Demeter - Tremulator

Torchy · Post by **Torchy** » 27 Jul 2007, 09:18

lmkv15 - thanks, missed that one

didnt spot as I built mine on vero. thanks for all the tips, but I didnt have the problems others had, mine worked ok

bajaman · Post by **bajaman** » 27 Jul 2007, 09:36

Hi Torchy - didn't have any problems building mine - just my simulations were weird - I will recheck them again - still puzzled about those 4.3v zeners though. Can anyone confirm they are correct

Cheers
Steve

invictus · Post by **invictus** » 27 Jul 2007, 09:46

bajaman wrote:Thank you lmkv15

I also took Invictus's advice but connected the pilot light led with 4.7k in series to pin 6 of the LF351 - I rerouted the red wire from the 3 pole switch and soldered directly to pin 6 on the board
Cheers
bajaman

ooops...yeah, pin6 should be better point to connect it... gotta edit that one. another better thing to do is to attach the negative side of the LED to the 3PDT where it could connect to ground when the circuit is active, then disconnect ( LED OFF) when in bypass mode..

i'll try to edit the schematic and post it here for those who could use it..

.

bajaman · Post by **bajaman** » 27 Jul 2007, 09:49

Hi Invictus - I was going to switch the earth end too, but got lazy and just moved the red wire from +9v to pin 6 - it doesn't click or thump when switched

bajaman

bajaman · Post by **bajaman** » 27 Jul 2007, 23:21

Hi folks
I ran some more simulations and I am now getting a perfect triangle wave oscillator - not lopsided or with rounded edges etc

Also the zeners have no effect on the simulated waveform or the physical implementation of this schematic - save your money and leave them out

bajaman

bajaman · Post by **bajaman** » 30 Jul 2007, 01:24

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

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

)
I wonder if I should give Ry Cooder a phone call

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.

Stay tuned
bajaman

Kaos · Post by **Kaos** » 30 Jul 2007, 06:15

This Application Note?

http://www.national.com/an/AN/AN-263.pdf#page=7

bajaman · Post by **bajaman** » 30 Jul 2007, 07:08

No - but I had seen that one - far too complicated

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
bajaman

Kaos · Post by **Kaos** » 30 Jul 2007, 07:43

thank you

i'm looking forward to see your schematic

bajaman · Post by **bajaman** » 30 Jul 2007, 10:18

Here is the schematic - board layout and pc tracks to follow

bajaman
Baja Trembulator Schematic

Goop_buster · Post by **Goop_buster** » 30 Jul 2007, 11:20

Great stuff bajaman, thanks !

bajaman · Post by **bajaman** » 30 Jul 2007, 12:44

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.

Try it out - i think you will like what you hear

cheers
bajaman

bajaman · Post by **bajaman** » 31 Jul 2007, 10:47

Here is the printed circuit board track layout for my Baja Trembulator
( board placement to follow soon )
enjoy
bajaman
Baja Trembulator Tracks

bajaman · Post by **bajaman** » 31 Jul 2007, 12:44

Here is the parts layout for my Baja Trembulator

bajaman
Baja Trembulator Board layout

invictus · Post by **invictus** » 31 Jul 2007, 13:00

.
.

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?

.
.

bajaman · Post by **bajaman** » 31 Jul 2007, 13:05

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
bajaman

Goop_buster · Post by **Goop_buster** » 31 Jul 2007, 13:06

Thanks a lot bajaman

.
What (frequency) is the slowest setting on that oscillator?

invictus · Post by **invictus** » 31 Jul 2007, 13:09

,

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

,

bajaman · Post by **bajaman** » 31 Jul 2007, 13:09

Slow as you would ever need - if you change the 50k lin pot for a 500k lin you will get very sloooooow speeeed

bajaman · Post by **bajaman** » 31 Jul 2007, 13:16

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)