With fully integrated stereo ADC and DACs, the FV-1 can be treated like any other analog component in your products signal path. The FV-1 can access a total of 16 programs, 8 are built in to the internal ROM and the designer may elect to connect a serial EEPROM with 8 additional programs. By using an external EEPROM, the designer can create a custom program set(8 programs) without the need for a microprocessor in the system. The rich instruction set allows users to program effects of all kinds. With instructions like LOG and EXP, users can easily program audio expansion and compression routines. Integrated digital LFOs and ramp generators allow for programming chorus, flange and pitch shift.

The unit is with 32K(8x4096) delay RAM and  with the rich set of commands as part of  Spin Semiconductor's development environment it is capable of providing the multi-tap/multi amplitudes functionality we require assuming the maximum required time is less then 1000mS. As an example, a partial code, representing one head's timing, is  here:

mem   delay   32768 ; is exact 1000 mS (obviously this could be .6 times 32768 = 19661 if 600mS is the maximum  leaving some

; RAM left for other goodies like W&F flangers and filters.

;

rdax    addr_ptr_bu,0.246   ; read add_ptr and multiply by 246 mS and place result in acc

wrax   addr_ptr,0       ; write acc to addr_ptr and clear acc

rdax   d_out,1             ; load acc with previous value

rmpa   1               ; read delay memory at address set by pointer and add to acc

sof 0.63,0 ;  adjust acc with  - 4dB  (based on Lv = 20log10 (V/V0) in dBV)

wrax   d_out,0             ; write acc to d_out and clear acc

...............

rdax   d_out,1

wrax   dacr,0 ; write to DA convertor = out to the world

For a six heads device it could be written in only 38 steps leaving ample room for filters and other elements required.

 A guitar effect solution

The SKRM-C8 reverb and effects modules are available pre-programmed from OCT and can be even custom programmed for your product. Modules operate from 5V to 12V DC to ease integration. The module is based on the Spin Semiconductor FV-1 DSP processor and provides a complete reverb solution (and more) in a single IC. Furthermore the ability to read the 32K delay buffer at required locations makes the unit a perfect candidate also for vintage echo devices. With integrated stereo ADC and DACs, the FV-1 can be treated like any other analog component in the signal path. 

 Schematics (click image for large image)

To support the DIY community the schematics and board design in Eagle format is made available for non commercial use: 

• Download Eagle files (Schematics and mini mother board)
• The procedure to optimize the FET transistors 

A board that's smaller is available now. This board allows for components to be placed beneath the SKRM daughterboard while resulting in minimizing the size to  94 mm x 65mm ( Eagle 5.7.0 with a free license can be used). Below is the 3D representation of this nice little board. The space between the SKRM daughterboard and the motherboard, due to the male and female PCBA headers, is exactly 14mm .There is therefore sufficiant room for resistors and capacitors. This smaller board  is sent for manufacturing in Germany production date 15/3.

3D CAD Representation of the small 94mm x 65mm motherboard 

The outside world (solder)  connections are:

• Horizontal: from left to right: BCD switch (four connections) , potentiometers 1,2 and 3 each 3 connections.
• Vertically:  two groups of 3 connections are (top) left in/ground/right in and (bottom) left out/ground/right out
• Red LED:  Signal clipping
• Green LED: Power On

Manufactured boards as received 22/3 

Here a complete build board including the daughterboard. 

assembled and testing...and working 

The unit is now under test. The first step was to understand the output of the guitar so the opamp could be adjusted to 80% of the max allowed voltage as per FV-1 spec.  The opamps are now calibrated and further measurements are now taken place before the daughterboard will be tested.

The current is measured to be around 78mA and with the LED connected 83mA.

 The way the power is connected is here with a terminal block. This location provided on the motherboard would also take the femal power connectors, it's universal!

The 2N3819 FET's used  are now correctly placed (error in layout caused by Eagle PCB CAD library). The actual required p/p voltage to the daughterboard is too low. Another FET (J201) will be applied as simulation revealed this to be sufficiant for the required signal strenght. The unit already provides plate reverb!

The bias resistors R19/R10 are removed and the feedback resistors R10/R18  for the input amplifiers  are now 68K to allow for sufficiant amplification. Also, both FET's are now J201. The unit works for all functions now.

Some finetuning towards amplification is the last step before it moves from the testphase to production. The downloadable schematics/board information is now updated with the latest information. Temperature measured under full operations of the 7809 voltage regulator (without heatsink) is < 70 C. The measured current is now < 85mA. I'm considering adding a heatsink as the enclosure is rather small.

Multi or Single Channel Device 

One of the key features of this design is that the unit can be build/used as a single channel device (mono in/out) or a dual channel build/used (stereo in/out). It is also possible to have mono in and stereo out. By leaving the FET's out it's even possible to cascade two units for more advanced effects. The following provides a view of the differences of component placements when building the device for your specific requirements:  

 double click for enlarged picture

double click for enlarged picture 

 Recommended Assembly steps 

1. Before the assembly starts the board should be inspected for shorts.
2. The general methode to start the assembly process is to start with the resistors.
3. The powersupply (connector, voltage regulator, capacitors then test for 9 volts and temperature of regulator) 
4. Test LED with 1.2K resistor on the powersupply and approve light intensity. change resistor if required 
5. The VCC/2 components ( IC3 and other required components, then test for 9volts/2) 
6. The capacitors
7. The female connector
8. Although solderpins are shown, it's recommended to just solder the wires directly to the board is the best way.

Available (to be) Emulations

 A shortlist of the emulations part of this unit:

As the main objective is to build a device capable of emulating the old Meazzi/VOX echo gear as used by the Shadows the selection for the Echomatic 2 as first emulation is based on the fact that >60% of all Shadows recordings are done using this device.  The not interested in the Shadow sound can still use this device with the preloaded reverbs and echo's.

Remark: A I2C programming will be added later so the user can develop and/or upload the resulted emulation to the device!

Emulation set-up 

 In order to create the DSP programs the development board is hooked-up with the motherboard utilizing the now empty 2x8 female connector.

To obtain correct filter settings for the Meazzi Echomatic#2 I've used the existing SPICE model for the Meazzi Echomatic#2  already used for the last couple of years supporting patch development. In this particular  study the other signal paths are fully taken out so it's the bare bones of the path the guitar signal will follow from the input to the output.

Simulating the wet signal is more difficult as the head/tape/head function is an unknown. For that I've split up the wet signal in it's functional blocks and obtained initial plots that will be published later. There is a write-up on this site on the effect of head gap spacing. I'm sure this should be taken into account also in the chain of events as it's a key contributor.

A CAD/CAM impression of an I2C programmer based on Claudio Lanconelli's design including his PonyProg programming utility. The purpose of this programmer in our project is to enable the user to re-program the EEPROM (24LC32 from Microchip part of the daughterboard  (actually, it's not programming the echo unit but a kind of using the available hex file, provided by me, and "burn" it to the EEPROM part of the daughterboard. Using this methode the logistics of re-burning is minimized. A proto wil be build to check functionality and create procedure.

How small can you get?

Here is a 4.4" x 3.4" x 1.0"   88mm x 112mm x 25.4mm(inner dimensions) box  with all that's required inside. The two output plugs (corner blue knob) are to tight with the rest and should have been moved about 5mm towards the input plug location. The BCD selector did not fit so I'm here using a binary selector.  The heatsink, the input plug and (2) output plugs are not yet connected but provides an impression of the total look. This box will be used for initial testing of the vintage echo DSP programs. The 19" rack and a 7" enclosure is also in the process of being completed. The metal parts I've added to the 19" rack's panel  (to mount the pot's) are of a poor workmanship(me!!). It seems that I need some machines to make at a proper part. Making this just by hand is not producing desired quality. As it's vacation time here finding some pro is not possible. I did also get decals but the background is white. I'm sure to play around with some idea's to get the lettering and scales done. I recall while developing the motherboard the size of the board required a very small enlargement to avoid complex (unresolved) routings. It's amazing to see that all fits in a very small enclosure. I guess therefore that this is the minimal enclosure possible assuming normal electronics is used. There is no dry/wet pot here as the green and cyan knobs are together the wet channel. Fitting an additional pot is just not possible. I'm now looking into the pot assembly to make it different so the interference with the jack could be fully resolved.

A stompbox with minimal dimensions 

Temporary paper scales for the 3 pot's  added so it's ready for the testphase. I'm sure decals will have a better cosmetics but this will do for the time being. Remember Echomatic 2 is with a set of 3 heads (cyan) and a fourth head(green) and feedback(yellow). This is all that's required!! The user will set 5,4.2,6 as an example for a couple of tunes. It's so easy and so cheap!! The decal printout was perfect! However, I've decided to go for another type of potentiometer with a 300 degree swing iso 270 degrees. New waterslides are ordered.

The component cost based on the BOM was carried out and is still around the 67 Euro. This is without the binary switch,3 potmeters+knobs.enclosure and the 12V mains adaptor. There are some opportunities to bring this down a little bit pricewise.  Although the strong recommendation is to build it as a mono device the cost impact of a stereo build  would only be 3 Euro savings. 

A (s)milestone for me!! A kit is now prepared for a first try-out. The kit for the pilotgroup will be pending outcome of this first build. Agreed with one vendor to deliver all motherboard parts (coded PBOSFV1). The try-out build with the in the kit contained parts and instructions are now within a couple of days. As the supplied motherboards in the pilot group are the first batch. They are provided for free. There are two locations on this board for resistors to be kept empty and the holes for the 1mm pins are .995m A small rework on the pins is required to assure they don't damage the plated-tru holes. Also suggested, as part of the instructions, is to mount one resistor slighly higher and one pin of one capacitor to keep a little bit longer. By doing so a dry/wet retrofit is easy done.

 An impression of the complete DIY kit as will be sent

 Presently I'm making one enclosure ready that's a bit larger (7") then the already shown minimal sized box. This larger box will take  the tape artifacts, input pot and a dry/wet pot. Powdercoating will be done when all holes are in. A new assembly approach is try-out to avoid more parts then the potmeter shafts on the outside. Having the knob close to the scale is rather important to assure correct setting/reading of values is possible.

Tip!Altough I'm not a mechanical person. The groundrules I've applied during the construction of the enclosures and assemblies is to stay within the 0.1" inch raster for the drillplan. By doing so it's easy to connect/solder installed components directly to Veroboards (or designed boards) 

 Extended Echo unit with advanced Tape Artifacts (DRAFT)

The extended unit with advanced tape artifacts is based on the standard unit but limited to mono only. In this design use of external controls is used so the FV-1 Daughter board's controls are for patch and filter variations. At the present there is one spare control. The draft block diagram  shows the required functional elements. The actual build will be initiated after completion of the first simple echo unit. At the present some testing for artifacts is ongoing to assure this  extended unit can deliver.

to be continued.....

/eof/