FVerb - a simple reverb/modulation pedal

[gcwills]

Oops
Just realised there are a couple more missing links in the above photo of my perfboard.
Anyone building a FVerb please disregard that photo and stick with Alex's layout!

[gcwills]

Well finally finished a FVerb using Alex's layout.
We can call that layout verified as long as you reverse the orientation of the 78L33.

Here is the perfboard installed in a 1590B:



Here is the layout used:



Any FVerbs in the pipeline?

[gcwills]

For some reason unknown to me, all of my postimage images have disappeared from my FVerb thread.
So I am reposting them here for any prospective builders.
To view the images in detail, just click on them.
Thanks to Rob Strand for his advice

Hi all,

The motivation for this project started some time ago when I heard a Blackstar amp equipped with reverb. The reverb was generated by a Spin FV-1 DSP IC and I was very impressed with how good it sounded.

Some research followed including the good work by Ice 9 and others here. However I was not too keen to have to program an external EPROM and there didn't seem to be much out there in the way of a really simple diy implementation of a FV1. I started wondering how simple a basic pedal could be using the internal ROM programs with minimal extra circuitry.

So after quite an amount of digging around and prototyping, I came up with this design which is about as simple as a FV1 pedal could be. It was developed with the hope that it will inspire those who have built basic PT2399 pedals to have a go - it uses less components than a Rebote for much more functionality. The simplest incarnation offers hall reverb, tremolo, pitch shift and vibrato and sounds great!

It is also easy to build, using a perfboard rather than a custom pcb.

More constructional information to come!

[gcwills]

Thanks for the interest in my FVerb.

Here is the schematic - click on it to enlarge



As you can see it is a minimal implementation of a FV-1 with not much more than the FV-1 and a TL072 as input buffer and dry/wet mixer.
Some economies have also been taken with only two controls - one for the FV-1 which bridges the POT0 and POT1 inputs in a similar arrangement to the EHX Holy Stain. This allows for adjusting reverb decay, tremolo speed, pitch bend and vibrato with one control. The POT2 input is pulled high to maximise the tremolo and vibrato depth. The second control adjusts the amount of wet signal in the mix. Adjusting this control also adjusts the amount of tremolo and vibrato.

To keep things simple, a SPDT centre off switch is used to switch between the internal ROM programs. I initially used a BCD switch to select all 7 programs, but found that of these 7 programs the two reverb and two pitch modes are quite similar. Also I found that the two remaining chorus and flange modes can be approximated when the pitch mode is set close to unison to create a pretty lush chorus/vibrato mode which I preferred to the chorus or flange modes. This meant that a simple mini centre off toggle switch could be used to select between hall reverb, tremolo, pitch shift and vibrato/chorus. The toggle switch was also much easier to use in operation.

A simple buffered bypass is used which works well, simplifies wiring and uses a cheap SPST switch.

To come are some comments and photos of the pedal internals and on parts availability

[gcwills]

Moving on to building the FVerb.

Perhaps one reason that the FV-1 is not used in diy as much as say a PT2399 is that it is housed in a 28 pin SMD package which is difficult to use in a conventional through hole perf or vero board.
To get around this, I used a pcb adapter which converts the SOIC package to a conventional 28 pin DIL arrangement. The FV-1 can be soldered fairly easily to the adapter with a fine soldering tip and if you happen to bridge adjacent pins during soldering, the excess solder can be removed with solder wick.

Here is a photo of the adapter pcb - AU$1 including post from ebay



By the way, thanks to Ice-9 and MetalGuy for the heads up on sourcing the FV-1 - you can also buy them from Aliexpress.

[gcwills]

Here is an internal shot of the completed FVerb:



After the FV-1 has been soldered to the DIP28 adapter board, the adapter board was mounted on a 24 by 12 hole perf board. The adapter board is fixed to the perf board by soldering a loop of wire through pins 1 and 2 through the perf board and soldered there. Similarly a loop is soldered through pins 12 and 13 and then another loop through pins 24 and 25. This fixes the adapter board firmly to the perf board and allows for the other connections to be made to the FV-1.

There is not a lot more to the board - the TL072 and a 3.3V voltage regulator. I have been too lazy to generate a perf board layout, but perhaps some kind soul here may oblige

The FVerb was built into a standard 1590B with the two pots, mode switch and footswitch mounted on the front, the DC connector at the rear and input/output sockets at the side. I built the prototype initially with a 3 position DIP switch for program selection before the SPDT centre-off program selector switch was installed. This is not needed in a build.

I found that some care needs to be taken with grounding the controls and input and output sockets. I'll provide more details later, but suffice to say I was able to eliminate any extraneous noise with proper grounding.

More to come!

[gcwills]

Have just received another FV-1 so thought I'd post some images of the build.
This time I'm using DrAlx's 22 X 18 perf board layout:



Here is the FV-1 mounted on the adapter board:



You can see that the FV-1 can be soldered to the adapter board fairly easily with a fine tipped iron. I tinned the pads on the adapter board first to make the soldering easier. If neighbouring pads are accidentally bridged when soldering, the excess solder can be removed with solder wick or a solder sucker.
I decided to use header pins between the adapter board and the perf board, but you could just use cutoff resistor leads to mount the adapter board.

I'll post some more images as the board is assembled to assist any builders of the FVerb

[gcwills]

Been a bit distracted with other projects
Finally populated the new perfboard with Alex (DrAlx)'s great layout.
A big thanks to Alex for really tidying up the layout making it straightforward to build.
And by the way, as Alex mentioned, the 78L33 is shown backwards in the above layout diag.
Speaking of which, any FVerb builds in the pipeline??

Here is the populated board:



And the board underside:

[gcwills]

Well finally finished a FVerb using Alex's layout.
We can call that layout verified as long as you reverse the orientation of the 78L33.

Here is the perfboard installed in a 1590B:



Here is the layout used:



Any FVerbs in the pipeline?

[PRR]

> For some reason unknown to me, all of my postimage images have disappeared

Postimg.org got in a tiff with somebody and lost control of that domain name.

Everything is (as you seem to know) on Postimg.cc, same urls except .cc in place of .org

[gcwills]

Thanks PRR!

[gcwills]

Updated thread title to point to reposted images