Thanks for this video. I bought one of these, making SURE I got the one with dual-polarity since I needed a bit over 800v. first used just the positive polarity like you did, and could get about 415vdc out. After using this a wild the positive capacitor exploded. After looking for the cause of failure, I noticed that the output capacitors were only at 400v (Chinese 400v rated) each. I could also blow the negative voltage capacitor at slightly over 400v and blow it also. Now, I have ordered a couple more, and before I use them, I replace both 400v 10uf capacitors with 450v 10uF caps, and no more trouble! It seems things are pushed to the absolute limit in this design. One thing to be very careful of is to get the 10mm diameter diameter version of the 450v capacitors, NOT the 12.5mm diameter caps, or they will NOT squeeze into the top of the board. Use care in removing the original caps as they don't come out so easily. I connected my load to the + and - outputs (with the - output used as ground would be) and had no problems quickly charging a 120uF capacitor (load) to 850v. Any comments on if this is OK to do with skipping the ground connection of the output HV?
Befor i use that 2 capasitor version and it work i mean it can can release out 390v but i buy a new one 3 capasitor with v- and i dont know it cant release the output what's the difference?
i want to use this converter to boost dc voltage for doing ground electrical resistivity surveys. Can I go directly from the dc-dc booster out put to my ground probes, or will I need something additional?
@@CraigHollabaughThanks for writing back. Not sure what you mean, but I want to induce a 300v DC current into the ground. Here is a description of the method. I have been doing the Wenner method but with limited voltage. I got the booster to get more volts to get better resolution and depth. wiki.seg.org/wiki/Electric_resistivity_methods
@@davefield8100 OK, I understand both Wenner and Schlumberger now, thanks for the link. I can't really say if this PS will work due all the variables involved. It is inexpensive, you might as well try it, be careful with the high voltage output.
I played with one of these a few years ago to power the B+ on a vintage stereo preamp (Acrosound S1001); @ 250V or so. I can't recall the current draw; maybe 30mA. The downside was that I could hear the boost converter operation. Not the 75kHz obviously, but the pulses to 'fill" the boost circuit: 2-10Hz spikes. "Tick...tick...tick..". in my speakers. Tried to filter with 1000 uF, but it didn't make that much difference. Very hard to filter at that low frequency.
No problem! When I first found these I was pretty enthusiastic, to make a tube preamplifier run off 12v. Still searching for a good audio grade HV SMPS.
Did you try loading the PS with a load that's much greater than tube bias currents? Something like 250 milliamps or so, what do you would happen to the low frequency ticks?
Have you tried it in a small tube amp, yet? I would like to use it to supply the 285V voltage for the tubes in a preamp (30 mA). Do you think it can be done? (If I add a 400V 50 uF capacitor to filter out the ripple) The other supply you mentioned is no longer available
Craig Hollabaugh oh okay. I have the same boost converter and I cant seem to get 300v to run through capacitors to coil and SCR to ground terminal. Do I need to send a wire from my 12v dc supply to high voltage side ground?
Craig Hollabaugh I’m new to building circuits and I built this circuit I found on UA-cam and it pulses but in my case it won’t dump voltage through coil for some reason. www.ritalie.com/store/images/Bob_Beck_Magnetic_Pulser_Circuit.jpg
Yes, but it might be noisy. Caution, voltages above 50V are lethal. Be careful and read about tube amp safety. robrobinette.com/Tube_Amp_Safety.htm www.aikenamps.com/index.php/safety-tips-for-working-on-tube-amplifiers valveheaven.com/2015/01/safety-considerations-for-valve-amp-building/
Just about to play with one of these. So, good to see what to expect first, and a likely failure point. Thanks, I won't run it at 100mA! Also, the MOSFET probably needs better cooling when running at 30W, but how does lack of cooling explain the diode failure? (BTW: 3000R/Ohms not 3000K)
Thanks for watching and writing. Yes, that 3000K was a clearly wrong, I should have corrected this during editing. Good catch and keeping me honest! Good luck with yours.
The problem with these modules is not the transistor -it doesn't get hot, the heatsink is plenty big enough. It's the transformer that gets hot when you push it above 30W! I also blew a schottky diode like you did (I swapped in the one from the negative side), so these also seem to be a failure point. Not sure why since they're US3M diodes, 1000V 3A rated, so maybe they're grey market knock offs?
could be very well a counterfeid part....these cheapo stuff usually using Cgrade components throughout....i xray´d a claimed nippon chemicon the other day....there was a smaller cap inside and when i opened it it as a "Woo Huang Loo" type rated 85degreeC 47µ/350Volts type inside, while on the outer claimed NC cap it was reading: 47/400 at 105degreeC...so watch out guys... couterfeit stuff is here...
did you watch this guy: ua-cam.com/video/QYCEcFFO5Do/v-deo.html ;) but he measured both outputs and the negative one put out a little more voltage. My guess is that when the negative voltage output is not used but populated and you run that thing at full swing, it end up bowing out the unused side, as it may producing some nasty spikes as it loaded unequally, as i doubt they checking for overvoltage and or do a regulation on both output voltages.
Hmm, I don't think that theory holds. I blew the used diode, as did Craig. There shouldn't be any spikes on the secondary side since they will be clamped by transformer action (if one leg of the transformer secondary tried to swing an abnormally large voltage then it will be reflected across to the other leg, forward biasing the corresponding diode and so clamping it.) I still think these are just bum diodes.
It is not a jumper that you pull out and move. If you look VERY closely you will see the two ranges printed on the back of the board. There is a single SMD ZERO ohm resistor (just a shorting block, I think) that you can, with a soldering iron, move from one location to the other.
I have not actually. The comments below mention issues with its use. I will eventually use it or something similar for some small amps I'm thinking about. Thanks for writing and for watching.
How are you getting such a stable output? I have a couple of these and experimenting with them, I can't get stable output like you have? I'm using a stable bench power supply like you, but i also checked it with other supplies. I'm not loading the output as much as you, due to lack of power resistors (i'm using 10k). But the output voltage is swinging around, maybe 2v and i see input current changing slightly too. I'm only looking for between 100vdc and 250vdc for a tube tester project, but it does need to be stable!
ive bought this to power a preamp i guess id stick with 120v then RC RC RC to get 10ma to the plates. I do however have to power the heaters at 6.3v 0.3a x 2 using a voltage divider coming off from the 12v dc supply. hope i dont blow it up im a total newb and this would be my first project thats not just modding
hello are these safe to use with guitar amp ? cause normally stepup xfr are not isolated do we have to use it with isolated transformer ? for safety thanks
Thank you! I am looking to build a couple single ended practice amps at under 5 watts...I will give this a try! I think I will go with Rob Robinette’s Micro Champ (1W). Or a squirrel monkey. (2w) first. That is a huge savings over a power transformer! (If it is reliable)
I'd use a different HV power supply, here's one I considered for tube amps, K04-UP300 385V@0.8A www.aliexpress.com/item/32888650918.html. I have 2 of these and they have very little ripple. Thanks for watching, stay safe.
I can't try this yet since my house flooded and most of my bench was destroyed, but I would really like to know if you can connect ONLY the + and - output (two wires, no ground) and get double the output power that you get with just the + and ground. Have you tried this yet? I can easily charge a 120uF capacitor (load) to 850v like this, but this is hardly a sustained load. I think the resistor load would make a better test. If you are going to try this, please reply to me. THANKS FOR THE SUPER-HELPFUL VIDEO!!!
Dale, Thanks for the watching. You're working with such high voltage that I can't help you. You should find a local experienced electrical engineer to help with your design to keep your circuit, your environment and you safe from electrical shock.
@@CraigHollabaugh bro wtf do u mean u cant help U LITERALLY HAVE THE THING just probe the 2 terminals, u literally could have done such simple action in the video too but anyways, the voltage double but not the power, the transistor as well as transformer dont suddenly and magically become able to handle more than what they are rated for
Don't know how, but I blew up 2 of these in my little 6V6 amp. Input voltage 12 Volt, output voltage 250V and 20mA load!?!? Maybe bad QC?? Number 3 is now in the amp and waiting to blow out. lol
I powered this with adapter 12vdc - 4A And the output was stable and It worked so great for a few days, a week later the third capacitor blew up, i measured the output voltage it goes up to 600v!!! Why?! And since the datasheet say it has an output overvoltage protection i was really surprised!!
These modules are not isolated! But I wonder why should it be isolated??? You are feeding it with a 12 volt power adapter and the adapter is your isolation. They have common ground just as the secondary of a normal tube amp power supply. These modules are great for low wattage tube amp HV supply. I use it in a little se 6V6 amp and it works perfect. Remember to use the common 54 or 47 micro/450V elco's in the HV resistor chain. Otherwise you get terrible HF noise!
Frans, thanks for the comment. You may also want to put a smaller cap, ~0.1u, in parallel with your 47u or 56u HV caps because electrolytic caps aren't too capacitive at high switching frequencies. Do you happen to know the switching frequency? 100kHz or higher?
For what I found around 70kHz switching freq. Great idea for the 0,1 uF caps. Maybe it prevent unwanted oscillation, I will use them in addition. The amp is now dead quiet with the filter caps. kind regards Frans
Btw I feed the 6V6 filament with an 1A 7805 with two series diodes on the earth leg, so 6,2 Volt is the voltage. Simple and very lightweight power supply.
I've used this board in tests and prototypes, but I'll be using it for a final build for the first time very soon. Concerned about it being overloaded, I came up with the following mod to get the full power it can deliver, at +390v : www.wattkins.com/files/wattkins/B+%20Board%20MOD.png 1) Remove and re-install negative side's diode backwards; 2) Remove negative side's capacitor (you can re-install it backwards if you want, but it's not necessary); 3) Add jumper connecting both diode's cathode terminals; This way you will be using the whole transformer's secoundary winding instead of half! I'll be using it for about 300v B+ on a push-pull amplifier.
Hi, it doesn't work the way you hope because of the flyback converter topology. During the transistor on time energy is stored in the core of the transformer, when the transistor is turned off the core flux collapses and energy is induced into the secondary winding.The voltage at the secondary will only be available if the diode polarity and the secondary winding phase is right. These voltage boosters will induce the positive and negative voltage in the secondary relative to the centre tap AT THE SAME TIME! So turning the diode round won't be useful.
What do you use these for. The reason I ask is I am baffled that thses kinda crappy units exist and a MUCH better design is a no brainer. As a retired design engineer I am thinking of doing just that and see if it sells on eBay, but I do not want to waste my time for even such a simple item. So please give me some ideas. Also the high noise output is easy to fix as well byt using a different topology (the board uses FlyBack topology, which is VERY noise).
Agree, there's one aspect about the noise, I've seen the switching frequency as low as 8k. You're not filtering this out. I've also seen 100k up to 1M units but you're right, these are crappy little HV supplies that people are using for something. Most of them use unlabeled boost controllers, I did a little reverse and determined the old IC their using, been so long I can't remember which one (probably a National part). It will hard to touch the price of these even if you get PCB made in China.
@@CraigHollabaugh for such a lift in voltage, simple booster is out of the question. Any topology using a transformer with suitable coil ratio is needed, so a simple push pull topology, commonly used in the boost stage of main AC Inverters would do the trick. I have seen s similar unit, but with only a couple of fixed voltages (essentially a copy of the Inverter boost stage using a SG3525 controller. To make it variable would require a hybrid push pull forward topology. Common and easy to do, but more parts needed so I guess that is why they do not do it.
Thanks for this video. I bought one of these, making SURE I got the one with dual-polarity since I needed a bit over 800v. first used just the positive polarity like you did, and could get about 415vdc out. After using this a wild the positive capacitor exploded. After looking for the cause of failure, I noticed that the output capacitors were only at 400v (Chinese 400v rated) each. I could also blow the negative voltage capacitor at slightly over 400v and blow it also. Now, I have ordered a couple more, and before I use them, I replace both 400v 10uf capacitors with 450v 10uF caps, and no more trouble! It seems things are pushed to the absolute limit in this design. One thing to be very careful of is to get the 10mm diameter diameter version of the 450v capacitors, NOT the 12.5mm diameter caps, or they will NOT squeeze into the top of the board. Use care in removing the original caps as they don't come out so easily.
I connected my load to the + and - outputs (with the - output used as ground would be) and had no problems quickly charging a 120uF capacitor (load) to 850v. Any comments on if this is OK to do with skipping the ground connection of the output HV?
Is it okay if I just want to get 100v from a LiPo battery 11.1v? Or should I change the capacitors too?
Befor i use that 2 capasitor version and it work i mean it can can release out 390v but i buy a new one 3 capasitor with v- and i dont know it cant release the output what's the difference?
How does this product change the input voltage from 8-16v to 16v-32v?
it's called a boost converter. en.wikipedia.org/wiki/Boost_converter
i want to use this converter to boost dc voltage for doing ground electrical resistivity surveys. Can I go directly from the dc-dc booster out put to my ground probes, or will I need something additional?
What's your estimate on resistivity?
@@CraigHollabaughThanks for writing back. Not sure what you mean, but I want to induce a 300v DC current into the ground. Here is a description of the method. I have been doing the Wenner method but with limited voltage. I got the booster to get more volts to get better resolution and depth. wiki.seg.org/wiki/Electric_resistivity_methods
@@davefield8100 OK, I understand both Wenner and Schlumberger now, thanks for the link. I can't really say if this PS will work due all the variables involved. It is inexpensive, you might as well try it, be careful with the high voltage output.
can these devices be connected in series and parallel to get higher voltage and current?
Series, definitely no, it's not an isolated power supply. Parallel maybe, I'd just find something that meets the requirements.
I played with one of these a few years ago to power the B+ on a vintage stereo preamp (Acrosound S1001); @ 250V or so. I can't recall the current draw; maybe 30mA. The downside was that I could hear the boost converter operation. Not the 75kHz obviously, but the pulses to 'fill" the boost circuit: 2-10Hz spikes. "Tick...tick...tick..". in my speakers. Tried to filter with 1000 uF, but it didn't make that much difference. Very hard to filter at that low frequency.
Well, that's interesting. Thanks for the info.
No problem! When I first found these I was pretty enthusiastic, to make a tube preamplifier run off 12v. Still searching for a good audio grade HV SMPS.
Did you try loading the PS with a load that's much greater than tube bias currents? Something like 250 milliamps or so, what do you would happen to the low frequency ticks?
No, I did not. I would gather the "ticks" would get more frequent with heavier loading.
Have you tried it in a small tube amp, yet? I would like to use it to supply the 285V voltage for the tubes in a preamp (30 mA). Do you think it can be done? (If I add a 400V 50 uF capacitor to filter out the ripple) The other supply you mentioned is no longer available
I have not tried to use these inexpensive boost power supplies. Seems like it should work through. Thanks for watching.
Are the ground terminals on input and output wired together in your video?
Yes, it is non-isolated.
Craig Hollabaugh oh okay. I have the same boost converter and I cant seem to get 300v to run through capacitors to coil and SCR to ground terminal. Do I need to send a wire from my 12v dc supply to high voltage side ground?
Craig Hollabaugh I’m new to building circuits and I built this circuit I found on UA-cam and it pulses but in my case it won’t dump voltage through coil for some reason. www.ritalie.com/store/images/Bob_Beck_Magnetic_Pulser_Circuit.jpg
@@corybrown5583 be safe.
@@corybrown5583 I can't/won't offer assistance with high voltage questions. Sorry. You'll need to find someone local with experience to help you.
I just want to use one as a flash cap chargrr. hope it wont pop on me
Hi,great work! can I use this for two 12AX7 tubes for a pedal?
Yes, but it might be noisy. Caution, voltages above 50V are lethal. Be careful and read about tube amp safety.
robrobinette.com/Tube_Amp_Safety.htm
www.aikenamps.com/index.php/safety-tips-for-working-on-tube-amplifiers
valveheaven.com/2015/01/safety-considerations-for-valve-amp-building/
Just about to play with one of these. So, good to see what to expect first, and a likely failure point.
Thanks, I won't run it at 100mA!
Also, the MOSFET probably needs better cooling when running at 30W, but how does lack of cooling explain the diode failure?
(BTW: 3000R/Ohms not 3000K)
Thanks for watching and writing. Yes, that 3000K was a clearly wrong, I should have corrected this during editing. Good catch and keeping me honest! Good luck with yours.
What is the value of the potentiometer on the pcb?
Vijay joshi I'm traveling for a couple days, will check next week.
...looks like 50K
The problem with these modules is not the transistor -it doesn't get hot, the heatsink is plenty big enough. It's the transformer that gets hot when you push it above 30W!
I also blew a schottky diode like you did (I swapped in the one from the negative side), so these also seem to be a failure point. Not sure why since they're US3M diodes, 1000V 3A rated, so maybe they're grey market knock offs?
I bet your correct on the US3M diodes being grey.
could be very well a counterfeid part....these cheapo stuff usually using Cgrade components throughout....i xray´d a claimed nippon chemicon the other day....there was a smaller cap inside and when i opened it it as a "Woo Huang Loo" type rated 85degreeC 47µ/350Volts type inside, while on the outer claimed NC cap it was reading: 47/400 at 105degreeC...so watch out guys... couterfeit stuff is here...
did you watch this guy: ua-cam.com/video/QYCEcFFO5Do/v-deo.html ;) but he measured both outputs and the negative one put out a little more voltage.
My guess is that when the negative voltage output is not used but populated and you run that thing at full swing, it end up bowing out the unused side, as it may producing some nasty spikes as it loaded unequally, as i doubt they checking for overvoltage and or do a regulation on both output voltages.
oh for sure there are counterfit parts. 1000V part replaced by 300V clone, no problem, right?
Hmm, I don't think that theory holds. I blew the used diode, as did Craig. There shouldn't be any spikes on the secondary side since they will be clamped by transformer action (if one leg of the transformer secondary tried to swing an abnormally large voltage then it will be reflected across to the other leg, forward biasing the corresponding diode and so clamping it.) I still think these are just bum diodes.
Thanks for this video.
can this converter be used to test the leakage current of capacitors
bro its literally a power supply wtf do u mean
It says to run from 8v there's a jumper on the back of the circuit board but damned if I can see one. Default is 10v.
It is not a jumper that you pull out and move. If you look VERY closely you will see the two ranges printed on the back of the board. There is a single SMD ZERO ohm resistor (just a shorting block, I think) that you can, with a soldering iron, move from one location to the other.
@@dalenassar9152 thanks i will look. Oh great! You are right! Top man. Ebay sellers could never tell me anything!
Hi, thank you for the review. Have you used it in a tube amplifier? If so could you share what did you do with the output noise?
I have not actually. The comments below mention issues with its use. I will eventually use it or something similar for some small amps I'm thinking about. Thanks for writing and for watching.
How are you getting such a stable output? I have a couple of these and experimenting with them, I can't get stable output like you have? I'm using a stable bench power supply like you, but i also checked it with other supplies. I'm not loading the output as much as you, due to lack of power resistors (i'm using 10k). But the output voltage is swinging around, maybe 2v and i see input current changing slightly too. I'm only looking for between 100vdc and 250vdc for a tube tester project, but it does need to be stable!
You have to load it.
ive bought this to power a preamp i guess id stick with 120v then RC RC RC to get 10ma to the plates. I do however have to power the heaters at 6.3v 0.3a x 2 using a voltage divider coming off from the 12v dc supply. hope i dont blow it up im a total newb and this would be my first project thats not just modding
I'm thinking about doing exactly that as well. How did it go for you?
Nice review, btw where did you get that PCB holder?
hello are these safe to use with guitar amp ? cause normally stepup xfr are not isolated
do we have to use it with isolated transformer ? for safety thanks
these are not isolated
Thank you! I am looking to build a couple single ended practice amps at under 5 watts...I will give this a try! I think I will go with Rob Robinette’s Micro Champ (1W). Or a squirrel monkey. (2w) first. That is a huge savings over a power transformer! (If it is reliable)
I'd use a different HV power supply, here's one I considered for tube amps, K04-UP300 385V@0.8A www.aliexpress.com/item/32888650918.html. I have 2 of these and they have very little ripple. Thanks for watching, stay safe.
I can't try this yet since my house flooded and most of my bench was destroyed, but I would really like to know if you can connect ONLY the + and - output (two wires, no ground) and get double the output power that you get with just the + and ground. Have you tried this yet? I can easily charge a 120uF capacitor (load) to 850v like this, but this is hardly a sustained load. I think the resistor load would make a better test. If you are going to try this, please reply to me. THANKS FOR THE SUPER-HELPFUL VIDEO!!!
Dale, Thanks for the watching. You're working with such high voltage that I can't help you. You should find a local experienced electrical engineer to help with your design to keep your circuit, your environment and you safe from electrical shock.
@@CraigHollabaugh bro wtf do u mean u cant help
U LITERALLY HAVE THE THING
just probe the 2 terminals, u literally could have done such simple action in the video too
but anyways, the voltage double but not the power, the transistor as well as transformer dont suddenly and magically become able to handle more than what they are rated for
It says to let it run low fir 5 min before you crank it up and if you had a fan on it it probably won’t break
bro wtf is this
an engine?
Don't know how, but I blew up 2 of these in my little 6V6 amp. Input voltage 12 Volt, output voltage 250V and 20mA load!?!? Maybe bad QC?? Number 3 is now in the amp and waiting to blow out. lol
great! just great. is the switching mosfet shorted?
Have to look at it, still tweaking with the amp.
Mikrowave1 is using one of these to supply 200 Volts to a WW2 vacuum tube radio.
See his youtube "930s TX - DC-DC Converter - Part 2" at 8 minutes.
good to know, thanks.
I powered this with adapter 12vdc - 4A
And the output was stable and It worked so great for a few days, a week later the third capacitor blew up, i measured the output voltage it goes up to 600v!!!
Why?! And since the datasheet say it has an output overvoltage protection i was really surprised!!
These modules are not isolated! But I wonder why should it be isolated??? You are feeding it with a 12 volt power adapter and the adapter is your isolation. They have common ground just as the secondary of a normal tube amp power supply. These modules are great for low wattage tube amp HV supply. I use it in a little se 6V6 amp and it works perfect. Remember to use the common 54 or 47 micro/450V elco's in the HV resistor chain. Otherwise you get terrible HF noise!
Frans, thanks for the comment. You may also want to put a smaller cap, ~0.1u, in parallel with your 47u or 56u HV caps because electrolytic caps aren't too capacitive at high switching frequencies. Do you happen to know the switching frequency? 100kHz or higher?
For what I found around 70kHz switching freq. Great idea for the 0,1 uF caps. Maybe it prevent unwanted oscillation, I will use them in addition. The amp is now dead quiet with the filter caps. kind regards Frans
Btw I feed the 6V6 filament with an 1A 7805 with two series diodes on the earth leg, so 6,2 Volt is the voltage. Simple and very lightweight power supply.
Read more electrolytic frequency response here, en.wikipedia.org/wiki/Electrolytic_capacitor#Impedance
nice work.
I've used this board in tests and prototypes, but I'll be using it for a final build for the first time very soon.
Concerned about it being overloaded, I came up with the following mod to get the full power it can deliver, at +390v :
www.wattkins.com/files/wattkins/B+%20Board%20MOD.png
1) Remove and re-install negative side's diode backwards;
2) Remove negative side's capacitor (you can re-install it backwards if you want, but it's not necessary);
3) Add jumper connecting both diode's cathode terminals;
This way you will be using the whole transformer's secoundary winding instead of half!
I'll be using it for about 300v B+ on a push-pull amplifier.
Hi, it doesn't work the way you hope because of the flyback converter topology. During the transistor on time energy is stored in the core of the transformer, when the transistor is turned off the core flux collapses and energy is induced into the secondary winding.The voltage at the secondary will only be available if the diode polarity and the secondary winding phase is right.
These voltage boosters will induce the positive and negative voltage in the secondary relative to the centre tap AT THE SAME TIME! So turning the diode round won't be useful.
What do you use these for. The reason I ask is I am baffled that thses kinda crappy units exist and a MUCH better design is a no brainer. As a retired design engineer I am thinking of doing just that and see if it sells on eBay, but I do not want to waste my time for even such a simple item. So please give me some ideas. Also the high noise output is easy to fix as well byt using a different topology (the board uses FlyBack topology, which is VERY noise).
Agree, there's one aspect about the noise, I've seen the switching frequency as low as 8k. You're not filtering this out. I've also seen 100k up to 1M units but you're right, these are crappy little HV supplies that people are using for something. Most of them use unlabeled boost controllers, I did a little reverse and determined the old IC their using, been so long I can't remember which one (probably a National part). It will hard to touch the price of these even if you get PCB made in China.
@@CraigHollabaugh for such a lift in voltage, simple booster is out of the question. Any topology using a transformer with suitable coil ratio is needed, so a simple push pull topology, commonly used in the boost stage of main AC Inverters would do the trick. I have seen s similar unit, but with only a couple of fixed voltages (essentially a copy of the Inverter boost stage using a SG3525 controller. To make it variable would require a hybrid push pull forward topology. Common and easy to do, but more parts needed so I guess that is why they do not do it.