# Which version of the Ghost Echo (1, 2 or 3) does the Spirit Box most resemble?



## the_grumpy_gnome

They made several tweaks across versions, however the most important to me is the ability to self-oscillate with the extended 'Dwell' control.  This change was made going from V2 to V3 in mid-2017.


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## Devoureddeth

Judging from the PCB it looks like an older version but you could probably make like V3. Upgrade the opamp to one of the low noise op amp like maybe OPA134? And the ocillation sounds like either a pot value change on a resistor addition to prevent it from going full feedback but hard to tell from what it says. Do you have a demo describing this effect?


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## Robert

I'm pretty sure the schematic used was based on the older version.     I'll see what I can find out about the newer versions.


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## the_grumpy_gnome

Devouredeth:  I'd be perfectly happy modding this circuit.  In addition to wanting one of these pedals, I really want to learn more about reverb and delay circuits for future custom projects.  I can eyeball distortion mods but I'm just learning about PT2399, so this would be a great learning experience.  

Hearsay is is that V1 and 2 are pretty much the same, but EQD enumerates the changes between the 2 & 3 here.  Differences listed include:


“Attack” control adjusts 30ms-150ms of pre-delay - this was not available in V1, it was always set to minimal pre-delay.  I can probably figure out how to increase this range in both directions.
Upgraded op-amps for better performance and lower noise - yep, that OPA134 or a NE5532 would be perfect.
Stronger reverb signal with 2x the output
Accutronics Reverb Tank
Recalibrated “Dwell” control capable of self-oscillations when all the way up - this is the main thing I'm chasing.  Want to be able to get it to self-oscillate (probably a very easy value adjustment in the "Dwell" control and I'll be able to figure it out).   The link above has an embedded video in it. Here's the link to the spot in the video with the dwell cranked.  Also, here's another similar circuit that's even closer.  It's the higher-pitched parts the the reflections I'll be focusing on, with the longer-term goal of developing something very similar to the Mr Black 'Eterna.'  Though, that's digital and incorporates octave effects, I'm going to very much enjoy learning how to develop a similar analog version.


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## Devoureddeth

I would get a breadboard and try some things out. If I had some time I would give it a go a bandmate has been wanting one for a bit. Just looking at the schematic try some different values at R8. This is where I don't know my shit so take it with salt and experiment, decreasing R8 would cause it to feedback easier and increasing R8 should do the opposite. You could probably also mess with the value of the dwell pot. If someone of more knowledge knows how the stuff works take a stab. I would just mess with R8 and maybe the pot.


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## ChrisSchwarzkopf

Hey there, any updates on this? I just finished building my Spirit Box, sounds great but modding it so it can oscillate would be great. So have you tried changing the pot or the resistor?


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## the_grumpy_gnome

ChrisSchwarzkopf said:


> Hey there, any updates on this? I just finished building my Spirit Box, sounds great but modding it so it can oscillate would be great. So have you tried changing the pot or the resistor?


No, not yet. I have a stack of several pedals that I'm trying to get done.  However, when I get to this I'll post.


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## ChrisSchwarzkopf

Perfect, thanks. Really hope that it can be done by just replacing the pot as the Brick now covers most of the backside and I really dont feel like removing it again


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## robinton03

start simple and just jumper R8 and replace the Dwell Pot w a higher value pot like 20k or 25k. its an easy mod and easily reversible if it doesn't work. Dont start with the dwell control dimed!! Work it up slow and see what happens. The Dwell control is really just the feedback control for the PT2399. Go check out the build docs for the Cataclysm, the Sea Horse, The Magnatron, The Chalumeau,  and the Pitch Witch for some more ways the PT2399 Chip is hacked to create glorious tone.


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## the_grumpy_gnome

robinton03 said:


> start simple and just jumper R8 and replace the Dwell Pot w a higher value pot like 20k or 25k. its an easy mod and easily reversible if it doesn't work. Dont start with the dwell control dimed!! Work it up slow and see what happens. The Dwell control is really just the feedback control for the PT2399. Go check out the build docs for the Cataclysm, the Sea Horse, The Magnatron, The Chalumeau,  and the Pitch Witch for some more ways the PT2399 Chip is hacked to create glorious tone.


 I'll try this with my Pitch Witch


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## ChrisSchwarzkopf

Please let me know when you have done the mod


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## ChrisSchwarzkopf

Just a little update on this: I rehoused the thing and also swapped R4 for 1 15k I had flying around for Unity Volume and I feel as if the oscillation is now finally there or maybe just more audible! Now it's perfect


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## twebb6778

That's a great looking build. Sorry if you've been asked a million times, but how did you get the graphics on your enclosure?


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## ChrisSchwarzkopf

twebb6778 said:


> That's a great looking build. Sorry if you've been asked a million times, but how did you get the graphics on your enclosure?


Thanks  no you are the first one that asked  i used white laser decal paper (bought it on Ebay) for the first time and it came out pretty nice.


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## eaglehat

I’m about to build one of these and thinking about trying some of these suggestions. But I was wondering if anyone ever figured out definitively what changes EQD made in V3?


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## lcipher3

ChrisSchwarzkopf said:


> Thanks  no you are the first one that asked  i used white laser decal paper (bought it on Ebay) for the first time and it came out pretty nice.



Can you share your ebay source?  I've been wanting to try this but there's a million different laser decal paper versions.


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## ChrisSchwarzkopf

lcipher3 said:


> Can you share your ebay source?  I've been wanting to try this but there's a million different laser decal paper versions.


Sure, its this one: https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.de/ulk/itm/131908789829


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## daeg

the_grumpy_gnome said:


> “Attack” control adjusts 30ms-150ms of pre-delay - this was not available in V1, it was always set to minimal pre-delay.  I can probably figure out how to increase this range in both directions.



Whatever version the PedalPCB is cloning, it already gets you that. The 10k 'Attack' pot will give you 1k-11k at Pin6 of the PT2399, gets you about 40ms-160ms of predelay. You wouldn't want more than 150ms for this type of effect and getting down to 30ms is only safe if you use an anti-latch circuit. I doubt the v3 really does that; more likely they're just fudging the numbers a little bit to look nicer on paper (3-15 is just more aesthetically pleasing than 4-16).

Source: https://www.electrosmash.com/pt2399-analysis


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## daeg

Devoureddeth said:


> I would get a breadboard and try some things out. If I had some time I would give it a go a bandmate has been wanting one for a bit. Just looking at the schematic try some different values at R8.



The consensus over at FuzzDog is that lowering R8 from 25k to 12k, then swapping that 5k 'Dwell' pot with a 25k pot is the perfect solution.


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## daeg

the_grumpy_gnome said:


> Stronger reverb signal with 2x the output



Also from the FuzzDog comments; try changing R5 from 10k to 17k. That's supposed to solve the volume drop issues and probably gives you a little extra when 'Depth' is fully cranked. If you make the that change, you might as well also use a 5k pot for 'Depth'. No reason for that special value pot except to bring the gain slightly up.

Disclaimer: I haven't tried these mods yet.


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## NKCPedals

I have a 5k on the depth, no issues here. I was wondering if anyone could chime in a way to maybe get a shorter dwell minimum to really make this thing anything from a tight springy slap to a cavernous beast?


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## daeg

NKCPedals said:


> I have a 5k on the depth, no issues here. I was wondering if anyone could chime in a way to maybe get a shorter dwell minimum to really make this thing anything from a tight springy slap to a cavernous beast?


TLDR; no.

The way it's designed, you'll never be able to get a slap. The signal goes from a delay with a minimum of 30ms (IIRC) and then into a pseudo reverb chip with a non-adjustable 2.85 seconds of delay time. You can turn Dwell to zero to kill any regeneration, but then you'll still have about 3 second of happenings happening.

It wouldn't be impossible to route the delay around the reverb, but then you'd need extra controls, and you simply can't fit much more in a 125B enclosure with the Belton Brick IC.


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## daeg

Also, I built the Spirit Box with a few of the mods suggested in Fuzzdogs comments. If I were to build another I'd do whatever mod was suggested to bring up the output volume a little. The mod to increase max regen was kind of pointless because once it starts to do runaway feedback the volume goes through the roof and becomes unusable. You could add some clippers at the PT2399 input to limit the swing, but then you have a filtering section not designed for those harmonics.

After months of tinkering, I decided the Ghost Echo simply sounds as good as any PT2399 reverb is going to get. Especially in the 125B footprint. It _does_ sound surprisingly good, so try to enjoy it for what it is.


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