I am using an LT1054 as the heart of a 9V to 12V charge pump in a circuit and I suspect that it is adding some unwanted frequencies and noise into the output. So, my question is....
Can anyone see a way to change the frequency of the oscillator like you can with the MAX1044 chips (Freq Boost)?
Link to datasheet:
http://cds.linear.com/docs/en/datasheet/1054lfg.pdf
Thanks for the help ;D
Huh. I wish I knew how to help, but the clock frequency (25KHz) in the LT1054 should be waaaay above human hearing. This is worrying because I really like using it ever since the forum taught me it was safer. :(
Take a look at the Texas Instruments datasheet for this chip. I think I remember seeing something about setting the oscillator frequency in it.
i had a whine on the first klon(e) i built... if i remember correctly, grounding i think it was pin 7 directly took care of the whine.
sorry greg, i don't remember which was either vref (pin 6) or osc (pin 7) that did the trick. i think it was pin 7...
i don't have that klon(e) anymore, so i can't check.. but according to this on the forbidden planet, yah, pin 6 or 7...
http://.......org/viewtopic.php?f=13&t=1256&start=440#p180878
yah, pin 7. if it whines, short that to ground, that should take care of it bro.
Put a 5-25pf cap between pins 2 and 7.
You can socket the cap until you find the "magic" value, then install permanently.
Havent tried the cap idea suggested by armdndry (have to give that a shot!) but i can tell you first hand the LT1054 in certain circuits will produce excessive whining. FSH1 could be a candidate havent tried swapping that one yet, but fairly certain the LT isnt filtering well enough. FL301 is DEFINITELY a candidate. I swapped that one over from an LT1054 to a TC1044(scpa -> the low noise type). Reduced noise significantly. But alas, still some noise...
The LT in fuzzes and even some modulations can be fine though. If i could find the TC1044 at a reasonable price i would just get them. Havent had any reliaiblity issues with the TC, like the LT.
I wouldnt recommend a MAX to my accountant. They are terribly unreliability imo.
Paul
Quote from: armdnrdy on January 28, 2013, 09:38:56 PM
Put a 5-25pf cap between pins 2 and 7.
You can socket the cap until you find the "magic" value, then install permanently.
larry, why a cap between 2 and 7?
Quote from: pinkjimiphoton on January 28, 2013, 09:08:19 PM
yah, pin 7. if it whines, short that to ground, that should take care of it bro.
Careful!
Quote from: pinkjimiphoton on January 28, 2013, 10:08:18 PM
larry, why a cap between 2 and 7?
From page 6 of the datasheet:
QuoteThe frequency can be lowered by adding an external capacitor (C1, Figure 2) from Pin 7 to ground. This will increase the charge and discharge times which lowers the oscillator frequency. The frequency can be increased by adding an external capacitor (C2, Figure 2, in the range of 5pF to 20pF) from Pin 2 to Pin 7.
Don't ground it as that will lower the oscillator frequency into the audio range.
weird!! worked good on the klon, only way i could get the whine to stop.
Can anyone comment on using the TC1044SCPA in a circuit? Couldn't find the current output limits on the datasheet. I "think" the circuit I am using is pulling somewhere between 15-20mA.
Quote from: Govmnt_Lacky on January 29, 2013, 07:48:41 AM
Can anyone comment on using the TC1044SCPA in a circuit? Couldn't find the current output limits on the datasheet. I "think" the circuit I am using is pulling somewhere between 15-20mA.
What are you trying to power? And what proximity is the pump to the circuit and have you used shielded wire.
Quote from: Scruffie on January 29, 2013, 08:07:51 AM
What are you trying to power? And what proximity is the pump to the circuit and have you used shielded wire.
Trying to power a Deluxe Electric Mistress clone at 12V. I have verified that the circuit has "some" noise but it is tolerable however, when I run an LT1054-based pump circuit, the noise gets much worse. The wiring is not affecting the noise as it is barely audible when I directly inject 12V regulated power into the circuit and bypass the pump portion of the circuit.
I experimented with the power input electro cap and discovered that it needs to be larger however, I am still wondering if the LT1054 is still injecting noise. This is still at the experimental stages and I would just like to rule out the pump as a source of noise.
Gov, you may be having heterodyning problems. Two oscillators (the LFO one and the one in the charge pump) running at different speeds can produce sum and difference "beating" frequencies through the power or ground. I know because years ago I had that problem with a 301 flanger that I added a charge pump to, to be able to use it with a 9V power supply. I solved it by adding lots and lots of caps to the power (something like ten 100 uF´s. Really funny looking).
Quote from: Govmnt_Lacky on January 29, 2013, 08:20:00 AM
Quote from: Scruffie on January 29, 2013, 08:07:51 AM
What are you trying to power? And what proximity is the pump to the circuit and have you used shielded wire.
Trying to power a Deluxe Electric Mistress clone at 12V. I have verified that the circuit has "some" noise but it is tolerable however, when I run an LT1054-based pump circuit, the noise gets much worse. The wiring is not affecting the noise as it is barely audible when I directly inject 12V regulated power into the circuit and bypass the pump portion of the circuit.
I experimented with the power input electro cap and discovered that it needs to be larger however, I am still wondering if the LT1054 is still injecting noise. This is still at the experimental stages and I would just like to rule out the pump as a source of noise.
The LT1054 has a clock, the mistress has one, you'll have to be careful where it is located to prevent heterodyning which may be the noise you're experiencing.
The LT1054 chip itself is not noisy, i've used them loads as have others, it's layout, cross talk and power conditioning that are causing it to work noisily with the circuit most likely. So don't give up on it yet, add more filterng and try and move the charge pump out of the way of anything, shield the wires from it, keep them short etc. a regulated 12V source doesn't need the same treatment as a circuit doubling the voltage.
Edit: Morocotopo got there first with the heterodyning suggestion. It can certainly add some strange noise when you experience it.
Thanks for the suggestions about heterodyning.
Ill try to parallel a 1000uF electro and see what it does ;)
Should the larger cap go between power and ground BEFORE or AFTER the charge pump? When I did some experimenting, I noticed the greatest change in noise when I paralleled an electro before the pump input.
If I remember correctly, the Mistress clock starts at ~40KHz. If I were to replace the pump with a TC1044SCPA and added the boost, this would cause the pump oscillator to run at 45KHz. Would this cause BIGGER problems since they would be soo close? :icon_eek:
Quote from: Govmnt_Lacky on January 29, 2013, 09:02:39 AM
Thanks for the suggestions about heterodyning.
Ill try to parallel a 1000uF electro and see what it does ;)
Should the larger cap go between power and ground BEFORE or AFTER the charge pump? When I did some experimenting, I noticed the greatest change in noise when I paralleled an electro before the pump input.
If I remember correctly, the Mistress clock starts at ~40KHz. If I were to replace the pump with a TC1044SCPA and added the boost, this would cause the pump oscillator to run at 45KHz. Would this cause BIGGER problems since they would be soo close? :icon_eek:
I guess the big cap should go after, but try it in both locations, can´t rememeber where I had it since it was so long ago... and that pedal is no longer in one piece.
Regarding the frequencies, my (limited) knowledge is that the produced frequencies are sum and difference of the two original ones, so for example if you have a 45 kHz and a 40 kHz, you could have heterodyning at 45-40=5 kHz (ouch! right in the middle of the audible spectrum), 40+45= 85 kHz (only problematic if you are a bat), and so on (all the harmonics).
Thanks Ariel! ;D
So, with what has been said so far.... If the charge pump is going to be mounted on the same PCB as the circuit...
Is there any way to get rid of, or at least minimize the oscillator interference that would be coming from the pump circuit?
Also, the 35KHz (found the correct frequency elsewhere on the forum) is the MINIMUM clock frequency used my the DEM. When the Range pot is adjusted, the frequency gets much higher (I believe it can go up to and even above 500MHz) Not sure of the exact numbers right now but, I believe it would be a range just like any other flanger-type circuit (MXR M117, etc.)
Sorry for the delay in my reply. Sick with the FLU!!!!
Take a look at the better detailed Linear Technology data sheet.
http://cds.linear.com/docs/en/datasheet/1054lfg.pdf (http://cds.linear.com/docs/en/datasheet/1054lfg.pdf)
Just speculating, but if difference frequencies are the issue here, then raising the oscillator frequency might not solve the problem. According to the spec, the nominal oscillator frequency is 25kHz which would produce difference frequencies of 10k and upward as the the range pot is adjusted (assuming the 35kHz is right). If you raised the osc freq to 40k, then you'd have differences from 5k down to zero then back upward as the pot is adjusted. If you raise it to anything above 35k, there will be some sections of the range pot where the difference frequencies will be audible, since the range pot will sweep its frequency from 35k up to the osc freq and beyond. On the other hand, if you lowered the osc freq to 15k or 20k, you'd have differences of 20k or 15k on upward. While 15-20k is still technically audible, it might not be in this circuit and could probably be filtered out without too much negative impact. The spec isn't clear exactly how high or low you can adjust the frequency however. Again - just playing around with the math and speculating here - so maybe none of this applies in the real world?
Quote from: GGBB on January 29, 2013, 12:38:20 PM
Just speculating, but if difference frequencies are the issue here, then raising the oscillator frequency might not solve the problem. According to the spec, the nominal oscillator frequency is 25kHz which would produce difference frequencies of 10k and upward as the the range pot is adjusted (assuming the 35kHz is right). If you raised the osc freq to 40k, then you'd have differences from 5k down to zero then back upward as the pot is adjusted. If you raise it to anything above 35k, there will be some sections of the range pot where the difference frequencies will be audible, since the range pot will sweep its frequency from 35k up to the osc freq and beyond. On the other hand, if you lowered the osc freq to 15k or 20k, you'd have differences of 20k or 15k on upward. While 15-20k is still technically audible, it might not be in this circuit and could probably be filtered out without too much negative impact. The spec isn't clear exactly how high or low you can adjust the frequency however. Again - just playing around with the math and speculating here - so maybe none of this applies in the real world?
Hey Gord!
So, are you suggesting that trying the small-ish cap between Pins 2 and 7 of the LT1054 to lower the pump's oscillator frequency might be worth a shot?
I do have some MAX1044 and TC1044SCPA pumps here. I may try those as well just to see if I get any noise changes.
Quote from: GGBB on January 29, 2013, 12:38:20 PM
While 15-20k is still technically audible...
Depends how long you've been gigging with drummers ;)
Quote from: garcho on January 29, 2013, 01:56:56 PM
Depends how long you've been gigging with drummers ;)
;D
Quote from: Govmnt_Lacky on January 29, 2013, 01:41:41 PM
Hey Gord!
So, are you suggesting that trying the small-ish cap between Pins 2 and 7 of the LT1054 to lower the pump's oscillator frequency might be worth a shot?
I do have some MAX1044 and TC1044SCPA pumps here. I may try those as well just to see if I get any noise changes.
I think anything is worth a shot - you'll never know until you try it. According to the datasheet, a cap between 2 and 7 will raise the frequency whereas a cap from 7 to ground will lower it. Both are pretty easy to try. I was suggesting that raising might
not work, whereas
lowering it might. But it all comes down to what the noise is that you are hearing. If the osc freq is 25k, then you aren't hearing that, so maybe it's the difference frequency that Morocotopo mentioned. If it is the difference between the mistress range freq and the osc freq, then the noise should change as you adjust the range pot. Does this happen? It should be audible only at the low end of the control because once the range pot gets you up to 45k and higher, the difference freq goes above audible. At min, the range control is 35k (according to you), which produces 10k difference freq with the 25k osc freq. 10k is probably audible. To move difference frequencies outside the audible range, you need to separate the two frequencies by ideally more than 20k without having either frequency below 20k. Lowering the LT1054's 25k osc freq to 15-20k gets you close to this, probably close enough for a pedal. But I have to stress that all this is purely mathematical speculation on my part - the only way to find out is to try it.
Quote from: GGBB on January 29, 2013, 02:04:29 PM
If it is the difference between the mistress range freq and the osc freq, then the noise should change as you adjust the range pot. Does this happen?
ABSOLUTELY! When running on either the charge pump OR with 12V regulated I get the "Tune in Tokyo" effect in flange mode. The noise changes with the rotation of the Range pot. The Color and Speed pots have their indicated effects as well (Color = Louder. Speed = Faster/Slower). Of course, when in Filter mode, the noise is "static" and constant depending on where the Range pot is set. There are a few "sweet spots" where I can get a good clean flange/filter signal but most of those appear to be lumped towards the middle of the Range pot rotation (from 10 o'clock to 2 o'clock)
What is killing me is that the noise I am hearing is WAY WORSE when using the charge pump circuit like I described above. When running on the 12V regulated, the noise subsides considerably!
Quote
It should be audible only at the low end of the control because once the range pot gets you up to 45k and higher, the difference freq goes above audible. At min, the range control is 35k (according to you), which produces 10k difference freq with the 25k osc freq. 10k is probably audible. To move difference frequencies outside the audible range, you need to separate the two frequencies by ideally more than 20k without having either frequency below 20k. Lowering the LT1054's 25k osc freq to 15-20k gets you close to this, probably close enough for a pedal. But I have to stress that all this is purely mathematical speculation on my part - the only way to find out is to try it.
I'll try some smallish caps (5pF to 22pF) between the pump's pin 7 to ground and see where that leads me. I also still want to try a TC1044SCPA in there and see what happens (with and without the boost)
Thanks for the replies everyone. More info to follow later ;)
Here is a link to another thread that I started that deals with the situation I am in right now. There is a short video in one of the posts that shows exactly what type of noise I am getting.
Posting a link to the other thread for more info and continuity.
http://www.diystompboxes.com/smfforum/index.php?topic=98903.0
Quote from: Govmnt_Lacky on January 29, 2013, 02:50:20 PM
I'll try some smallish caps (5pF to 22pF) between the pump's pin 7 to ground and see where that leads me. I also still want to try a TC1044SCPA in there and see what happens (with and without the boost)
If the small caps don't seem to do anything, try bigger (100pF - 470pF). I *think* the idea is to raise the built-in 150pF capacitance so that the cycle time increases (osc freq drops), but there's no guideline as to how much capacitance causes how much freq shift. I'm not even sure it's clear whether the pin 7 to ground cap is parallel or in series with the internal cap - my guess would be parallel.
Also - thinking way outside my level of knowledge now - could lowering the osc freq increase voltage ripple and therefore require higher filtering caps? Something to consider perhaps.
UPDATE--
I tried the TC1044SCPA in the circuit and it did not go very well. Constant hissing and static in the audio even with the Boost feature in use. I am guessing that the current limit of the TC1044 became a factor. Switched back to the LT1054.
Tried different values of caps (5pF to 27pF) between Pin 7 of the LT1054 to GND. This seemed to help quite a bit although not entirely. With the 27pF cap, the noise on the CCW end of the Range pot (highest frequencies) seemed to have dissipated however, there was still noise on the CW end of the pot travel which is where the lower clock frequencies reside. I was playing it safe and going with the recommended values in the datasheet so I did not have anything bigger to try.
Inserting caps between Pins 2 and 7 did not seem to help with the noise and in some cases made it worse.
The next step is to slowly move up, starting at about 33pF, and see if the noise on the CW end of the pot rotation will disappear ;D
More to follow.....
I took a listen to the noise issue that you are encountering in the link that you provided.
I have used LT1054s in quite a few builds with nothing even close to that occurring. I am well versed in the art of "not leaving any stone unturned" while troubleshooting a problem, but it is my humble opinion that you might be "barking up the wrong tree".
The "classic" charge pump whine that I've encountered is a constant frequency produced by the charge pump and dumped throughout the circuit it is feeding. I have never encountered being able to manipulate the frequency with any of the effects controls. The fact that you state that the problem persists even with a regulated 12 volt supply (albeit a lessoned problem) solidifies my reasoning.
If you haven't already, I would audio probe the circuit to see where the sound in question is entering the signal path.
Quote from: armdnrdy on January 30, 2013, 12:47:05 PM
I took a listen to the noise issue that you are encountering in the link that you provided.
I have used LT1054s in quite a few builds with nothing even close to that occurring. I am well versed in the art of "not leaving any stone unturned" while troubleshooting a problem, but it is my humble opinion that you might be "barking up the wrong tree".
The "classic" charge pump whine that I've encountered is a constant frequency produced by the charge pump and dumped throughout the circuit it is feeding. I have never encountered being able to manipulate the frequency with any of the effects controls. The fact that you state that the problem persists even with a regulated 12 volt supply (albeit a lessoned problem) solidifies my reasoning.
If you haven't already, I would audio probe the circuit to see where the sound in question is entering the signal path.
The sound in the video is exactly what I hear when I am using the charge pump circuit AND I rotate the Range knob. When I use the rectified 12V, the noise is still there however, it is much, much less pronounced. I don't doubt that the noise is possibly originating from a possible noisy BBD chip.... I am just saying that something with the charge pump circuit is causing it to be WORSE. I was able to filter out about 1/2 of the noise with the 27pF cap from LT1054 Pin 7 to GND. I think that the above statements about heterdyning may be correct in some fashion. I am going to try larger caps this evening to tell.
In the mean time, I do have some new BBDs (all be it from a Hong Kong source) on the way... hoping for an arrival today. I think between squashing the heterodyning issues, some better power filtering, and possibly better and quieter BBDs, this should be a fairly quiet and awesome circuit.
Fingers crossed and more to come!
PROGRESS REPORT:
I mocked up the original power supply section of the DEM. Schematic below:
http://www.metzgerralf.de/elekt/stomp/mistress/images/deluxe-electric-mistress-v4-schematic.gif
When I bypassed the onboard charge pump circuit and injected the power from the mocked up version I got ABSOLUTLEY NO NOISE AT ALL!! ;D
So, this tells me that the circuit is good. It also tells me that the Charge Pump circuit is what is creating all of the unwanted noise. >:(
Next, I am going to breadboard the pump circuit AWAY FROM THE PCB and inject the power from there to see if it is just a matter of keeping the pump away from the circuit pcb.
More to come later (when I order a new breadboard :icon_redface:)
Do you have an image of the layout that you're using for the DEM?
What values are you using for filter caps for the charge pump circuit? Do you have a layout image for that circuit?
Quote from: armdnrdy on February 01, 2013, 10:44:45 AM
Do you have an image of the layout that you're using for the DEM?
What values are you using for filter caps for the charge pump circuit? Do you have a layout image for that circuit?
I have a PCB layout but it is not mine. Basically, the intention is to work out the bugs and then share with the forum ;D
As for filter caps, I am using the generic values according to the voltage doubler circuit on the datasheet for the LT1054 Sheet 10.
Something just hit me though... after looking at the PT80 circuit on GGG, I noticed that they DO NOT ground Pin 5 of the MAX1044. Like the LT1054 positive doubler circuit in the datasheet, the MAX1044 says to ground this pin for positive voltage doubling however, the PT80 does not and it works quietly and just fine.
I wonder if removing Pin 5 of the LT1054 from this circuit will help :icon_idea:
Quote from: Govmnt_Lacky on February 01, 2013, 11:00:32 AM
I wonder if removing Pin 5 of the LT1054 from this circuit will help :icon_idea:
Huh. I've NEVER grounded pin 5. I didn't even notice until you said this that the datasheet has it grounded.
Quote from: midwayfair on February 01, 2013, 01:21:53 PM
Huh. I've NEVER grounded pin 5. I didn't even notice until you said this that the datasheet has it grounded.
Yeah... it kinda hit me to look at some other circuits that use charge pumps. I looked at the PT80 and noticed this. I also looked at Brian's Road Rage and he uses it for the negative voltage output but, if you do not hook it up it is essentially left floating.
Fingers crossed!! :-X
> a 9V to 12V charge pump
Charge-pumps are really, IMHO, best used "no"-load. Substrate bias, static CMOS, etc.
Yes they can power small chips.
But there are more serious approaches.
http://www.pololu.com/catalog/product/799
True, it's $12, but you've spent that much time already.
And it can approach 1 AMP out for 9V in 12V out, far beyond any $1 pump.
Tried the circuit with the LT1054 Pin 5 removed. STILL NOISY!! :icon_evil:
Next up.... breadboard the charge pump circuit and run it away from the flanger circuit and put the charge pump ground path in parallel to the flanger circuit ground path.
Im now thinking this is either a series shared ground issue OR it is a proximity issue with the flanger circuit being too close to the charge pump's oscillator.
More to follow....
Hey Gov, did you end up working out the solution? I've got a FL301 that has the same sound as in that video you mentioned. My FL301 did benefit from the low noise TC1044 but unfortunately, its still noisey. Might have to try some of the suggestions in this thread.
Paul
Quote from: chromesphere on March 09, 2013, 10:33:16 PM
Hey Gov, did you end up working out the solution? I've got a FL301 that has the same sound as in that video you mentioned. My FL301 did benefit from the low noise TC1044 but unfortunately, its still noisey. Might have to try some of the suggestions in this thread.
Paul
Sorry Paul but I was unable to get the noise to go away with any kind of pump circuit. My only solution was to incorporate a transformer or run the circuit from a wall wart and incorporate regulation within the circuit.
Thanks for the reply gov. Shame theres no way of getting the charge pump working :(
All the best
Paul
Quote from: chromesphere on March 11, 2013, 11:33:37 PM
Thanks for the reply gov. Shame theres no way of getting the charge pump working :(
All the best
Paul
If you figure it out without using about 10 or 15 filtering caps.... :icon_eek:
I'll be the first one to give you mad props! ;D
haha, i think it might be a bit beyond me, but i will definitely post here if i do work it out.
Paul
In an earlier reply I asked what size filter caps you were using. You replied "As for filter caps, I am using the generic values according to the voltage doubler circuit on the datasheet for the LT1054 Sheet 10"
I use BFC! The data sheet states small caps (cheaper, less board space = production friendly) but 99% of the time I would bet that the LT1054 or any other model of charge pump is not being used in an audio circuit.
I use 100 to 220µf filter caps. Think of it as a.....well...power supply!
For CIN across pins 1 & 4, I also use a larger cap than the specified 10µf.
If none of the above fixes the problem....I think it might be an issue with the "sewer ground" ( to quote R.G.) getting mixed in with the signal ground.
Quote from: armdnrdy on March 12, 2013, 12:56:09 AM
In an earlier reply I asked what size filter caps you were using. You replied "As for filter caps, I am using the generic values according to the voltage doubler circuit on the datasheet for the LT1054 Sheet 10"
I use BFC! The data sheet states small caps (cheaper, less board space = production friendly) but 99% of the time I would bet that the LT1054 or any other model of charge pump is not being used in an audio circuit.
I use 100 to 220µf filter caps. Think of it as a.....well...power supply!
For CIN across pins 1 & 4, I also use a larger cap than the specified 10µf.
If none of the above fixes the problem....I think it might be an issue with the "sewer ground" ( to quote R.G.) getting mixed in with the signal ground.
@Larry
I used 470uF from the 9V input to the LT1054 and I used 220uF for the Vout before the regulator. I DID NOT try altering the CIN cap though. Every voltage doubler config that I have seen has always used 10uF there :-\
As far as the "sewer ground" goes. I isolated the grounds from the charge pump portion of the circuit and ran them in parallel with the signal grounds to the DC jack. Still no change in the noise.
@chrome
If you find a way to get it to Shhhhhhhhhh. Please let us know! ;D
Quote from: PRR on February 01, 2013, 05:42:07 PM
> a 9V to 12V charge pump
Charge-pumps are really, IMHO, best used "no"-load. Substrate bias, static CMOS, etc.
Yes they can power small chips.
But there are more serious approaches.
http://www.pololu.com/catalog/product/799
True, it's $12, but you've spent that much time already.
And it can approach 1 AMP out for 9V in 12V out, far beyond any $1 pump.
This looks the bomb! For sure, you could DIY for a lot less than $12, right? Any idea what the schematic looks like?
~ Charlie
Quote from: moosapotamus on March 12, 2013, 12:02:33 PM
This looks the bomb! For sure, you could DIY for a lot less than $12, right? Any idea what the schematic looks like?
I agree Charlie however, after you invest the time and energy in gathering the materials and reversing the layout.... you are way past $12 into it.
This would be an outstanding idea for a Group buy however, it is not allowed here :'(
If you got 50 of them it would be down to $10/ea.
This power supply can be made with through hole parts for next to nothing! I believe that the DIP-8 converter IC is the MC33063. You can find these IC's for as little as .45 cents.
If you look at the components on the board in the link, you'll see that it looks very similar.
http://www.e-gizmo.com/KIT/NEGATIVE%20DC%20DC.html
I've had parts waiting in a box to breadboard a power supply based on the MC33063 for a Bi-Phase build.
Check out the data sheet for the MC33063, try to bread board a supply and see if it "plays nice" with your build.
Well, rather than reversing it, I was thinking that someone here might already have a pretty good idea of what's going on with it. At the same time, I might try reading up on switched-mode power supplies, myself, for fun.
~ Charlie
Quote from: armdnrdy on March 12, 2013, 12:41:04 PM
This power supply can be made with through hole parts for next to nothing!
... and, there we go. Thanks, Larry!
~ Charlie
Finally had some time to start following up on this...
I can confirm that the boost/regulator that PRR pointed to works!
http://www.pololu.com/catalog/product/799
Thanks, PRR!
IOW, it silences the "short wave radio like" noises that occur in the low freq range of the sweep in my MN3007 ADA flanger clone when powering it with a 9VDC wall wart and the onboard LT1054 voltage multiplier. I'll bet it would also do the trick to solve the similar noise issues that people have mentioned having with other flanger circuits, too.
This seems like a pretty slick little DC-DC converter circuit to me (but, then, I don't get out much). It's only a little bit bigger than the single-chip solutions that are available from Traco, Murata, etc... and it costs a lot less, and handles a lot more current! But it would still be nice to come up with a DIY solution for this.
I can't tell what converter chip is in the Pololu circuit. looks like a dip-10 smd package printed with the following...
4501
1120
G920
There also appears to be a diode with the following marking...
33
M17
Anyway, the MC33063 mentioned by armdnrdy does look like it would do the same thing, but I'm still trying to figure out how to adjust the output. :icon_redface:
LM2577 also looks like a good candidate. Need to do some more research... 8)
~ Charlie
Hey Charlie,
The MC33063 is kind of "old" technology. There have been many improvements based on this design. I don't have any part numbers offhand so you'll have to look around on the net.
The MC33063 being "old" technology has quite a bit of support available on the net including a design tool that allows you to calculate component values.
http://www.nomad.ee/micros/mc34063a/
I been busy with other projects and still haven't bread boarded the MC33063 bipolar supply. Will report results when I do.
Thanks for that link, Larry.
FWIW, I believe the Pololu circuit uses a SC4501 (available from DigiKey). Looks like another good option.
~ Charlie
Hey Charlie,
There are so many DC to DC converters! It just clouds the issue when trying to choose one for an application!
I took a look at the SC4501. It has a couple downsides for my use. It's not through hole, (not that I'm afraid of SMT) It's a step up converter, (I run a DC brick that has 18 volt and 9 volt outputs so I usually start at 18 and step down) and for bipolar purposes, I didn't see an inverter application in the data sheet.
That makes sense, Larry.
The application that I'm interested in is the same as Govmnt_Lacky and others - powering a modulation effect, like a flanger, that requires an internal voltage of 15V from a standard 9v pedal supply or wall wart. So step-up regulation is what I'm looking to do, for now. These DC-DC converters don't seem to have the noise problems that charge pumps like MAX1044 and LT1054 can sometimes have.
I've been looking at a few different DC-DC converters. Yes, there are a lot of them out there, and some are even more expensive than that Pololu PCBA. So I keep coming back to your original suggestion - MC33063. Seems to have the biggest bang for buck that I have found so far. I'll probably get a few to play around with. 8)
Thanks
~ Charlie