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 Post subject: JLH diy amplifier
PostPosted: 02 Feb 2017, 17:31 
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Joined: 31 Dec 2008, 15:34
Posts: 441
i've always heard the JLH 1969 cl. A amp mentioned as a good amplifier, so i were thinking about ordering a pair of diy kits on ebay. It seems there are a lot of differens between component quality of those kits sold on ebay. the one i've found, it seems the seller actually has done some thoughts about the components ...if you guys in the forum disagree, i would like to hear about it, before i'm going to order. feel free to tell here.

also an important question, is it necessary to use a regulated psu ? or will it work with an ordinary well filtered psu, as in the picture below ?

Ebay kit: JLH 1969



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 Post subject: Re: JLH diy amplifier
PostPosted: 05 Feb 2017, 11:28 
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Joined: 28 May 2008, 21:53
Posts: 4591
Location: Winnipeg, CANADA
There is a good background by Nelson Pass on the JLH in this article: http://6moons.com/industryfeatures/zen/plh.pdf

And this site has the most info on the JLH amp circuit: http://sound-au.com/tcaas/index-1.htm

The original JLH amplifier used a smoothing circuit in the power supply.

As far as ebay kits go, that one looks pretty good. The transistors look decent.

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 Post subject: Re: JLH diy amplifier
PostPosted: 06 Feb 2017, 02:50 
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Gio wrote:
There is a good background by Nelson Pass on the JLH in this article: http://6moons.com/industryfeatures/zen/plh.pdf

This site has the most info on this circuit: http://sound-au.com/tcaas/index-1.htm

The original used a smoothing circuit in the power supply.

As far as ebay kits go, that one looks pretty good. The transistors look decent.


thanks :up:

i've often been into exactly those links and been very confused, because there's a lot of different variations of the jlh amp. okay, no more confussion, i'm just going to order this ebay kit.


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 Post subject: Re: JLH diy amplifier
PostPosted: 06 Feb 2017, 13:53 
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You should be good close with the proposed supply. The circuit is push-pull, so the PSRR won't be as awful as SE, but it is a class A design, so you will need a robust and quiet supply to keep unwanted noise down.

As you noted, it looks like they did a good job (judging by looks) with their choice of transistors and the multiturn (Bournes) pots.

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 Post subject: Re: JLH diy amplifier
PostPosted: 11 Feb 2017, 08:04 
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thanks gio


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 Post subject: Re: JLH diy amplifier
PostPosted: 23 Feb 2017, 17:17 
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I'd sugest that you change the output capacitor to a audio capacitor for better sound quality.
Also If you can get 40 000uF of more capacitors for the build it should be allright.
On the otherhand regulators may give better perfomance but may cost more than putting extra capacitors in the build.


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 Post subject: Re: JLH diy amplifier
PostPosted: 27 Feb 2017, 11:00 
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KochiyaYamato wrote:
I'd sugest that you change the output capacitor to a audio capacitor for better sound quality.
Also If you can get 40 000uF of more capacitors for the build it should be allright.
On the otherhand regulators may give better perfomance but may cost more than putting extra capacitors in the build.


thanks Kochiya i'll try a better quality of output cap. also no problem with a large bank of caps for the ps, i could give it ½ F if needed :thumbsup:


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 Post subject: Re: JLH diy amplifier
PostPosted: 22 May 2020, 04:55 
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Joined: 18 May 2020, 17:10
Posts: 6
Hello all,

I'm having a bash at the JLH 1969 and made up the circuit on Veroboard the stuff with the copper strips, it didn't work, such is life.

I'd bought just one of these kits being a little curious about them and decided to make it up to see what it would be like

Image

I'd found out those little blue trimmers especially the one to adjust the quiescent current would burn out being only 1/2 watt. I then found out that this circuit got around that by limiting the maximum current to 0.58 amps I was using a 12v smps brick to see if it would work. At 12v 0.58 amp = 1 to 2 Watts, at 24v 0.58 amps = 3 to 4 Watts.

As for changing components forget it, the holes are so small it would be very difficult to unsolder anything. It's made to take the components they send and any others would not fit and just look a mess. To add insult to injury the holes are too small to take Veropins, they didn't want anyone to fiddle with it!

But, even at 1 Watt or so it sounded really nice and with quite some volume through one speaker. There was a tiny bit of noise so I dug out an old mains 'cleaner' that stopped it.

Well I thought what next, I've gone back to the source to find out how Mr Hood made his and I'm going to do the same, Cricklewood Electronics still sell Perfboard and I will be able to alter any component I wish, should have done that in the first place, this is what you find.

Cheers - J


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 Post subject: Re: JLH diy amplifier
PostPosted: 03 Jul 2020, 17:04 
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Joined: 03 Jul 2020, 16:58
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I have the same boards and am using a computer power supply. 24 volts and 4 amp rated. Is there a ratio to the current setting and the half way voltage setting. Currently set at .8 amp. Are the heat sinks the limiting factor?


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