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★★ Free PCB for JLH 2005 Class-A Amplifier
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Old 8th March 2014, 02:46 AM   #191
e_fortier is online now e_fortier  Canada
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★★ Free PCB for JLH 2005 Class-A Amplifier
Power supply for JLH 2005

Can someone help please.

I have read on this forum that the JLH 2005 works wonder at +- 19Vdc, 1A bias and it's better to use a regulated supply vs unregulated.

I have built the Amp Camp with the proposed 19Vdc switching mode supply and it sounds amazing therefore I was thinking of the following for the JLH 2005 ;

Buy two small switching mode power supply each rated 19Vdc, 3.5A but I would make sure to buy the double insulated version..i.e. the type with the floating output this way I can easily create a bipolar supply while using two unipolar +19Vdc supply.

I know this would work but do you think that having a supply of +-19Vdc, 3.5A enough to power a stereo JLH 2005 amp ? I could simply buy a 36Vct, 160-200VA but it wouldn't be regulated...this is the reason I would really like to use these Switching power supply.

Most of the supply (19Vac, 3.5A) are available without a ground pin and if properly built they are double insulated with floating output. The more powerful one like the 19Vdc, 90W are mostly grounded on the primary side and the DC output is tied to ground so a bipolar supply can't be created without blowing something ;-)

Thanks for your help.
Eric

Last edited by e_fortier; 8th March 2014 at 02:50 AM.
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Old 8th March 2014, 08:18 AM   #192
Wildwater is offline Wildwater  United Kingdom
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Hi e_fortier with 38v across the rails you will have close to 13v RMS max at the output. So a nominal 8 ohm load will draw slightly over 1.5A for an output power close to 21w. Your supply looks fine for one 8 ohm channel but getting a bit tight for a 4 ohm load or for two channels.

Over many lunchtimes at work I have read the main thread on this amp and there is a recurring theme that current to spare is a GOOD thing and the experienced builders that tried out different supply rails use 2A or more so that dips in the loudspeaker's impedance are well catered for.

It doesn't seem a common view that a regulated supply is needed just a low noise one as these amps don't have the highest Power Supply Rejection Ratio. The Cap Multiplier is a good, historical, match as that was the authors recommended supply for the original design.

I am (VERY) slowly building a Siliconray 2005 version and an original (single rail) version as the mid and high amps for a 3 way active system and research on this site has led me to have big heatsinks and plenty of current.
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Old 8th March 2014, 09:33 AM   #193
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by speedless View Post
Hi
Sorry
Just cant get used to WIN 8

Jan
is that the size of a real 3055 chip?
Are all the different source but genuine 3055 the same size chip?
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Old 8th March 2014, 02:30 PM   #194
e_fortier is online now e_fortier  Canada
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★★ Free PCB for JLH 2005 Class-A Amplifier
Hi,

WOW this really helped me, I was under the impression that the JLH 2005 was also rated 10W output just like the 1969 version...boy was I wrong ;-)

I'm aiming for 10W output power, 22W is way too much. The 1969 would be great since I already have a 27Vdc, 8A power supply but I want to avoid the output cap.

Thanks to your text I did some calculation, with a +- 12Vdc supply with 1A bias I would get 9W at the output...I just wonder if using a different voltage will screw up the bias and sound...

Rgds,
Eric
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Old 8th March 2014, 02:46 PM   #195
speedless is offline speedless  Denmark
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Hi
Quote:
is that the size of a real 3055 chip?
Its the size off the "originals" 2n3055 chip ("ON") produced today,older Motorola may be larger.

Quote:
Are all the different source but genuine 3055 the same size chip?
Im not sure,I have got a few old STs and motorolas but they won't be sacrificed.
(Been faithfully more than 20 years and still working perfectly in my lab. psu's.)

Jan
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Old 8th March 2014, 06:50 PM   #196
johngalt47 is offline johngalt47  United States
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★★ Free PCB for JLH 2005 Class-A Amplifier
Quote:
Originally Posted by siliconray View Post
We are offering free PCB for JLH 2005 class-A amplifier
Please get it here:
Free JLH-2005 Class-A Amplifier PCB

Each order is limited to 2pcs.

If you don't have the components please go with this cheap kit:
JLH-2005 Class-A Amplifier Kit for only $24
Ok, I am confused. Are we talking about two different products in this thread? I ordered the above and got a headphone amplifier kit. The power transistors were not in the TO-3 case.
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Old 9th March 2014, 03:11 PM   #197
Wildwater is offline Wildwater  United Kingdom
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Quote:
Originally Posted by e_fortier View Post
Hi,

WOW this really helped me, I was under the impression that the JLH 2005 was also rated 10W output just like the 1969 version...boy was I wrong ;-)

I'm aiming for 10W output power, 22W is way too much. The 1969 would be great since I already have a 27Vdc, 8A power supply but I want to avoid the output cap.

Thanks to your text I did some calculation, with a +- 12Vdc supply with 1A bias I would get 9W at the output...I just wonder if using a different voltage will screw up the bias and sound...

Rgds,
Eric
The amp will produce power according to the rails you use (within limits, ) and have heatsinks able to to keep it cool.

With +- 12 volts you will have +- 11.4 v swing available (caused by the 1 diode drop across each output transistor) 11.4/sqrt(2) = 8v rms so closer to 8W than 9 but this is an inaudible difference.

With this PSU you'll be dissipating 12W per output transistor which shouldn't be exactly hard to keep cool, just decide the approximate heatsink temperature you are comfortable with and size accordingly.

Since its a class A amp you are going to pull 1A from the PSU all the time so you need to be happy that this is its continuous rating. I am pretty sure that what siliconray supply can pull up to 1.5 times the quiescent (bias) current so you may be limited by the PSU if you are driving something that can look like a lower impedance than it's nominal 8 ohms.

You shouldn't be concerned that a low power version won't be as good; siliconray also supply a headphone amp which is pretty much the same circuit way less powerful that you are intending to use and is also very well regarded.

As long as your PSU and heatsinks are a reasonable match for whatever level you decide to run at you'll not be disappointed.
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Old 10th March 2014, 01:44 AM   #198
e_fortier is online now e_fortier  Canada
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★★ Free PCB for JLH 2005 Class-A Amplifier
Hi Wildwater,

Thank you very much for your help and tips, this is GREAT.

Now, I must find some power supplies with floating output so I can do a bipolar arrangement.

I will order most parts tonight

Can't wait to start building, I heard so much good stuff about JLH.

Best regards,
Eric
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Old 29th March 2014, 07:29 PM   #199
joaobernarda is offline joaobernarda  Portugal
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How does the jlh2005 goes with 4ohm loads . Can it drive ribbon Midrange driver like Apogee actively Xovered .
Regards
Joo
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Old 30th March 2014, 10:29 AM   #200
AndrewT is offline AndrewT  Scotland
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1pr output stage and limited peak current due to (partially) single ended topology, tells me that it is not suited to high current duties.
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