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Chinese JL Hood 1969 Class A amplifier off Aliexpress

typericey

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#1
So my first attempt at buying from Aliexpress was a success and I received a well packaged, assembled DIY amp derived from the JLH 1969 design, in no less than gaudy gold color!
20180530_131357.jpg

20180530_160419.jpg

Hooked it up to a Chromecast Audio and Elac B5's and played Spotify for a couple of hours and it worked fine. I can't comment on the sound quality yet but there seems to be no distortion, no hiss, no nasty power on/off thumps despite of a lack of a relay (as far as I can tell). And I didn't have to whip out the fire extinguisher either, so all good! I'm not a technical guy but I love the "dual mono" (sort of) design and the premium components used: ON Semicon transistors, Panasonic and BC capacitors, Alps volume pot, assuming they are not counterfeit. Really curious about how this measures.

About the sound: one thing I noticed off the bat is the lack of dynamics, punch, attack or whatever you call it. It's one of the "laziest" sounding amps I've ever heard.

Anyone care to comment about what you see in the amp's guts?
 

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RayDunzl

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#2
Anyone care to comment about what you see in the amp's guts?
There's not much visible there...

The inputs go to a passive attenuator and then to ???

The cover for the transformer crunches the input/output wiring.

The GBI2510 is a rectifier.

About the sound: one thing I noticed off the bat is the lack of dynamics, punch, attack or whatever you call it.
Where's the driver section? There's a little bit hiding at the far end of the boards.

Got a schematic?

Maybe there's a clue in here:

http://sound-au.com/tcaas/jlhnotes.htm
 
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typericey

typericey

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Thread Starter #3
Unfortunately, no schematic from the seller (although other assembled DIY amps in Aliexpress have them!)

I saw many versions of the JLH1969 in Aliexpress but based on the photos alone, the one I got seems to be the "best" version. Others have either cheesy fake "Krell" branding, old recycled Motorola transistors, cramped cases, and typos on the faceplate i.e. PWOER AMPLIFIER. LOL

No power on thump, and only the faintest power off sound with the woofer visibly "breathing" about 1mm.

The Elac B5's are not the most efficient and they're rated at 6 ohms, but didn't seem to stress the amp. Although I haven't really cranked it up above "conversation" levels (too scared!)

My el cheapo Benetech infrared thermometer reads ~50 Celcius at the transformer cover and about ~42C where the transistors are mounted. My Asus router gets warmer on a summer day and I remember those old Musical Fidelity A1's being much more painful to the touch.

This may sound weird, but I find the lack of punch soothing and relaxing, pleasant even! This is the amp you'd want to listen to if you want to fall asleep and I say it as a compliment!

I plan to report more findings/observations here as I spend more time with the amp.
 

amirm

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#4
Thanks for the picture. It is really puzzling to see three TO-3 power transistors there for each channel. There should be two and then a less beefy one for driver.

It is cute and clean nevertheless.
 

cjfrbw

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#6
One of the TO3s is a gain stage/phase splitter, the other two push pull. It is interesting to read Nelson Pass article in the JLH 1969 circuit. He liked it.
 
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typericey

typericey

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Thread Starter #7

amirm

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#8
One of the TO3s is a gain stage/phase splitter, the other two push pull. It is interesting to read Nelson Pass article in the JLH 1969 circuit. He liked it.
Usually one uses lower power/higher beta driver transistor, not one identical to the power trannies. And it is cheaper to boot. But maybe there is a point there I am not seeing. :)
 

amirm

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#9
currently US$134. I paid $38 extra for shipping to Manila.
Wow, that is pretty cheap. The case and power supplies would be worth more than that.

Can you give us a sense of scale? How wide is it?
 
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#10
I can tell you from experience that single pass clone in parts is atleast 400bucks.... that price is worth in just the transformer and casing. DAMN good color i must say (laughs in acuphase)
 
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typericey

typericey

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Thread Starter #11
Wow, that is pretty cheap. The case and power supplies would be worth more than that.

Can you give us a sense of scale? How wide is it?
It's just over a foot wide. Yeah the price is quite unbelievable, but these products don't have sales, marketing and advertising overhead.

Thanks Amir and @cjfrbw for the comments on the transistors. Was also guessing if the circuitry is faithful to the original (or the 1996 revision). There are two MJ15025G's and one MJ15024G per channel.

Screen Shot 2018-06-03 at 8.04.16 AM.png


Aside from the relaxing, laid back character, the sound is nothing to write about. They are, uhh, neutral. I will need a few more hours of critical listening to comment on things like detail and resolution. I have decided to keep it for my secondary (casual listening) system in the living room. The NAD C316BEE it replaced is now for sale as it has now become even more boring compared to this cute, gaudy, mysterious, rare, and slightly shady conversation piece.

Btw, here's the link to Aliexpress.
 
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restorer-john

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#12
I am a little concerned that the IEC fused input socket appears to NOT be earthed?

no earth.JPG


I would be correcting that safety oversight immediately- you have no idea how good the insulation on the potted toroid is or even if the primary and secondaries are insulated to appropriate standards. A chassis earth is a serious safety issue, especially with the primary wires clearly being squashed under the toroid case flange as they exit towards the front of the unit.
 
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#13
Hi,
I am new here and forgive my english , I am French .My knoledge in electronics is very low , but i think I still have good ears .
This is my first post ,
I wanted to share my very recent experience with my new LP Spirit T-01 Pure Class A HiFi 2.0 Classic 1969 Wiring Construction Power Audio Amplifier 10W+10W Linear Power Supply DC24V/5A . Shipped to Spain for 134 € from Aliexpress. here.

It is connected to a FX Audi Tube 01 and a SMSL SU-8 DAC .I followed Amir's recommendation for the DAC and fully satisfied, thank you .
My speakers are 93 dB /1w/1m .I listen to music from my computer using Foobar, formats from Flac to DSD.
I am very happy with combination , never had before such a clear and detailed sound , whatever the kind of music , Jazz, Voices or Classic.
Thank's to the power out of the DAC+Tube01, I use the amp at quite low volume, I would say one fifth of total potentiometer capacity .

Working temperature went yesterday at 42º centigrades maximum for the amp.The linear power supply remaining cool all along.
I may tried to disconnect the Tube 01, next to listen to the sound and see power still available .
In fact I was a bit afraid about the only 10W+10 W power amp , but I have still a lot of power reserve.

I am rather happy with this amp considering it's a very good quality/price solution .
Any advices or comments welcome :)
 

solderdude

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#14
Thanks for the picture. It is really puzzling to see three TO-3 power transistors there for each channel. There should be two and then a less beefy one for driver.

It is cute and clean nevertheless.
One of them is power supply regulation (capacitance multiplier), the other 2 are output devices.



It basically is a small variation of the most classic and simplest amplifier JLH design (shown below). it uses an output capacitor that is not in the feedback loop.


Below yet another variation with some improvements using more linear current sources instead of bootstrapping and dual power supply to get rid of the output capacitor.


HERE is some more info about the original design and this improved design

Below the 'standard' circuit (which does have the output cap in the feedback loop b.t.w.) and is class-AB where as the JLH above is class-A

 
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#15
I'm newby in this forum and not familar with electronic knowledge.

I came to the Review of the chinese clone of JL Hood 1969 power amp.
https://www.audiosciencereview.com/...d-1969-class-a-amplifier-off-aliexpress.3372/

I wonder if the LP Spirit T-01 (post #31 - Lorenzo) is the newest model of the Hood 1969 clone.

Maybe, you can give me your advice to this amp. Lorenzo's impressions (also newby) have been quite good.

But for technical Background I'm not sure about build quality.

There is a thread about LP Audio Spirit 01-L1 at
https://theartofsound.net/forum/sho...Audio-20w-single-ended-Class-A-amp-from-Valab

but this seems to be a different unit (clone of Nelson Pass power amp, I gueass).

Really no informations and tests about the LP-Spirit T-01 beside the offers from aliexpress.

So maybe, you could tell me your thoughts about this amp.
 

solderdude

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#20
Hi jokel 77,

I can't tell you if it is the newest model of the Hood 1969 clone . It seems there various model at aliexpress.
What i can say after almost a month exprerience , amp is working at least 7 hours every day , and fully satisfied with brilliant sound.
Change from my last post , I wrote : " I may tried to disconnect the Tube 01, next to listen to the sound and see power still available ."
I did. I set the DAC at maximum power out and have still plenty of power . Pot is at 12h15 in terms of clock to get a very confortable level of sound .
Temp remains stable around 42º centigrades for the amp and the linear power supply remaining prefectcly cool .
Technically nothing I can say , but i'm really enjoying this amp , quality/
Lp Spirit T-01.jpg
price for 134€ outstanding !
 
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