Yes,
And its a good idea. Nelson has suggested 2 feet away. Power supply 2 feet from amp. On the other hand I have heard, and so have you, plenty of amps with the power supply in the same enclosure and it can be done well and free of any power supply induced noise.
Proper grounding and maybe some ferrous dividers will help a lot.
Uriah
And its a good idea. Nelson has suggested 2 feet away. Power supply 2 feet from amp. On the other hand I have heard, and so have you, plenty of amps with the power supply in the same enclosure and it can be done well and free of any power supply induced noise.
Proper grounding and maybe some ferrous dividers will help a lot.
Uriah
I am trying to build the Aleph 30 version. Can I use a 400VA 2x18V transformer? Is that big enough?
I had the same question. Just bought the 400VA 18V from Antek.
Here is what a friend told me when I asked him about the toroid size and voltage:
As you can see, I am also using Brian's PS board with Peter Daniel's Aleph board. To estimate
the rail voltage to the circuit, here is what I did:
1. Let X be the voltage from the secondary of the toroid.
Then the voltage after the rectifier at the first set of caps will be X * 1.4 = V1
2. Adjust V1 according to the toroid's specs, i.e the input primary.
For example, the Antek 18VAc x 2 toroids has 115VAC primary. If you main is
at 120VAC all the time, then new X will be 120 / 115 * 18.
In other words, the voltage at the first set of caps will be at 120 / 115 8 18 * 1.4 = V2.
3. Remember Brian's PS board can be used as C or CRC. If you use a jumper in place of the
R, it is like one big C, then stop. V2 is your answer.
==. It is CRC. ==
4. Estimate the current drawn by the main circuit. According to the A30 service manual,
each rail draws 2.1A (don't trust my memory, check the manual), so total will be like 8.4A
5. Calculate the the resultant R, e.g. you // 4 x 0.47 per rail, then the R is 0.47/4.
6. Calculate the voltage drop by the R, Vdrop = the current from #4 * R.
7. Subtract the answer from #6 from V2. That will be be the voltage at each rail.
Caveat, I didn't take consideration of the toroid's regulation and cap's series resistance. So,
the actual voltage will be slightly less than #7. The little variation is not that important to the
sound, but for reliability, you want to use 35VDC caps, 25VDC can be to close to comfort.
For an A30 (or most of the NP amps for that matter), 300VA 18x2 secondary is minimum requirement
for the transformation. 2 most popular toroids are the Antek 18 x 2 400VA and the Piltron 18 x 2 300VA.
In terms of the R, I use 2 x 0.25 5W Dale for each rail. My calculation is as following:
2 in // resulted net 0.125R. I assumed that each rail would draw no more than 3A. Therefore,
the dissipation of the resistors will be 0.125 * 3 * 3 = 1.125W total. My resistors are good for
10W total. So, they are good. Why this value, because I have a close to 100 of these 🙂
In general, shoot for around 0.1R. The most important part is the resistor must be rated as least 2x
of the dissipation. 3X is even better for long term. Second is you don't want the R to drop too much
voltage.
Here is what a friend told me when I asked him about the toroid size and voltage:
As you can see, I am also using Brian's PS board with Peter Daniel's Aleph board. To estimate
the rail voltage to the circuit, here is what I did:
1. Let X be the voltage from the secondary of the toroid.
Then the voltage after the rectifier at the first set of caps will be X * 1.4 = V1
2. Adjust V1 according to the toroid's specs, i.e the input primary.
For example, the Antek 18VAc x 2 toroids has 115VAC primary. If you main is
at 120VAC all the time, then new X will be 120 / 115 * 18.
In other words, the voltage at the first set of caps will be at 120 / 115 8 18 * 1.4 = V2.
3. Remember Brian's PS board can be used as C or CRC. If you use a jumper in place of the
R, it is like one big C, then stop. V2 is your answer.
==. It is CRC. ==
4. Estimate the current drawn by the main circuit. According to the A30 service manual,
each rail draws 2.1A (don't trust my memory, check the manual), so total will be like 8.4A
5. Calculate the the resultant R, e.g. you // 4 x 0.47 per rail, then the R is 0.47/4.
6. Calculate the voltage drop by the R, Vdrop = the current from #4 * R.
7. Subtract the answer from #6 from V2. That will be be the voltage at each rail.
Caveat, I didn't take consideration of the toroid's regulation and cap's series resistance. So,
the actual voltage will be slightly less than #7. The little variation is not that important to the
sound, but for reliability, you want to use 35VDC caps, 25VDC can be to close to comfort.
For an A30 (or most of the NP amps for that matter), 300VA 18x2 secondary is minimum requirement
for the transformation. 2 most popular toroids are the Antek 18 x 2 400VA and the Piltron 18 x 2 300VA.
In terms of the R, I use 2 x 0.25 5W Dale for each rail. My calculation is as following:
2 in // resulted net 0.125R. I assumed that each rail would draw no more than 3A. Therefore,
the dissipation of the resistors will be 0.125 * 3 * 3 = 1.125W total. My resistors are good for
10W total. So, they are good. Why this value, because I have a close to 100 of these 🙂
In general, shoot for around 0.1R. The most important part is the resistor must be rated as least 2x
of the dissipation. 3X is even better for long term. Second is you don't want the R to drop too much
voltage.
mini-A Biasing
Hi,
I'm looking at my previous notes but don't remember what I did
I'm looking to build another mini-Aleph with Brian's Chipamp Aleph Boards.
Which resistors and values do I need to change for
a 4ohm load with about 15watts output power?
I think R12 that is TBD on the schematic is by default 47k.
I also changed the .47R to .33R I think.
I'll be using a 12V toroid to get the 15V rails.
thanks.
Hi,
I'm looking at my previous notes but don't remember what I did
I'm looking to build another mini-Aleph with Brian's Chipamp Aleph Boards.
Which resistors and values do I need to change for
a 4ohm load with about 15watts output power?
I think R12 that is TBD on the schematic is by default 47k.
I also changed the .47R to .33R I think.
I'll be using a 12V toroid to get the 15V rails.
thanks.
udailey said:
Thanks for the reply, I have the same transformer from Antek as well.
Can you please explain or point to me somewhere where I can find what C, CRC or CCRC means?
Thanks! 😎
if you are asking the basics, C is capacitor and R is resistor.
it's just a different combination of the stages depending
on what you want to use, Capacitor-Resistor-Capacitor,etc...
on the mini-A. R12 per Brian's BOM is 850R. I used 750R
in my previous build. what happens when you decrease
this value?
thanks.
Thanks, but sorry for being such a newb. What's the advantage of having resistors in between capacitors when it comes to power supplies? Thanks again.
I asked the same question not too long ago 😀
helps to reduce noise.
I use Brian's aleph psu boards. it works great, makes things easier to assemble. His has the rectifiers onboard and CCRC arrangement. If you use those boards, just remember two of the resistors are bleeders.
helps to reduce noise.
I use Brian's aleph psu boards. it works great, makes things easier to assemble. His has the rectifiers onboard and CCRC arrangement. If you use those boards, just remember two of the resistors are bleeders.
I have to say I have hardly seen boards as superb as the power supply boards and Mini A boards from BrianGT. Absolutely fantastic quality and the price is rock bottom. $9 per PSU board and these things are large and in charge and then another 9 for the amp board. Really cheap, really good, really fair.
Uriah
Uriah
I built one channel of the aleph 30 configuration and it worked for about a minute and then one of the 3watt 0.47 resistor hooked up to the output transistor fried. I ordered the transistors from digikey and didn't do the matching, is it possible that's the reason? Thanks.
I cant say as I have any clue and am just asking this out of curiosity. Did you use the BrianGT boards, make your own boards, use P2P, etc?
Uriah
Uriah
Checked the FET that has the blown 0.47R to see whether it is still good. It sounded like this FET was passing all the current.
pchw said:
Thanks Fred, the FET was blown...
But now, I got another problem, the FET's on one side are not getting any current at all. One side of FET's are running nice and warm, the other side of FET's are cold. I am trying to check the soldering.
The mis-matched FET's shouldn't cause a melt down providing the part that failed wasn't faulty.
One fet board is a current source, the other is for the output devices, and all connections between the two are routed via the main board. For a start check continuity on all your wiring from the main board to the fet boards is ok - I suffered a major failure on one of my Aleph30's due to a broken gnd connection to the main board so it can be something as simple as that! Also check that there are no shorts to the chassis especially on the FET boards.
If wiring is ok then move on to checking the components on the main board starting with sections around Q5, Q7 and Q4, Q6. You can see from the schematic that the FET boards are an integral part of these circuit blocks, so this is where I would focus my investigations for now.
cheers
Paul
One fet board is a current source, the other is for the output devices, and all connections between the two are routed via the main board. For a start check continuity on all your wiring from the main board to the fet boards is ok - I suffered a major failure on one of my Aleph30's due to a broken gnd connection to the main board so it can be something as simple as that! Also check that there are no shorts to the chassis especially on the FET boards.
If wiring is ok then move on to checking the components on the main board starting with sections around Q5, Q7 and Q4, Q6. You can see from the schematic that the FET boards are an integral part of these circuit blocks, so this is where I would focus my investigations for now.
cheers
Paul
Thanks for all your help, it was one of the rectifier connection. I resoldered it and I have music for one channel! Sounds good so far.. I am happily soldering the other channel now. 😀
By the way, how important is the matching FET's having an effect on sound? Should I order a set of matching ones if I really want the most out of this amplifier?
By the way, how important is the matching FET's having an effect on sound? Should I order a set of matching ones if I really want the most out of this amplifier?
It's alive! Great sound and fantastic bass for my Druids MK4's. I am going to order some matching FET's to see if it can even sound better. Thanks for all your help guys!
I'm ready to fire up my MiniA... yes a long time ago I've begun this project.
Now I'm a little bit confused before trying it in "real" conditions.
My PSU is tested Ok, fuses ready too, Amp PCB checked, MosFets are using Kerafol Keratherm Red Isolators.
How do I proceed, I've got some questions :
Do I need a load at the output ?
What are the usual measures to be done ?
Thanks for your advices and help 😉
Now I'm a little bit confused before trying it in "real" conditions.
My PSU is tested Ok, fuses ready too, Amp PCB checked, MosFets are using Kerafol Keratherm Red Isolators.
How do I proceed, I've got some questions :
Do I need a load at the output ?
What are the usual measures to be done ?
Thanks for your advices and help 😉
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