Maestro FSH-1 / Oberheim VCF / Tonepad Filter/Sample/Hold  [schematic]

Discussion regarding early stompbox technology: 1960-1975 Please keep discussion focused and contribute what info you have...
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chicago_mike
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Post by chicago_mike »

My 9 volt power supply I use is actually putting out closer to 13 volts.

Could this kill the max 1044?
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Post by okgb »

I have an maestro unit that produces no sample & hold sound and erratic envelope tracking
any tips on where to investigate ?

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Post by bhill »

chicago_mike wrote:My 9 volt power supply I use is actually putting out closer to 13 volts.

Could this kill the max 1044?
13 volts will kill a 1044 a lot faster than I can type this. They are rated at 10v max.

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Post by Masuto »

Hi boys. i am taking the plunge once again with this. This time around i will try to build it as per tonepad+grrrrunge specs.
Yes because after a couple of day i built mine (see post on page 3) with tonepad-compatible alternatives, while i was fiddling with the multiturn trimmers, something in there literally caught fire. I have the feeling it could have been a cap, but looking at the pcb i cant see traces of burns or anything. So i ordered a new one, new max1044 (large ones this time) and i have all your suggestions put down on paper.
lets go! I will keep you updated

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Post by grrrunge »

Masuto wrote:Hi boys. i am taking the plunge once again with this. This time around i will try to build it as per tonepad+grrrrunge specs.
Yes because after a couple of day i built mine (see post on page 3) with tonepad-compatible alternatives, while i was fiddling with the multiturn trimmers, something in there literally caught fire. I have the feeling it could have been a cap, but looking at the pcb i cant see traces of burns or anything. So i ordered a new one, new max1044 (large ones this time) and i have all your suggestions put down on paper.
lets go! I will keep you updated
Good luck mate! ;)
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Post by Nocentelli »

Yeah, good luck. I've breadboarded this four times now without success. I shall try again this holiday. If you get it working, please post the parts you used.
Steven_M wrote: 21 Jan 2011, 17:52
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Post by Zokk »

Masuto wrote:Hi boys. i am taking the plunge once again with this. This time around i will try to build it as per tonepad+grrrrunge specs.
Yes because after a couple of day i built mine (see post on page 3) with tonepad-compatible alternatives, while i was fiddling with the multiturn trimmers, something in there literally caught fire. I have the feeling it could have been a cap, but looking at the pcb i cant see traces of burns or anything. So i ordered a new one, new max1044 (large ones this time) and i have all your suggestions put down on paper.
lets go! I will keep you updated
Hi Matsuo, I would suggest to use a LT1054 instead of that crappy max1044 which always frys above 9V.
I've perfboarded the GGG version with Tonda mods, and setting up the trimmers for the S/H is very tricky, you may want to test several transistors as noise generator.
Good luck for your build, that's an awesome effect!

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Post by rivervalley »

ch1 wrote:Yeah, nice build! What's the name of that box size?

And rivervalley! Whats the size of your box? Maybe it look's a bit tight?
Yeah standard 1590BB from tayda, its a bit crammed in there, but mainly because of the length of the cables I used, might re-do the wiring as I've been racking my brains lately trying to figure out whats wrong with this thing
resoldered everything, cleaned the board and despite what I said earlier I think that it's the up/down switch, works in one position but not very functional in the other - mainly ticking
the envelope position doesn't seem to do anything but tick a bit, sounds like a bleed from one of the clocks...... mmmm any suggestions? have to reread over my notes
other than that I think its 80% functional
sample hold works, can get some amazing arpegiated sounds and the auto-wah is pretty nice, just the up/down bit......

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Post by Masuto »

Hi there. Build finished. Took me something like 10 hours, but i set out to take all the time i needed for a careful build. It is my second round with this mother. The first one worked well, then as i was fiddling with the trimmers something inside caught fire. I changed the max1044 with a new one and the bugger now makes sounds if i touch the bottom of the pcb..strange. when it was in working order i seem to remember that it didnt tick.
Ok for my new build i socketed every transistor and ic (yes cos ye first time around i didnt.. :oops: ), used:

Q1: 2N2222 metal can (cos BC639, an alternative to 2SC1815 was too weak sounding)
Q2: MPF102 (an alternative to 2N5457)
Q3: BC560
Q5 & Q6: MPF102

IC1: LM13600N
IC2 & IC3: LM358JG (an alternative to LM258)

I fired it up and only filter up was working (wah).. I realised that by touching the bottom of the board i was getting sample hold too, but i had to keep my finger there. Strange. I swapped transistors, same thing.
I started to fiddle with the trimmers and the range and resonance knobs. My recent builds include 3 uni-vibe clones: with those, you had to have the effect full on to set the trimmers for the lamp, dry/wet mix. With this in mind, it was clear that the range and the resonance could help me find the sample hold spot. First a muffled low end burble appeared. Then, by trimming both the mothers in that direction, sample and hold appeared.
It is ticking, but it is a way fat sound.. It only ticks on sample/hold. The wah is tickless!
I will try with an LM13700 that i used on my first build..maybe that will solve the ticking. Also, wah down works only when i plug the external 9v psu. Maybe i drained the battery trimming..ehm it was NEW less than 1 hour before. Also...wah down: work with the resonance/range on that, it is a very wide sweep, it may not be noticeable when you just strum quickly..give it time to come up. Remember to set the sample hold, when you have that, also the two other effects will show up.
Since i have everything socketed, i will try different permutations. But as is, it works.

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Post by Masuto »

https://www.facebook.com/photo.php?v=10202076044195667
Cheque ze video!
Also...i meant that WAH UP works with the 9v psu.. All the notes i made on wah down...it really was wah up!

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Post by Zokk »

Congrats! seems your build is near perfect 8)
In wah mode the attack and release pots have huge influence on the filter sweep range, it's possible to have very good "reverse enveloppe" effects with a some tweaks of those three pots (attack/release/range).

The ticking is normal in s/h mode, but it seems to me that the s/h range is a bit too wide in your video: good for synth but too wide for guitar in my opinion; maybe you'd have to try a more "reasonable" setup so the filter won't move so far in the low and high frequencies.
Remember guitar frequencies are between 82Hz and 1.39KHz (but you have to deal with harmonics which can go up to 20KHz)... so it's important to have a good setup for the filter center frequency which will react correctly when a moderate amount of modulation is applied... this will reduce the impression of ticking, but to get rid of that you'll need a lag generator to smooth the changes between the steps and make them like curves.
Unfortunately on the Maestro the amount of modulation in s/h mode is fixed by a trimmer... once set up and the pedal closed, you can only play with the resonance pot to simulate the weak or strong modulation.

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Post by Masuto »

Cheers!
Well...mine is not housed properly yet... i will take into account your words when i will finalise it. As it is, it sure is funky ahaah..makes your guitar sound like a synth!
Thanks to everybody who posted and keeps the thread alive...

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Post by petey twofinger »

i havent spent much time testing and adjusting but everything is working . when i get it finalized i will write up my findings , i plan to try some mods , and have more parts on the way including a13700 to see if there is a difference that is the 13600 in there .

i do have a question , i did search quite a bit , what is the function of the 100k trimmer ?

i am sure its just me being an idiot , i spent quite a bit of time looking for this answer .

i did have to spend an hour swapping jfets . i found the mpf102 to be the ones with the widest sweep of poper function on r27 or the ten k trimmer . i would advise folks to try those first as others seemed to have a much narrower range of function , especially j201 , and others , i just couldnt get anything as well .

notmuch difference between the mpf102 and the 2n5457 , but the j201 was more tick and less volume output )

at first i didnt think the env filter mode was working , until i adjusted the outboard pots .

q1 2n1815
q3 bc560
q2,5,6, jfetts mpf102 ( 2n5457 worked , j201 , narrow range , but worked , bf25a no go , but i only had three to try ... )

charge pump 1054
op amps 4558 , lm3358
ic1 lm13600

mod ideas : starve , mark hammer sampling freq cap switch , chromospheres led mod ... anything else i am missing ?

thanks so much to all for you guys saved me a ton of time .

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Post by DonAdriano »

Yo!
With the BF245 is the mistake, on pcb they are wrong pins.
Cheers

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Post by grrrunge »

DonAdriano wrote:Yo!
With the BF245 is the mistake, on pcb they are wrong pins.
Cheers
Not quite. The gate-pin is marked down right. it's just the outline of the transistor case that might be "wrong" depending on the pinout of the JFET you decide to use. The drain and source pins are interchangeable in this application afaik.
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Post by Masuto »

Ok brothers.. third time around for me! Francisco gifted me with a board for my 40th birthday!
It seems i build one of these every 6 months or so ahaha.
I printed this whole thread (as always, thank you all and Grunge in particular) so i have all the stuff ready (and a buncha fets trannies and stuff from previous builds too!).

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Post by grrrunge »

You are absolutely more than welcome, and congrats with the big 4-oh ;)
I've built a few of those, and they've all worked straight out of the assembly-jig. Be careful with your components placement, and use multi turn trimmers. You'll be glad you did!
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Post by chicago_mike »

I picked up some ICL7660S' and should have the LT1054's soon.

Maybe I can get these dam things working now! :D
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Post by chicago_mike »

Hey...

What about a Zener diode instead of the noise transistor?
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Post by grrrunge »

chicago_mike wrote:Hey...

What about a Zener diode instead of the noise transistor?
I think the point here is that when we leave the base leg floating, the only thing the transistor is amplifying is the static noise it picks up through the base along with any noise produced by the transistor itself.
At least that's how I imagine it's working. I have no idea about whether it's correct or not.
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