Tonepad FSH1 Any issues, or ready to build?

[nelson]

Got all the parts for the FSH1 in the box (I think), I remember there were issues with the initial builds.

Has anyone built it without issues?

[Ry]

Mine has some pretty bad bleedthrough of the noise source.  I was actually going to build that part of the circuit on a daughter board today to see if a less compact layout in that area fixes it.  Other than the bleedthrough, it sounds superior to the original circuit (I built the GGG version some years ago).

Ry

[nelson]

Thanks for the reply Ry

Now I am wondering whether the bleedthrough is symptomatic of the layout or if it is an isolated problem.

[nelson]

I have plenty of CA3080 and plenty 13700 which should I build, the tonepad or the GGG?

[Ry]

I would assume that the layout is responsible.  I built my daughter board, populated with the exact same parts from my original build, and the bleedthrough went away completely.  If you look at the noise transistor and how closely it is oriented with the FETs and pots around it, there is a high likelyhood that the oscillations can travel.

If it were up to me to do again, I would build FP's circuit.  It contains all of Tonda's mods and it sounds a lot 'clearer' to me.  I would, however, create a separate perf board for the noise source and make sure you place the noise transistor far away from the FETs at the output of it.

Ry

[snykanen]

I guess there's no easy way to build just the sample/hold-feature? I'm really happy with my Roland funny cat and maybe some day I'll build a Mutron or something so the filter half of it would be useless. Is there filtering going on when the sampla/hold is on? Would be a really cool Zappa-esque effect...  Are there any other effects like this and I don't mean those Zvex-stuff, they're out of my league 

[Paul Perry (Frostwave)]

Is there filtering going on when the sampla/hold is on? Would be a really cool Zappa-esque effect... 

The filter is always on. How it works is, there is a noise source which is fed to the sample and hold, whichproduces a LFO with random step heights. Which then act to control the filter setting. So it is like a wah, but the wah pedal instantly jumps to a new setting every half second or so. No reason why you can't make a random step voltage generator & control another kind of filter, but some would be easier than others.

[Fp-www.Tonepad.com]

Ry,

I got your PM. Could you please take pictures of your build? I would try to incorporate the changes to the layout.

Thanks.

Fp

[nelson]

There is another one I need to wait for. 

Guess I will build a Ross phaser while I am waiting lol.

[Fp-www.Tonepad.com]

Well, it all works except there's an issue with the block that has the noise circuit (top right corner of the pcb), you can build it like Ry did.

I'm really looking forward to seeing pictures of Ry's solution.

Fp

[soggybag]

I'd like to see what Ry did also. I made this from the tonepad layout and it worked well. Though some of the lfo can be heard.

[Ry]

I have promised FP picures and a write up of what I did.  Please be patient with me, however, I have inlaws arriving shortly for a week long stay.  I will get it done as time allows, but don't expect it for a little while.

This is a brief explanation of what I did:

1)  I spent a lot of time drawing out a layout for the noise source that was both spacious and had a limited number of jumpers.  What I ended up doing was swapping which side of the op-amp each part of the circuit was used for.  This allowed me to place the FET and noise transistor on separate ends (roughly) of the circuit board because of where the power supply connections were for the op-amp.

2)  I built the circuit up to the input of the last FET of the noise source.  I ran the connection of the first FET and .05 cap back to the board.

3)  I ran ground and both power supply lines from the pads where they connected to the op-amp.

A picture is worth 1000 words, I will send a few to FP.

Ry

[soggybag]

Hey Ry, I've been looking to try and get back to this project. If you have gotten around to drawing up your changes let us know. If not no pressure. Maybe you could answer a few questions so I can try and work it out for myself.

It seems the noise is coming in either through the op-amp (IC3 on the TonePad layout), or it is leaking in through the power supply going to the noise source. Does this sound close? Any comments?

If the problem is through the power supply connection, which runs from +9v past the LFO op-amp and then to the noise source, maybe a filter cap in here might help? Or maybe a sepparate connection running from the noise source to the +9v?

If the problem is with the op-amp, maybe some filter caps at pins 4 and 8 might help?

Of course I should just try all this out and let you all know how it works out. But I thought I'd just throw these ideas out there and see if anyone had something to add.

[Ry]

Soggy,

I sent FP a picture of what I did.  I will send you one as well. 

It seems the noise is coming in either through the op-amp (IC3 on the TonePad layout), or it is leaking in through the power supply going to the noise source. Does this sound close? Any comments?

The noise in mine was generated by the traces for the noise transistor (Q1) being in such close proximity to the other components around it.  Are you getting noise even in the filter mode?  If so, an easy test to see if you have the same problem I did is to remove Q1 and see if the noise goes away.  It would seem like the noise is coming from IC3 in this case.

If the problem is through the power supply connection, which runs from +9v past the LFO op-amp and then to the noise source, maybe a filter cap in here might help? Or maybe a sepparate connection running from the noise source to the +9v?

I didn't have any problems with noise from my power supply.  I tried running it off of two batteries ealier just to see if the 1044 chip was causing noise.  Filter caps would likely help, but I would try diagnosing Q1 before focusing on the power supply.

If the problem is with the op-amp, maybe some filter caps at pins 4 and 8 might help?

It is possible that filter caps might help, but I really think the problem is in the proximity of the traces carrying the oscillation (noise) source near other traces.  The other thing I did early on was to cut the really long traces to the Resonance pot and solder it directly to the 100k pots it goes to.  I was concerned that it ran under jumpers and the traces were close to the noise source.  I can't say that it helped much, though.

Ry

[soggybag]

Thanks for the reply, I'll give these ideas a test tonight...

[Fp-www.Tonepad.com]

Ry,

I got the pictures you sent. I'll study them and come up with a solution. It's most likely the physical power supply routing scheme.

Thanks!
Fp

[soggybag]

I finally found some free time to get back to this project.

After a few tests I find:

In the sample and hold mode I here the clock signal bleed through. The clock pulse is being filtered by the filter section.

After removing the noise transistor I can still hear the clock pulse.

In the filter mode I do not hear the clock when I am not playing anything. If I strum a chord I can hear a ticking as the filter goes through its sweep. When it dies away the ticking is gone again.

Probing with the scope I see a good random stairstep at B2. But there is a sharp tick at each step. To imagine the image I see on the scope, picture a random stair step with a bright line between each step which is taller than each step.
It seems the clock seems to be bleeding through the sample and hold section built around Q5 and 6.

I don't seem to see this spike in the noise coming from pin 1 of IC3.

I wonder if the clock spike could be filtered out at B2 with a cap?

I'm having a hard time picturing how the noise is getting into the system between Q5 and 6, does anyone have any thoughts?

[BILLYL]

Howdy All-

Been awhile since I have posted.  Started the build of TonePads FSH and awaiting the arrival of some parts.  So far so good.  And as a good user of this board I did a search to find any info on the build and came across this thread.

FP -  Any conclusions after you saw the photos.  Is there anything I need to be concerned about?

Great  site-

Bill

[Fp-www.Tonepad.com]

The only conclusion I've come up with is that the power traces need to be redone, which is no easy task. At the moment I don't have the time to work on it, but it's on my (long) to do list.

Fp

[hank reynolds 3rd]

I built the fs+h (with the mods),using the ggg layout ages ago, and I've never had problems with bleed through..i changed the trimmers for pots aswell,for more range on the s+h part (could probably do with changing the values as at the far end of the range there's no sample and hold coming through)...