Ringdroid - a sample and hold ring modulator

[~arph]

Here is a VERO layout I'm working on, it's complete but I am not satisfied yet (the wire connection to the middle of the board)
I need your guys help to spot errors, which I assume there are.

EDIT: Oh and it should fit a Hammond B.. if you don't mind excluding the jacks and the footswitch   

[jonasx26]

That would only work if the vco in pin on the pll has a very high input impedance, which I don't recall it is. the buffer ic2b is needed to keep the sample cap C4 from discharging.. You could replace it with a fet and a diode plus resistor.. But then you have about the same footprint as a dual opamp

It is a high-Z input, works just fine for S&H. See page 11 here: http://www.ti.com/lit/an/scha002a/scha002a.pdf

[~arph]

Cool, I will have to try it again then.. I recall it drifting madly, but that was when I had a TL072 instead of a TL062 there. Would save some $ and real estate   Thanks for the suggestion!

EDIT: What it will give us is a low frequency switched capacitor to GND in the audio path. I do think this will produce clicks. As per schematic it's isolated now

[slacker]

Woah, that's a lot of jumpers, looks nice and compact though, I'll try and check it out over the weekend. Might even build it, think I have most of the bits to hand.

[~arph]

Haha..yeah loads of jumpers. Mind the ones that connect two IC pins.. do that after installing them. But i'd like to stress that you should not build it from that vero. There are some errors in there I already spotted (like the resistor right after the input cap, which is R1 and is connected totally wrong there..and some trace cuts.). I have also managed to move that wire in the center of the board to the side.  

And here is an update on the PCB boards: They are in!!  I just checked them. Look very nice. Two small errors though. Two vias had a drillsize that was too small for the manufacturer (their DRC did not pick that up!). So it's going to need two wire jumpers at the bottom of the board... GRRRRR..  I already fixed this on the PCB, so possible next runs will not have this problem.

I will try to send a message to everyone who ordered a board over the weekend with details, I am a busy man.

[Paul Marossy]

That's a very wild sounding thing you've got there. 

[earthtonesaudio]

Cool, I will have to try it again then.. I recall it drifting madly, but that was when I had a TL072 instead of a TL062 there. Would save some $ and real estate   Thanks for the suggestion!

EDIT: What it will give us is a low frequency switched capacitor to GND in the audio path. I do think this will produce clicks. As per schematic it's isolated now

I'll have to dig up my 4046s and give it a shot.

[~arph]

And here is an update on the PCB boards: They are in!!  I just checked them. Look very nice. Two small errors though. Two vias had a drillsize that was too small for the manufacturer (their DRC did not pick that up!). So it's going to need two wire jumpers at the bottom of the board... GRRRRR..  I already fixed this on the PCB, so possible next runs will not have this problem.

 Ok, that was based on visual inspection. I've measured them all and all vias check out fine! no need for jumper wires the boards are good.

EDIT:  I've just sent everyone who's in a PM with payment details etc. I you are in this run and did not get a PM, please let me know.

[~arph]

And to top it off here is a vero that I think is correct. Have checked it with the schematic. Did not build it.

Mind the tricky jumpers. In some places there are some under resistors. Plus there is one overlapping jumper (turquoise, middle right)

[mongo]

PCB layout PLEASE!

[~arph]

Not going to do a single sided layout. I've already done a double sided one and I was selling my surplus ordered boards here. Maybe if there is another run you can get one too if you're interested.

[~arph]

All payments are in!, I'll try to get them out this week. Meanwhile I've started putting one together, almost there.

[glops]

I can't wait for this board

[~arph]

It still has a second ocean to cross 

[glops]

That's actually perfect because I'll forget about it and the Santa will pay me a visit. Plus I can do my box graphics first for once!

[~arph]

One important thing to note already.

The Quad opamp must be a LM324. Otherwise the gate will not function properly. The comparator at the end of the envelope follower must be able to operate near zero volts. A TL074 won't do this.

Last thing I have to figure out on my build is why the clock bleedthrough is so loud. I had simply solved this on the breadboard so it's either a simple fix or a cold joint somewhere.

[earthtonesaudio]

TL07x gets unhappy when its inputs get too close to the neg rail.  One solution, without altering the existing board layouts, is to raise up the input voltage bias:

1. Replace D1 with 10k or higher resistor.  (IC4c now biased to at least 4.5V)
2. Replace R15 with zero-ohm jumper.    (with IC4c biased higher, the compared-to voltage has to go up also)
3. Replace D2 with a regular Si diode or Schottky.

You could bias IC4c substantially higher (~7V) and maybe get away with not replacing D2, but the gate might not work as well.  Maybe somebody has this on a breadboard and can figure the optimal bias point for IC4c using a TL074...

[~arph]

Good suggestion, that should definitely work. Btw the board are shipped today!

[krellmusician]

Looks like I picked up this thread too late.  If you have any spare boards, or get enough requests to make another run feasible, I'd like one.  Thanks.

[~arph]

I'm not sure there will be one more, but I'll put your name none the list.