Cherub - another PT2339 pseudo chorus and vibe

[Crontox102098]

^Yep, in a breadboard... sounds great and is it absolutely noiseless.

Excellent.

What lay is the verified??; you have photos?

Disculpa, hermano, but I have no photos. This is the second version, i checked the schema with the new layout and so I made ​​sure that were correct.

[bilo01]

I can post a scaled version of the trace if you like.

I'lld like that very much Samhay. And i'll take your advice and breadboard it first as soon as i've got my PT2339.

Thanks!!

[samhay]

Here's the version 2.1 PCB layout - not verified!
https://dl.dropboxusercontent.com/u/11996927/Cherub_PT2399_Chorus_V2o1_PCB.pdf

[samhay]

It seems that if the circuit is powered up when the depth is set to minimum, the PT2399 can latch up.  If the circuit is powered up with the depth set to max, it doesn't latch up, so this may be sufficent anti-latch up protection for some. However, I have added optional anti-latch up protection to the schematic in the first post and a perf layout incorporating this is below.

This is NOT verified, and the anti-latch circuit will effect the depth control to some extent, so the value of the 100k resistor (R13) that sets the minimum depth may have to be reduced. When I have some time, I will add the anti-latch circuit as a daughter board and see how it goes.

[samhay]

Added the anti-latch up protection shown in the schematic as a small daughter board. Works fine, and no need to change the depth control.

Note to self - modifying perf circuits is a PITA.

[samhay]

Some housekeeping:

Freppo has put together a vero layout for the Cherub, which I believe is verified:
http://parasitstudio.weebly.com/uploads/2/4/4/9/2449159/cherub_chorus.png / http://parasitstudio.weebly.com/guitar-fx.html.

I also made a quick direct recording yesterday to show how quiet the circuit is.
Recorded with tele single coils -> compressor -> Cherub -> audio interface:
https://dl.dropboxusercontent.com/u/11996927/Cherub2.mp3

[deadastronaut]

sounds great sam...nicely done.

[Elijah-Baley]

Seems to me a good alternative to the Little Angel Chorus.
Thank you!

[samhay]

You're welcome, and thanks Rob.

Have been thinking about revisiting this for a while in the context of a 'Fat Cherub' with variable delay and maybe envelope control. As soon as I get the DiSCO built, I will have another play.

[davidspence]

Hey everybody, this is my first time posting in the forum, any forum for that matter. I etched the 2.1 version and got everything working but the lfo seems to be a full wave rectified sine wave instead of a sine wave. I'm not sure if it's the transistor that's biased wrong or what. I'm using a 2n3904 instead of a 2n5088 if that makes much of a difference. The effect sounds ok the way it is but it bouncing up and down instead of normal wavy. Sam, thanks a lot for designing and posting this btw.

[samhay]

Does the wavy-ness of the modulation improve/get worse as you adjust the depth pot?

[davidspence]

It seems like the effect is most symmetrical at the highest depth setting and at the lowest setting it sounds like how this looks. I'm guessing that the transistor isn't "on" for the full cycle at this low setting... but i'm still new at transistors.

[samhay]

There is a 100k resisor in series with the depth pot to set the minimum depth. If you find there is a usable minium depth at some point mid-way through the depth control, then increase this resistor to set a new minimum depth.

It was a few years ago I last played with this on the breadboard, and I can't remember if I auditioned different transistors or not. However, I don't think I would have spec'ed at 2N5088 if a lower gain transitor worked as well. So... Alternatively, try a higher gain transistor.

[davidspence]

awesome, I'll try the resistor first and I've got some 5088's on order. Thanks a lot for the help!