Author Topic: 18V Electric Mistress with reworked LFO & VCO  (Read 4800 times)

DrAlx

Re: 18V Electric Mistress with reworked LFO & VCO
« Reply #20 on: May 19, 2020, 04:35:57 AM »
Boards arrived in the post. Just need to populate and test.

DrAlx

Re: 18V Electric Mistress with reworked LFO & VCO
« Reply #21 on: May 19, 2020, 04:40:59 AM »
How would you do both regulations here then? Powered in 18v DC then regulate in 12v and 9v with 78L12 and 78L09?

Do you already have a schematic?
Exactly that method.  The LFO/VCO/CD4013 run of a 78L12.   The audio op-amps/BBD/CD4050 run off a 78L09.

I will post a schematic as soon as I have tested the build.  There are a couple more component values that need a tweak and I don't want to post a schematic with incorrect values.

DrAlx

Re: 18V Electric Mistress with reworked LFO & VCO
« Reply #22 on: May 19, 2020, 04:58:00 PM »
Almost there.  I just need to find suitable values for the output gain stage to bring it to unity.  The new build will have an op-amp based gain stage (like the Madbean Current Lover) as tests showed it to be quieter than the single BJT stage used on the SAD1024 build.

I noticed something interesting while doing a sound comparison.  I compared the sound of my BL3207 based build to the SAD1024 based build I did a few years back.  As my BL3207 build isn't populated with an output gain stage yet, I took signals from before the output gain stages on both boards.  The BL3207 build appeared to sound warmer (bassier) than the SAD1024 build.  It was not a rigorous test because I was just plugging/unplugging jacks and trying my best to "remember the sound".  In fact if I remembered incorrectly it invalidates what you're about to read below!!!
Now I spent a lot of time carefully comparing the BL3207 against the SAD1024 (lots of measurement results posted on the EM3207 thread) and I know for a fact that in this particular circuit, the difference in BBD gain between these chips is a fraction of a dB, and often close to 0dB.  So the use of different BBDs could not explain the difference in sound. So I removed the BBDs from both boards to compare the sounds without any sort of delay in the circuit.  Guess what?  The MN3207 build still sounded warmer.  The audio paths are the same (i.e. same opamps and same R and C values) in the two circuits.  The opamp (TL072) is run at lower voltage in the 3207 circuit (9V instead of 12V) but I don't believe that is relevant.  I think the difference may be in the quality of film caps that I used.  I used Panasonic's in the MN3207 build (brown things in the picture below) and cheaper box caps in the SAD1024 build (yellow).  Normally I don't pay too much attention to what caps are made of, but there was another occasion about a year ago where I had two caps of the same nominal value giving a noticeable difference in the amount of bass (though in that case I was comparing an electrolytic to a film cap).



« Last Edit: May 19, 2020, 05:08:43 PM by DrAlx »

StephenGiles

Re: 18V Electric Mistress with reworked LFO & VCO
« Reply #23 on: May 20, 2020, 02:18:51 AM »
I built a TDA1022 version of the Electric Mistress a few years ago, which also included the Eventide Instant Phaser/Flanger bounce circuit for fun - must have been early 2000s. I'll try to locate the circuit which I drew out on that old large stripey computer printer paper, and also a few sound samples I did.

I found the samples:
https://www.dropbox.com/sh/4z6mog10ibaqh6o/AACReznX-f8p1hIVNkX7p4I9a?dl=0
« Last Edit: May 20, 2020, 08:06:19 AM by StephenGiles »
"Gods teeth", he muttered, "if these things bite one will be singing soprano".

DrAlx

Re: 18V Electric Mistress with reworked LFO & VCO
« Reply #24 on: May 20, 2020, 06:37:02 PM »
OK I have finished with the MN3207 conversion.  I couldn't think what to call it so "EMV2 Flanger" will have to do.




So basically the LFO and VCO run from 12V supply.  The clock buffer, BBD and audio run from 9V supply.  You don't need to power the circuit with 18V of course (15V is enough).

Compared to the reworked SAD1024 circuit that started off this thread, I changed the output gain stage to an op-amp since its lower noise than the LPB style output boost I had before.

The only other LFO/VCO related changes are:

R27 in above schematic: Reduced from 220k to 180k as that was sufficient to stop the VCO "thumping".

R31 in above schematic: Reduced from 10k to 3k9.  This was key to getting the sweep range correct for the doubled clock.
If the ratio of R32/R31 is too low then it not possible to get a decent sweep range. Using a ratio of (220/3900) I can set the clock trimmer in Filter Matrix Mode and have the clock going from around 50kHz to around 400kHz (depending on Range pot setting).

Document with parts list here:   https://1drv.ms/b/s!AvrH61utWEtEjig_4U8k7-fGwkbv?e=69cQg1

I have 4 boards but can't say how quickly I could get them delivered under current circumstances.  PM me if interested.  If there is sufficient interest I will order more.

DrAlx

Re: 18V Electric Mistress with reworked LFO & VCO
« Reply #25 on: May 22, 2020, 09:47:05 PM »
One other thing.  The circuit will run on a 12V supply (rather that 15V supply) without the need to reset the bias (because that runs off the 9V regulator) however the sweep range will be reduced.

I have not actually powered it with an 18V supply, only 15V.  I also have a cheap wall-wart that is labelled as 15V output but actually supplies over 20V.  When I used that the 12V regulator got really hot and died.  So I would recommend that the circuit supply is limited to 15V (despite what is says on the schematic).

I am not sure why the regulator died because when I calculate a worst case current draw from the 12V circuitry it comes to less than 10mA, which should be easily handled by the 78L12.  So I am not sure what is going on there.


rankot

Re: 18V Electric Mistress with reworked LFO & VCO
« Reply #26 on: May 23, 2020, 04:46:14 AM »
One other thing.  The circuit will run on a 12V supply (rather that 15V supply) without the need to reset the bias (because that runs off the 9V regulator) however the sweep range will be reduced.

I have not actually powered it with an 18V supply, only 15V.  I also have a cheap wall-wart that is labelled as 15V output but actually supplies over 20V.  When I used that the 12V regulator got really hot and died.  So I would recommend that the circuit supply is limited to 15V (despite what is says on the schematic).

I am not sure why the regulator died because when I calculate a worst case current draw from the 12V circuitry it comes to less than 10mA, which should be easily handled by the 78L12.  So I am not sure what is going on there.

Couldn't you run it on 9V with, for example, 15V generated with LT1054 or something similar? It could use normal PS then.
50 pedals and counting!

DrAlx

Re: 18V Electric Mistress with reworked LFO & VCO
« Reply #27 on: May 23, 2020, 05:03:56 AM »
Couldn't you run it on 9V with, for example, 15V generated with LT1054 or something similar? It could use normal PS then.
Not sure it's a good idea. You could get heterodyne noise due to the clock from the charge pump beating with the clock used for the BBD. That's the case for all BBD based effects. Low pass filtering on the audio is very light on the EM and that is part of the sound, so it is more likely to be a problem on this circuit than on other BBD circuits.

I have not actually used a charge pump with a BBD, so maybe that could work. Layout would be important.
You could always try to use a small daughter board (or is it motherboard?) to do the 9v to 15v conversion.
« Last Edit: May 23, 2020, 05:43:25 AM by DrAlx »

diffeq

Re: 18V Electric Mistress with reworked LFO & VCO
« Reply #28 on: May 23, 2020, 05:46:27 AM »
One other thing.  The circuit will run on a 12V supply (rather that 15V supply) without the need to reset the bias (because that runs off the 9V regulator) however the sweep range will be reduced.

I have not actually powered it with an 18V supply, only 15V.  I also have a cheap wall-wart that is labelled as 15V output but actually supplies over 20V.  When I used that the 12V regulator got really hot and died.  So I would recommend that the circuit supply is limited to 15V (despite what is says on the schematic).

I am not sure why the regulator died because when I calculate a worst case current draw from the 12V circuitry it comes to less than 10mA, which should be easily handled by the 78L12.  So I am not sure what is going on there.

Couldn't you run it on 9V with, for example, 15V generated with LT1054 or something similar? It could use normal PS then.
Not sure its a good idea. You could get heterodyne noise due to the clock from the charge pump beating with the clock used for the BBD. That's the case for all BBD based effects. Low pass filtering on the audio is very light on the EM and that is part of the sound, so it is more likely to be a problem on this circuit than on other BBD circuits.

I have not actually used a charge pump with a BBD, so maybe that could work. Layout would be important.
You could always try to use a small daughter board (or is it motherboard?) to do the 9v to 15v conversion.
You can use capacitance multiplier at the charge pump output - 1 transistor, 1 resistor and 2 electro caps will shave of all of high frequency noise (at the expense of 1V drop).

DrAlx

Re: 18V Electric Mistress with reworked LFO & VCO
« Reply #29 on: May 23, 2020, 06:07:58 AM »
Found this that has 9V -> 18V followed by a regulator to 15V that powers the circuit.

http://moosapotamus.net/images/FlangerClone_SCH_rev5_MN3007_jan2010.gif

So daughter board might do it.

StephenGiles

Re: 18V Electric Mistress with reworked LFO & VCO
« Reply #30 on: May 23, 2020, 06:38:58 AM »
Me being me would use 2 x rechargeable 9v PP3 batteries for testing during building, then a battery pack of rechargeable AAs - only because I don't mess with mains on effects!
"Gods teeth", he muttered, "if these things bite one will be singing soprano".

DrAlx

Re: 18V Electric Mistress with reworked LFO & VCO
« Reply #31 on: May 23, 2020, 06:59:41 AM »
Me being me would use 2 x rechargeable 9v PP3 batteries for testing during building, then a battery pack of rechargeable AAs - only because I don't mess with mains on effects!
I'll give that a try (test with 2PP3s).  So just figured out why my regulator died. It is rated as being able to supply 100mA at 12V but this circuit draws less than 10mA at 12V, so the excess voltage fed into the reg gets converted into heat.  Damn wall-wart cost me a load of hassle trying to unsolder/resolder parts on my PCB which was very fiddly to handle with the cramped space and plated through holes.

Question:  Does anyone have a technique for easily replacing parts on a PCB with plated through-holes?  I found it hard to get the parts out and they always left a hole filled with solder.  I ended up trying to push a needle into the hole and wiggle it while heating the pad, so the needle point would push the solder out.  I am wondering if there is some tool for the job (an awl of some sort)?
« Last Edit: May 23, 2020, 07:03:52 AM by DrAlx »

diffeq

Re: 18V Electric Mistress with reworked LFO & VCO
« Reply #32 on: May 23, 2020, 07:45:02 AM »
You can use capacitance multiplier at the charge pump output - 1 transistor, 1 resistor and 2 electro caps will shave of all of high frequency noise (at the expense of 1V drop).
Better still, is to use to use BBD clock itself to run a voltage multiplier (doubler@9V, x3/x4 @5V ), followed by regulator/cap multiplier  filtering. Solves the noise issue.

Question:  Does anyone have a technique for easily replacing parts on a PCB with plated through-holes?  I found it hard to get the parts out and they always left a hole filled with solder.  I ended up trying to push a needle into the hole and wiggle it while heating the pad, so the needle point would push the solder out.  I am wondering if there is some tool for the job (an awl of some sort)?
I did the same but using toothpick. Ends being conical work better than a needle. Ideally one would use hot air gun and a copper wick, but I imagine fixing through-holes would still require lots of practice.

bluebunny

Re: 18V Electric Mistress with reworked LFO & VCO
« Reply #33 on: May 23, 2020, 08:34:35 AM »
Yep, toothpick every time.  :icon_cool:
Ohm's Law - much like Coles Law, but with less cabbage...

Aurae

Re: 18V Electric Mistress with reworked LFO & VCO
« Reply #34 on: May 23, 2020, 09:13:58 AM »
Quote
Question:  Does anyone have a technique for easily replacing parts on a PCB with plated through-holes?  I found it hard to get the parts out and they always left a hole filled with solder.  I ended up trying to push a needle into the hole and wiggle it while heating the pad, so the needle point would push the solder out.  I am wondering if there is some tool for the job (an awl of some sort)?

The best solution for me is the desoldering pump with the addition of tin, until the hole is free. (sometimes I need three additions to make it right but it works all the time).

Have you tested antoher reg 12v ? Maybe the first was not so good

DrAlx

Re: 18V Electric Mistress with reworked LFO & VCO
« Reply #35 on: May 23, 2020, 11:09:06 AM »
I got the same overheating with the new regulator if I powered it with too much voltage.
With 20V input, regulator stops regulating and I measure 20V on all the circuitry that should be running at 12V.  C20 which was rated for 16V could have got damaged in the process, so when I changed the regulator I replaced it with a 47uF cap rated at 35V.

Assuming circuit takes 10mA, power disipated in reg = (20-12)*0.01 = 0.08W.   Multiply by 200 degrees C per W = 16 degrees C increase.  That's not big but the reg was way too hot to touch, so I can only guess that the circuit is actually using a lot more than 10mA.  I'll have to measure current consumption.


rankot

Re: 18V Electric Mistress with reworked LFO & VCO
« Reply #36 on: May 23, 2020, 12:35:37 PM »
I got the same overheating with the new regulator if I powered it with too much voltage.
With 20V input, regulator stops regulating and I measure 20V on all the circuitry that should be running at 12V.  C20 which was rated for 16V could have got damaged in the process, so when I changed the regulator I replaced it with a 47uF cap rated at 35V.

Assuming circuit takes 10mA, power disipated in reg = (20-12)*0.01 = 0.08W.   Multiply by 200 degrees C per W = 16 degrees C increase.  That's not big but the reg was way too hot to touch, so I can only guess that the circuit is actually using a lot more than 10mA.  I'll have to measure current consumption.

Maybe you have a short somewhere?
50 pedals and counting!

rankot

Re: 18V Electric Mistress with reworked LFO & VCO
« Reply #37 on: May 23, 2020, 12:37:35 PM »
Better still, is to use to use BBD clock itself to run a voltage multiplier (doubler@9V, x3/x4 @5V ), followed by regulator/cap multiplier  filtering. Solves the noise issue.
Sounds good, could you draw a schematic for that?
50 pedals and counting!

DrAlx

Re: 18V Electric Mistress with reworked LFO & VCO
« Reply #38 on: May 23, 2020, 02:42:05 PM »
Measured current consumption. Whole circuit takes 30mA when clock is at maximum rate.

DrAlx

Re: 18V Electric Mistress with reworked LFO & VCO
« Reply #39 on: May 23, 2020, 02:51:05 PM »
Better still, is to use to use BBD clock itself to run a voltage multiplier (doubler@9V, x3/x4 @5V ), followed by regulator/cap multiplier  filtering. Solves the noise issue.
Sounds good, could you draw a schematic for that?

+1. Interested to see how such a circuit would fire itself up.