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Author Topic: JLH classic class A amp  (Read 3169 times)

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Offline efren_

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JLH classic class A amp
« on: Aug 23, 2009 at 11:51 AM »
Hi to all,

this is my first post here as this site was recomended by a friend, glad to know that there is a pinoy version of audio forum, I have built several version of JLH amp (1969 orig, 1969 dual rails & 1986 with ccs), I have also built the hiraga 20w, i have an unfinnished 8w le monster due to part thats not available or maybe very rare nowadays; but what stays with me is the JLH 1969 dual rails, warm almost tube like, very fine texture, very detailed and open, no distortion/clipping even at full volume. The limitation in my set up (i guess) is my ONKYO D-032AX thats not that sensitive. Looking forward to have a LOWTHER or FOSTEX as these speakers has a reputation of being sensitive (105dB/W?!) and as i heard from audiophile community is an excellent match for tube and class a amps. Any second opinion is highly appreciated.

Best regards to the admin of this site  ;)
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Offline ojofool

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Re: JLH classic class A amp
« Reply #1 on: Aug 23, 2009 at 12:02 PM »
Hi to all,

this is my first post here as this site was recomended by a friend, glad to know that there is a pinoy version of audio forum, I have built several version of JLH amp (1969 orig, 1969 dual rails & 1986 with ccs), I have also built the hiraga 20w, i have an unfinnished 8w le monster due to part thats not available or maybe very rare nowadays; but what stays with me is the JLH 1969 dual rails, warm almost tube like, very fine texture, very detailed and open, no distortion/clipping even at full volume. The limitation in my set up (i guess) is my ONKYO D-032AX thats not that sensitive. Looking forward to have a LOWFER or FOSTEX as these speakers has a reputation of being sensitive (105dB/W?!) and as i heard from audiophile community is an excellent match for tube and class a amps. Any second opinion is highly appreciated.

Best regards to the admin of this site  ;)

welcome to pinoydvd sir efren noble! refreshing to have a "newbie" member who's a diyr.

yes, lowther and fostex are efficient drivers, excellent match for lowpowered amps. from time to time you can also find vintage highsensitive speakers at the marketplace.

cheers!

Offline efren_

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Re: JLH classic class A amp
« Reply #2 on: Aug 24, 2009 at 07:05 PM »
I recommend class A amplification to those looking for a straightforward amp, not really high powered (10W+/ch.) is more than enough in an averaged sized room. I have used branded commercial amps before with processors and all that "blingblings", but when i heard a JLH class A, i know this was i have been looking for, I heard tube amps before and IMHO more or less, or perhaps marginal performance, very subjective indeed. i dont worry about the bass as i am using sub to compensate for it. I know many will agree with me that primary factors are drivers, room area, materials & workmanship, as JLH is a DIY amp. One thing though, you got to have good ventillation, as all makes of class A are massive heat generators, we are in a tropical country and it is best used during rainy and cold season ;D. Cramped up room? Forget it unless you enjoy listening to tchaikovsky's swan lake or 1917overture or listening to your favorite heavy metal while in a spa, sweating it all out! :D I have read and heard other constructors comments foreign and local, all but a favorable comment.

   
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Offline JojoD818

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Re: JLH classic class A amp
« Reply #3 on: Aug 24, 2009 at 08:32 PM »
Hi Efren,

You didn't mention in your PM that you already started a thread, anyway, welcome to PinoyDVD sir.

Since you are into Class A amps, why not give Nelson Pass's First Watt a try too, these uses Mosfets while the JLH used BJTs. Mosfets are known to be the more "tubey" of the sand devices and you can even exploit their gate properties to "force" a warmer overall sonic character.

Or if you want to go extreme, something that lights up but still turns your room into a spa, then build yourself a tube amp.  :)



Warm Regards,

Jojo

Offline efren_

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Re: JLH classic class A amp
« Reply #4 on: Aug 24, 2009 at 10:15 PM »
Sir Jojo,

I am not against mosfets, but since i have  to toss 2 ch of Le Monster in a box because i cant find 2sj74, i feel a bit colder about them.  :(. I used other values with similar specs (2n54..) but my gain clone ta8216h sounds far more better. ;). But perhaps one of these days, when i want the smell of solder, i think i'll try R. elliots single ended mosfet amp running @ 40vdc /Iq of 2.5 Amps :o



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Offline JojoD818

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Re: JLH classic class A amp
« Reply #5 on: Aug 26, 2009 at 10:11 PM »
you need to host your pics in websites like tinypic or photobucket before po ninyo pwede i-post. not sure lang sir about the newbie thing, baka nga lang may restrictions po... :)

Offline JojoD818

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Re: JLH classic class A amp
« Reply #6 on: Aug 27, 2009 at 11:12 AM »
thanx sir jojo, sa Facebook ko nalang tuloy na- post. :)


create an account na lang sir at tinypic or photobucket, it's easy and free. then upload there and copy/paste the img here. that's it po sir.  :)

Offline efren_

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Re: JLH classic class A amp
« Reply #7 on: Aug 27, 2009 at 11:15 AM »

create an account na lang sir at tinypic or photobucket, it's easy and free. then upload there and copy/paste the img here. that's it po sir.  :)

okz sir, i'll give it a shot ;D
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Offline efren_

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Re: JLH classic class A amp
« Reply #8 on: Sep 07, 2009 at 09:09 PM »

<a href="http://s646.photobucket.com/albums/uu184/efrennoble/?action=view&current=Image082.jpg" target="_blank"><img src="http://i646.photobucket.com/albums/uu184/efrennoble/Image082.jpg" border="0" alt="JLH"></a>

during test period, the new psu under construction., the old one get so hot you cant touch the core, under rated. new one has a lot of headroom @ 24 amps +/- 20VDC.
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Offline ATJr.

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Re: JLH classic class A amp
« Reply #9 on: Sep 08, 2009 at 08:49 AM »
hi,
welcome to the forums.....
my first encounter with the jlh topology was with locally assembled "Avegon" transistorised radios running on flashlight batteries....as i recall they really sounded wery good...i used to put it on top of a half filled "banga" and the bass came out even stronger, ;D

they used germanium type transistors.....that whas around 1968.... ;D

classA amps are superior to the other classes in terms of distortion, but many stay away becuase of the heat generated....

perhaps, we should have a DIY section here, yes?
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Offline efren_

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Re: JLH classic class A amp
« Reply #10 on: Sep 08, 2009 at 09:06 AM »
hi,
welcome to the forums.....
my first encounter with the jlh topology was with locally assembled "Avegon" transistorised radios running on flashlight batteries....as i recall they really sounded wery good...i used to put it on top of a half filled "banga" and the bass came out even stronger, ;D

they used germanium type transistors.....that whas around 1968.... ;D

classA amps are superior to the other classes in terms of distortion, but many stay away becuase of the heat generated....


Sir Tony T,

Yes sir, I totally agree, although there were few DIY'ers on this excellent site, it will be a good start, not to mention educational as well.

Thanks a lot sir! :)

"just keep 'em glowing"

Offline efren_

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Re: JLH classic class A amp
« Reply #11 on: Sep 08, 2009 at 09:19 AM »
Sir TonyT,

my version is a slight cross between JLH & Hiraga, i used for output Hiraga's D844 instead, to drive the output i used the antique 2SC24 mfd. by NEC. The result is outstanding! btw i still have a lot of germaniums stock on hand i got from surpus australian importer. I also remember using germanium outputs mfd. by National/Matsusita on my high school A.M radio projects, particularly by CMC/Celco. Indeed sir, they do sound very good.

 :D
"just keep 'em glowing"