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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grrrunge
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Post by grrrunge »

rrroo wrote:has anybody else had problems with the gain of the circuit? mine is very weak. are there any ideas to improve the gain or do i have to add a booster in front. Also what would i have to tweak to make the LFO go faster? I really can't find any use for the very slow sample&hold..
The 330nF cap next to IC3 affects lfo speed. Smaller values makes the lfo go faster. I put a 220nF in my builds for more usable speeds, but for ultra fast S/H filter action i would try a 100nF, but for my taste it's crazy fast already at 220nF.
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Post by GhostofJohnToad »

Just wanted to post and say I just built a tonepad fsh-1 and I am having the same problem as Mike. I have S+H but no filter sweep. I have done numerous op-amp and transistor swaps and nothing has affected the filter section. When switching to filter I get a really bassy sound that is only slightly effected by playing with the resonance. No auto wah sweep sound at all.

Currently I have a KIA358 in the oscillator opamp and a NE5532 in the other spot. Using 2n5457, 2n3906, and a crappy unmarked tranny from an old transistor radio for the noise transistor. Speaking of which, I tried like 10 old crappy trannies from this old radio I salvaged and every single one worked really well but slightly different in the noise Q3 spot. Newer trannies that i purchased 2n2222, BC550, 2n3904 all sounded uninteresting.

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rivervalley
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self made beavis board for breadboarding/testing

true bypass looper box (two send and return channels)

noisefoc Deluxe from Leap audio (small synth)

Maestro Filter Sample Hold - headache in progress

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Post by rivervalley »

Building two of these at the minute, one by the tonepad book - the other using different transistors for Q1,2,5,6 plus the lower rated Cap near IC3!
This is my progress so far today, just waiting on some spare bits to finish the boards (stupidly have 3k6 resistors, shy a few 100ks) then just have to the drilling, painting and silkscreening the enclosure to look forward to.
Image

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rivervalley
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my favorite amplifier: silverface fender bassman 100
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(self oscillating noise generator with high-pass and low-pass distortion)

self made beavis board for breadboarding/testing

true bypass looper box (two send and return channels)

noisefoc Deluxe from Leap audio (small synth)

Maestro Filter Sample Hold - headache in progress

//////////other //////////
Tiny VGA - small vga generating chip

Arduino TV/Out - generates VHS signal from an Arduino
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Post by rivervalley »

So my progress, swapped out the Ceramic Caps from the last picture for Mylar ones. Substituted some 0.047uF's for the 0.05 suggested (am in Europe, cannot get that measurement so easily) and a 0.033uF for a 0.03uF - was talking to the "parts wizard" at Segor (fucking great shop) and he said that there should be no discernible difference, though that is up for debate considering the results........

board one: Image
LM13700 IC 1
JRC 1458 IC 2&3
2k Res instead of the 3k3 as per Grunge's suggestion
FETS BF 245A - could not get 2n5457's for love nor money
weird clicking sound and not much else, realised though that the bypass was working so board had to be at fault, no cold joints, IC's in right direction, no wires poking their heads out (though I did re-orientate the pots, long story) the FETS need to be flipped around (as stated in some reviews at tonepad). ]That got the Filter/Sample working, sounds quite good, though some ticking still which can override signal. Up/Down switch works great, though substituted some 3pDT switch and footswitch for the DPDT's suggested (just ignored the central column, seems to work). The Hold function doesn't seem to do anything, just ticks. And not in a good way
Tried playing with the trim pots 100k at 65% 10k at 10%, got some interesting sounds when the screwdriver made some temp contacts, otherwise seemed ok. Re-boxed it and now seems like I made one push too many, is a tight fit and now the tick from the IC is coming through even when bypassed, must be making some connection somewhere. BALLS!

Also would suggest adding a voltage limited (similar the the "dyin battery" effect of yore - you know a POT interrupting the voltage going to the board), because this circuit really makes some interesting sounds when the power is almost out!

Board two
Same set up
but with a different DC supply (Conrad didnt have the plastic 9v's in stock when I rocked up, so took what was offered), and looks like I have a short (other pedals in the chain turn off when this is engaged - am using a looper to send signal to it for testing). Bypass is working, but when engaged there is just ticking on all fronts, and the LED doesn't light at all, despite being swapped out for another one. Not sure whats going on there as I made both at the same time, with similar attentionn to detail (lots of shrinkies and tape-labelling).

DENIED
suggestions?


Here's what it looks like boxed up, pretty but not working......... Image
Image

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grrrunge
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Post by grrrunge »

rivervalley wrote:So my progress, swapped out the Ceramic Caps from the last picture for Mylar ones. Substituted some 0.047uF's for the 0.05 suggested (am in Europe, cannot get that measurement so easily) and a 0.033uF for a 0.03uF - was talking to the "parts wizard" at Segor (fucking great shop) and he said that there should be no discernible difference, though that is up for debate considering the results........

board one: Image
LM13700 IC 1
JRC 1458 IC 2&3
2k Res instead of the 3k3 as per Grunge's suggestion
FETS BF 245A - could not get 2n5457's for love nor money
weird clicking sound and not much else, realised though that the bypass was working so board had to be at fault, no cold joints, IC's in right direction, no wires poking their heads out (though I did re-orientate the pots, long story) the FETS need to be flipped around (as stated in some reviews at tonepad). ]That got the Filter/Sample working, sounds quite good, though some ticking still which can override signal. Up/Down switch works great, though substituted some 3pDT switch and footswitch for the DPDT's suggested (just ignored the central column, seems to work). The Hold function doesn't seem to do anything, just ticks. And not in a good way
Tried playing with the trim pots 100k at 65% 10k at 10%, got some interesting sounds when the screwdriver made some temp contacts, otherwise seemed ok. Re-boxed it and now seems like I made one push too many, is a tight fit and now the tick from the IC is coming through even when bypassed, must be making some connection somewhere. BALLS!

Also would suggest adding a voltage limited (similar the the "dyin battery" effect of yore - you know a POT interrupting the voltage going to the board), because this circuit really makes some interesting sounds when the power is almost out!

Board two
Same set up
but with a different DC supply (Conrad didnt have the plastic 9v's in stock when I rocked up, so took what was offered), and looks like I have a short (other pedals in the chain turn off when this is engaged - am using a looper to send signal to it for testing). Bypass is working, but when engaged there is just ticking on all fronts, and the LED doesn't light at all, despite being swapped out for another one. Not sure whats going on there as I made both at the same time, with similar attentionn to detail (lots of shrinkies and tape-labelling).

DENIED
suggestions?


Here's what it looks like boxed up, pretty but not working......... Image
Image
Check that you have the pinout right on the JFET's - you might have to turn then 180° to get the gate leg in the right hole. ;)
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rivervalley
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my favorite amplifier: silverface fender bassman 100
Completed builds: tester
(self oscillating noise generator with high-pass and low-pass distortion)

self made beavis board for breadboarding/testing

true bypass looper box (two send and return channels)

noisefoc Deluxe from Leap audio (small synth)

Maestro Filter Sample Hold - headache in progress

//////////other //////////
Tiny VGA - small vga generating chip

Arduino TV/Out - generates VHS signal from an Arduino
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Post by rivervalley »

images didnt work.... for some reason

Image
see what I mean about it being a tight squeeze, shouldfind a better way to get them all in there, right now am using ignorance
Image

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rivervalley
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Joined: 03 Jun 2009, 20:46
my favorite amplifier: silverface fender bassman 100
Completed builds: tester
(self oscillating noise generator with high-pass and low-pass distortion)

self made beavis board for breadboarding/testing

true bypass looper box (two send and return channels)

noisefoc Deluxe from Leap audio (small synth)

Maestro Filter Sample Hold - headache in progress

//////////other //////////
Tiny VGA - small vga generating chip

Arduino TV/Out - generates VHS signal from an Arduino
Location: space
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Post by rivervalley »

grrrunge wrote: Check that you have the pinout right on the JFET's - you might have to turn then 180° to get the gate leg in the right hole. ;)
Yeah, I already turned Q2 Q5 & Q6 180 degrees, do you mean I should also turn Q1 and Q3 (havent tried that yet!)

gonna go over all the solder points too, damm though there is a lot of shrinky in this

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Post by chicago_mike »

I still need to test y 2. Being away on a cruise ship gig for 3 months really messes you up. :(
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Post by grrrunge »

Sold this one last week :)
VCF_gutshot.jpg
VCF_exterior.jpg
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Post by chicago_mike »

nice build :)
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Post by ch1 »

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?

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Post by grrrunge »

It's a 1590DD afair. I got it from musikding.de a while back :)
On a sidenote I ended up using LM833's for IC1 and LM358's for IC2 in my builds. Lowest noise of alle the configurations I've tried so far.
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Post by chicago_mike »

do we still flip the fets on a Rev. 2 board?
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Post by grrrunge »

chicago_mike wrote:do we still flip the fets on a Rev. 2 board?
That depends on the pinout ;) The gate hole is marked correctly on the silk screen. It's just the outline of the transistor casing that doesn't match with all JFET's ;)
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Post by chicago_mike »

Ah...thank goodness for SIP sockets. :D

As long as the G is oriented correctly oon the pcb..I can go with that. :)
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Post by Masuto »

Update on this thread..
Just chiming in to say i built this as per stock/compatible parts when not available and it works fine. On the Tonepad site it is classified as not verified but it really is. Just remember to mount the jfets respecting their pinout and NOT the icon on the silkscreen.
Took a couple of days but with a little patience.. No headache whatsoever. Lovely pedal, sh*ts on my Q-Tron for sure.

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Post by inlifeindeath »

3 years after building this pedal, I finally troubleshot the envelope filter part!
S & H was working all along, but I found a cold solder joint on IC2's power pin.
Now it works great, although the env filter is an odd effect to work with.
Tonepad definitely verified.

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Post by chicago_mike »

I must be cursed! :mrgreen:

These fuckers still aint workin!

Could anybody with working units from the Tonepad pcb post close up piccies of component side? Pleae oh please! :hug:
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Post by grrrunge »

chicago_mike wrote:I must be cursed! :mrgreen:

These fuckers still aint workin!

Could anybody with working units from the Tonepad pcb post close up piccies of component side? Pleae oh please! :hug:
My image from earlier on this page is the tonepad layout, but home etched ;) viewtopic.php?f=19&t=16673&start=40#p209303
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Post by chicago_mike »

I mean CLOSE up! :mrgreen:
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