v3207 Modded Ultraflanger

[thomasha]

Hi guys,
It's a long time since my last post. The last months I was in a rabbit hole called BBD flangers...  So what I did was adapt the ultraflanger to use a v3207 BBD. I also made some other changes trying to improve this pedal. The schematic now looks like this:


I added the decoupling after de BBD and adjusted the bias of the second OPAMP, now it won't distort as easy.
I added a trimmer to set the gain of this stage, since now it was giving me twice as much swing.

I tried to measure the clock frequency with the cheap chinese scope (from the 20 bucks kit) and it seemed to oscillate between 35khz and 220khz. So the lower limit is ok, the top limit I guess is just too close to the scope's limit of 500khz, where the input capacitance gets most of it (probably)
The final result:


The ground plane is totally worth it. I had to add some resistors at the lower side to get the shortest path to the inputs as possible. That solved the weird switching noises from my first board. Now I can say that it is really  quieter.




Now some curious stuff I observed...

1- With the depth/width pot fully at CCW there is still some small signal of the LFO coming through when the speed is set at minimum. It is just noticeable when combined with a distortion pedal. Is it because of the 47uF capacitor to ground? Should I put a 1000uF in there, or can I ground one of the sides of the pot?

2- Even with lot's of caps I couldn't get rid of the ripple at the LFO 3.9v. When using a zener I had to put a 1k resistor in place of the 10k normally found in the old schematic. That can't be right. Is this LFO really this hungry at lower speeds? Note that the CD4046 and de 4049 have their own node.

3- I should adjust the mix (actually the gain of the second opamp) so that both signals are mixed 50/50 right? I'll have to reduce the 100k after the BBD too, otherwise the gain of the BBD + unity gain stage still is more than the dry signal.

It's sounding good as it is, but really intense, I only can get the jet like sound when using distortion. Even with the Regeneration at full CCW it's like a parked jet...on the other hand, it is not oscillating unless the gain of the second opamp is higher than 1.5!  I guess I'll have to adjust the trimpot at the first opamp too...

[jimilee]

Daaaammnn That's nice and small. That looks very neat.

[dawson]

Wow- these tiny builds of yours leave me in a stupor.  The circuit building, pcb planning/etching, the micro-soldering, the pro' shoe-horning, the waste-less wiring, all topped off with super cool and detailed artwork..  Just-Wow, dude- thanks for sharing, I really enjoy looking at these!

[gordo]

I'm going to pretend I never saw this and quietly back away...

[Caedarn]

Wow- these tiny builds of yours leave me in a stupor.  The circuit building, pcb planning/etching, the micro-soldering, the pro' shoe-horning, the waste-less wiring, all topped off with super cool and detailed artwork..  Just-Wow, dude- thanks for sharing, I really enjoy looking at these!

What he said....amazing work

[TheDude]

If this was a competition this would be my cue to give it up. Unreal work sir

Sent from my LM-X410PM using Tapatalk

[287m]

i have favorite builder when addicted to pain build small headphone amp, the miniaturization guru, the one and only sijosae

now, in pedal build, i found LB Master again. You Krazee. I like it.

my commision build in LB, Freddy fuzz and Eternity give me enough stress and hold my courage to build LB again. Hahaha

You Rock!

[DLW]

i have favorite builder when addicted to pain build small headphone amp, the miniaturization guru, the one and only sijosae

You might need to pick a new favorite micro amp builder, because thomasha does that too... https://www.madbeanpedals.com/forum/index.php?topic=29072.0

Everything about this pedal is fantastic- the layout, the build, the graphics. All of it

[Scruffie]

If you adjust the gain with R9/10 you'll adjust the Q of the filter, it can only reach a Q of ~3 Before it oscillates, it's not a good place to adjust gain at all, you'd be better off either adjusting gain via R7 or R13.
Or you could change R8 to 100k, move R32 to the other side of it and reduce it to 91k, the node will look ~47k to the filter, you'll have your reference voltage and the signal will have been divided.

Your sweep is probably poor due to the new 10k/10k divider for the LFO, at 3.9V it was swinging further to ground.

[thomasha]

Thank you guys for the kind words!
Sijosae still is a motivation to build smaller tube amps for me too!
Thanks Scruffie for the tips!

you'd be better off either adjusting gain via R7 or R13

I tried it. To get te same swing the resistor should be 11k instead of 100k. It is probably working with the 4.7k resistors as a divider, that's why the low value. At this value the bias voltage is also better and the decoupling cap is not necessary. So that is a different way to correcting the circuit.

Your sweep is probably poor due to the new 10k/10k divider for the LFO, at 3.9V it was swinging further to ground.

I changed the resistor to ground, to get closer to the 3.9v. The thing is that it has a ripple from 3.7 to 4.0, that looks huge, even with the 47uF capacitor to ground.

[Scruffie]

TL072 is a a lousy LFO op amp, try an LM1458 or LM358 and see if that helps the ripple.

[nzCdog]

Such an impressive build. Hope you can sort the oscillation

[cooder]

Friggin' unreal.... 

[selfdestroyer]

Awesome! Thomas, can you take a pic of all your tiny arsenal plugged into one of your kick ass mini tube amps? It would be such a cool pic.

[m-Kresol]

Awesome! Thomas, can you take a pic of all your tiny arsenal plugged into one of your kick ass mini tube amps? It would be such a cool pic.

and put a Lego figure next to it as reference!

I never stop to be amazed by your work. no idea how the pcb fits with jacks and stomp...