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The LFO won't work with a TL072. I really don't think the problem is LFO tick, it's more a VCO tick... obviously the LFO's swing does impact the amount of control voltage though and the swing does differ between chorus & vibrato mode. Notice how your vibrato mode clock is higher than chorus...

So the thump is probably less LFO tick and more the BBD thumping when the clock goes wonky. Quickly try tacking some small caps in parallel with C1 & 2 (22pF or something) to see if getting the max clock frequency down will stop it overshooting, it is a little high, may be down to the chip...

8.6V x 2 minus two diode losses and charge pump inefficiency is let's say... 16.2V and the regulator needs at least 17V to do its job. That'll probably be your issue.

Check your values and polarities first and foremost, also depth should be measured at the middle leg of the depth pot, sounded more like you were measuring it on the LFO op-amp output. See what your clock frequencies are as well while you're there.

Hooray! What are the noise levels and headroom like? Are they as poor as the datasheet indicated or was it being conservative?

Guardians said it had a volume drop, fixes that without impacting the frequency response.

That was just your Art Nouveau period, now you've moved on to minimalism.

You make it sound so secret! And it is, if any one uses these new values, I'll have to torture Guardians with the soft cushions and the comfy chair. Just reduce R8 & 27 equally to keep the mix/feedback levels right so R8 would become 100k and R27 54k6 but you can probably get away with 56k...

Can anyone explain this thunking to me? I assume it's in time with the rate but does it disappear with depth? Does increasing any of the controls make it more apparent? Has anyone bothered to check what the voltage offset is like on the phase stage op-amps?

For what it's worth, I saw someone on Modwiggler tried to play with this chip and found the chip wouldn't function with a less than optimal duty... which makes one sort of wonder why they didn't just put a flip-flop instead of an inverter inside the chip. Also, don't know if it's of any use but...

I see the problem here... Put it in a fancy/unique enclosure, add a toggle switch that says 'tube' that does... something, give it some buzzwordy development spiel and hound a celebrity guitarist with a large following to use it and post about it online. Everyone will care. I thought your...

I care! Sounds like a pretty cool design. Are you going to make it a DIY project, market it as a product or is this just for your self... if it's just for your self and you keep showing everyone you meet your tiny headphone amp then snatching it away when they go to look that might explain it 😜

What are your bias voltages, the transistor buffer is relying on the J-FET in this situation for optimal bias. Poor bias, poor signal swing and unfortunately, the J-FET's biasing is also impacting its gain.

Well have you tried just putting the source and emitter resistors and J-FET's biasing 1M to -12V? But more to the point, have you checked what kind of voltages you're currently getting on the J-FET and transistor?

Try a four quadrant multiplier (an LM13700 can be set up as a dirty one).

No, that one's a Buffalo FX circuit so neither I nor Verlie did those, I think it was a small French company and the owner got sick? I think there's a TGP thread about the whole saga, any way, she ended up taking over the designs. A large majority of the stuff I've done hasn't even been...

I do 'em like this, that about the same as your method? But uhh... that Stonedeaf schematic is... well it's certainly an interesting approach. Edit: Just realised this read like I was complaining about Rob's CD4007 drawing, was referring to Stone Deaf's approach to the MPF-1!

The problem you're finding there, is there isn't a FET in that circuit.

Don't need a scope, you can just build an audio probe. If you post full voltages may be possible to spot the fault.

Oh how ironic would it be to find out you'd bought a hastily released heavily gooped clone. That must be it :unsure: lifting all those spools of 63/37 will do that to a man, entire kilo's of pure, somewhat adulterated lead. 🤣 Do you reckon you'd been caught out before and not cottoned on?