need help : Jean Hiraga 30W Super Class A build plan

[all4music]

hi friends,

i have been more of a lurker on this forum and i particularly like DIY section . i have been thinking of building a class a amplifier for long and finally i have decided to take a first step.

i do not understand the complete nitty-gritties of amplifier working yet. after some readup on net [this forum and diyaudio] i have understood few stuffs - though it is still a long way to go. couple of DIY Class a amp threads by experienced members have started off with final product display and some change later on. but this one going to be slow starter as i am trying understand and also procuring the required parts. so please bear with me! and also i would need lot of guidance and help

now about the amp - i have chosen Hiraga 30W Super Class A amp design as,

-i felt the schematics are comparatively simple
-availability of spares
-and relatively small size of the amp itself [i am planning to build it as a dual mono though - separate chassis]

queries!

for amplifier PCB, i am planning to order them from Jim's audio - only PCB and not the entire kit. [i have exchanged couple PMs with FMs Bibin and Sachin in this regard. both of them suggested LeMonstre [8W] version. but i want to try the 30W version.]


now out of the 2 PCBs listed on ebay.com which do you suggest?

this one fairly simple..
Stereo Amplifer PCB Hiraga Super 30W Class A | eBay





the one with Kubota rebulator [earlier i thought it is a physical device need to be procured separattely. later realised that the PCB has the circuit built in ]

Stereo Amplifer PCB Hiraga Super 30W Class A w Current Source Kubota Reg | eBay



in case of the first PCB, won't the bank of capacitors take care of filtering? my worry is about availability of parts and complexity of execution case of Kubota PCB.

o/p transistor:
2SC5200/2SA1493 pair or something else?

power supply:
one of the builds on diyaudio [sergiu's on diyaudio] uses 300VA 25 0 25 toroidal. i am planning to stick to the specified ratings [one for each channel]. any suggestions in this regard?

capacitor bank:
6X22000uF for each channel

please help me with you responses!

PS: i am planning to build a passive speaker later for this amp. for now i have an Aiwa passive stereo speakers [rated at 6ohms - that came with 30W pc Aiwa mini hifi] for testing.

 

[omishra]

First of all both are same and only extra differential error correction added into later one which has constant current source.

Complexity: Both are same
Parts: Available online - element 14 and RS components; diyaudiocart.com and many site. Explore DIY section here to buy components online.

Power supply: These need dual supply +/-24VDC. So you need at least 18-0-18 or (2x 18-0) 150VA transformer per channel (safe margin otherwise 100VA /ch will also do). If you are planning 2nd PCB then still requirement remains same.

See, 2SC5200/2SA1493 are still available and this pair has fakes too. You try to source originals.

capacitor bank is okay 6x22000 uF /channel but still these amplifier are notorious for hum due to PS ripple. So PS must be better, we tried capacitance multiplier with extra capacitors.

And finally not to rain your party - for 30W class A you need big (no bigger ) heatsink weighing atleast 4K per channel. That is my experience.

Don't forget to add speaker protection at the amplifier output

 

[all4music]

Power supply: These need dual supply +/-24VDC. So you need at least 18-0-18 or (2x 18-0) 150VA transformer per channel (safe margin otherwise 100VA /ch will also do). If you are planning 2nd PCB then still requirement remains same.

thanks for the suggestion. even the following link explains similar stuff []File Not Found . but i saw couple of examples where people were using 300VA toroidals -hence the numbers.

And finally not to rain your party - for 30W class A you need big (no bigger ) heatsink weighing atleast 4K per channel. That is my experience.

i know but 4kgs per channel! . one of the reasons i am planning for a dual mono build. enclosure would be planned only after procuring heat sinks! for now thinking of one of these UPS cabinets: Sheet Metal Cabinets, Inverter Cabinets, Inverter Trolleys, CFL Inverter Cabinets, UPS Cabinets, Online UPS Cabinets from India

this is gonna be a garage build not one of those slick looking amps!

Don't forget to add speaker protection at the amplifier output

i definitely have plans to add speaker protection/soft start. still figuring out what would fit where?

i will be procuring parts over the period of time so that i will have enough resources [time and money]

@Omishra do you have build thread for your Hiraga 30W over here!? i could find your find the F5 turbo build log though which has a mention about Hiraga amp.

 

[omishra]

There is Jean Hiraga Amp thread by other FM here in DIY section. I designed PCB for it and helped few members to build theirs. It isn't logged.

 

[hifiramr]

Hi my recommendation is not to build 30w hirage as it need huge heatsink and power supply which is very expensive also lot of heat.If you need class A I will suggest you a link
Ovation sx-Amplifier: A 15 W RMS class A Current Feedback Amplifier

this is based on Hirage also it is well documented and pcbs are avilable also you will have very good forum support.I have build his NX amps also traditional hiraga 15w class A that is enef to drive any speakers with ease.

Now its your decision.

 

[keith_correa]

Hi my recommendation is not to build 30w hirage as it need huge heatsink and power supply which is very expensive also lot of heat.If you need class A I will suggest you a link
Ovation sx-Amplifier: A 15 W RMS class A Current Feedback Amplifier

this is based on Hirage also it is well documented and pcbs are avilable also you will have very good forum support.I have build his NX amps also traditional hiraga 15w class A that is enef to drive any speakers with ease.

Now its your decision.

I agree. It's modern and probably will blow the Hiraga & JLH designs away - if one takes away the rose tinted bias [no pun intended] for the "old" designs, that is.

 

[hifiramr]

Actually he designed both sx and nx amplifier from both Hiraga & JLH designs. He adopted advantages of both old designs in his design.It have superb performance in class A .You will blow away with there sound.

 

[all4music]

@hifiramr
thanks for your informative post [and threads!]. are there any other simple class A amp designs that can output little higher. 30W is what i am targeting at .

@omishra
it would be of great if you can post pics of your amp internals. i haven't come across anybody who has built 30W Hiraga on hifivision - it would be of great help for me especially!
for the toroidals i am going with : 18-0-18 or (2x 18-0) 150VA per channel as you suggested!

@George : thanks for your guidance. as suggested BOM list coming up soon !

 

[hifiramr]

Why I said to you that is from my experience I dont know why you targeting 30w dont compare class A with AB class A is much more powerful than we expect.if you are keen to build 30w yes you can I have the jims audio assembled kit with me as i have tried at the beginning then dropped it.

In our forum I think there is no 30w hiraga build only 15w.You can check below link to to get an idea about it

Jean Hiraga's Super Class-A Amplifier

 

[all4music]

@hifiramr

thanks for the linky! that is the link where i started off with. later read couple of threads on diyaudio too [which includes Dan' build log too].

 

[diesel engine]

If you are a first timer with audio amps, my advice is to stay away from class A amps. sings a small bit better but cumbersome to build. need ridiculously big heatsinks and power trafos. try some simple class Bs first. anyway, Hiraga is a stable boy, once grown up. wish you happy DIYing!

 

[all4music]

all in good time. right now hibernating and tied up with some personal commitments.

spoke with couple of forum members. really felt happy with the warmth and information received thus far. it is going to be a slow build for sure.

 

[hifiramr]

all in good time. right now hibernating and tied up with some personal commitments.

spoke with couple of forum members. really felt happy with the warmth and information received thus far. it is going to be a slow build for sure.

Great I have decided to build NX amplifier after getting direction from experienced diyaudio forum members they have good result with this build.The build will take some time to complete cannot be completed in a hurry but really interesting project.

When you start let me know I have some parts with me so that you dont want to get it from outside

 

[all4music]

hi Ratheesh, i thought you have already built the NX or did you mean SX [class A] amp!?

PS: it was great speaking to you!

 

[turgid]

"for the toroidals i am going with : 18-0-18 or (2x 18-0) 150VA per channel as you suggested!"

Where are you gettin the torroids from? How much is it costing you and what is the order TAT?

Class A has at most 40-50% efficiency due to the duty cycle of the output FET but at the advantage of linearity of input signal. This means for every watt driving the load, there is likely more than a watt going to the amp itself. Prepare for monster Heatsinks!

 

[jls001]

Class A has at most 40-50% efficiency

50% theoretically, but more like 25% in practical implementations.

 

[hifiramr]

hi Ratheesh, i thought you have already built the NX or did you mean SX [class A] amp!?

PS: it was great speaking to you!

Hi all4music I have build NX amp the NX amp class AB 100w but the design is evolved from SX amp which is 15W class A.Both are similar SX is biased to class A.

 

[all4music]

@turgid :
-actual requirements as suggested on diyaudio is 400VA 25-0-25 [per channel]. planning to get it from Torotrans Pune
-Heatsinks 4kg per channel.

@Ratheesh got it. i am still fascinated about Hiraga [probably the lure of 30W!] . but gonna have to wait for some time till the vacation time gets over and i have some resources at my end [time and money!]. time for annual pilgrimage to Goa