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JLH 10 Watt class A amplifier
JLH 10 Watt class A amplifier
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Old 9th February 2018, 08:24 PM   #4421
cumbb is offline cumbb
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I meant the TEs run as power transes in the/my 32-V-JLH: 2 x 16 V. Fan at moment. Passive later.
The Hiraga sounds very very ugly. No reason to use 3 kg alu for horrible sound. No modify sensible. No doubt. Cause: 4-stage-complementary-parts and "2-rail-psu". Sorry. Had have any, tuned too, had built any. Trust me.-)
Build a JLH;-)
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Old 9th February 2018, 08:42 PM   #4422
cumbb is offline cumbb
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Evidence photos;-)
To close the lack of imaginations - repeatedly;-)
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Old 9th February 2018, 08:51 PM   #4423
Ian Finch is offline Ian Finch  Australia
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Originally Posted by sergiu2009 View Post
..... 32w disipation for a bd139 like transistor is like melting hot capsule dont you think? ...
Fair comment but we can't be sure what current cumbb is talking about - could be for both channels....or, uh.. something different/relative,-)
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Old 9th February 2018, 08:54 PM   #4424
sergiu2009 is offline sergiu2009  Romania
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I think it depends on many things (passive and active components, psu, wiring and tastes) and as a matter of fact i do have a 69 jlh with a bunch of upgrades aded and listened to them both and at the end of the day i cannot choose beetween them. I like them both. To me, if i where to build one of them again the winner will be the jlh but not because of its sound, its just because i'm more laisy now and i dont have to sort and painly match tons of transistors like the hiraga.
None of them is sounding 'very very ugly' neither to my ears neither to 30 other people who compared them to push pulls pentodes and triodes at a valve amp meeting in 2017 in Romania... They just sound very very good and have a different sound signature. You cannot choose the best, you just want them both.
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Old 9th February 2018, 08:59 PM   #4425
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Speakers and sources? Which do you use?
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Old 9th February 2018, 09:16 PM   #4426
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Bootstrap removed;-?

May be, the JLH runs after warm up with just a trimmer and a resistor. Per switcher the resistors ...-? Audible the difference of more or less circuits-salad is;-?
"Electrons"-"physics"-?

Earache at a glance in a Krell or ML or ... power amp;-))) Or multiways or soooooo many many, much much more;-)
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Old 10th February 2018, 03:26 PM   #4427
fredbloggstwo is offline fredbloggstwo  United Kingdom
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Originally Posted by cumbb View Post
Evidence photos;-)
To close the lack of imaginations - repeatedly;-)
Cumbb, there is no lack of imagination, belief of disbelief. I think there is a problem about communication.

We come to this site because we have an interest (some might say a passion) about building and listening to audio equipment.

We read/listen, discuss and learn from each other. To do so we communicate and share. If you cannot communicate and share with the community, (which is genuinely what other members are asking you to do) I think you are wasting your (and our) time with you posts.

Regards

Mike

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Old 10th February 2018, 05:16 PM   #4428
gaborbela is offline gaborbela  Canada
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Originally Posted by fredbloggstwo View Post
Cumbb, there is no lack of imagination, belief of disbelief. I think there is a problem about communication.

We read/listen, discuss and learn from each other. To do so we communicate and share. If you cannot communicate and share with the community, (which is genuinely what other members are asking you to do) I think you are wasting your (and our) time with you posts.

Regards

Mike
I agree with you, I follow these tread and I would love to see Cumbb schematics also. Genuine interested but it is up to him if he decides does not share that is too bad to all of us. I want to learn also.
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Old 10th February 2018, 09:49 PM   #4429
freddi is offline freddi  United States
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JLH 10 Watt class A amplifier
hi Ian Finch - fwiw I ordered an amp "like" yours as was less than $200 shipped. Is there a schematic which likely represents most of the amp? - the seller had posted a FET schematic.

would it be pretty much - ? http://www.startfetch.com/jlh/jlh-1969-amplifier.gif

What would you estimate for the case and heatsink temperature relative to normal room temperatures after an hour or so of heating? I hope some fans under it can keep it going for awhile.

my right hand stays numb a lot of the time - just can't do much of anything anymore

Last edited by freddi; 10th February 2018 at 09:52 PM.
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Old 11th February 2018, 05:11 AM   #4430
Ian Finch is offline Ian Finch  Australia
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[QUOTE=freddi;5337175]....... - the seller had posted a FET schematic.
would it be pretty much - ? http://www.startfetch.com/jlh/jlh-1969-amplifier.gif....../QUOTE]Yes, that's the schematic of the basic amplifier without the power supply or capacitance multiplier filter that are included in the clone. Parts now fitted will be substitutes if its an honest clone. If the smaller transistors look like 1960s metal case transistors that are strangely brand new looking, they may work OK but they will be fakes, good or bad. The semis in my clone may be all plastic types but likely to be fair substitutes.

Today the indoor temperature rose to a humid 33C and the thick front panel was up to 46C. The heatsinks were hotter by 9C, about 56C in the centre. Of course, it depends where you live as to how hot it will get but in the UK for example, temperatures seldom go much above 22C in the Summer and there wouldn't be much of a problem. I think slow fans are probably the solution, boxed in one or two little housings under the amp and supporting it, exhausting towards the sinks and upwards, but out of harm's way. It only remains to check that the volume pot, doesn't lose its lubricant and become noisy over time so I'm planning on insulating the shaft on mine - maybe it will help.

Have you looked at The Class A Amplifier site I linked to? It's archived here from the main index under articles and information. Tons of details, originally from JLH and from later contributors too. Lots of suggestions for DIY builds of most versions. You can also download the original Wireless World magazine articles archived at this great US site - virtually a complete magazine library: WIRELESS WORLD: Technical and experimenter magazinefrom the UK 1913-1986 'hope this is helpful.
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