JLH 10 Watt class A amplifier

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#3,382
I would prefer the Alpair or the Betsy. May be, you have to cut the high-cone of the betsy a little bit. And all these membranes you have to damp. But these fullrange will sound very good. Than,-)
I would not use the Audio Nirvana, because it has a phase plug. The Audio Nirvana does scratch and distort - relative to the others. I would never use a phase plug speaker.
My mind,-)
 
#3,384
HELLO everyone;

I do not have electronic knowledge only know how to solder 🙂

I bought JHL kit here below on aliexpress;
An externally hosted image should be here but it was not working when we last tested it.


http://www.ebay.co.uk/itm/1pc-JLH-1969-Assembled-class-A-amplifier-Board-high-quality-PCB-MOT-2N3055-/121808157174?hash=item1c5c54f9f6:g:4xwAAOSw7hRWPGLS

It uses 2N3055 + 2N1711 + 2N2907 (I dont know which version it is but i want to use same pcb and upgrade it as described here below😉

jlhupdatefig2.gif

The Class-A Amplifier Site - JLH Class-A Update

i can buy the componenets but what modifications i need to make on pcb itself?

Thanks....
 
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#3,386
Hi Potstip,

If you don't know electronics at all I seriously suggest that you enjoy the JLH 1969 board just as you bought it.

The architecture of the updated circuit is fundamentally different.

Personally, I would prefer to build the updated circuit by hand from scratch rather than trying to adapt the 1969 board.

If you really want the updated version, I suggest you search for a board designed especially for this.

Also adjusting the DC offset for the newer version takes care & time and if you get it wrong you could blow up your speakers.

Sorry to appear unsupportive but I honestly think you should build the power supply for the one you have and see how good it sounds.

best wishes

mike
 
#3,388
I cannot say for sure, but the circuit could oscillate if you upgrade the transistors.

The thing is this: Creating a "finished" design can take weeks or months of fiddling around to get everything working properly. When you buy a finished kit, someone has done all of that work for you. If I were you I would take advantage of that so you can get to enjoying the music as soon as possible.

Then, if you feel like being more adventurous later you can try to build the newer version but at least you will have a working amp quite soon.

If however you don't trust the people who sold you these boards then best not to buy from them.



good luck

mike
 
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#3,389
I have had pretty good luck with several kits I have bought from Aliexpress. Build it as is with parts supplied and it should be ok. The vendors on Aliexpress don't want a black eye rating so will try to sell you a product that will actually work. The output BJTs may not be name brand but will probably work and are different than fakes where they take a puny BJT and encase it in a big BJT. Those blow up immediately. That board looks pretty nice actually so you should build it and enjoy the original sound of the 1969 variant.

Always use a mains bulb tester for initial power on test and adjusting. Or use 10ohm 10w safety resistor in power rails.
 
#3,390
Hi Potstip,

The 1969 version sound very good to my ears. The other version with the +Ve/-Ve also sound great and you could simply buy the free PCB at Siliconray.com which is a vendor on this forum. Try to buy 2-3MHz ft output transistors to avoid possible oscillation.

Good luck,
Eric
 
#3,391
That looks like a very good quality kit/build and there is nothing wrong with the JLH'69 amplifier. As others have suggested, yes - finish this version and test it carefully, then enjoy. The sound quality will be fine as I doubt there are fakes there that are a problem - from the appearance of your pic. at least.
 
#3,392
JLH 10w PNP Version

It’s been a while since I postet here. I built a 96 version a couple years ago with MJ15003 and was very pleased with it. Been using different amps since then. One day I came over this amp on Fleebay:
Nobsound HD1969 Gold Pure Class A Finished Power Amplifier HiFi Stereo Amp DIY | eBay
and I thought what the h…, I give it ago. Small cabinet and high WAF and I have MJ15003 laying around. Tested it 2 days now and it is definitely something there that reminds me of my old amp.
Took of the top cover today to check it out and to my disappointment there where MJ2955 PNP on the output. I’ve now ordered a couple of MJ15004 that i’m gone try. I searched the internet for schematic the PNP version but only get eBay JHL amp modules. Any one got a schema on this? I see some eBay sellers claim that the PNP versions is better sounding. Anyone have a comment on that?
 
#3,397
I see some eBay sellers claim that the PNP versions is better sounding. Anyone have a comment on that?
Click to expand...

As usual some unsubstantiated claims but with some basis. RCA's original 2N3055 had an ft of 800kHz. The MJ2955 was built using epitaxial technology and had a 4 MHz ft. So comparing these, you would expect a better performance from the MJ2955. (The MJ15004 BTW are only 2MHz). However, that was then. TOday's datasheets claim only 2.5MHz for the MJ2955/2N3055, which is the standard epitaxial 2N3055. So comparing the MJ2955 with the epi 2N3055 probably makes very little difference.
 
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