JMRead

The stingy old git's build of a John Linsley Hood's 1969 Class A

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Hello all,

I'd made a couple of chip amps 3876 (3875 with a mute) and a couple of years ago a 3886. Always at the back of my mind was the JLH1969. After loads of searches on the web and finding so much conflicting information I decided to go right back to the source. This is a link to it: https://drive.google.com/file/d/1p5k4YgTPAYa-aCtt6DpfE6CCekHOhV6k/view?usp=sharing it's the complete cleaned up version. The one on the Class A site is incomplete, no photographs, sadly.

My first concern was heat sinks and I looked at what JLH did;
49996246896_f56dd3f7f4_o.jpg

Two 100 x 120mm finned with two MJ480's on each one and in a metal box, I couldn't find anything similar.

I did find these though 100 high x 146 wide x 22 high
Black-Heat-Sinks.jpg

From a nice man in Herefordshire: https://futureeden.co.uk/collections/aluminium-heatsinks/products/aluminium-heatsink-t-series-profile-a-86mm-x-22mm I sprayed them with heat resistant paint and baked them in the oven at Gas Mk5 for one hour.

More soon

Cheers - J

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Hello all,

The output transistors that JLH used are no longer available, fortunately one year after the article he said that 2N1711 and 2N3055 would be an OK match. I would be unable to fit the 2N3055's to my heat sinks so I chose the 'plastic' versions TIP3055.
49860858646_c73d528be9_o.jpg

The box is 17" long 12" wide and 4" deep, not including the heat sinks, I like to be able to change stuff easily I made my 3876 and 3886 on wooden sub assemblies. The heat sinks hang from some Aluminium angle which in turn are supported on some treated roofing lath, really strong stuff. The plywood is 5.5 mm I bought a 4ft x 2ft piece from the local DIY shop.

I drilled the heat sinks 2.5mm and tapped them M3, I realised after that it would have been just as easy to drill a couple of 3.5mm holes from the front with a clearance area drilled for the nuts, before I painted them and used nuts and bolts. I then countersunk the holes slightly with a drill held in my hand to take off the drill burr and then smoothed it off with some wet and dry paper. I polished the heat sink surface with some Brasso, the TIP3055's are insulated with some silicon pads and the 'sticktion' effect is quite strong, they are quite difficult to remove.

Cheers - Jim

Even more soon

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Posted (edited)

Hello all

I've made some mistakes and stuff that didn't work, my fault, bit boring, so I'll go onto to something that does work :-)

This is the modified schematic I am going to use, with the transistors that Mr Hood said in 1970 would be OK replacements for the originals, Good job too, they are still available. I can't use 2N3055 with my heatsinks so I'm using the 'plastic' variation TIP3055.
49981928988_b7f359003f_o.jpg

I then looked closely at the photo of the circuit board Mr Hood used after fiddling with it to make as clear as I could in Photoshop.
49929781087_1a095147a5_o.jpg

He used Lektrokit board, I was able to buy some Matrix board from Cricklewood Electronics very similar with single copper pads on the reverse side.

This is the Matrix board fully populated and ready to be installed, it's so easy to use and the components can be changed very easily they just slide out. I used U shaped pieces of wire to hold some parts down onto the board, soldered to the pads on the other side.
49981928968_145845c312_o.jpg

1/. I changed this resistor until I got the Amperage I wanted, using a cheapo digital multimeter set at 10 Amps, Pos lead to the supply Neg lead to the circuit. The resistor here has to be 1 Watt or as I have used 2 - 1/2 Watt ones in parallel. There are online calculators to do this, if like the above you use two the same then half the resistance. To work out the Wattage output multiply your chosen Voltage by your chosen Amperage and multiply that by 0.31, not entirely accurate but within half a Gnats knacker.
2/. There are two veropins here connected under the board, these are to take Tr1 Collector, Tr2 Emitter, R1, C1 and the output to the capacitor
3/. Return the -V from the loudspeaker here.
4/. Another veropin here this goes to the Star ground, which then goes back to the -V or 0V in the power supply
5/. The lead on R5 is soldered to the base of Tr4 then under the board to the R5 trimmer, this sets the 1/2 supply voltage at 2/.
6/. A veropin where the 39k resistor and the 100uf Capacitor meet, connected to the trimmer under the board, the centre lead of the trimmer is attached to the one of the outer leads.

The pic above is a 2D of a 3D object
49982706532_b4c579de80.jpg

To make it clear that the leads from C3 to R4 are just connected to each other.

It does work and I'm doing a comparison: JLH vs my 3886
And I'm going to use, in my cheapskate fashion a switch mode power supply.

Cheers - J

Edited by JMRead
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Hello all,

JLH 1969 vs LM3886

I did this test for 8 days I wanted to be sure that my opinions were right. I was also concerned not to use the daft metaphors one sees on, for instance six loons.

I used the setup you can see here;
50008250701_166922d4bf_o.jpg

Input = One channel from my CD/DVD player through to a switch with two metres of wire
Output = left loudspeaker from the JLH 1969, the right one from the LM3886

By doing this I am able to switch from one amplifier to another instantly and can use the return on the CD/DVD remote to repeat a passage in seconds.

My first reaction was there's not that much difference. After half an hour or so I realised that the JLH sounded a little brighter. This was with Mahler's 1st symphony. The following day I tried some old Jazz, Bessie Smith and Clarence Williams's acoustic recordings from the early 1920's and Lady Day's from 1937, both sounding a bit clearer on the JLH.

I'd listened to these recordings many times and realised that I was listening to what I expected to hear i.e. the 3886 and 3876 before it and not what the JLH was giving me. The JLH still sounded a bit brighter though.

Next up was Norah Jones and 'What am I to you' this time I listened to her and realised that her voice was more up front with the JLH, this is where the switch came into it's own, being able to swap amps instantly identifies ones thoughts like nothing else.

The piano version of the Enigma Variations was next and one particularly loud and fast variation sounded quite brighter on the JLH but a little dull from the 3886. Oh dear I thought there must be something wrong with my speaker on the right.

I removed the drive units and the input lugs from both, re-soldered them and undid and re-tightened the cables, I then swapped the speakers left for right and right for left.

Back to the variations and the same result, it wasn't my speakers at all! I thought now I'm on to something here. On another forum there is a member who calls himself Poultrygeist he mentioned shimmer in a post with reference to Cymbals. My goodness! A bright light in ones brain, that awoke a recent memory, I'd never heard of the term as aural only as pictorial and thanked him.

Straight back to Norah Jones and yes there it was, a barely heard and rather dull Cymbal from the 3886 and a clear and fast Shimmer from the JLH. What's going on here I thought and back to the Variations, there it was again that instant brightness as I listened carefully to the JLH.

It then dawned on me what was going on (forgive me I'm just a slow old cheapskate git) it was the ADSR the JLH gives me the spike between A and D the 3886 doesn't;
50008258966_18f2e673f5_o.jpg

After that I tried Glenn Gould's Goldberg's I could hear him better on the JLH, maybe not such a good thing! Then Julian Breams BBC series Guitarra I could hear his breathing and his jacket rustling and his fingers sliding up the fret (not just the squeaks) at first I didn't believe it and played them over and over again on a couple of days to make sure.

Back to Mahler and the 1st symphony by this time I was used to the brighter sound and listened for the bass drums in the background, a dull rumble on the 3886 I'd never taken much notice of, on the JLH a clearer more concise sound, by this time I wasn't surprised at all everything the 3886 did was a little better on the JLH.

I'd saved Tangerine Dream for a few days, this is the new trio with their wall of full frequency sound recorded at high volume (into the red as I found out in Audacity), deep bass to high treble and everything between. Clarity is what I got from the JLH and a slight confusion from the 3886.

I tried other recordings of course I won't bore you with the names the ones above were the occasions when something dawned on me and was repeated with lots of other music.

The last eight days have been rather strange I did have to look for differences they were not immediately apparent. The 3886 is a fine amplifier no doubt about that, the JLH is slightly better being brighter, faster and more analytical.

What will I be listening to now for the foreseeable future, the JLH :-)

Cheers -J

In another forum I had some detractors saying that 'bright' is not 'right'. It would appear that I've uncovered a yet another dichotomy.

But then from one of the experts was this and I quote it from Mr Nigel Pearson;
Really good valve amplifiers have an analytical sound that is bright and fast. Less good valve amplifiers sound soft and pleasing. Most valve lovers let their designs drift towards the soft. A true Williamson (state of the art valve jobbie) which is rare are not soft.

Mr Hood said this in the 1969 article
The "Williamson" and the present class A design (the JLH) were both better than the other valve amplifier, and so close in performance that it was almost impossible to tell which of the two was in use without looking at the switch position. In the upper reaches of the treble spectrum the transistor amplifier (the JLH) has perhaps a slight advantage.

Stereo
The test was conducted in mono and I was asked if it would be possible to compare the two amps in stereo, I agreed. But on further reflection and some sketches I realised that in order to do this I would need two sets of speakers if I were to use switched inputs as above. To use the outputs and two speakers I could do it but would need 22 metres of speaker cable and two double pole double throw switches. Hmmmm considering what I'd got above I decided not to.

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Posted (edited)

I am so impressed with your project.

I use a JLH Square flat FM aerial mounted in the area twixt 2 bedrooms in the loft eaves (behind toilet), I live in a top floor flat where external aerials are not allowed,   the JLH provides sufficient signal to feed a Leak Troughline  which a 5 element never did. the man was a genius I have lusted after his parametric graphic equaliser for decades after reading an article  about brick built horns B139 speakers 12-14 feet long horns from loft to lounge  with a kelly ribbon tweeter with JLH parametric equaliser apparently Quad 57 clarity with 64 ft organ pipe bass depth.  

Edited by John (big)
phone call

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Hello John,

Thanks for the nice comment good of you and I like the story about JLH and aerials, amazing bloke. I'm really surprised that so much that is still relevant today is expressed in his 1969 article. That so simple a circuit should sound so good continues to amaze me.

Cheers - J

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Posted (edited)
18 hours ago, JMRead said:

Hello John,

Thanks for the nice comment good of you and I like the story about JLH and aerials, amazing bloke. I'm really surprised that so much that is still relevant today is expressed in his 1969 article. That so simple a circuit should sound so good continues to amaze me.

Cheers - J

There is a potted  life history of JLH on the internet that's worth a read 

Edited by John (big)
accuracy

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Hello all,

Having done my comparisons and being quite happy with them I put the amp in a box. Switched on cranked up the volume ... distortion ... lots of it. Fiddled with it to no avail, took it apart and went back to the way I had it set up for the comparison and it was OK until I turned the volume up ... distortion! I could have kicked myself for not doing it before,  such is life, this is what you find.

I stripped out the box threw the components in the bin and am now awaiting the delivery of a Class D TPA3116D2 board. I will do the same comparison with my LM3886 when it arrives and another one when I have modified the board. Apparently one can improve the sound considerably by doing  so.

I didn't have the necessary expertise to overcome the problem with the JLH but I have learned a lot in the process of failing.

Cheers
 

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That's a bit sad, do I take it you don't have an oscilloscope? was it just not making enough power?

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Interesting read, thanks.  Sad it didn't turn out too well.

I had the Chinese take on the JLH circuit.
Very impressive sound, actually, though I have no idea how closely they really followed the JLH circuit!
-- the wonderfully named Nobsound NS-02G.
Some info and user review here --
https://www.amazon.com/Nobsound®-NS-02G-Perfect-finished-Amplifier/dp/B00WTNXWOC
Taut and controlled and a little smoothed off - it sounded like a mini-Krell, particularly the older KSA series.

Some joker here actually put a Krell badge on the front - but have a listen and you'll hear why.
Although I don't think that Krell themselves would be happy with a 10wpc amp. :)

th?id=OIP.7e9gUBO7KL1NIK9YDp55OAHaE4%26p

Also, you've piqued my interest - what's the details on the piano version of the Enigma variations that you mentioned?!

Edited by JANDL100

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