JLH 10 Watt class A amplifier

Jump to Latest
#1,342
HOEK said:
At this moment i use a JLH69 .
It runs on 29V 1.2Amp.
For the output it uses 2xa MJ15003 each on a heatsink
of 0.7W/C (per channel)
I wonder what is the maxium voltage/ current,
and will this better the performance.
Click to expand...

I ran my JLH balanced wkg at 1.2A ( per side ) for a long time with 30V

recently I changed to 24V and 1.6A

even with this small current increase the difference ( with my speakers ) was quite pronounced.

In light of this for an unbalanced standard version I would go for about 44V & 2.0 - 2.5A

Also for other major improvements I would also go for one of the later versions as shown on Geoff's site.

mike
 
  • Like
Reactions: myfirstamplifier
#1,344
JLH 69 chassis and heatsinks

I just got a pair of JLH 69 boards. I have started planning and saw this thread. Perhaps I can get an opinion on size of heatsinks and drivers.

I realize the heatsink capability is related to Iq and at a particular supply voltage. And that the Class A operation demands the best heatsinking you can reasonably get.

So if you refer to the attached picture I found.....is the smaller case something appropriate to the 10W JLH 69 or bigger? The medium size case is fairly large.....is it appropriate or too big?

Also I am looking at using MJL21193 and MJL21194. Would these be a good choice?

thanks,
Tommytube
 

Attachments

  • heatsink chassis.jpg
    heatsink chassis.jpg
    90.4 KB · Views: 1,450
#1,345
Re: JLH 69 chassis and heatsinks

tommytube said:
I just got a pair of JLH 69 boards. I have started planning and saw this thread. Perhaps I can get an opinion on size of heatsinks and drivers.

I realize the heatsink capability is related to Iq and at a particular supply voltage. And that the Class A operation demands the best heatsinking you can reasonably get.

So if you refer to the attached picture I found.....is the smaller case something appropriate to the 10W JLH 69 or bigger? The medium size case is fairly large.....is it appropriate or too big?

Also I am looking at using MJL21193 and MJL21194. Would these be a good choice?

thanks,
Tommytube
Click to expand...

Geoff tried MJ21194 (TO3 versions of MJL...) and reports that they sounded good but gave a low level hum that wasn't a problem with MJ15003. MJL21193 are PNP and not suitable.

There is no such thing as a heatsink that's too big.

These are nice looking boxes but you really need to know their degreesC/watt rating before you can be confident that you won't be able to fry eggs on them.

Have a look at the ESP pages http://sound.westhost.com, Geoff's site http://www.tcaas.btinternet.co.uk/index-1.htm and National Semiconductor's data sheet http://www.national.com/ds/LM/LM3886.pdf which has a very nicely written step-by-step guide to designing heatsinks.

Enjoy!
 
#1,346
Geoff tried MJ21194 (TO3 versions of MJL...) and reports that they sounded good but gave a low level hum that wasn't a problem with MJ15003.
Click to expand...

Actually it was I who reported a low level hum with the MJ21194 in what was, at the time, pretty much the standard 1996 (updated by JLH) circuit. I believe this device has been used in the JLH by others without problem. It sounded very good, perhaps improving a little on the MJ15003 in some respects.

Tim.
 
#1,347
TimA said:


Actually it was I who reported a low level hum with the MJ21194 in what was, at the time, pretty much the standard 1996 (updated by JLH) circuit. I believe this device has been used in the JLH by others without problem. It sounded very good, perhaps improving a little on the MJ15003 in some respects.

Tim.
Click to expand...

Sorry, Tim, credit where credit's due!
 
#1,352
Upupa Epops said:
It's funny for me....I'm reading it with pleasure ( how deep roots have this superstition ) 😀 .... Best amp is Halcro and it is not class A.... 😉
Click to expand...

With the greatest of respect, could you just read it with pleasure and not press the 'submit reply' button til you have something constructive to add? Otherwise I'll have to start posting opinions on the Halcro thread (wherever that is).

Peace!
 
#1,353
Peace... I have peace in my soul 😉 ... I can't destroy somebody's enjoy, mainly if if somebody is begginer. Yes, I know, these five transistors are glory and it is attractive offer, but it was new before 36 years and is the time for new thinking, isn't thruth ? I'm making amps all my life and also JLH I had before cca twenty five years....Exist better amps, but inertia is great and you can't listen...your mind is closed...I'm sorry guys...
 
#1,354
Upupa Epops said:
Peace... I have peace in my soul 😉 ... I can't destroy somebody's enjoy, mainly if if somebody is begginer. Yes, I know, these five transistors are glory and it is attractive offer, but it was new before 36 years and is the time for new thinking, isn't thruth ? I'm making amps all my life and also JLH I had before cca twenty five years....Exist better amps, but inertia is great and you can't listen...your mind is closed...I'm sorry guys...
Click to expand...

Isn't that a bit like saying 'why are you listening to the Beatles they're 40 years old, Gorillaz are much better'?

edit: this is not to imply that I think the Beatles are better than Gorillaz, just different.

Our minds aren't closed, we build all sorts of amps too, I'm sure there are guys contributing to this thread have built valve amps one day and class D chip amps the next. On the other hand anyone who says 'class A is the only way, everything else is rubbish' is fair game for that accusation.

Anyway, each to his own, you don't like class A you don't have to build it.

I'll say no more, this is probably boring everyone else to sleep and I'm not trying to pick a fight, you seem like a nice guy.
 
You must log in or register to reply here.
Top Bottom