30w Jean Hiraga Power Supply Design, one large capacitor or several?

Hi All

I've been trying to finish the amplifier project for a year now, one because of cash flow and the other because i became a father some 10months ago! This put the project at a major halt!

Since then i have been slowly buying parts and i am just about ready to get this thing built!

Im planning on building a dual mono amplifier in one massive chassis, so each channel has its own power supply

So far i have:

4 Full wave ultra fast rectifier boards to do dual bridge rectification for each channel.

2 Selectronic R core transformers 500va 2x24v (i dont know anything else about them except they are new and they were such a bargain) These things are big and weigh quite a bit!

I also invested in a pair of lundhal LL2733 chokes as i want to do a CLC power supply of some form.

Next on my list is the capacitors, which have come down in price since last year.

I know that around 1.2F is what is common i was thinking perhaps each channel can have 0.6F each or even 1F each if i want to go big.

It actually works out cheaper for me to buy one large capacitor like a 0.75F cap instead of 3 x 0.22F capacitors. Does this make a difference? I think i read somewhere that a group of capacitors has better ESR? please correct me here.

My thoughts were i could go first cap something like 0.1 or 0.2F capacitor then the 0.75F capacitor. Or 3 x 0.33F for each channel. Also should i go 35V or higher like 40-50V. At a guess with the rectifiers, choke and capacitors my rail voltage shouldn't exceed 35V.

I am so new to this, and this will be my first major power supply build. I have read many threads and looked at examples but thats as far as my knowledge goes.

I wish i knew how to calculate and design this sort of thing, i have know idea whether i need snubber capacitors, another resistor in place etc. Also not sure if i need a soft start, read and been told i may not because i'm using an R core and a choke.

Would i benefit from using a EMI filter? Also do i need a star ground?

Ive attached a drawing of my attempts to start designing the power supply, if someone could assist and guide me it would be greatly appreciated.

Just want to know the best route and design i need, so please pick it apart, curse me and correct me!

As i said i would love to understand what i am building and why, if there is anyone in north london that could help, sit down with me and teach me that would great, i would even pay for this service or buy you a really nice drink.

Clearly i am not making my life simple, but i thought i might as well go in large and hard or go home!

nCgQ1bB.jpg
 
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Hi,


very nice, I'll be following it! :)


Can you also provide parts list?


Cheers!


Sure Karl.


Hiraga super 30W class A w/ current source + kubota reg partial assembled kit ! | eBay

Pair of JIMS Audio Hiraga super 30W class A w/ current source + kubota reg boards

With 2% gain matched output transistors MJL4302A/MJL4281A

1 Pair of Lundhal lls733 chokes

http://www.lundahl.se/wp-content/uploads/datasheets/2733.pdf

1 Pair of Selectronic R core transformers

bEHmwXE.jpg


4 of these full wave rectifier boards: Do you think 30A is enough?

30A Class A Amplifier Power Supply Rectifier Filter Kits Schottky Rectifier DIY

30A Class A Amplifier Power Supply Rectifier Filter Kits Schottky Rectifier DIY | eBay

I liked the ease of the boards so i can always change the recitifiers to better ones, like Vishayy

http://www.vishay.com/docs/94022/vs-60epu04p.pdf

1 Massive Chassis!

Dimensions: 16.1*15.7*9.8in

Internal dimensions: 15.3*11.8*9.4in
QZ2CTzs.jpg


UJthwmQ.jpg


And other various parts such as speaker protection module, rca connectors, speaker posts, etc etc main thing is the power supply!
 
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Hi,

The schematics for the psu are not ok. Also if those psu trannies are indeed 24V secondary's you wil get something like 32-33 V rail voltages. This might be to much. If you keep the quiescent current at 1,5A dissipation would be something like 50W per output transistor.


I have not looked at the datasheets for the chokes. Will try to give you a schematic of a psu i Would do.


grtz

Joris
 
Hi,

The schematics for the psu are not ok. Also if those psu trannies are indeed 24V secondary's you wil get something like 32-33 V rail voltages. This might be to much. If you keep the quiescent current at 1,5A dissipation would be something like 50W per output transistor.


I have not looked at the datasheets for the chokes. Will try to give you a schematic of a psu i Would do.


grtz

Joris

I gathered they are not ok :confused: 50w would be awesome Joris! I got a massive chassis with big heatsinks so it should be fine. Ill just have to make do with whatever the rail voltage is.

I would very much appreciate a schematic of a psu you would do!

Thank you :)
 
50W dissipation per transistor might very well be outside the SOA of the transistor. In that case the transistors would fail. Not so awesome…. could take out your speakers as well. What transistor do you plan to use and what is the C/W rating of the heatsinks?
 
50W dissipation per transistor might very well be outside the SOA of the transistor. In that case the transistors would fail. Not so awesome…. could take out your speakers as well. What transistor do you plan to use and what is the C/W rating of the heatsinks?

I have these:

https://www.onsemi.com/pub/Collateral/MJL4281A-D.PDF

and i also have these:

http://www.onsemi.com/pub/Collateral/MJL21193-D.PDF

as for the C/W of the heatsinks, i cant tell you as i dont know!

New aluminum amp chassis /home audio amplifier case (size 16.1*15.7*9.8in) | eBay

all i know is this thing is heavy and very large!
 
Hi,

Had a closer look at your links. The transistors specified have much higher dissipation rating then the originals. Yet looking at the datasheet i expect dissipation will be to high. Even with that chassis. very nice one by the way.

Sorry to say but try and change those trannies to ones with 18V AC secondaries.

Joris
 
Hi,

Had a closer look at your links. The transistors specified have much higher dissipation rating then the originals. Yet looking at the datasheet i expect dissipation will be to high. Even with that chassis. very nice one by the way.

Sorry to say but try and change those trannies to ones with 18V AC secondaries.

Joris


Oh man, its so hard to find R core transformers and really expensive to get them made. Thing is if you look at this link:

Jean Hiraga's Super Class-A Amplifier

He has 35V rail voltage, think i have to take the risk and see how it goes, yes the chassis is really very nice, i was very happy with the quality and delivery! And its great value.
 
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Hi,

Ok well, it is not what i would do but go ahead. Don't see a way to use one choke per channel. Use the supply he is using. I'd suggest upping the resistor in het psu line to something like 1 ohm at least. sim it using psu designer to keep check of dissipation on that resistor. Don't go above 50% of it's rating i'd suggest.

grtz Joris
 
Hi,

Ok well, it is not what i would do but go ahead. Don't see a way to use one choke per channel. Use the supply he is using. I'd suggest upping the resistor in het psu line to something like 1 ohm at least. sim it using psu designer to keep check of dissipation on that resistor. Don't go above 50% of it's rating i'd suggest.

grtz Joris

Thanks Jazz, just playing with PSU designer and figuring it out.
 
Also sim a choke input power supply; the Lundahl choke can do choke input supply.
With an LCRC you might nicely hit the target DC voltage.
Choke input supplies have advantages and go well together with class A amps.

This is what i am hoping pieter! Although learning how to use the software is taking me a while, and as i said i am guessing how to put it together!
 
Hi,

lcrc like Pieter says looks more like the attached schematic. Sims out to something like 18V. Don't know what effect using the lundahls as common mode chokes would have though. Perhaps someone else can chime in there.
 

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