Demeter - Tremulator

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Demeter - Tremulator

Postby Torchy » 20 Jul 2007, 21:18

Corrected schematic.

Demeter Tremulator
Torchy
 

Postby briggs » 21 Jul 2007, 05:15

Cheers Torchy!
A hybrid of vintage sound and state-of-the-art quality, the Demeter Tremulator is designed for years of trouble-free operation.

Designed to emulate the classic Fender tremolo effect (or vibrato as it is often referred to), the Tremulator features "lopsided" amplitude modulation with a rounded off traingular modulant waveform. Suffice it to say, the Tremulator sounds like the classic effect found on many vintage amps, but with less noise and hum and a greater range of speeds and depths.

Operation is fairly straightforward. There are two inputs on the front side of the unit: a 1/4" input jack on the right and a 1/4" output jack on the left with a battery-ground switch on the input jack.

There are two controls on the unit: Depth and Speed, plus a footswitch to bypass the effect, and an LED to indicate effect operation. On the side there is a trim pot to set the bias for the optical unit.

Depth affects the amount of amplitude modulation on the signal or the amount of effect. The tremulator design incorporates a small amount of gain (approx. 1dB) to allow for proper "tremulation." Also, by turning the Depth all the way off, the TRM-1 will function as a low noise volume boost. It's low-impedance output allows it to act as a line-drive, eliminating signal loss on long cable runs.

Speed increases and decreases the frequency of the low-frequency oscillator, enabling you to time the effect as desired.

Trim Pot sets the bias of the optical tremolo unit. It effects the signal on and of time ratio. Turned up to height it will squeeze the signal, low it will loosen it. The unit comes preset to Ry Cooder's preferred setting.


From here: http://www.demeteramps.com/products/accessories/trm1.html
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Postby Torchy » 21 Jul 2007, 13:58

I need to tidy this up, but for now this is the layout of the original ...

Original PCB
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Postby bajaman » 21 Jul 2007, 14:51

Hi Torchy - nice work :wink:
Have you built one - and - does it sound as good as he says in his blurb :?:
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Postby Torchy » 21 Jul 2007, 22:23

Yeah, I built one to make sure the schematic was correct (first post), then found the layout. I havent used the layout I posted.

It sounded good, but the blurb is a bit OTT. FWIW I prefer MarkM's Heartthrob Trem :shock:

I'll verify the pcb layout and post an all-in-one schem/pcb/vero soon :)
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Postby markm » 23 Jul 2007, 16:45

Torchy wrote:Yeah, I built one to make sure the schematic was correct (first post), then found the layout. I havent used the layout I posted.

It sounded good, but the blurb is a bit OTT. FWIW I prefer MarkM's Heartthrob Trem :shock:

I'll verify the pcb layout and post an all-in-one schem/pcb/vero soon :)


Thank you Torchy!! :D
It's a "hacked-up" version of the Schaller and I love the thing!
I was trying to come close to the Swamp Thang trem and I think it seems to do it.
So it's a modded Schaller circuit Renamed......The Traditional Boutiquer
method of doing things!!
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Postby analogguru » 23 Jul 2007, 20:26

So it's a modded Schaller circuit...


:?: :?: :?: What the Demeter Tremulator has in common with a Schaller Tremolo ?

it looks more like a Fulltone Supa-Trem (clone?) without the Hard/Soft switch when you compare the Fulltone Supa-Trem guts with the Demeter Tremulator guts

This would explain why there is the Op-amp with a gain of 20 after the LFO to produce an (additional) square wave. There is actualy a square-wave at pin 1 of the LFO Opamp. Also the zener-diodes with 4V3 are useless at 9V: The Opamp is at 4,5V, 4,3V + 0,7V (of the other zener diode) is 5V in positive direction the diodes start work at 9,5v and in the negative direction at -0,5V hmmm... "And they don´t know what they are doing..."

The schematic contains some minor errors e.g. the Led resistor is 3k6 instead of 1k.

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Postby Torchy » 23 Jul 2007, 21:12

Mark was talking about his Hearthrob not the Demeter ...
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Postby analogguru » 23 Jul 2007, 21:18

The shown resistor is orange/blue/blk/bwn = 3 6 0 (1x)0 = 3k6.

In the (first) schematic it is marked as 1k.

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Postby bajaman » 25 Jul 2007, 04:48

Hi Torchy
How sure are you that there are 2 x 4.3v zeners in the oscillator output - methinks they could be disimilar types to give a lopsided response as Demeter states in his blurb!!
ALSO the 1k in series with the led is most probably a 10k!
Can anyone verifythe zeners - is one a 1N4148 instead???
Cheers
Steve
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Postby invictus » 25 Jul 2007, 06:05

Torchy wrote:I need to tidy this up, but for now this is the layout of the original ...

Original PCB


most of you know this but i'll say it anyway...

in this original layout, the LED resistor connection might as well be connected to pin 6 of the LFO OPamp, to double the purpose of the LED as a flashing "rate indicator"...


.
Last edited by invictus on 27 Jul 2007, 10:46, edited 1 time in total.
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Postby bajaman » 25 Jul 2007, 11:28

OKAY - Briggs quoted Demeter thus:
the Tremulator features "lopsided" amplitude modulation with a rounded off traingular modulant waveform.

Analogguru analysed Torchy's schematic and observed:
Also the zener-diodes with 4V3 are useless at 9V: The Opamp is at 4,5V, 4,3V + 0,7V (of the other zener diode) is 5V in positive direction the diodes start work at 9,5v and in the negative direction at -0,5V hmmm... "And they don´t know what they are doing..."

SO - I thought I would build one of these using Torchy's layout. I reduced the board trace with coreldraw to the correct size - ran off a transparency on the laser printer, got out my trusty UV sunlamp and exposed the board, developed and etched it while the wife was out :lol:
drilled the holes, inserted the components, and then I thought - "hang On Steve, some of those component values don't seem right"
So tonight, I analysed the oscillator in multisim v10 ( all right I know you don't like simulators AG, but wait....) and surprise surprise, I could not get it to oscillate at all :shock:
After a few minutes though, I had it working fine, but only after changing some of the components.
Here is what I changed on Torchy's schematic / layout / board trace picture.
C1 changed from 4.7uf bp to 0.47uf bp
P1 from 500k to 50k
R11 from 33k to 3.3k
R12 from 10k to 100 ohms

Then, having got the oscillator working, I turned my attention to those two 4.3v zener diodes, which AG rightly observed are useless in this 9 volt powered circuit. My simulations show they have absolutely no effect on the oscillator whatsoever, which incidentally is producing a damn near perfect triange wave function :wink: :wink:
SO - here is the punchline - I changed the zeners to 3.3v for one and 2.4 v for the other - I don't know if these are the "correct" values, but now I am getting (as in Demeter's blurb) a lopside triangle wave with slightly rounded off peaks 8) 8) 8) 8)
In conclusion - if any one in the group has access to the Demeter Tremulator, could they please measure the components and verify their values - clearly the two schematics posted here (and on other sites) contain many errors.
Cheers
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Postby analogguru » 25 Jul 2007, 12:52

but now I am getting (as in Demeter's blurb) a lopside triangle wave with slightly rounded off peaks


Must be very slightly... I don´t know where it should occur....
IC2a is acting as a comparator at pin 1 is a square wave. R12 acts as a current limiter and the (changed Zener-diodes act as a Voltage limiter to cut the square-wave voltage, so there is still a square wave only with lmitied level. this squarewave charges/discharges the capacitor via R11, P1. Ic2b acts as an integrator and at pin 7 is a triangle-wave. If the level exceeds the comparator level of IC2a the comparator switches and now the game goes in the opposite direction.

The change of R11, P 1 and C1 only affects the speed (time needed), not the oscillation itself.

You can achieve a huge triangle signal at IC2b if it is well constructed. Output level is influenced by R8/R13. For this reason it is not clear for what IC3 is good for with a gain of more than 20. can only be used as a "Square-waver" so not really necessary.

For reference look at the schematic of the Boss BF-2, CH-1, HF-2, PH-2, TR-2, Ibanez PT-9, PH-10, PH-5 and a lot of others.

Funny part is that the Fulltone Supa-trem (guts see above) and the tremulator use identical chips, similar component placement, so I assume, that one of both made a sh*t-design and the other one copied it. Have a look at the Fulltone-guts.

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Postby lmkv15 » 26 Jul 2007, 14:59

Hi Torchy,

At the PCB paint by Ebernd, is a bug. The connection of IC2 after GND is missing.

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Postby bajaman » 27 Jul 2007, 10:01

Thank you lmkv15
Your circuit board error was very timely - I just built one and have been evaluating it. Big thanks to ebernd too.
I like it - the pots are 500k lin and 50k lin - the oscillator is lopsided in response, even without the zener diodes fitted. I used two 3.9v zeners (didn't have any 4.3V) and I detected a slightly less choppy response - not very much though - I will continue to experiment and let everyone know of the results.
The vactrol devices are almost unobtainable in NZ and expensive to import from the USA, so, I made my own with a cheap philips LDR and a hi bright led inserted in a piece of black plastic tube ( garden watering system) I sealed both ends with black RTV silicone - works great!!
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 8)
Cheers
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Postby Torchy » 27 Jul 2007, 10:18

lmkv15 - thanks, missed that one :oops:
didnt spot as I built mine on vero. thanks for all the tips, but I didnt have the problems others had, mine worked ok :?:
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Postby bajaman » 27 Jul 2007, 10:36

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
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Postby invictus » 27 Jul 2007, 10:46

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 8)
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..

.
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Postby bajaman » 27 Jul 2007, 10:49

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 :wink:
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Postby bajaman » 28 Jul 2007, 00:21

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 :? :?: :!:
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