It seems that, largely thanks to Jimi Photon, we now have a rash of new Harmonic Tremolo designs (well two). Jon (midwayfair) beat me to it, but here is another approach to getting something that sounds (something)like the old Fender harmonic tremolo. As I am late to the table, I bring an added bonus - you can vary the crossover frequency of this design. It is still on the breadboard - and has been for some time now - and I need a push to get it off the bread board and boxed up. It should fit in a 1590B, but it will be fairly snug. At the moment, it has four pots (rate, depth, crossover frequency and level) plus two switches (treble/harmonic tremolo and squarewave/sinewave LFO). These are not cast in stone.
How it works: U1b and U2a form a fairly typical crossover circuit that splits our signal into bass and treble components. We then pan between them using a quick-and-dirty LDR-based voltage divider, which is modulated using an LFO-driven LED (or a vactrol).
Notes:
- U1b is an almost-Butterworth 2-pole Sallen-Key LPF and the 'frequency' dual-gang pot can vary the frequency of this filter from ~100Hz to ~10kHz. Whether this range is entirely useful is debatable, but I like it. Note that because I can't find a C100k dual-gang pot, this works backwards - clockwise = lower frequency.
- U2a is a differential amplifier that creates our HP (treble) signal by subtracting the outuput of U1b (i.e. the bass) from out clean amplified signal from U1a. This means we can easily control the crossover frequency by only having to wory about varying the LPF corner frequency. This is a compromise as the HPF is not as steep as the LPF, but it keeps us out of voltage-controlled OTA territory.
- The 'treble/harmonic' switch essentially determines the gain of the HPF, which in turn determines whether we have tremolo'ing of both the bass and treble (harmonic) or only the trebble. I think Jon's design does something similar and it is a nice way to add a little shimmer.
- We pan between the LP and HP signal using a voltage divider. One half of the voltage divider is a LDR, which is modulated with an LED being driven by an LFO. This method is discussed a little bit in another thread (http://www.diystompboxes.com/smfforum/index.php?topic=102414.0 (http://www.diystompboxes.com/smfforum/index.php?topic=102414.0)) and was chosen over a more complicated OTA-based solution. Basically, it is a low parts-count way of doing the job. It isn't perfect, and you do not get a particulalry clean crossover frequency, but it works pretty well in this application. The trimmer is used to set the resistance of the other half of the voltage divider to be similar to that of the LDR when the LFO is a min 'depth'. Note that when you mix the LF and HP signals equally, you get an almost-flat response.
- the LFO (U3a) is the standard Phase 45 LFO design, which is used almost everywhere you want to wobble something. I have used slightly different component values here because I have a lot of 100k resistors and because I'm contrary. If you want more control of the LFO, the 'Tremulus Lune' LFO (among others) is a drop-in replacement.
- U3b buffers the LFO and acts as our depth control - it has gain from 0 to 4.5. I used this approach as, for the LDR to work as a voltage divider, we want it to have an intermediate resitance at minimum depth. To achieve this, we want, at minimum depth, the LED pointed at the LDR to be as bright as it is in the middle of the LFO swing at max depth. I gave U3b gain so that at high gain the LFO is clipped by the op-amp (U3b) rails - the LFO gets progressively more square as you turn up the 'depth'. I like this, but have also added the option of a switch to use a 'proper' square wave LFO, which sounds pretty cool too.
- As seems to be my way, the 4 audio op-amps are all DC-coupled. I have tried uncoupling them and can not hear any good reason to do so.
- I have tried using both a home-rolled LED/LDR combo and a Silonex NSL 32SR3 'vactrol'. Both work equally well and you can get a pretty deep tremolo out of this design.
- The power stage is a little more elaborate than usual as I really don't like LFO noise. The LFO and audio sections are isolated from each other and the LFO ground should be kept away from the audio ground as much as possible too. On the breadboard, I can still hear a little LFO noise, but I think this is a product of the spaghetti of jumpers involved. I guess we won't know until it is boxed up, whether this approach is worth while.
I will post a soundclip this evening and any suggestions are most welcome.
Cheers,
Sam
(https://dl.dropboxusercontent.com/u/11996927/Anharmonic_Tremolo.jpg)
Annnnnnnnnd you're awesome. Can't wait to hear it!
Well at least one thing that is not awesome is my playing tonight. I haven't played much with a tremolo and it would appear that I have a lot to learn. I am also starting to think that I might have to think about make this thing tap tremolo capable.
Here is a quick demo that might give you an idea of what this thing sounds like.
https://dl.dropboxusercontent.com/u/11996927/Anharmonic_Tremolo_demo.mp3 (https://dl.dropboxusercontent.com/u/11996927/Anharmonic_Tremolo_demo.mp3)
Setup: telecaster(ish) bridge single coil -> optical compressor (A-OK; just a touch) -> tremolo -> amp (Fender Greta; used as a tube preamp) -> line out -> audio interface.
It sounds a little darker than it does through a set of speakers - got to love home recording.
What you might be able to hear -
0:00 - harmonic tremolo, sinewave; crossover frequency at about noon; depth at about 1 o'clock
0:27 - harmonic switched to 'treble' setting
0:53 - 'harmonic'
1:10 - 'treble'
1:33 - 'harmonic'; varying the crossover frequency
2:30 - 'harmonic'; varying the speed then depth then to square wave
3:25 - 'harmonic' then 'treble' then clean
Edit - you might note that it doesn't sound like a harmonic tremolo at each end of the crossover frequency pot range and you would be right. If the crossover frequency is well above or below the notes you are playing, then you are just going to have a tremolo with a slightly funky frequency response. I call that a feature, but if it is not to taste, it is easy enough to reign in the frequency range that the pot sweeps over.
Edit - The depth was at about 1 o'clock from 0:00 to 2:30. This is near the point where U3b starts clipping the LFO.
Good one!!
What is the Frequency pot for?
EDIT: Forget it, didn't read the description ;D
The frequency pot is very effective. Was this at max depth the whole time?
The stuff in your edit is exactly how these things work.
I did hear the whining sound you were talking about. Those are some pretty hefty bypass caps in the buffers ... Wish I had a good way to help. Hopefully it'll turn out to just be a breadboard issue.
I realised there was a typo in my last post, but the depth was at about 1 o'clock for most of the demo. It doesn't get much deeper from there, but rather more square.
The filter cap values are not cast in stone. I have big caps in the power filtering section on the breadboard, but to be honest, using 22u or 47u in their place doesn't make any audible difference.
The 'Shoot the Moon' tremolo uses a decoupled power supply to clean up the LFO noise relative to the 'Tremulus Lune'. I believe this works quite well, so I am hopefull that it will work here too. I would love to hear any suggestions as to how I can improve this however.
Just a quick post to say that it sounds really good. :)
another tremolo, bloody hell, I'd better get started on mine .......
duck_are - you know what Andy Warhol said: 'three's a party'
Did your design ever make it onto the breadboard?
"my design" is so far still spread across 3 or 4 different bits of paper, which have complete circuits on them with names like tremface, or slow gear, or something. my circuit, with "world's best ever tremolo" written on it, is still blank.
but I have a vero for my customised fet-based cardinal drawn .....
Quote from: duck_arse on May 16, 2013, 12:00:28 PM
"my design" is so far still spread across 3 or 4 different bits of paper, which have complete circuits on them with names like tremface, or slow gear, or something. my circuit, with "world's best ever tremolo" written on it, is still blank.
You're not alone
Quote from: duck_arse on May 16, 2013, 12:00:28 PM
but I have a vero for my customised fet-based cardinal drawn .....
Now that sounds interesting. I guess if you are at the layout stage then it works - nice job.
I just compared the heap on the breadboard to a modified EA tremolo that I built a good while ago. The EA is a lot noisier than the breadboard, so I guess that means I need to box it up. Only problem is that I am not quite sure how to squeeze the layout into a 1590B. I guess the fun continues.
Quote from: samhay on May 16, 2013, 04:31:21 PM
Only problem is that I am not quite sure how to squeeze the layout into a 1590B. I guess the fun continues.
Not even joking, based on the parts count I could get this into a 1590A with a double sided board, probably without resorting to 1/8W resistors. Do you have an Eagle schematic? I could give it a go if you like.
Jon - Initially I thought I might just about be able to squeeze it into a 1590A. While I've got 6 op-amps into one before, I have gone off that idea as I want to be a little careful about the layout to try and keep the LFO noise down. Also, don't discount the extra height you will lose with the dual-gang frequency pot - I guess if you use a double-side board with the back as a ground plane it would help, but there is not likely to be enough room for components on both sides unless you use SMD. I am happy to stand correctly though.
I am sure the circuit will easily fit in a 1590B if I use perf or a PCB. I initially thought about vero, but that is going to be tight. However, this is with a few fairly stringent layout requirements, which you may wish to relax. I was/am planning on keeping the LFO and audio sections completely separate (including ground) on the board and I also am a bit funny about flying connections and jumpers.
Anyway, I have tidied up the Eagle schem a little bit and you (and anybody else who is interested) are most welcome to work your magic on it. I have also updated the schem in the initial post with the new version - only changes are the power filtering caps, which will need to be tweaked once we have a layout.
The Eagle .sch should be here:
https://dl.dropboxusercontent.com/u/11996927/Anharmonic_Tremolo.sch (https://dl.dropboxusercontent.com/u/11996927/Anharmonic_Tremolo.sch)
Quote from: samhay on May 17, 2013, 09:52:56 AM
Jon - Initially I thought I might just about be able to squeeze it into a 1590A. While I've got 6 op-amps into one before, I have gone off that idea as I want to be a little careful about the layout to try and keep the LFO noise down. Also, don't discount the extra height you will lose with the dual-gang frequency pot - I guess if you use a double-side board with the back as a ground plane it would help, but there is not likely to be enough room for components on both sides unless you use SMD. I am happy to stand correctly though.
I am sure the circuit will easily fit in a 1590B if I use perf or a PCB. I initially thought about vero, but that is going to be tight. However, this is with a few fairly stringent layout requirements, which you may wish to relax. I was/am planning on keeping the LFO and audio sections completely separate (including ground) on the board and I also am a bit funny about flying connections and jumpers. , I have tidied up the Eagle schem a little bit and you (and anybody else who is interested) are most welcome to work your magic on it. I have also updated the schem in the initial post with the new version - only changes are the power filtering caps, which will need to be tweaked once we have a layout.
The Eagle .sch should be here:
https://dl.dropboxusercontent.com/u/11996927/Anharmonic_Tremolo.sch (https://dl.dropboxusercontent.com/u/11996927/Anharmonic_Tremolo.sch)
Well, I wasn't seriously suggesting a 1590A layout for this. Just pointing it out to indicate that 1590B was more than big enough. I'll see if I can get some time over the weekend to work on a layout. I accept no jumpers or flying leads in an Eagle layout, only on perf. ;) Also, I would hav isolated the LFO even if you didn't ask, and probably will not use a ground plane.
BTW, I use these in some tight builds with dual gangs:
http://www.smallbearelec.com/servlet/Detail?no=1276
And here's the 100KC dual gang if anyone is looking for the reversed taper, just not in 9mm:
http://www.smallbearelec.com/servlet/Detail?no=1032
I bend the solder terminals out slightly on 1590B builds that use those. Works fine.
Hey guys,
2 quick questions :
a) Would it be possible to swap both TL072P for a single TL074 ?
b) I don't understand the dotted rectangle marked as "LED/LDR VACTROL" What does this mean ?
Thanks !
Thanks Jon - those links are handy. I hadn't seen a dual-gang 9mm pot before.
Quote from: Hemmel on May 17, 2013, 11:34:44 AM
Hey guys,
2 quick questions :
a) Would it be possible to swap both TL072P for a single TL074 ?
b) I don't understand the dotted rectangle marked as "LED/LDR VACTROL" What does this mean ?
Thanks !
a) yep, a TL074 would work fine. I left it that way as it is often easier to lay out 2 dual op-amps than 1 quad and it also gives you the option of using e.g NE5532s, which work fine.
b) It is supposed to signify that the LDR and LED are collectively a 'vactrol' or home-rolled LED/LDR combo.
Quote from: samhay on May 17, 2013, 11:43:46 AM
b) It is supposed to signify that the LDR and LED are collectively a 'vactrol' or home-rolled LED/LDR combo.
Ooooh... never worked with LDRs before... I think I have one is my sapre parts.
But I have no idea how to breadboard it... anyone have a pic of how to put them on a breadboard ?
Thanks for the info !
Quote from: Hemmel on May 17, 2013, 11:49:56 AM
Quote from: samhay on May 17, 2013, 11:43:46 AM
b) It is supposed to signify that the LDR and LED are collectively a 'vactrol' or home-rolled LED/LDR combo.
Ooooh... never worked with LDRs before... I think I have one is my sapre parts.
But I have no idea how to breadboard it... anyone have a pic of how to put them on a breadboard ?
Thanks for the info !
The resistance of the LDR is dependent on how much light is shined on it, so we usually point an LED at it. Problem is that unless you work in the dark, the room lights will fully saturate it. I wrap my LED and LDR up together with heat-shrink tubing. Others use insulation tape. At a pinch, you can just throw a black cloth over everything.
One thing to know about LDRs is that they are not all created equal. They have different wavelength responses, so you will have to try different colour LEDs to find the ones that play nice - I usually use yellow ones. Also, the dark and light reistance of LDRs vary wildly. I usually try find ones with the biggest difference between their light and dark resistances, but a good place to start is any with a dark resistance of 1M or more. The trimmer in this design is there to cope with the different LDRs or vactrols one might use.
Happy experimenting.
I think there may be some drawing errors in your schematic, as there are some bizarro connections around U1B and U2A. Note the LDR isn't blending between anything- it's just in series with the output of U2A.
Quote from: merlinb on May 17, 2013, 01:31:36 PM
I think there may be some drawing errors in your schematic, as there are some bizarro connections around U1B and U2A. Note the LDR isn't blending between anything- it's just in series with the output of U2A.
That will teach me for trying to use Eagle properly - thanks Merlin, good spot. I have updated the schem and replaced the .sch linked in an earlier post.
Quote from: samhay on May 17, 2013, 02:08:05 PM
That will teach me for trying to use Eagle properly - thanks Merlin, good spot. I have updated the schem and replaced the .sch linked in an earlier post.
For those of us who don't have Eagle, could you repost the schematic in an image please ?
Thanks !
Sorry Hemmel - I updated the schematic in the first post at the same time. It should be correct (or at least more correct) now.
Quote from: samhay on May 15, 2013, 09:17:54 AM
It seems that, largely thanks to Jimi Photon, we now have a rash of new Harmonic Tremolo designs (well two). Jon (midwayfair) beat me to it, but here is another approach to getting something that sounds (something)like the old Fender harmonic tremolo. As I am late to the table, I bring an added bonus - you can vary the crossover frequency of this design. It is still on the breadboard - and has been for some time now - and I need a push to get it off the bread board and boxed up. It should fit in a 1590B, but it will be fairly snug. At the moment, it has four pots (rate, depth, crossover frequency and level) plus two switches (treble/harmonic tremolo and squarewave/sinewave LFO). These are not cast in stone.
How it works: U1b and U2a form a fairly typical crossover circuit that splits our signal into bass and treble components. We then pan between them using a quick-and-dirty LDR-based voltage divider, which is modulated using an LFO-driven LED (or a vactrol).
Notes:
- U1b is an almost-Butterworth 2-pole Sallen-Key LPF and the 'frequency' dual-gang pot can vary the frequency of this filter from ~100Hz to ~10kHz. Whether this range is entirely useful is debatable, but I like it. Note that because I can't find a C100k dual-gang pot, this works backwards - clockwise = lower frequency.
- U2a is a differential amplifier that creates our HP (treble) signal by subtracting the outuput of U1b (i.e. the bass) from out clean amplified signal from U1a. This means we can easily control the crossover frequency by only having to wory about varying the LPF corner frequency. This is a compromise as the HPF is not as steep as the LPF, but it keeps us out of voltage-controlled OTA territory.
- The 'treble/harmonic' switch essentially determines the gain of the HPF, which in turn determines whether we have tremolo'ing of both the bass and treble (harmonic) or only the trebble. I think Jon's design does something similar and it is a nice way to add a little shimmer.
- We pan between the LP and HP signal using a voltage divider. One half of the voltage divider is a LDR, which is modulated with an LED being driven by an LFO. This method is discussed a little bit in another thread (http://www.diystompboxes.com/smfforum/index.php?topic=102414.0 (http://www.diystompboxes.com/smfforum/index.php?topic=102414.0)) and was chosen over a more complicated OTA-based solution. Basically, it is a low parts-count way of doing the job. It isn't perfect, and you do not get a particulalry clean crossover frequency, but it works pretty well in this application. The trimmer is used to set the resistance of the other half of the voltage divider to be similar to that of the LDR when the LFO is a min 'depth'. Note that when you mix the LF and HP signals equally, you get an almost-flat response.
- the LFO (U3a) is the standard Phase 45 LFO design, which is used almost everywhere you want to wobble something. I have used slightly different component values here because I have a lot of 100k resistors and because I'm contrary. If you want more control of the LFO, the 'Tremulus Lune' LFO (among others) is a drop-in replacement.
- U3b buffers the LFO and acts as our depth control - it has gain from 0 to 4.5. I used this approach as, for the LDR to work as a voltage divider, we want it to have an intermediate resitance at minimum depth. To achieve this, we want, at minimum depth, the LED pointed at the LDR to be as bright as it is in the middle of the LFO swing at max depth. I gave U3b gain so that at high gain the LFO is clipped by the op-amp (U3b) rails - the LFO gets progressively more square as you turn up the 'depth'. I like this, but have also added the option of a switch to use a 'proper' square wave LFO, which sounds pretty cool too.
- As seems to be my way, the 4 audio op-amps are all DC-coupled. I have tried uncoupling them and can not hear any good reason to do so.
- I have tried using both a home-rolled LED/LDR combo and a Silonex NSL 32SR3 'vactrol'. Both work equally well and you can get a pretty deep tremolo out of this design.
- The power stage is a little more elaborate than usual as I really don't like LFO noise. The LFO and audio sections are isolated from each other and the LFO ground should be kept away from the audio ground as much as possible too. On the breadboard, I can still hear a little LFO noise, but I think this is a product of the spaghetti of jumpers involved. I guess we won't know until it is boxed up, whether this approach is worth while.
I will post a soundclip this evening and any suggestions are most welcome.
Cheers,
Sam
(https://dl.dropboxusercontent.com/u/11996927/Anharmonic_Tremolo.jpg)
holy cow, sam, this is awesome dude!!! well done!!!
Jimi - thanks for the motivation. I have to say that I am really enjoying the harmonic element of the tremolo - makes it an entirely different beast.
Quote from: samhay on May 17, 2013, 03:37:30 PM
Sorry Hemmel - I updated the schematic in the first post at the same time. It should be correct (or at least more correct) now.
Wow I'm still kind of lost ...
It thought I'd see a connection between the top part (with the depth and rate) connected to the input/output circuit...
Does the top part only have an impact on the LED that affects the LDR ?
I really need to try this out ...
Quote from: Hemmel on May 18, 2013, 02:15:42 PMDoes the top part only have an impact on the LED that affects the LDR ?
I really need to try this out ...
Yes. The circuitry on IC3 is an LFO (low frequency oscillator), wired so that it oscillates the brightness of an LED. The audio path contains a light-dependent resistor, the resistance of which is varied by the LED. They're still connected by the light from the LED. It's not like photons moving through air are that different from electrons moving through copper. Right?
I took electronics for 3 months and that was 13 years ago, when I smoked a lot more green stuff than I do now.
There are some aspects of circuits I understand, others that elude me. I'm having a hard time understanding how just one resistor can tell a circuit how to oscillate through depth, rate, and even if it should do so by sine or sqaure waves...
I hope breadboarding this will help me understand...
I found an old LDR and when I tested it, it showed in almost total darkness 500K, and in direct sunlight, 50 Ohms. Will it do for this circuit ?
I understand I'll need to put the LED/LDR pair in a small box or something, to prevent outside light sources to have an impact.
Quote from: Hemmel on May 18, 2013, 03:04:48 PM
I found an old LDR and when I tested it, it showed in almost total darkness 500K, and in direct sunlight, 50 Ohms. Will it do for this circuit ?
I understand I'll need to put the LED/LDR pair in a small box or something, to prevent outside light sources to have an impact.
most commonly available ldr's tend to go from a few K to a few meg so that should be fine - if you check the schematic again you'll see that the ldr is paralleled by a 1m resistor...
yes - the more light the less resistance, the darker it is the closer to one or two meg the ldr becomes. hence the need to house the contraption in a light proof box for consistency. beware time - aka - response.
also: http://www.ti.com/sc/docs/apps/msp/journal/aug2000/aug_07.pdf (http://www.ti.com/sc/docs/apps/msp/journal/aug2000/aug_07.pdf) and http://www.fairchildsemi.com/an/AN/AN-118.pdf (http://www.fairchildsemi.com/an/AN/AN-118.pdf)
Hemmel - your LDR should work ok. It doesn't need to have a particularly large swing in resistance to give a decent tremolo effect, and for reference, mine are spec'd at 8k-24k at 10 lux & 1M dark resistance. You should be able to set the trimmer to make most LDRs play nice with this circuit, but I guess we may have to wait and see.
To hopefully clarify how it works. If you have two signals connected to pins 1 and 3 of a variable resistor (pot) and you listen to what comes out of the 2nd pin as you twist the knob, you have a basic stereo panner. This is how this circuit works, but instead of a pot, the LDR is one half of a voltage divider and the other half is the trimmer. The LFO, which is the top half of the circuit, makes sure the LED pointed at the LDR changes brightness in a rhythmically interesting way. As the brightness of the LED changes, the LDR's resistance changes and we 'twist' the voltage divider, thus panning between two signals. In this case, our two signals are bass and treble and we get something approximating a harmonic tremolo.
There is some advantage to electrically separating the audio and LFO sections of the circuit, not least that it can help to keep noise from the LFO down.
Jon - I think a physicist would argue there are a few difference between photons and electrons, but in this case they both get the job done.
artifus - nice job noticing the 1M resistor (R12). It is actually not really required in this circuit with the LDRs and vactrol I have tested it with, but I figured I should add it as I have always used something like this to linearise the LDR and to make sure it plays nice. This can always be tweaked if need be.
lawdy. Started on the layout and it's going to take me a bit. I used a quad for the audio path but might go back to a pair of duals to save my brain. I honestly think the layout challenges have something to do with my reticence to work with op amps.
Quote from: midwayfair on May 18, 2013, 07:00:44 PM
lawdy. Started on the layout and it's going to take me a bit. I used a quad for the audio path but might go back to a pair of duals to save my brain. I honestly think the layout challenges have something to do with my reticence to work with op amps.
Yep - op-amps can be a little more awkward to layout than discretes, but it probably comes down to what you know best (which in your case seems to be things that come in a TO-92).
I have most of a vero layout done, which I might try first. Will post once I am fairly certain it will both work and fit in a box.
if you're working up a vero, i'm gonna hang back then... i'm looking at this shaking my head going...man!!!
personally, i hate using vero on anything with more than a chip or two... it gets to be a drag trying to lay out. the clone theory was a nightmare, and i'm STILL trying to get all the noise and crap out of it.
Quote from: pinkjimiphoton on May 19, 2013, 09:45:50 AM
if you're working up a vero, i'm gonna hang back then... i'm looking at this shaking my head going...man!!!
personally, i hate using vero on anything with more than a chip or two... it gets to be a drag trying to lay out. the clone theory was a nightmare, and i'm STILL trying to get all the noise and crap out of it.
This is bigger than I would generally try on vero too, but it is a baby board next to some of digi2t's layouts, so I figured I would give it a shot.
can't wait to see it. this thing sounds great and i'm a lazzzzzzzzy man sometimes. ;)
sam, is the value of C10 1uF?
Quote from: duck_arse on May 20, 2013, 10:45:41 AM
sam, is the value of C10 1uF?
Yes, but you probably will not hear much difference if you try 100n.
It took a little while, but I have a vero layout that should both work and fit in a 1590B. I have split the LFO and audio sections to seperate boards, which saves quite a lot of space as the LFO board should fit vertically on board-mounted pots. Will check a couple of dimensions and do another trace before I post.
In the meantime, I stumbled upon the Baja Vibrotrem on the other forum. Harald (SabroTone) has done a vero layout too. It looks to be a fairly faithful op-amp implementation of the original Fender harmonic tremolo, but I haven't found any audio clips.
Quote from: samhay on May 24, 2013, 10:48:10 AM
It took a little while, but I have a vero layout that should both work and fit in a 1590B. I have split the LFO and audio sections to seperate boards, which saves quite a lot of space as the LFO board should fit vertically on board-mounted pots. Will check a couple of dimensions and do another trace before I post.
Excellent. I started a vero layout, but it grew to 21x21 holes very rapidly. Spliting it into two boards seems like a great idea.
can't wait to see it... i heard a demo of baja's vibrotrem on youtube i think, but this one sounds like, REAL close to the "real deal"....
anxiously awaiting!! ;)
Not being entirely confident with my layout, I thought I would verify (or verofy?) it first. The LFO works, but there is a bug in the audio section, so I need to spend a little more time with the fine-tooth comb.
I did find another error in the schematic, which crept in when I re-drew it - C5 should be 10n not 22n. Not a major problem, but it will have a flatter (almost Butterworth) response this way. The schem in the first post and the Eagle file have both been updated.
Here's a vero layout - it works, but I haven't squeezed it into a 1590B yet. Sorry about all the jumpers and the odd vertical resistor - I had a hard time laying this out how I wanted it. Anybody and everybody is encouraged to better my efforts.
The LFO section is designed to be pot-mounted and sit at the non-foot switch end of the box. I know this will fit. It might also just fit in a more traditional orientation.
The audio board should float over the volume and frequency pots and hopefully will fit if you put the jacks or foot switch near the bottom - sorry, there is not likely to be room for a battery.
I set the space between the LFO pots to be quite wide so that I can fit a switch between each pot. You may need to use smallish switches or lay it out differently.
The circuit is reasonably easy to get working. Setting the trimmer is quite easy to do by ear - you want the volume to be similar when the frequency pot is at each extreme of its rotation - at one end, you will have volume with the LED on, and the other end when it is off. You may have to play with R28 and R29 (LED resistors for the vactrol) to get a pleasant duty cycle.
I currently have a home-rolled LED/LDR working with 1k resistors at both R28 and R29 (as marked on the vero layout). I may replace this with a Silonex NSL-23SR3 'vactrol' and will probably have to bump R28 and R29 up a bit if I do.
The frequency pot works by decreasing the crossover frequency as you turn the pot clockwise. If you use a C100k pot, then wire it backwards (pin 1 <-> pin 3).
Edit - you may have to increase the value of R23 (1k restor to pin 3 of the rate pot) as the LFO may lock up near max speed (unless you see this as a feature). I need to investigate this a little further.
Edit - I left room in the top right corner for a trimmer, so if you don't want a frequency pot, you can set-and-forget the volume. There is a volume boost when using the 'treble' function, so I think a volume pot is probably a good idea. YMMV.
Edit - oh and there is one significant change from the schematic. I changed the order of the audio op-amps. The input and output op-amps are now one dual package (a TL072), while U1b and U2a are now the other dual package - which I used an NE5532 for. I found the layout easier this way and it gives you the best of both worlds - the TL072's fet input impedance and the low(er) noise of the NE5532 for the filtering. However, you don't need to use an NE5532 - anything with a TL072 pinout should work.
(https://dl.dropboxusercontent.com/u/11996927/Anharmonic_Tremolo_Vero.jpg)
:icon_eek:
looks sweet!! gonna try and give 'er a go!!
Hope you like it Jimi.
I gave the LFO values a tweak last night - it seems that the dodgy connections on the breadboard were helping with its mojo.
1k R to pin 3 of the rate pot -> 1.8k (stopped the LFO locking up)
220k R -> 680k R (gave a better range of depth)
22u C -> 10u (gave a better range of LFO speeds.
Should get it somewhat boxed up this evening, so I guess we shall see if it all fits.
Here are a couple of simulations of the frequency response of the circuit with the frequency pot set to 10k. Both assume that the LDR can swing an order of magnitude either side of it's resistance when the depth is 0. This is probably a little over-optimistic, but you get the idea.
Of note - and in response to a thread by tca (http://www.diystompboxes.com/smfforum/index.php?topic=103114.0 (http://www.diystompboxes.com/smfforum/index.php?topic=103114.0)) - is that in this circuit the crossover frequency moves around as it pans. The simulations look pretty ugly, but it sounds pretty good...
The first sim is 'anharmonic' mode and the second 'treble' mode.
Edit - I should probably stress that this circuits works very differently than the original Fender design, which may well have a much cleaner crossover frequency.
(https://dl.dropboxusercontent.com/u/11996927/Anharmonic_Tremol_Sim1.jpg)
(https://dl.dropboxusercontent.com/u/11996927/Anharmonic_Tremol_Sim2.jpg)
Thanks for posting this, Sam. The sims are very interesting.
I had thought that the circuit would pan between a fixed HP and a fixed LP filter.
But in your sim, if I understand it right, it is varying the amount of filtering of both passes out of phase from each other, but not panning between them. (is that correct?)
No problem. The crossover frequency of the HP and LP filters is fixed (by the frequency dual-gang pot and the 10n and 22n caps). However, when we pan between them, we are using a voltage divider consisting of an LDR and a trimmer. This is the least parts-count approach (for other options, it might help to take a look at RG's 'panning for fun' article), but it has some drawbacks, one of which is that the amplitude of both signals change during panning. In this case, this causes the apparent crossover frequency to move all over the place. I thought long and hard about whether to do the panning in a 'better' way, but decided against it for the time being as it would double the circuit size.
Well I finally got it boxed up. It is a bit of a mess, as I have been tweaking as I go, but it fits in 1590B (with a few trick borrowed from my 1590A builds) and works as intended. .The wiring is all a lot longer than I would generally like, but I kept it like this so I could readily pop the boards in and out. Despite the rat's nest, it is pretty quiet - the LFO noise is all but absent.
The audio board is identical to that shown in the schematic and vero layout, but a few of the LFO values have changed again, and I decided to drop the square wave switch as it wasn't adding much. These are all essentially 'tweaking to taste' changes, but I will update the schem etc shortly.
For anybody interested in building it - be warned. As-is, it is a squeeze and you will probably have a lot more fun nicely laying it out in a larger enclosure. That said, a better (PCB) layout would help a lot. I could do with some help on this front. I will probably get round to doing this one day, but I will next be trying to get it to play nice with the TAPFLO chip.
(https://dl.dropboxusercontent.com/u/11996927/Anharmonic_Tremolo_guts.jpg)
I'm interested in building either this or Jon's Xardinal Trem...any way to get rid of LFO noise or switch to normal tremolo? Your demo sounds great
I realised after building this and playing with it for a while that my direct recording setup doesn't have a very good earth - USB powered audio interface to a laptop - so it can get noisy with LFOs that throw hash onto the ground. If I play my Anharmonic tremolo through my amp, which is grounded via a 3 prong power plug, the LFO noise is very difficult to hear - certainly no worse than a Tremulus Lune and far better than an EA tremolo.
I would suggest that if you are interested, you put the circuit together on a breadboard and see how it sounds. The LFO noise will likely be at its worst in this case, so if it is ok like that, it should be fine in a build.
What is the p-p voltage of your LFO? I'm trying to get a square/triangle option on another trem, and the square is much hotter. If i voltage divide it down it crashes after about 5 seconds. Not sure I understand what your switch is doing. Do you attenuate the square to match the triangle? Thanks
^What is the p-p voltage of your LFO?
The square and triangle LFO voltage swings should be similar and you can change the square wave amplitude by varying the value of R22.
However, a square and triangle LFO with the same amplitude will probably sound like they have different depths when used in e.g. a tremolo.
Anyone have the schematic for this? Seems to have vanished.
Sorry - this is on my list of stuff to migrate from my dropbox public folder.
Schematic:
https://www.dropbox.com/s/43wbr6cu6ejobwr/Anharmonic_Tremolo.jpg?dl=0
Vero layout:
https://www.dropbox.com/s/1drqi9af31eoa5l/Anharmonic_Tremolo_Vero.jpg?dl=0
(this is a pretty tight fit in a 1590B):
https://www.dropbox.com/s/rpetyli12usrqaq/Anharmonic_Tremolo_guts.jpg?dl=0
Thanks! Much appreciated.
You posted some interesting ideas for LED drivers in this thread. Any chance of reattaching those?
http://www.diystompboxes.com/smfforum/index.php?topic=102551.0
''Sorry - this is on my list of stuff to migrate from my dropbox public folder.''
yep, know the feeling.. :icon_frown:
Quote from: Chugs on May 08, 2017, 03:27:04 AM
Thanks! Much appreciated.
You posted some interesting ideas for LED drivers in this thread. Any chance of reattaching those?
http://www.diystompboxes.com/smfforum/index.php?topic=102551.0
No problem.
For this post:
http://www.diystompboxes.com/smfforum/index.php?topic=102551.msg909902#msg909902
I think this is the relevant picture:
https://www.dropbox.com/s/lib4ge1mvqjjbyy/LuneLFOLEDDrivers.jpg?dl=0
I'm not sure how well 'B' will work, but 'C' is how it works in the Anharmonic tremolo.
However, to make 'C' work well, you have to make R3 large enough to not load down the LFO circuitry too much - i.e. probably 100's k or more.