Author Topic: Maestro Filter Sample and Hold  (Read 16424 times)

Fp-www.Tonepad.com

Maestro Filter Sample and Hold
« on: June 14, 2005, 02:42:34 PM »
New project:

http://www.tonepad.com/project.asp?id=50

I will need some of the experienced builders (Mark comes to mind) to check this adaptation of the Maestro FS1 using LM13600 otas and including Tonda's mods.

Fp
www.tonepad.com : Effect PCB Layout artwork classics and originals : www.tonepad.com

Bill Bergman

Maestro Filter Sample and Hold
« Reply #1 on: June 14, 2005, 02:58:19 PM »
Cool!! Wish I didn't already have one...... although it only the 2 knob model.

Ry

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Maestro Filter Sample and Hold
« Reply #2 on: June 14, 2005, 03:38:11 PM »
Dang, I built one from the GGG site too.  I may have to build this one just to see if it sounds any different.  I really love this pedal.

Fp-www.Tonepad.com

Maestro Filter Sample and Hold
« Reply #3 on: June 14, 2005, 03:40:56 PM »
Please DO :)

And report back. As I said, not only is the layout not verified, but the circuit uses different chips and adds a bunch of mods.

I've checked it out many times and haven't found errors... but then again... who knows.

Fp
www.tonepad.com : Effect PCB Layout artwork classics and originals : www.tonepad.com

StephenGiles

Maestro Filter Sample and Hold
« Reply #4 on: June 14, 2005, 04:53:58 PM »
Hi Francisco - buenos tardes, correct me if I'm wrong but the filter section is a normal triggered filter? If so what is the ripple like in the control voltage?
Stephen
"I want my meat burned, like St Joan. Bring me pickles and vicious mustards to pierce the tongue like Cardigan's Lancers.".

Fp-www.Tonepad.com

Maestro Filter Sample and Hold
« Reply #5 on: June 14, 2005, 05:09:33 PM »
Stephen,

Look at the DPDT switch that selects between filter and s/h modes:

the "A" spdt biases the pnp transistor. (when in s/h mod you set it with the trimpot)

the "B" spdt selects the source for the CV from the envelope detector (highly modified by Tonda to include direction, attack and decay) and the sample and hold which is the noise and LFO.

So, to my understanding, the filter section (made with the two otas and surrounding parts) is a band pass filter, controlled by the CV. So yeah, I would say it's a normal triggered filter.

This brings us to the next experimentation: since the circuit blocks are so well defined, one could use other CV filters (or anything CV controlled), or use other CV sources to control the filter. (manual control for example)
 
Fp
www.tonepad.com : Effect PCB Layout artwork classics and originals : www.tonepad.com

moosapotamus

Maestro Filter Sample and Hold
« Reply #6 on: June 14, 2005, 07:05:06 PM »
Wow, that looks great, Fp! Beautiful work, as always.
I just might have to build myself another, too. 8)

~ Charlie
moosapotamus.net
"I tend to like anything that I think sounds good."

Fp-www.Tonepad.com

Maestro Filter Sample and Hold
« Reply #7 on: June 14, 2005, 07:26:40 PM »
HEY CHARLIE!

Remember how long it was when we started working on this!!?

What? two years??

Fp
www.tonepad.com : Effect PCB Layout artwork classics and originals : www.tonepad.com

wui223

Maestro Filter Sample and Hold
« Reply #8 on: June 14, 2005, 07:52:44 PM »
why there are two transistor join together after the input stage?
why is Q4 missing ?
the mark '9' '10' at the transistors near the input stage meaning what?

moosapotamus

Maestro Filter Sample and Hold
« Reply #9 on: June 15, 2005, 12:29:20 AM »
Quote from: Fp-www.Tonepad.com
What? two years??

What? ohmygod. That long, really? :shock:
Wow, I'm almost as fast as you at finishing up projects. :lol:

Thanks 8)
~ Charlie
moosapotamus.net
"I tend to like anything that I think sounds good."

Ry

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Maestro Filter Sample and Hold
« Reply #10 on: June 15, 2005, 12:47:18 AM »
I might have to give it a go.  I have yet to etch a board, though...this may not be my best bet as a first try!  I will report back if I get up the courage to try it out.

Ry

Transmogrifox

Maestro Filter Sample and Hold
« Reply #11 on: June 15, 2005, 02:56:32 AM »
Quote from: wui223
why there are two transistor join together after the input stage?
why is Q4 missing ?
the mark '9' '10' at the transistors near the input stage meaning what?


a)  This is called a darlington connection.  Using transistors like this significantly increases the input impedance.  The late Crybabies use the darlington input transistor.

b) I don't know why Q4 got skipped, but it may have been something present early in the design that had been determined to be unecessary and was removed, and it was easier not to rename everything else after the layout had been finished.

c) The LM13600 IC chip includes a darlington transistor built-in which is used as a buffer for OTA's, in fact, it is designed to be used how those JFETs are used.  It must have been determined by the designer that the filter had a warmer tone using FETs instead of the built in darlingtons.

Since the darlington pins would otherwise be useless, why add another seperate transistor to the design?  Simply use the extra unused transistor for an input buffer.

The short answer is this:  Pins 9 and 10 refer to the base and emitter of the darlington built in to the OTA chip.
trans·mog·ri·fy
tr.v. trans·mog·ri·fied, trans·mog·ri·fy·ing, trans·mog·ri·fies To change into a different shape or form, especially one that is fantastic or bizarre.

wui223

Maestro Filter Sample and Hold
« Reply #12 on: June 15, 2005, 03:21:22 AM »
thanks i check out the datasheet and give me the same explanation. but can i ask why the MAX1044 usage in Geofx differ from tonepad's schematic? the Geofx use two caps and tonepad use one only.
geofx connect pin2 to 4 by a 10uF cap but tonepad ground the cap and ground the pin 4 as well.
Can someone explain this, which one is right?
In fact i built this effect before but i didnt works, i wonder why

Joe Viau

Maestro Filter Sample and Hold
« Reply #13 on: June 15, 2005, 09:29:45 AM »
Also, R. G. had a schematic for a CMOS pseudo-random generator on his site:

http://www.geofex.com/FX_images/pseudorandom2.pdf

Has anyone tried this with the old S/H and is anyone planning on trying it with the new revision? I've read threads about how persnickety the noise transistor is.  I have schematics for an ARP 2600, and I may look to see how that synth did its noise source.  It had pretty good S/H, too.

Fp-www.Tonepad.com

Maestro Filter Sample and Hold
« Reply #14 on: June 15, 2005, 10:26:55 AM »
Transmogrifox got it right.

I'll re-check the max1044 part of the ckt.

Fp
www.tonepad.com : Effect PCB Layout artwork classics and originals : www.tonepad.com

wui223

Maestro Filter Sample and Hold
« Reply #15 on: June 15, 2005, 05:51:10 PM »
i think the one in tonepad is right coz i try the connection shown in schematic, and i get -9V from pin5. But i use a 7660 instead of MAX1044
How to choose for the noisy transistor? i couldnt get one that is working right. For the FET can i simlpy use any FET like 2N5458?

Fp-www.Tonepad.com

Maestro Filter Sample and Hold
« Reply #16 on: June 15, 2005, 05:54:43 PM »
Wui,

I just checked and it does match the schem at geofex. It's correct.

You can use the 2N5458, just make sure the pinout matches the pads of the layout.

About the noisy transistor, get a few 2n2222 or nte123ap and use a socket to try different ones.

Fp
www.tonepad.com : Effect PCB Layout artwork classics and originals : www.tonepad.com

soggybag

Noise transistor
« Reply #17 on: June 15, 2005, 06:16:11 PM »
I made the FSH from the layout at uStomp. I used 2N3904 for the noise transistor. I hooked my scope to the noise opamp that amplfies the noise and tested a handfull of transistors until I found one that worked well.

I remember reading a few posts, as I was building mine, where people had tried several different varieties of transistor.

I'm a total novice, but if I understand what's going on the only two leads of the transistor are used and it is acting like a revese biased diode. So I would guess that you might even be able to use a diode here.

Fp-www.Tonepad.com

Maestro Filter Sample and Hold
« Reply #18 on: June 15, 2005, 06:49:28 PM »
I remember RG once said something about transistors becoming more noisy after being biased in a certain way... maybe it's time to search the archives. Perhaps we can make a noisy transistor noisier.

Fp
www.tonepad.com : Effect PCB Layout artwork classics and originals : www.tonepad.com

LP Hovercraft

Maestro Filter Sample and Hold
« Reply #19 on: June 15, 2005, 10:58:09 PM »
Good work FP!  On a previous thread I saw somebody mention that a leaky NPN germanium like a not-so-to-spec NTE101 might do the trick.  I'd be curious to see if anybody has tried it.  As for this layout, this makes a lot more sense to me than a bunch of icky 741's and the now "obsolete" CA3080.  Though I'm in the middle of perfboarding the GGG version,  I'm sure I'll make another using this version eventually. :)