[badmojo]

Hey Guys,
 
I recently bought a JDS Labs CmoyBB for my sister and she loves it. She's a IT Professional and spends most of her time at the computer. Since she does not need portabilit, I have been searching for a power supply for her Cmoy. After many hours spent it looks like I will have to build the power supply because sourcing one with a reasonable price seems impossible.
 
Big thanks to Tangentsoft, his website has proved to be an invaluable resource in this undertaking. I have spent several hours reading through his articles/guides and that has, well, given me courage to try this.
 
As he mentioned the LM7824 to be a good choice for this purpose, I have been looking for a schematic simple enough for me to execute with high chance of success, and I have settled on this: http://www.circuitdiagram.org/24v-dc-power-supply-using-lm7824.html

To save time and money I plan on only building the regulating circuit, stick it into an enclosure, and put it between this: http://www.lelong.com.my/24v-1a-switching-power-supply-adapter-100-240v-ipstore-F41244-2007-01-Sale-I.htm and the Cmoy. (that power supply listing is RM20 which is less than 6 USD) (I reside in Malaysia, therefore the 220v UK plug).
 
One of the important requirements Tangent talks about when it comes to power supplies is "Isolation". However I'm not clear how to incorporate that into the circuit. What changes should I make to ensure Isolation?
 
Right now this project is completely in the planning stage, and as such, I am fully open to Suggestions and Recommendations. It would also be really helpful to get circuit ideas from those of you who have built a linear regulated power supply for a Cmoy or similar amp and has had good results.
 
Looking forward to hearing from you guys.
Isaac

 

[MisterX]

The LM7824 has a dropout voltage of 2 volts.
You need at least 26 volts in to get regulated 24 volts out.
And then there is the isolation thing to deal with.
 
I would replace the switch mode PSU with an AC to AC adapter, build the LM7824 circuit as drawn in the example schematic and call it a day.
 
AMB offers a circuit board if you wish to go that route.
 
http://www.amb.org/audio/sigma25/

 

[Ocean7]

Why get a cheap and noisy switching power supply and then regulate it with the LM7824?

Build the whole power supply straight yourself. Get this and a small toroidal transformer and put the whole thing in a nice enclosure. Done.

If you want to be more into DIY the same eBay seller also sells the bare PCB but it will cost you more in the end and maybe will not look as nice (I got a bunch of those modules and they are really well made).

 

[badmojo]

  The LM7824 has a dropout voltage of 2 volts.
You need at least 26 volts in to get regulated 24 volts out.
And then there is the isolation thing to deal with.
 
I would replace the switch mode PSU with an AC to AC adapter, build the LM7824 circuit as drawn in the example schematic and call it a day.
 
AMB offers a circuit board if you wish to go that route.
 
http://www.amb.org/audio/sigma25/

Wow, that AMB is a great link/resource! Thanks for that. Given that they have a circuit board, I think that's the route I'm gonna go, to keep things simple.
Still trying to wrap my head around transformer ratings. The one I plan on using is the EKK 12V-0-12V-36VA (http://connectronics.com.my/index.php?route=product/product&path=89_163&product_id=1935)
I picked it after looking through the calculation method provided by AMB, the only problem being I cant seem to find the max draw of the CmoyBB 18v. Is it overkill? Should I get the EKK 12V-0-12V-25VA instead?

 

[badmojo]

Why get a cheap and noisy switching power supply and then regulate it with the LM7824?

Build the whole power supply straight yourself. Get this and a small toroidal transformer and put the whole thing in a nice enclosure. Done.

If you want to be more into DIY the same eBay seller also sells the bare PCB but it will cost you more in the end and maybe will not look as nice (I got a bunch of those modules and they are really well made).

fantastic! less work for me. that's perfect, plus its cheap. About using a "Toroidal Transformer", is there a noticeable advantage where the CmoyBB is concerned? because its a little out of my budget. Thanks for this link, best part is the free shipping.

 

[tomb]

Why not just buy a ready-made linear-regulated power supply?
 
http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_174861_-1
 
I've used these for PIMETAs, Millett Hybrids, Mini3's, etc.  In my experience, the measured ripple is much better than spec'd - on the order of tenths of milliVolts or less.  For $14.95, you'd have to DIY AMB's Sigma power supply to get much better performance.
 
There's no building, no transformers or line-voltage to worry about killing yourself, etc.

 

[badmojo]

  Why not just buy a ready-made linear-regulated power supply?
 
http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_174861_-1
 
I've used these for PIMETAs, Millett Hybrids, Mini3's, etc.  In my experience, the measured ripple is much better than spec'd - on the order of tenths of milliVolts or less.  For $14.95, you'd have to DIY AMB's Sigma power supply to get much better performance.
 
There's no building, no transformers or line-voltage to worry about killing yourself, etc.

well something like this would be ideal, however i cant seem to find one with 220v and also i'm having trouble believing its actually linear regulated. as tangent wrote "linear regulated power supplies cost more and require extra parts, so a manufacturer is quick to point out if it is" that jameco datasheet also does not show any regulation inside.

 

[tomb]

 

  Why not just buy a ready-made linear-regulated power supply?
 
http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_174861_-1
 
I've used these for PIMETAs, Millett Hybrids, Mini3's, etc.  In my experience, the measured ripple is much better than spec'd - on the order of tenths of milliVolts or less.  For $14.95, you'd have to DIY AMB's Sigma power supply to get much better performance.
 
There's no building, no transformers or line-voltage to worry about killing yourself, etc.

well something like this would be ideal, however i cant seem to find one with 220v and also i'm having trouble believing its actually linear regulated. as tangent wrote "linear regulated power supplies cost more and require extra parts, so a manufacturer is quick to point out if it is" that jameco datasheet also does not show any regulation inside.

No offense, but if you were the least bit knowledgeable about this stuff, it's as plain as day in the spec sheet.  Heck, the LM7812 is pictured and listed on pages 4 & 5.
 
I have no vested interest in persuading you, though - you do what you want to do.

 

[badmojo]

  No offense, but if you were the least bit knowledgeable about this stuff, it's as plain as day in the spec sheet.  Heck, the LM7812 is pictured and listed on pages 4 & 5.
 
I have no vested interest in persuading you, though - you do what you want to do.

you are right, i am totally new to all this. i should have taken a closer look, the entire data sheet looks like egyptian hieroglyphics to me which is why i missed it. thanks for pointing this out. it would be a good solution and its cheap. even with the shipping it would be a good deal, unfortunately i cant find a 220v version on their site. if you do come across one somewhere else i would be grateful.
thank you.

 

[tomb]

Well, there's this:
http://www.jameco.com/webapp/wcs/stores/servlet/CategoryDisplay?langId=-1&storeId=10001&catalogId=10001&categoryId=458540
 
Or this:
http://www.ebay.com/itm/50W-Watts-Voltage-Step-Down-Foreign-Travel-Converter-Converts-220V-to-110V-/321600898790?pt=LH_DefaultDomain_0&hash=item4ae0e846e6
 
There are many more.  However, I would still strongly recommend the first one from Jameco.  I have had very bad experience with the little ones like the link from ebay.  The Jameco one is not really that expensive, either - many of the little ones are $15 anyway.  You'll pay half that at many places just for the cord on the Jameco one.  Of course, you would still need the linear-regulated walwart, but these would give you something to plug into at 220V.

 

[badmojo]

  Well, there's this:
http://www.jameco.com/webapp/wcs/stores/servlet/CategoryDisplay?langId=-1&storeId=10001&catalogId=10001&categoryId=458540
 
Or this:
http://www.ebay.com/itm/50W-Watts-Voltage-Step-Down-Foreign-Travel-Converter-Converts-220V-to-110V-/321600898790?pt=LH_DefaultDomain_0&hash=item4ae0e846e6
 
There are many more.  However, I would still strongly recommend the first one from Jameco.  I have had very bad experience with the little ones like the link from ebay.  The Jameco one is not really that expensive, either - many of the little ones are $15 anyway.  You'll pay half that at many places just for the cord on the Jameco one.  Of course, you would still need the linear-regulated walwart, but these would give you something to plug into at 220V.

thanks for this suggestion, however i'm leaning towards the idea from Ocean7. Still thank you.

 

[tomb]

 

  Well, there's this:
http://www.jameco.com/webapp/wcs/stores/servlet/CategoryDisplay?langId=-1&storeId=10001&catalogId=10001&categoryId=458540
 
Or this:
http://www.ebay.com/itm/50W-Watts-Voltage-Step-Down-Foreign-Travel-Converter-Converts-220V-to-110V-/321600898790?pt=LH_DefaultDomain_0&hash=item4ae0e846e6
 
There are many more.  However, I would still strongly recommend the first one from Jameco.  I have had very bad experience with the little ones like the link from ebay.  The Jameco one is not really that expensive, either - many of the little ones are $15 anyway.  You'll pay half that at many places just for the cord on the Jameco one.  Of course, you would still need the linear-regulated walwart, but these would give you something to plug into at 220V.

thanks for this suggestion, however i'm leaning towards the idea from Ocean7. Still thank you.

You're welcome.  Just don't get killed or start a fire messing with the 220V wiring required for your toroid.

 
EDIT: I've been into DIY headphone electronics since 2006 and messing with transformers and line voltage wiring still scares the heck out of me.  I just don't do it, period.  It's one reason I talked Dsavitsk of ECP Audio into designing Beezar's Torpedo.  The transformers are all PCB mounted, so no power wiring to fool with.  Even then, I'm very careful powering one up after I've built it until I'm certain there are no shorts to the case. 

 

 

[badmojo]

 
You're welcome.  Just don't get killed or start a fire messing with the 220V wiring required for your toroid.

 
EDIT: I've been into DIY headphone electronics since 2006 and messing with transformers and line voltage wiring still scares the heck out of me.  I just don't do it, period.  It's one reason I talked Dsavitsk of ECP Audio into designing Beezar's Torpedo.  The transformers are all PCB mounted, so no power wiring to fool with.  Even then, I'm very careful powering one up after I've built it until I'm certain there are no shorts to the case. 

 

Wow, I Google'd the Beezar Torpedo, thats a nice looking kit. Thanks everyone for all the input, I'll let you'all know how it goes.

 

[badmojo]

Hi MisterX
 
Looking at the table on the sigma25 page it says a "Desired Voltage of 24VDC requires a Transformer secondary voltage of 24VAC" does this mean I can get away with using a this 24v transformer? http://connectronics.com.my/index.php?route=product/product&path=89_163&product_id=1934 because the next higher voltage transformer available is 30v which I'm guessing is gonna make the regulator quite toasty.
 
What do You think?
 
Thanks
Isaac

 

[badmojo]

  The LM7824 has a dropout voltage of 2 volts.
You need at least 26 volts in to get regulated 24 volts out.
And then there is the isolation thing to deal with.
 
I would replace the switch mode PSU with an AC to AC adapter, build the LM7824 circuit as drawn in the example schematic and call it a day.
 
AMB offers a circuit board if you wish to go that route.
 
http://www.amb.org/audio/sigma25/

Hi MisterX
 
Looking at the table on the sigma25 page it says a "Desired Voltage of 24VDC requires a Transformer secondary voltage of 24VAC" does this mean I can get away with using a this 24v transformer? http://connectronics.com.my/index.php?route=product/product&path=89_163&product_id=1934 because the next higher voltage transformer available is 30v which I'm guessing is gonna make the regulator quite toasty.
 
What do You think?
 
Thanks
Isaac