Jean Hiraga Super Class A 30w Build

[SanjeevM]

Not a Hiraga, but Nelson Pass did a JLH using FETs. He first looked at it with BJTs, and shows distortion measurements. Link.

Apparently, Papa was quite pleased !!

 

[vishalk]

Lock down - Time to finally finish this amplifier

I do hope you all keeping well and in good health especially with everything that is happening surrounding the covid 19 pandemic.

Here in the UK we are on lockdown for the safety of everyone, this has given me the chance to actually have time to finish this overdue Hiraga Build.

So to all my Hiraga building brothers here is the progress so far!

 

[vishalk]

PSU almost finished! Once everything is bolted to the chassis i can start neatly wiring it all.

 

[vishalk]

Making this wiring neat and tidy! All about neatness and it looking the part.

 

[vishalk]

Worth the time and effort to get it looking like this.

 

[gary s]

Nice build so far - one point, if it was me I would be putting insulation over the copper braids from the PSU caps to the chokes.

Also, what output transistors are you using, and what is the total capacitance per +/- DC rail?

Keep up the good work.

 

[vishalk]

Thanks Gary, it's only copper sleeving and I was planning to use Clear heat shrink over it. Just forms part of the look I'm going for.

0.66F per channel 28.6v (voltage have to recheck once built)




Output transistors are 2% gain matched output transistors MJL4302A/MJL4281A.

 

[gary s]

Yes, clear heat shrink will finish it off nicely.

I assume when you say 0.66F per channel (660,000uF) - you mean that is 0.33F per rail for a channel total of 0.66F. That is one mean mono PSU and I seem to recollect that it reflects the original Hiraga design.

Were you able to buy gain matched output transistors, or did you buy a heap of them and test them yourself? Looks like you are using 4 in parallel per channel for each +/- rail.

Can you post the schematics of the amp and psu as you are building it, thanks.

 

[vishalk]

Yes sorry 0.33f per rail for Channel total of 0.66F.

Output transistors were bought from Jim's Audio who matched them.

 

[gary s]

Thanks for the info, appreciate it.

 

[Mark Tillotson]

View attachment 830975

Making this wiring neat and tidy! All about neatness and it looking the part.

Unsupported high current wiring can move due to magnetic fields, you'll want to

brace and/or insulate these braided straps for safety I think, they could deflect a little on each turn-on surge.

 

[vishalk]

Thanks Mark, its actually insulated solid copper wire with copper braided sleeving, it's not going anywhere, I'll also be putting clear shrink on it, that should stiffen it more.

 

[vishalk]

Getting there!

 

[novemberrain11]

agree with 2 * 3k6 since 1.8k will be very hot ><"

 

[Bigun]

Vish, your build is giving me envious thoughts, really well done!

my 2c, capacitors like it cool, but if I am understanding it right, you have them inside an ‘oven’ so can you create some air flow up through the bottom panel and out the top ?

 

[ralf]

Noise with Hiraga 30W

Dear,

i finshed my Hiraga 30W
switched-on and connected to a speaker it is dead quiet.
DC Offset is about zero

when i connect it to a JFET BOZ i have noise, some hum and higher frequencies, some buzz.
I tried with different Preamps- same result.

When i connect the same setup with same JFET BOZ to my Hiraga Le Monstre all works perfect without
any noise

some idea?

best

 

[ralf]

Dear,

i finshed my Hiraga 30W
switched-on and connected to a speaker it is dead quiet.
DC Offset is about zero

when i connect it to a JFET BOZ i have noise, some hum and higher frequencies, some buzz.
I tried with different Preamps- same result.

When i connect the same setup with same JFET BOZ to my Hiraga Le Monstre all works perfect without
any noise

some idea?

solved myself - it was the mains earth, connected to Gound of PSU

best

 

[vishalk]

Great stuff and well done for sorting it out, let's see some pictures please.

 

[ralf]

Anything to change for driving 12 Ohm speaker

Dear,

what should be changed, when 12ohm speaker is driven on Hiraga 30W?
increasing 0,33ohm resistors slightly?

best

 

[vishalk]

Finally Finished!

Guys it took me a while but it was worth the wait.

May I present my finished Amplifier for those who have patiently followed this thread!

What a journey this was I am so pleased with how this came out!