FV-1 Multi effect full forum project ready to go. (ShimmerVerb Also)

[Ice-9]

So..

with the regulator removed, the op-amp 4 & 8 is giving me the same as the input psu 9.12 - here's the wierd thing, it's exactly the same  ( ok, maybe 0.02 difference) when I DON'T have the alligator clip.. so the 33 Ohm resistor isn't causing a voltage drop when the regulator is removed...

Yes that result sounds normal as with the regulator removed the FV-1 part of the circuit is not taking any power (which is the main current draw in the circuit under normal use). The only part of the circuit using any current will be just a few millamps from the analogue side so there will be very little voltage drop when run without the FV-1.

Did you have a chance to test the audio path with the reg removed and linking between C6 and C8 to make sure the analogue path is still working as it should ?

Now the regulator I tested on a breadboard: it is not heating up anymore, the out put is 3.23 but the input voltage drops to 9.06 (this is the same for 3 regulators - two that I'd tried in the circuit earlier and an unused one)


[/quote]

[therealfindo]

here's a quick mp3 of what it sounds like with the c6 - c8 link and no regulator (clean first.. you'll hear when I activate the circuit!)

[Ice-9]

here's a quick mp3 of what it sounds like with the c6 - c8 link and no regulator (clean first.. you'll hear when I activate the circuit!)

That sounds terrible, the analogue side is just a buffer in and a buffer out so should not have any gain or distortion present, the sound level and tone should be almost identical when the footswitch changes between effect and bypass the way it is now wired with the FV-1 bypassed in circuit.
I don't have a built PCB to hand so will make one tonight to do some checking and voltage tests to compare your readings with.
It may be worth checking some voltage readings on each pin of the op amp to compare and check your Vref voltage is half supply voltage.

I can't see clearly from your pictures what you have in the pads for C9, C10, R11 and R12. If you could confirm for me this while I am building a test pcb that would be great.

[Ice-9]

Ok I have made up a pcb with the main audio parts on to test so we can try and get your PCB working correctly, I have also done some real time voltage checks and a sound file of how it should sound when bypassed and engaged. (FV-1 left unpowered and link between C6-C8).

here are some voltage readings

Main power input       =9.24v
Vref (R3-R4 junction) =4.6v

TL072 op amp (meter lead red to pin black to ground)
pin 1 = 4.6v
pin 2 = 4.6v
pin 3 = 4.37v
pin 4 = 0v
pin 5 = 4.55v
pin 6 = 4.6v
pin 7 = 4.6v
pin 8 = 9.24v

These readings will all be slightly different depending on what your input voltage reading is.

Here is a little recording, guitar plugged into FV-1 PCB, out to PC and recorded direct into Cubase.

https://soundcloud.com/micktaylor1/guitar-audio-03

The sound is in bypass then at 17 seconds you can hear a small click as the pedal is engaged, at 33 seconds it is turned off again. Near the end I strummed a couple of chords as hard as possible to try and over power the circuit. Guitar was a EVH wolfgang with high output humbuckers and the result was still clean.

Your fault as I can see sounds like a bad opamp or incorrectly biased opamp which could be down to a faulty component or even a wrong value component. I know you have checked values but could you check again that the values around the Vref components are correct. The voltage readings should put us on the right track.

[therealfindo]

Thanks Mick!!

Here are my readings:

          No links   |  R2 bypassed  |  C6-C8 linked  |  C6-C8 linked + R2 bypassed
PSU    9.05v           9.05                  9.05                     9.05
Vref    8.13            8.19                   7.83                     7.88

Pins
1       8.37            8.43                 7.88                  7.92
2       8.36            8.43                 7.88                  7.92
3       5.53            5.56                 5.33                  5.37
4       0                 0                     0                       0
5       7.4              7.45                1.00                  1.00
6       8.36            8.43                1.01                  1.00
7       8.37            8.43                1.00                  1.00
8       8.99           9.05                8.98                    9.05

The c6-c8 link was from c6 - to c8 + Should it have caused that huge drop?

But.. I just noticed that I've accidentally put a 4k7 resistor at R3 - those red and orange stripes look too similar!! So I'll change that out and see if makes a difference.
I already tried a new op amp chip back at the start.. but I can also try again.

[therealfindo]

slight eureka moment...

I replaced R3 with the correct 47k resistor but the c6/c8 link was still getting the  crazy distortion, so just out of interest (in case I had the link clipped on wrong) I played around with it and clipped the two + terminals to each other, and ta-da, clean sound.. no flubbiness.

so the voltage readings with that c6-c8 link (and r2 in circuit no regulator) are:

psu 9.12
vref 4.44

1   4.55
2   4.54
3   2.82
4   0
5   4.53
6   4.54
7   4.55
8   9.10


So... the problem lies somehow with c6 perhaps? As far as I can see, I've got the polarity for c6 and c8 correct. Would this relate to the overheating of the regulator? (I really fear that the obscene snowstorm of noise I hear when it's installed is indicative of a fried chip..)

[loylo]

No it's not C6, the voltage drop is définitively due to R3: Vref =  R4/(R3 + R4) x V+
So with R3 =4K7, you had Vref = 8,22V
With R3 = 47K, you now have the correct value of Vref = 1/2 V+

So nice job therealfindo!

I bought a FV1 because of this project months ago, but I still need to buy a PIC programmer... 

[Ice-9]

slight eureka moment...

I replaced R3 with the correct 47k resistor but the c6/c8 link was still getting the  crazy distortion, so just out of interest (in case I had the link clipped on wrong) I played around with it and clipped the two + terminals to each other, and ta-da, clean sound.. no flubbiness.

so the voltage readings with that c6-c8 link (and r2 in circuit no regulator) are:

psu 9.12
vref 4.44

1   4.55
2   4.54
3   2.82
4   0
5   4.53
6   4.54
7   4.55
8   9.10


So... the problem lies somehow with c6 perhaps? As far as I can see, I've got the polarity for c6 and c8 correct. Would this relate to the overheating of the regulator? (I really fear that the obscene snowstorm of noise I hear when it's installed is indicative of a fried chip..)

The problem points to the wrong size resistor R3, In your first readings Vref was over 8 volts when it should have been half the supply voltage, it was not possible for the opamp to be biased correctly.
If you have C6 and C8 installed the correct way around, (negative stripe facing away from the footswitch) all should be good here, but if one or the other was incorrect or damaged then a high voltage could have damaged the FV-1. It may be worth checking/changing C6-8 .
Next I would remove the link between c-6 c8 and put back in the regulator and check the voltage on its output, if 3.3 volts (3.2ish is fine) then check through your amp that it is now working. If all is not well, let me know as the FV-1 may be damaged.
Let me know how this works out.

EDIT- I posted at the same time loylo did, +1 on R3 .
Get that PIC programmer, you know it makes sense.

[Ice-9]

Here is the code for the  Reverb Room in case anyone wants to have a go at messing around with it. It is a slightly modified version of one of the room reverbs from the Spin site.

Code Select Expand





;Room.

;Pot0 = reverb damping
;Pot1 = reverb level
;Pot2 = reverb time


mem idel 4000 ;initial sound space
mem iap0 11
mem iap1 27
mem iap2 43
mem iap5 171
mem iap6 296 ;thickening all passes imbeded in intiial delay

mem ap1 134
mem ap2 256
mem ap3 562
mem ap4 763 ;reverb loop input all passes

mem lap1a 1421
mem lap1b 1945
mem d1 2434
mem lap2a 1894
mem lap2b 1767
mem d2 2645 ;loop constants

;write-first registers:

equ dry reg0
equ kirt reg1 ;coefficint to scale initial sound
equ krt reg2 ;coefficient to affect RT of loop
equ apout reg3 ;output of loop input all passes
equ kd reg4 ;damping coefficient (for shelving)
equ temp reg5 ;temp register for filter routines
equ gain reg6 ;adjust gain with RT
equ revoutl reg7
equ revoutr reg8

;read-first registers:

equ lf1 reg20 ;reverb loop filter 1
equ lf2 reg21 ;reverb loop filter 2
equ hf1 reg22 ;loop high pass 1 (fixed)
equ hf2 reg23 ;loop high pass 2 (fixed)
equ lfin1 reg24 ;LPF for imbedding in intial delay
equ lfin2 reg25 ;LPF for imbedding in intial delay
equ lf reg26 ;input low pass (shelving with kd)

;clear read-first registers:

skp run,endclr
wrax lf1,0
wrax lf2,0
wrax hf1,0
wrax hf2,0
wrax lfin1,0
wrax lfin2,0
wrax lf,0
endclr:

;initial sound tap positions (30.5uS/location, 100=3.05mS):

equ ld1 874 ;first tap, left
equ rd1 874 ;first tap, right
equ ld2 1156 ;and so on...
equ rd2 962
equ ld3 1345
equ rd3 1121
equ ld4 1456
equ rd4 1423
equ ld5 2121
equ rd5 2124
equ ld6 3245
equ rd6 3646

;initialize sin LFO:

skp run,endset
wlds sin0,25,100
endset:

;prepare decay pot:

rdax pot2,0.97 ;get pot, limit to less than infinite
wrax krt,1 ;write loop decay time
sof 0.4,0.6 ;scale to 0.6 to 1.0
wrax kirt,0 ;write impulse filter gains
sof -1,0.99 ;scale to decrease gain with RT
wrax gain,0 ;write gain factor

;prepare damping pot:

rdax pot0,-1
wrax kd,0 ;increases shelf to -1 (infinite loss)

;do inputs to predelay:

rdax adcl,0.5
rdax adcr,0.5 ;get inputs
mulx gain ;give greater gain to short RT
wrax dry,0

;read predelay and write initial response delay:

rdax dry, 0.5
rda iap0#,0.5
wrap iap0,-0.5 ;complicate input to initial delay
wrax temp,1
rdfx lf,0.4
wrhx lf,-1
mulx kd
rdax temp,1 ;low pass fiter entire input
wra idel,0 ;write initial sound delay

;complicate initial sound:

rda idel+500,1
rda iap1#,0.5
wrap iap1,-0.5
wra idel+500,0

rda idel+1000,1
rda iap2#,0.5
wrap iap2,-0.5
wrax temp,1 ;save filter input
rdfx lfin1,0.2
wrhx lfin1,-1 ;make HP filter
mulx kd ;multiply by negative shelving coef
rdax temp,1 ;add back input (shelving LPF)
wra idel+1000,0

rda idel+2500,1
rda iap5#,0.5
wrap iap5,-0.5
wrax temp,1 ;save filter input
rdfx lfin2,0.2
wrhx lfin2,-1 ;make HP filter
mulx kd ;multiply by negative shelving coef
rdax temp,1 ;add back input (shelving LPF)
wra idel+2500,0

rda idel+3000,1
rda iap6#,0.5
wrap iap6,-0.5
wra idel+3000,0

;do reverb input all passes:

rda idel,0.9 ;leave some headroom
rda ap1#,0.5
wrap ap1,-0.5
rda ap2#,0.5
wrap ap2,-0.5
rda ap3#,0.5
wrap ap3,-0.5
rda ap4#,0.5
wrap ap4,-0.5
wrax apout,0

;do reverb loop and sum all outputs:

rda d2#,1
mulx krt
rdax apout,1
rda lap1a#,0.5
wrap lap1a,-0.5
rda lap1b#,0.5
wrap lap1b,-0.5
wrax temp,1 ;save filter input
rdfx lf1,0.4
wrhx lf1,-1 ;make HP filter
mulx kd ;multiply by negative shelving coef
rdax temp,1 ;add back input (shelving LPF)
rdfx hf1,0.01
wrhx hf1,-0.5 ;roll out lows in loop
wra d1,0

;rda idel+ld6,-0.35
;mulx kirt
;rda idel+ld5,0.4
;mulx kirt
;rda idel+ld4,0.4
;mulx kirt
;rda idel+ld3,0.5
;mulx kirt
;rda idel+ld2,0.5
;rda idel+ld1,-0.55
;wrax revoutl,0

rda d1#,1
mulx krt
rdax apout,1
rda lap2a#,0.5
wrap lap2a,-0.5
rda lap2b#,0.5
wrap lap2b,-0.5
wrax temp,1
rdfx lf2,0.4
wrhx lf2,-1
mulx kd
rdax temp,1
rdfx hf2,0.01
wrhx hf2,-0.5
wra d2,1.99
rda d1,1.99
mulx pot1
mulx pot1
wrax revoutr,0

;rda idel+rd6,0.4
;mulx kirt
;rda idel+rd5,-0.5
;mulx kirt
;rda idel+rd4,0.5
;mulx kirt
;rda idel+rd3,0.6
;mulx kirt
;rda idel+rd2,-0.6
;rda idel+rd1,0.5
;wrax dacr,0

;do reverb smoothing:

cho rda,sin0,sin|reg|compc,d1+100
cho rda,sin0,sin,d1+101
wra d1+200,0

cho rda,sin0,cos|reg|compc,d2+100
cho rda,sin0,cos,d2+101
wra d2+200,0


[loylo]

Get that PIC programmer, you know it makes sense.

For sure, I know, and I will ! 

[therealfindo]

I replaced c6 and c8 even though they were the right way around, just in case - though I managed rip out a pad in the process, but it appears to have continuity with the trace still 

The regulator is still getting too hot to touch - i'm getting 6.06v on the iput side and only 3.04 on the output side.. have tried a couple of different ones, same thing.

But the sound is still crazy, and I think I might have fried the chip, perhaps I accidentaly bridged the input and output leg of the regulator while testing at one point (though it doesn't explain why it's overheating)

Here's an example (turn your speakers down!!)


I'm also still confused as to why going from the negative side of C6 to C8 causes distortion, but bypassing C6 stops the distortion? Even with new caps, it's still doing that - and I'm guess that if the FV-1 was working, that C6 would still cause distortion somehow.

[Ice-9]

I replaced c6 and c8 even though they were the right way around, just in case - though I managed rip out a pad in the process, but it appears to have continuity with the trace still 

The regulator is still getting too hot to touch - i'm getting 6.06v on the iput side and only 3.04 on the output side.. have tried a couple of different ones, same thing.

But the sound is still crazy, and I think I might have fried the chip, perhaps I accidentaly bridged the input and output leg of the regulator while testing at one point (though it doesn't explain why it's overheating)

Here's an example (turn your speakers down!!)


I'm also still confused as to why going from the negative side of C6 to C8 causes distortion, but bypassing C6 stops the distortion? Even with new caps, it's still doing that - and I'm guess that if the FV-1 was working, that C6 would still cause distortion somehow.

If the Reg is getting hot and the voltage is dropping with the reg fitted (you had correct voltage without the reg) then you have a short somewhere.
If your willing to pay postage fees then I would be happy to sort out any problems for you. Let me know and I will give you an address to send it to.

[slacker]

What do you mean by "bypassing C6"?  Does this stop the white noise

[therealfindo]

thanks Mick.

I can't see any shorts - I'm assuming it would have to be on the other side of C6? Though, again, using clips to jump R2 gives me 9.06v at the regulator input, (but as you say - I had proper volatage there, at the socket, until I plug the regulator into it, when R2 was in the circuit) but it still gets really hot.

I'll PM you..

[therealfindo]

What do you mean by "bypassing C6"?  Does this stop the white noise

When I jumped from the + of C6 to the + of C8 (with no regulator). There was no white noise, as it was just the analogue op-amp part of the circuit.. although going from the -of c6 to + of c8 added distortion and flubbiness (which I don't understand - because as far as I can see in the schematic, it's going from the - of c6 into the rest of the circuit.. The white noise only happens when I put the regulator in.

[therealfindo]

btw, I have R14 and R6 as wire jumpers as per these instructions but they are 1k resistors on the schematic.. is this a problem?

[octfrank]

While it is difficult to tell from the photos, it looks to me like IC4 may be backwards.

[deadastronaut]

^  i zoomed in and it looks it to me too...well spotted....unless its a trick of the light.

[therealfindo]

It does appear that the 'dot' of IC4 is on the footswitch end...

[loylo]

It does appear that the 'dot' of IC4 is on the footswitch end...

Yep, and if you look at the pics of Ice9 on page 1, the dot should be on the other side.