Maestro Filter Sample and Hold

[Ry]

I agree that the board size is somewhat to blame.  The GGG layout has a very minor amount of the same bleed through signal, but it isn't too distracting.

I will continue to play around with it.

Thanks for the work that went into this, we'll get the bugs worked out!

Ry

[Fp-www.Tonepad.com]

can you make a sound clip and email it to me?

fp AT tonepad (dot you know what).

Fp

ps: SPAM has gone insane in the last few weeks!

[Ry]

I will do my best to get a sample to you on Friday.

[soggybag]

After flipping the FETs around. The sample and hold effect seems to be working well. The filter sweep mode does not work.

When not playing I hear the sample and hold quietly in the background.

[Fp-www.Tonepad.com]

Cool. Did you wire the sweep direction DPDT switch?

Fp

[Fp-www.Tonepad.com]

I have decided to build this one, the pcb is etching right now.

I will build it by blocks, in order to try and find the possible problems/errors.

Fp

[soggybag]

After further testing I find

The sample and hold mode is working. But you can here the sample and hold effect in the background when not playing.

The filter mode is working but there is a background hum. I used a 10K pot for attack, didn't have a 5Kon hand, at some settings there is no effect.

What type is the decay pot? There is not much useable range.

The sweep switch seems to only be sweeping down. The up sweep doesn't seem to be working. Could be a problem with the wiring. The wiring on the layout was a little confusing. I will have to check it against the schematic I might have made a mistake here.

Playing on the high strings doesn't seem to generate enough signal to trigger the filter envelope.

I used some a pair of 1458 opamps I had sitting around for a first test. I think I will replace these with some TL072s and test again.

[Fp-www.Tonepad.com]

I have uploaded the mp3 Ry sent me. Here's the link:

www.tonepad.com/fpstuff/ry-fsh.mp3

The whining is terrible, and very much in audio frequency. Does it change with the speed of the LFO?

Soggy, do you have that same issue?

I believe it could be offboard wiring related too. Does moving the wires going to the s+h/filter change the noise?

Soggy, the envelope detector controls are mods by Tonda, maybe somebody who built using those mods can help with pot taper/etc.

I haven't had a chance to build my own, and it seems like it will be a while until I have the time, still, I am very interested in troubleshooting this one.

Fp

[Ry]

Oh, now that's embarassing!  I never thought that my crummy 30 second demo would be online.  Don't get me wrong, I'm not upset, but I would have made it more interesting...

The whine does not change with the lfo speed.  It is very faintly present in my GGG build as well, but only if I listen very, very closely to the S/H setting (it's not at all present in the filter mode).

The whine gets maybe 5% better when I move the in/out wires farther from the board (they tend to run over the entire board right now).  There is no difference in the sound if I move any of the other wires.  

I am planning on wiring up a different filter/s&h switch to see if maybe it is somewhat faulty.

My envelope control mods work.  They are very touchy, especially the decay one as Soggy mentioned.

Soggy, I used TL072's for my op amps and it filters pretty well.  I find that it's just a matter of getting the filter mod pots in the right spot to respond to my playing/pickup selection.

[niftydog]

I have uploaded the mp3 Ry sent me. Here's the link:

Wow, cool! I wish MY alarm clock sounded that funky!  

[Fp-www.Tonepad.com]

Ry,

Did you use the MAX1044 with the GGG build too?

I am trying to find the source for the whining.

Since it doesn't change with the LFO speed it may be the MAX1044, maybe worth it to try it without it and power it with a bipolar supply, just to discard that possibility.

Fp

[soggybag]

I used a MAX1044 in my build. I did the first test with a 7660 then switched over to the 1044 after the first round.

Yes I notice that the whine does not appear to be effected by the speed of the LFO. I thought the 1044 was supposed to be above audio. There's something on the datasheet about connecting two pins to (or maybe it's put a cap across two pins) to make the charge pump work at the higher speed.

[Bill Bergman]

I have several pedals with 1044 power circuits in them using the extra cap. They didn't seem to whine.

[Fp-www.Tonepad.com]

Bill,

I haven't had a chance to check the file you sent me, I will later today, and post the mods to the existing board. If that's the source of the whining the circuit would be verified, as that seems to be the only problem with it.

Thanks for the file!

Fp

[Fp-www.Tonepad.com]

Soggy,

Does your build sound the same as Ry's? Could you send me a sound sample?

Fp

(sorry for the two posts!)

[Ry]

Sorry FP, I missed the last question to me.  Yes, I built the GGG version with a 1044 as well.  I'm dubious that it is the problem.  I've built other pedals with it that didn't whine at all.

Here's what I'll do for you, though.  I will pull my 1044 from the circuit and wire up another 9v battery so that I can get -9v without using the charge pump.

Expect a report back.

[Fp-www.Tonepad.com]

Ry,

That'll be of great help.

Fp

[Ry]

That was quick and easy, just pulled the chip and plugged the battery snap into the correct socket locations.  It didn't help any of the bleed-through, sorry to say.

What else can I try?

[leonhendrix]

Im about to start the nuetron filter from geofex and he says the layout is designed to prevent whine but if you are still getting whining you can insert two chokes instead of two jumpers (you'll have to look at the layout to see which ones he means). The parts list has the choke values at 680uH.

leon

[Fp-www.Tonepad.com]

Ry,

Thanks for trying that. I have compared Bill Bergman's file for the MAX1044 and it's the same (without the transistor to switch the circuit off when there's no jack plugged in... which I will add to the next revision of the layout BTW).

What I find odd is that the whining's speed is not affected by the LFO's speed...

I'll study it a little more, in the meantime, any help from others is greatly appreciated.

Leon, I don't know about the neutron filter, I'll read about it as well.

Fp