Demeter - Tremulator

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Postby bajaman » 30 Jul 2007, 02:24

Hello again
I have re-designed the Demeter oscillator section of the tremulator schematic posted by Torchy, which is just a badly designed triangle wave.
First - I simulated the schaller oscillator in markm's heart throb tremelo, and found it to be a lot similar in design to the classic Fender 12AX7 oscillator (phase shift oscillator type), but realised with an NPN bipolar transistor. However the sine wave function is not very clean and I suspect it cuts the transistor off on it's negative sweep - SO - I simulated an opamp version which gave a very clean sine wave, BUT needed a triple ganged pot to shift the frequency of oscillation.

OKAY - I googled and came up with a National Semiconductors application note using LM101 and LM111 devices.
After several hours simulating and adjusting this, I came up with a damn near perfect pure sine wave oscillator that only requires a single ganged 50k linear pot to tune from slow to super fast.

Armed with this new oscillator schematic, I attacked the demeter board, cutting and moving tracks and replacing components etc.
I retained the LF 442 op amp and reduced the gain of the led driver that follows the oscillator to 13dB (was 27dB).

I plugged my guitar in and WOW, this tremelo is smooth as :D No sign of any choppiness or uneven - sounds almost like a leslie on very fast setting ( which is something I will be using this oscillator in in future :wink: )
I wonder if I should give Ry Cooder a phone call :lol:

ANYWAY - Enough raving - I will redraw the board layout and schematic etc. and post for all to build in the next few days - YOU will like it much better than the Heart Throb or stock Demeter versions.
8)
Stay tuned
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Postby Kaos » 30 Jul 2007, 07:15

The camel is a horse designed by a committee that never met.
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Postby bajaman » 30 Jul 2007, 08:08

No - but I had seen that one - far too complicated :wink: :lol:
bajaman

the application note is National Semiconductor Linear Brief LB-16 from March 1971 (figure 1), but I warn you now - I have changed it significantly - just a good place to start - be patient I am redrawing the board layout and schematic at present.
cheers
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Postby Kaos » 30 Jul 2007, 08:43

thank you :)

i'm looking forward to see your schematic
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Postby bajaman » 30 Jul 2007, 11:18

Here is the schematic - board layout and pc tracks to follow :wink:
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Baja Trembulator Schematic
Last edited by bajaman on 15 Jan 2008, 11:34, edited 2 times in total.
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Postby Goop_buster » 30 Jul 2007, 12:20

Great stuff bajaman, thanks ! :D
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Postby bajaman » 30 Jul 2007, 13:44

Hi Goopbuster - you are most welcome friend.
i plan to use this oscillator in an upcoming rotary speaker simulator - but don't hold your breath, other things to do first. :lol:
Try it out - i think you will like what you hear :wink:
cheers
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Postby bajaman » 31 Jul 2007, 11:47

Here is the printed circuit board track layout for my Baja Trembulator
( board placement to follow soon )
enjoy
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Baja Trembulator Tracks
Last edited by bajaman on 02 Aug 2007, 09:19, edited 1 time in total.
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Postby bajaman » 31 Jul 2007, 13:44

Here is the parts layout for my Baja Trembulator :wink:
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Baja Trembulator Board layout
Last edited by bajaman on 02 Aug 2007, 09:20, edited 1 time in total.
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Postby invictus » 31 Jul 2007, 14:00

.
.

superb job bajaman! thanks for this..

any suggestion for a good replacements for the LFXXX ICs? i want to try your creation. but i dont have any LFXXX ic here.

is your perfect sinewave oscillator (PSO? ) strictly designed for LFXXX IC?


.
.
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Postby bajaman » 31 Jul 2007, 14:05

ANY dual opamp will do - TL072 works fine and even a 4558 of any manufacturer will work.
Eventually I will redesign for a TL074 quad opamp to do the lot :!:
You can use pretty well anything in here - experiment - use IC sockets etc.
I made my own optocoupler - see previous post in this thread.
cheers
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Postby Goop_buster » 31 Jul 2007, 14:06

Thanks a lot bajaman :lol: .
What (frequency) is the slowest setting on that oscillator?
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Postby invictus » 31 Jul 2007, 14:09

,


ok thanks... i will give it a try when i have some time...

,
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Postby bajaman » 31 Jul 2007, 14:09

Slow as you would ever need - if you change the 50k lin pot for a 500k lin you will get very sloooooow speeeed
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Postby bajaman » 31 Jul 2007, 14:16

ALSO if you want to get it running ridiculously fast lower or short out the 10k resistor in series with the rate (speed) pot.
You may like to put a 20k trim pot ( replace 18k) in the feedback loop of the LF351 ( or TL071) etc., to adjust the optocoupler light intensity also.
cheers
bajaman - falling asleep - 1:13am here - yawn - back tomorrow ( or later on today) :lol:
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Postby bajaman » 01 Aug 2007, 01:20

I just sold two of my Trembulators already - i demoed the prototype to two guitarist friends - they are selling their Boss and Rocktron devices !!!
The true sine wave sweep gives a very subtle effect on low depth settings - adds a shimmer and warmth to the sound especially on acoustic guitar with arpeggios being played - Neil Young - Needle and the damage done.
Also it sounds great in front of an overdrive or distortion device on high depth settings - think The Who - Baba Reilly sounds
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Postby bajaman » 02 Aug 2007, 09:22

:oops: :oops:
I have updated the schematic (was missing 47n) and the board layout pictures and updated the links - Sorry for any inconvenience :oops:
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Postby bajaman » 07 Aug 2007, 10:52

Hello all
On July 31, I posted a link to my Baja Trembulator printed circuit board layout.
After building two pedals that did not work correctly, I discovered two errors which I have now corrected on my photobucket link. The circuit now works as it should - very nice tremelo!
Sorry for any inconvenience
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Postby sergedeep » 16 Aug 2007, 19:19

The Fulltone Supa Trem is definately based on the Tremulator.

The hard/soft switch is nothing more than a connection between two lugs of the depth knob (between the center lug and the wire coming from the VTL5C1).

The double speed is like this: change the value from C1 to 2u2 and change the speed knob to a dual 1M lin - the switch connects them in series or leaves one part unconnected.

The Fulltone also has a trimpot to adapt the level of the pedal - I'm not sure which resistor is replaced - I guess it's R10.

Here and there a resistor has another value, but I don't know all the details. The IC's are LF351N, LF442CN and AD711JN.
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Postby polarbearfx » 03 Oct 2007, 14:17

fulltone copied the tremulator which has been out for some time now. The supatrem is a copy with just some simple mods.
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