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PostPosted: 22 Dec 2011, 02:44 
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Joined: 21 Dec 2011, 23:01
Posts: 2
I designed and build a JLH class A amplifier a few weeks before. It follows the JLH updated circuit, but kept the 220uF capacitor in the feedback loop. This capacitor can either be kept or shorted for better bass performance. The sound quality is very good. Measured with VS7723 audio analyzer, the THD is 0.03% with MJ15003 and 2SC3280 and 0.05% with 2N3055.

In my own point of view, the good points of JLH are:
1. Simple circuit, easy to build
2. Good sound quality
3. Low distortion
4. Stable

The negatives are:
1. Very sensitive to power ripples
2. Low effeciency, too much hot, big heatsink needed

Below are photos of my project

schematic:
Image

PCB layout
Image

The PCB
Image

Assemblyed PCB
Image

With heatsink
Image


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PostPosted: 22 Dec 2011, 21:00 
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Joined: 17 Aug 2011, 06:05
Posts: 236
Location: Australia
Hi

Nice build there.
If you have power 'ripple' issues - what does your upstream power supply consist of? Working with this may improve your power ripple issue?

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PostPosted: 24 Dec 2011, 21:19 
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Joined: 14 Oct 2008, 17:35
Posts: 901
Location: Dartmouth, Nova Scotia
Pretty cool indeed, :smoking: if the filtering you have shown is all you are using for the power supply your going to need alot more than that to get good noise rejection, I recommend trying 30,000MFD per supply rail, if you don't have that much filtering all ready?

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PostPosted: 06 Nov 2012, 01:52 
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Joined: 28 Oct 2012, 21:47
Posts: 3
Good job!
Vr1 and Vr3 adjusted for what ?
Explain the detail ,pls!
Thanks!!!


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PostPosted: 03 Jan 2013, 13:25 
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Joined: 24 Sep 2011, 13:50
Posts: 2
The JLH Class A power amp project requires the use of either a regulated PSU or a capacitance multiplier, what with your quiescent current of over 1A, the largest capacitor is not going to suffice. Especially if you decide to go for the higher power version which will require a quiescent current of anything up to 4A. See An updated, regulated power supply for the 1996 version.


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 Post subject: JLH 1969 amplifier
PostPosted: 08 Jan 2013, 11:30 
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Joined: 08 Jan 2013, 11:09
Posts: 5
Location: italia
Hello everyone, I would like to build a simple amplifier in class and I saw the jlh 1969.
everyone seems to speak well and easy to build.
in the network, then, there are the pcb already 'ready ... what do you think?


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 Post subject: Re: JLH 1969 amplifier
PostPosted: 09 Jan 2013, 04:28 
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Joined: 08 Jan 2013, 11:09
Posts: 5
Location: italia
i try this pcb :
http://www.ebay.it/itm/271132020659?ssPageName=STRK:MESELX:IT&_trksid=p3984.m1586.l2649#ht_500wt_950


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 Post subject: Re: JLH 1969 amplifier
PostPosted: 09 Jan 2013, 23:07 
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Joined: 28 May 2008, 21:53
Posts: 4546
Location: Winnipeg, CANADA
Hi Francesco - what did you have in mind for the power supply? Also, what speakers were you planning to use with the amp.

Cheers

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[ DIY Mains AC Power Cable Cord ] - [ Gobo LM1875 Amp Kit ] - [ Tang Band D4-1 Horn Speaker Kit ] - [ Monoblock Push-Pull KT88 Tube Amp Kit ]


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 Post subject: Re: JLH 1969 amplifier
PostPosted: 10 Jan 2013, 03:46 
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Joined: 08 Jan 2013, 11:09
Posts: 5
Location: italia
hi ,for the psu , i have look for a Lm317 with a 2n3055 as follower .
my speakers are grundig hifi box micro 320.


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PostPosted: 11 Jan 2013, 13:09 
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Joined: 28 May 2008, 21:53
Posts: 4546
Location: Winnipeg, CANADA
Using a 2n3055 in the output stage could be interesting. What were you planning on using in the output stage? What is the sensitivity of those speakers?

BTW - there is more good info on the JLH 1969 10W amp at this old site: http://www.angelfire.com/sd/paulkemble/sound3b.html

Cheers

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[ DIY Mains AC Power Cable Cord ] - [ Gobo LM1875 Amp Kit ] - [ Tang Band D4-1 Horn Speaker Kit ] - [ Monoblock Push-Pull KT88 Tube Amp Kit ]


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