LP2+delay board Yellow Magic

Transcription

1 LP+delay board Yellow Magic This filter boards combines a raw OTA-C -pole filter, combined with a classic lo-fi delay. Using this filter board Important! The Phoenix/Shruthi- control board needs to send specific digital control signals to drive this filter board. Make sure that both the analog (CV to +5V) and digital (RX to +5V) ports of the filter and control boards are connected. Make sure that the Shruthi- firmware v0.97 (or above) is installed, and that the fil (filter board) setting is set to dly on the system settings page. The delay settings can be accessed by pressing the S switch (Filter page) a second time: The delay parameters are the following:. tim (time): Delay time. The delay time is expressed in arbitrary units. Due to parts tolerance, the actual delay time might vary by a few percents, and this parameter is not accurately calibrated. The delay time typically ranges from 30ms (0) to 550ms (7). This parameter has a logarithmic scale, so the intermediate delay time (6) is close to 0ms.

2 . lev (level): Delay level. This controls the wet signal level. No delay effect can be heard when this parameter is set to fdb (feedback): Delay feedback. This parameter controls the level of the signal taken at the output of the delay loop and fed back to the input.. eq. (fdbck. eq): Feedback tone color. A simple EQ circuit is present in the feedback loop. When this parameter is set to 0, the signal fed back into the delay is colored by a low-pass filter with a cutoff of 500 Hz. This causes the echoes to get darker and darker, an effect which is not unlike reverb with short delay times. When this parameter is set to 5, the signal fed back into the delay is colored by a high-pass filter with a cutoff of 500 Hz. This gives the echoes a dub flavor. A few observations about the lo-fi-ness of the delay: Using a longer delay time causes a degradation of the sound quality. Unlike traditional analog BBD delays, this degradation is not a bandwidth reduction, but rather a combination of a bandwidth reduction and the addition of quantization noise. This is due to the -bit sigma/delta conversion used in the PT399. The frequency response of the filter circuit in place around the PT399 has a slight bump near 3kHz. This means that when feedback level is too high, a 3kHz tone will build up into the delay line. Whether this build-up is musically useful or annoying is up to you to decide, but we deliberately allowed this to occur. Thus, some combinations of the fdb and eq. parameter, particularly with eq. set to a high value and fdb greater than 0, will cause pathological feedback to occur. In order to make quantization noise less audible when long delay times are used, the signal is heavily amplified in the mixer at the input of the delay line, with a soft-limiter in place to prevent clipping. Don t be surprised if the echoes are more fuzzy than the original signal. This is particularly noticeable with high feedback times when many echoes add up to each other, causing the soft-limiter to get into action and add harmonics to the sound. Schematics and PCB You can find the Eagle files for this board in the shruthi/hardware_design/pcb directory of the source code hosted on github

3 We use here the PT399 with R58 =39kOhm. All PT's are tested bevore shipping!! Start with the smaller resistors: 6x 0R (red, red, black, black). x 70R (yellow, purple, black, black). x.k (red, red, black, brown). 3x.7k (yellow, purple, black, brown).

4 More resistors: x 0k (brown, black, black, red). x k (brown, red, black, red). 7x 5k (brow, green, black, red). x k (red, red, black, red). x 39 k R 58 for the selected PT399 x 33k (orange, orange, black, red). x 7k (yellow, purple, black, red). x 68k (blue, grey, black, red). More resistors: x 00k (brown, black, black, orange). x 50k (brown, green, black, orange). x 330k (orange, orange, black, orange). x M (brown, black, black, yellow). Note that 3 bridges have been added on the IN, OUT and SW pads since we don t use input/output gain pots and power switches

5 Add 6x N8 diodes. They are polarized, make sure that the black ring follows the pattern silkscreened on the PCB. Add x.v Zener diodes (this photo of an older board shows.7v, but the right value is.v). They are polarized too. Add the polarity protection diode (N00 or N00). It is polarized.

6 Add the ceramic capacitors. They are not polarized: x 0pF (labelled 00). x 00pF (labelled 0). x 330pF (labelled 33). 6x 560pF (labelled 56). 0x 00nF (labelled 0). x 0nF (labelled ). Add the IC sockets.

7 Add the film capacitors (x 33nF, x nf, x 6.8nF or 5.6nF). They are clearly labelled with their value, and are not polarized. Add the x N3906 transistors, and the N390 transistor. Beware of their polarity!

8 Add the electrolytic capacitors. The 6x.7uF capacitors are not polarized (a + and are silkscreened on the PCB, don t bother with those). The 5x 00uF and x 0uF capacitors are polarized. The white stripe on the edge of the capacitor indicates the minus lead (which is also the shortest one). Here is another view of the board: Add the tantalum capacitor. A stripe indicates the + the lead.

9 Add the 0k trimmer. Add the connectors and the voltage regulators (7905 and 7805). Don t mix them up, these are different parts! You can finally insert all ICs The last step consists in tuning the filter, to make sure that the cutoff frequency of the filter follows a musical scale: increasing the cutoff setting on the Shruthi by (or playing a note octave =

10 semitones higher) should double the cutoff frequency. First, you ll need to assemble the filter and control boards. Maybe you can start screwing them together onto the bottom plate of the enclosure or you can just temporarily sandwich female x8 and x6 connectors between the boards for testing. Dial the following settings on the Shruthi-: Oscillator shape: none Oscillator shape: none Filter cutoff: 6 Filter resonance: 63 (maximum value) Filter envelope and LFO modulations: 0 Play on the keyboard. You should hear a pure tone (sine wave), which does not come from the Shruthi- oscillators but from the filter self-oscillating. Adjust the V/Oct trimmer so that the intervals are respected that is to say, when you play C3 then C, you should hear two notes, maybe not C3s and Cs, but they must be one octave apart. If you do not have a good sense of pitch, you can try a software tuner like Tuna Pitch on OS X. If the filter is correctly tuned, you should be able to play the filter self oscillation tone across roughly octaves with correct tuning. Troubleshooting RED: +5V BLUE: -5V : Mixer output (raw oscillators signal) : Filter output 3: VCA output : Delay mixer input (this is what goes into the delay: input signal + feedback) 5: Delay output. This signal is referenced to +.5V 6: Output amp output. This is the sum of the signal at the output of the VCA + the delay output attenuated according to the dry/wet control. F: Filter cutoff expo converter input. Should swing by +/- 00mV when cutoff is adjusted. C: Delay clock. High frequency signal visible with a scope, should speed up/slow down proportionally to delay time. M: Wet signal attenuation CV. 0V when delay level is set to 63 ;.V when delay level is set to 0. T: Delay time CV. 0V when delay time is set to 0 ;.0V when delay time is set to 7.

11 License This circuit and PCB layout is made available under a cc-by-sa-3.0 license. Releases v0. TubeOhm

12 Schematics

13 BOM YELLOW MAGIC Yellow magic for Shruthi/Phoenix R5, R8, R7, R6, R3, R57 Resistor % 0 R37, R, R53, R55 Resistor % 70 R, R5, R3, R5 Resistor %.k R9, R39, R0 Resistor %.7k R7, R9, R, R6, R8, R, R3, R5, R7, R33, R35, R36, R5, Resistor R5 % 0k R3 Resistor % k R6, R6, R7, R8, R9, R50, R56 Resistor % 5k R3, R0, R, R9, R58 Resistor % k R58 - PT from TubeOhm Resistor % 39k R0 Resistor % 33k R3 Resistor % 7k R38, R, R, R5 Resistor % 68k R, R8 Resistor % 00k R30 Resistor % 50k R Resistor % 330k R Resistor % M C Ceramic cap 0p C5, C8 Ceramic cap 00p C6 Ceramic cap 330p C8, C30, C38, C39, C8, C9 Ceramic cap 560p C0, C Film cap n C3, C3 Film cap 5.6n or 6.8n C3, C 33n C6, C7, C9, C, C3, C7, C8, C9, C, C33, C36, C0, C,Ceramic C, C3, cap C5, C7, C50, C5, C5 00n C0, C3, C9, C35 Ceramic cap 0n C tantalum cap, > 5V 0u C3, C, C5, C53, C5 Electrolytic cap 00u C, C6 Electrolytic cap > 0u D Diode N00x D, D3, D, D5, D6, D7 Diode N8 D8, D9 Diode Zener.V Q, Q, Q3, Q PNP transistor N3906 Q5 NPN transistor N390 IC Socket DIP 8 IC Socket DIP IC Socket DIP 6 R3 Trimmer 0k C, C, C5, C6, C7, C37 Electrolytic cap, NP/audio.7u IC LT05 DC/DC converter IC LM V Vreg IC6 LM7905-5V Vreg IC, IC9 TL07 dual op-amp IC TL07 quad op-amp IC3, IC5 LM3700 dual OTA IC8 V6 quad VCA IC0 PT399 digital delay IC7 MCP8 dual bits DAC J, J3 Neutrik Audio Jack 6.35 J DC Jack J 8 pins female header J6 6 pins female header PCB PCB Reichelt METALL 0 METALL 70 METALL,0K METALL,70K METALL 0,0K METALL,0K METALL 5,0K METALL,0K Metall 39.0K METALL 33,0K METALL 7,0K METALL 68,0K METALL 00k METALL 50k METALL 330k METALL,00M KERKO 0P KERKO 00P KERKO 330P KERKO 560P MKS-0,0N MKS-0 6,8N MKS--5 33N X7R-,5 00N Z5U-,5 0N TANTAL 0/6 RAD 00/6 RAD 0/35 N 00 N 8 ZF, N 3906 N 390 GS8 GS GS6 6W-0K Digi Key XBK-ND 75XBK-ND.KXBK-ND.75KXBK-ND 0.0KXBK-ND.KXBK-ND 5.KXBK-ND.KXBK-ND Farnell KXBK-ND KXBK-ND KXBK-ND KXBK-ND KXBK-ND KXBK-ND MXBK-ND ND ND ND ND BC659-ND ND 8567 BC650-ND BC8CT-ND ND ND P376-ND P097-ND ND 6508 N8TACT-ND 636 N5BDO35MSCT-ND 6758 N3906FS-ND 7078 N390FS-ND A000-ND 6537 A0005-ND A0006-ND 8357 T93XA-0K-ND 378 P75-ND LT 05 CN ND µa 7805 LM7805CT-ND µa 7905 LM7905CTFS-ND 9666 TL 07 DIP ND TL 07 DIL ND LM 3700 DIL LM3700N-ND Available at Mammoth Electronics, Small Bear Available at Tayda Electronics, Das Musikding, Banzai, Small bear MCP8-E/P-ND HEBW CP-0A-ND 7376 Sparkfun PRT-0007 or Coolcomponents TubeOhm Instruments LP+Delay v0. Mouser 660-MF/DCT5R00F 660-MF/DCT5R700F 660-MF/DCT5R0F 660-MF/DCT5R70F 660-MF/DCT5R00F 660-MF/DCT5R0F 660-MF/DCT5R50F 660-MF/DCT5R0F 660-MF/DCT5R330F 660-MF/DCT5R70F 660-MF/DCT5R68F 660-MF/DCT5R003F 660-MF/DCT5R503F 660-MF/DCT5R3303F 660-MF/DCT5R00F 59-K00K5C0GF53L 59-K0K5C0GF53L 59-K33J5C0GF53L 59-K56J5C0GF53L 80-MMK50K63J0TR8 80-FK8C0GH56J 87-B359C333J89 75-C0Z5U0M050B 80-FK8Y5VHZ 58-TAP06K06SRW 667-EEU-FRE0 667-ECA-HM 65-N00-E3/73 78-N8-TAP 78-N5B 5-N3906TA 5-N390TA PV36X03C0B00 67-UVPER7MDD 863-MC7805ACTG 863-MC7905ACTG 595-TL07CP 595-TL07CN 96-LM3700N/NOPB 579-MCP8-E/P E