Hello to all. I am a long time lurker and I finally decided to take the plunge into making a class A speaker amp, the Mini Aleph in particular.
I am a noob. I have trouble building from a schematic and I have no background in electronics other than the experience gained from building projects. I have built numerous AMB kits such as Mini3's, M3's Gamma2's and Sigma11 power supplies. The hallmark of Ti's projects are his excellent documentation and personal support.
I would like to go through the Mini Aleph build, sort through the various questions and lay down a solid, updated BOM and document the process so that subsequent builders like myself can get into the world of class A amplifiers.
I've already been in touch with jleaman and he has been very gracious. His enthusiasm is contagious. He was nice enough to dig through his archives and dig up a BOM for the power supply. I would like to edit the BOM to include only the parts for the Mini Aleph in order to keep the scope limited to this type of build. Also some of the parts seem to be deprecated or unavailable, so updated part numbers are needed.
I have no idea what CRC is. Basically, I need someone to tell me what part numbers to stick in where to make a power supply to run a Mini Aleph. Once the details and BOM are hashed out and updated and posted here then pretty much anyone who wants to build one has a good shot at making a Mini Aleph power supply.
Of course, the Mini Aleph BOM is next. One thing at a time.
I am a noob. I have trouble building from a schematic and I have no background in electronics other than the experience gained from building projects. I have built numerous AMB kits such as Mini3's, M3's Gamma2's and Sigma11 power supplies. The hallmark of Ti's projects are his excellent documentation and personal support.
I would like to go through the Mini Aleph build, sort through the various questions and lay down a solid, updated BOM and document the process so that subsequent builders like myself can get into the world of class A amplifiers.
I've already been in touch with jleaman and he has been very gracious. His enthusiasm is contagious. He was nice enough to dig through his archives and dig up a BOM for the power supply. I would like to edit the BOM to include only the parts for the Mini Aleph in order to keep the scope limited to this type of build. Also some of the parts seem to be deprecated or unavailable, so updated part numbers are needed.
I have no idea what CRC is. Basically, I need someone to tell me what part numbers to stick in where to make a power supply to run a Mini Aleph. Once the details and BOM are hashed out and updated and posted here then pretty much anyone who wants to build one has a good shot at making a Mini Aleph power supply.
Of course, the Mini Aleph BOM is next. One thing at a time.
There's no single BOM that is the "right one". You can use a lot of different rectifier diodes for instance. Most of them will work... Some prefer slow rectifier diodes, others prefer ultrafast rectifier diodes. Which one do you choose and why? Also bear in mind that some parts are difficult to find in other parts of the world. Many of us will have to make a few changes to the BOM.
The PSU BOM is a good starting point though. But feel free to make some changes as you see fit. For those not very knowledgeable, read the mini-Aleph threads first then ask your question.
A CRC PSU is used to attenuate mains hum.
Oh, and congrats on your choice, the mini Aleph is great amp!
The PSU BOM is a good starting point though. But feel free to make some changes as you see fit. For those not very knowledgeable, read the mini-Aleph threads first then ask your question.
A CRC PSU is used to attenuate mains hum.
Oh, and congrats on your choice, the mini Aleph is great amp!
Last edited:
We could list part numbers for instance, from Mouser, Digikey, and Farnell. I suppose options and footnotes are inevitable but as long as they are organized on the BOM/build instructions instead of scattered over 1000 pages of forum threads it will facilitate successful builds with a minimum of hassles for everybody and end repetitive noob questions.
Good documentation will only be a good thing. I can't see any downside to it.
The part number for the heatsinks has changed to HS351-ND at Digikey.
The diodes MUR2020CT-ND are not available at Digikey. I did read someone using MUR860's Digikey part number MUR860GOS-ND
Are those diodes a good all around choice?
Jack I'm with you on this thing. I totally agree. However it might not be easy to reach an agreement with regard to parts to be used. We all have our preferences.
Better use taller heatsinks than these 1" tall ones... I used 1.5" tall ones and now wish I would have used 2". Class A amps run hot.
Pick your parts with that in mind.MUR860's would work, MUR820's too. I used HFA08TB60's, could have used RHRP1560's too. I'm prettty sure someone can suggest another twenty TO220 diodes that would work too.
Jack I'm with you on this thing. I totally agree. However it might not be easy to reach an agreement with regard to parts to be used. We all have our preferences.
I understand. Getting engineer types to agree on minutia is difficult. My intention however, is not perfection, rather, a BOM somebody can use with currently available parts they can use with confidence so that if they order these parts and stick the power supply together that it will work. The original threads and the BOM appear to be from circa 2005...5 years ago.
Better use taller heatsinks than these 1" tall ones... I used 1.5" tall ones and now wish I would have used 2". Class A amps run hot.
Excellent tip. Digikey part number HS132-ND
Here's an excellent example. The parts you used are not available at Digikey or Mouser. The second one you mentioned has 3 leads...confusing to me as a noob because there's only 2 holes. The 860 and 820's are both available (and only have 2 leads
)MUR860's Mouser part number : 863-MUR860G
MUR860's Digikey part number : MUR860GOS-ND
jleaman suggested this transformer:
15Vx2 300VA Toroidal Transformer DIY HiFi Power Amp Kit - eBay (item 370271247500 end time Apr-04-10 20:20:05 PDT)
Antek AN-3215
I guess I should make it clear I intend to build a standard Mini Aleph using the IRFP240's mounted to a plate heatsink.
I take it you're referring to the PSU PCB that's available @ chipamp.com? If so then yes.
Bleeder resistors are a safety measure, they drain off the charge after switching off. The PSU will work without these installed, just bear in mind that when you're gonna do some maintenance the capacitors still hold a charge.
The other resistors form a first order RC filter with the final PSU cap. Example: With a 1 ohm resistor and a 10000uF cap in C3 you get a cut-off frequency of 15.92 Hz using this formula: 1 / (2*Pi*R*C)
The five resistors you can place are in parallel, choose a combined value for R, then calculate which values you have to place in parallel to get your value for R. You will want to use four or five 3Watt resistors in parallel so they share the load. Mount these resistors at least 0.25" off the board, they will get hot.
I am using R = 0.47,, 5 in parallel and 15000 aps
1 / (2 * pi * 0.094 * 15 000) = 0.000112875846
is that right?!?!
-joe
Thanks Beftus, you're helping me a lot. I don't understand what "my" R value is or should be. What is a good all around set up here with these resistors that's going to produce acceptable power supply results?
So I am assuming that if we fill the resistor slots then this line from the original BOM is not necessary:
2, none, short circuit jumper, R3,R4, for the standard CRC configuration, no R is needed
As far as the LED I used this calculator
Calculate Resistors for LEDs
to get @500 ohms PPC499XCT-ND (Digikey) for a 604-WP7104GD (Mouser)
Do those values look like it will make an indicator light and not a flashlight?
No. Capacitance is in Farads, so 15000uF = 0.015F
Equation becomes: 1 / (2*Pi* 0.094 * 0.015) = 112.88 Hz
The value of R in the CRC setup should be chosen with the value of C to give the cut-off frequency you want. Choose your frequency low, 30-40Hz.
Suppose you want a cut-off frequency of ~20Hz. With a 10000uF final cap you're looking at a value for R of about 0.825 ohm (4x 3.3 ohm). Make sure the resistors can handle the heat! Chosing a larger final cap results in a lower value for R meaning less heat to dissipate. Try to divide the load accross multiple resistors, five 3Watt resistors in parallel can dissipate a total of 15Watts.
That's right.
Some people prefer a very bright LED, some don't. And with all those different LED colours it's hard to give a single advice regarding LEDs. Mine has a blue LED with a 22K resistor. It's blue but not very bright.
The board seems to offer the flexibility to do all kinds of different setups. I am only interested in running 2 standard mini alephs off it.
Yes I'm using 10,000uF caps and I want to use 5 3 Watt resistors to dissipate heat and have a low cut off frequency. What is the value of the 5 resistors?
Last but not least the C1-C2 capacitors. What are they for and what type/value do I need there?
wow, so my cut off is too high then..
the mini-a bom says to use jumpers.. i figure jumpers would make the above equation approach infinity (i assume jumper = 0 ohm)
-joe
Pick your preferred cut off frequency and do the math yourself. Not because I don't want to help you but because it will make you understand the underlying principle.
Additional decoupling caps, a low value film cap would do, say 0.1uF.
With jumpers you don't have a low-pass filter and no attenuation of mains related hum.
I pulled up the list of available resistors in the pretty, baby blue line of Panasonic 3 w metal film resistors and picked the one in the middle.
How about 4.7 ohms 4.7 / 5 = .94
2 * 3.1415 * .94 * .01 = .0590
Seems like a nice number but it means absolutely nothing to me. Is this an acceptable resistor to use in R3-R12?
Also could I use the same resistors in R1-R2 to simplify things?
How about 4.7 ohms 4.7 / 5 = .94
2 * 3.1415 * .94 * .01 = .0590
Seems like a nice number but it means absolutely nothing to me. Is this an acceptable resistor to use in R3-R12?
Also could I use the same resistors in R1-R2 to simplify things?
Stop. Learn some basics first. Read a lot of relevant stuff on the forum first. Try to grasp what it means. Building an amp is more than connect the dots. Ignorance and electricity are a deadly combination.
Banned
Joined 2002
Cut-off Freq ?
Hello everyone. I to am thinking of possibly building a Mini-A. Though still having alot to learn, how does the psu cut-off frequency effect the amplifier please explain ? I plan on using the wonderful pcb's form chipamp.com and the power supply board is set-up for CRCC I think !
Hello everyone. I to am thinking of possibly building a Mini-A. Though still having alot to learn, how does the psu cut-off frequency effect the amplifier please explain ? I plan on using the wonderful pcb's form chipamp.com and the power supply board is set-up for CRCC I think !
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.