wires, then try to connect them to various point of the circuit.

 

 

 


B. CAPACITORS:


C1′: 2.2uF/16V* electrolytic
C2′: 1uF/16V* electrolytic
C3′: 100nF ceramic
C4′: 100uF /16V* electrolytic

*This value is the maximum voltage the capacitor can handle. I choose 16V but any higher value should work (25/35/50V).

C1′, C2′ and C4′ are polarized, be careful to the orientation.

The audio circuit is an enveloppe follower which convert an audio signal to a continous voltage that vary according to the amplitude of the audio signal. This signal will light an LED which will make the value of the photoresistor vary according to the amplitude of the audio signal at the input. This photoresistors, once place in the video circuit will make the picture more or less enhanced according to the sound.

C2′ value can be modified. The original value is 1uF, by lowering it to 0.47uF, the enveloppe is faster but there’s more parasites coming from the lower frequencies. Putting an hihger value for C2′ will attenuate parasites but makes the enveloppe slower in response.

 

Yellow: audio signal at the input
Blue: extracted enveloppe that drives the led.

On the left, C2’=1uF
On the right, C2’=0.47uF

We can see that attacks are faster with 0.47uF but parasites from the low frequency is higher.

 


 

 

C.SEMICONDUCTORS:


D1′: 1N4148
D2′: 1N4148

Q1′: 2N3904

U1: TL074

The TL074 can be mounted on a socket for easier replacement if there’s a problem.

 

 

 

 

 

 


 

D. HARDWARE:

VR1′: 100k potentiometer linéaire
S1′:SPDT switch ON – OFF – ON
J1′:  jack 3.5mm(PJ301BM)

Once again, only solder one leg of the component and check if it sit straight on the pcb, then solder other legs.

Other types of jack  (J1′) can be used,it must be wired like this: red -> jack tip (signal) / blue -> jack sleeve (ground) / green -> jack switch (so the input is grounded when nothing plugged).
When everything is at the right place, the last part is over.
We can now test audio reactivity:

1. Plug the power. Check that S4 is up, VR1 to max. Plug the source and the monitor.

2. Plug an audio source in J1′ and play something. Keep in mind that it reacts to amplitude of the sound, so percussive stuff is best for the circuit to react.

 

 

3. With VR1′ to minimum and S1′ in its middle position (OFF)’, D3′ shouldn’t be lit. By putting S1′ up, and VR1′ a bit up, the LED should start to lit up according to the sound, when the amplitude of the sound is at the max, the LED is completely lit and when the amplitude of the sound is at 0, the LED is off. By putting  S1′ down, it invert the enveloppe so the situation is reversed.

4. The sound should now make the brightness of the picture change, VR1′ can be used to change enveloppe amplitude, which change the depth of the audio modulation.

The modified enhancer is now ready to be used.

 

                                                                                                                                                                          SOURCES :

You can use different video sources, it just need to output a composite signal with an RCA connector (or SCART by using an adapator).

– Video game console
– Camera (useful for feedback)
– DVD player
– VHS player
– VGA/HDMI to RCA converter (useful to use video from a computer and quite often PAL/NTSC compatible.)

 

 

 

 

 

 

 

 

 

MONITORS:

There’s also a few options for the monitor.

– CRT TV: gives warm colors, pretty tolerant to heavy glitches (sync signal corruption). Most recent CRT TV (with a silver/grey case) seems to be less tolerant however, it displays an OSD thing like “AV1″” and drops to black when signal is to corrupted. Some are NTSC/PAL compatible so there might be an analogue to digital conversion at the input of the TV, which would explain their weaker tolerancy. Some also have a flat screen which is useful when recording with a camera.

– LCD TV: works as long as it has an RCA composite input. Possible loss of signal when signal is too corrupted, depends of the screen, some are more tolerant than others.

– Videoprojector: a common solution when VJing, work as long as it has an RCA composite input. Has the same problem as the LCD, signal loss (with possible blue screen, not cool when VJing) when it’s too intense.

– Video capture card: useful to display on a computer screen (streaming/recording), suffer the same problem as the LCD/videoprojector.

 

We can see that every time the video signal has to be converted to digital (it’s also true for a RCA to VGA/HDMI converter), if it’s too corrupted, converters must have trouble interpreting it resulting in a black/blue/freezed screen.

Solutions:

-Do not use effects that are too intense (it’s frustrating and not a solution)

– Time base correction: will restore the sync signal and stabilize it.There is some standalone device like this one, and some mixer have on-board TBC, and VHS player also. Results vary, the Panasonic WJ-AVE5 mixer freeze a part of the screen when the glitch is too heavy and reproduce well the sync corruption effect, the Videonics MX-1 TBC is less interesting, mine displays an image that is half black/half white when the signal is too corrupted. Check what works best with your setup.

– Rescanning: film a CRT TV screen to record directly or send the output of the camera to an RCA/HDMI that can be plugged in a video projector or a capture card.

 

TO put the enhancer to 0 (no effects, only enhancer)

– S4 is up (ON)
– VR1 max.
– VR2 center
– (S1 and S2 doesn’t have any effect since VR2 is centered)
– VR3 minimum
– (S3 has no effect since VR3 minimum)
– VR4 minimum
– VR5 center

– S1′ center (OFF)
– VR1 mininmum

The effects:

– VR2’s min and max position result in 2 effects alterable by S1 and S2.
– VR3’s max result in an effect alterable by S3, possible loss of synchronisation at the end of the pot.
– VR4’s max result in an effect, possible loss of synchronisation at the end of the pot
– VR5’s min and max reuslt in 2 effects.

 

Audio:

– Audio input jack 3.5mm mono (J1′)

– S1′ centered, OFF, video circuit doesn’t react to audio.

–  S1′ up, the circuit react to the enveloppe of the audio signal at the input.

–  S1′ down,the circuit react to the inverted enveloppe of the audio signal at the input.

– VR1′ modify the amplitude of the enveloppe.

– V2.1 BOM (XLS, PDF)
– V2.2 BOM (XLS)

– V2.1 Schematic
– V2.2  Schematic

– V2.2 Build guide

– Board measures (MillimetersInches)

– Enclosure cutting files (AI, SVG, EPS) (choose a 3mm thick material), Hardware needed for enclosure assembly (PDF, XLS)