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Thread: The garage cheapskate, FH3's, Needles, 3876, 3886, JLH 1969 class A

  1. #1
    Join Date: May 2020

    Location: England

    Posts: 19
    I'm Jim.

    Default The garage cheapskate, FH3's, Needles, 3876, 3886, JLH 1969 class A

    Hello all

    My little 7ft x 10ft room at the back of the garage, it has to double up for my other pastimes as well.
    This was taken a few years ago (after I'd tidied it up a bit); FH3's, a 3876 & modified Philips CD723.


    Niggling at the back of my mind for years was the JLH 1969 class A
    Would I be able to make it, would I be able to set it up, would it be any better than my 3886?

    The first mistake


    Not knowing much about it I'd looked at lots of stuff on the net and found lots of Chinese kits one of the things I'd seen was two little blue trimmers one to adjust the 1/2 voltage at the output and the other to adjust the amperage input. Thinking this was the 'modern' way of doing things I bought some trimmers.

    I got the 1/2 voltage OK but the other one went PfffT as I took it over 1 Amp. Fortunately I'd mounted some stuff on veropins and I was able to remove the trimmer and replace it with various resistors, until I got about 1.2 Amps. I was using a 12v 3 Amp smps brick just to try it out

    Connected it up switched on ..... nothing .... turned the board over and found a loose veropin, solder that back in .... nothing, turned the board over again more loose pins. Why? Nasty cheapo veroboard and pins with just plain shoulders not knurled, the board had been counter bored both sides, the pins could be pushed in with my finger nails adding up to a wobble made worse by the attached wires every time I turned it over. I found some old little bits of proper Veroboard and could only push the pins in the with a screwdriver handle.

    Ah well there we go this is what you find I'd bought one Chinese kit so I thought I'll have a go at that next, just to see if it works and feeling somewhat disappointed.

    Cheers - J

  2. #2
    Join Date: May 2020

    Location: England

    Posts: 19
    I'm Jim.

    Default

    Hello all,

    Buyer beware
    This is the title on eBay
    "Diy Kits 1pcs JLH 1969 class A amplifier Board high quality PCB MOT 2N3055"

    And here is the one kit I bought;


    The title does not stipulate any Wattage. There are two little blue trimmers under the capacitors. The one on the left adjusts the 1/2 Voltage and the other one the Amperage or Quiescent Current, this is 'on' all the time with class A amps hence the large heat sinks required.

    Since I burned a trimmer out on my failed veroboard I wondered how they got away with it with this. I use my 12v 3 Amp smps brick again to try it out, got the 1/2 Voltage easily enough. Screwed the other down to zero Ohms and got 0.58 Amps.

    12V x 0.58 = 6.96 x 0.31 = 2.16 Watts! This is derived from Mr Hoods 8 Ohm speaker recommendation for a 10 Watt output; 27V @ 1.2 Amps. 27 x 1.2 = 32.4 Watts QC, 10/32.4 = 0.31, 32.4 x 0.31 = 10.04 Watts QED

    At 24V the output will be about 4 Watts. Now I know why they don't nominate an output. I see lots of these kits and also ready made amplifiers with the two blue trimmers, I would advise anyone to stay away from them, unless you have some very efficient speakers.

    Trying to modify this would just make a mess, it's a very nice PCB but the holes are very small, will not even take a veropin and the the board is designed for just the components you get with the kit.

    After that, well, it did work and at a just listenable volume through one FH3 and it sounded very nice indeed.

    What next .... back to the source.

    Cheers -J

  3. #3
    Join Date: May 2008

    Location: Surrey

    Posts: 7,103
    I'm Rob.

    Default

    Well done for sticking with it. I used boards form a freebie offer by Siliconray on Diyaudio. Have you looked at any threads on there about the JLH 10w ?

    Link here.

    https://www.diyaudio.com/forums/soli...ml#post2948476
    Buy Bose...And get your parking validated!.

    https://youtu.be/ZCBe7-6rw4M

    No Highs...No Lows....It Must Be Bose!

  4. #4
    Join Date: May 2020

    Location: England

    Posts: 19
    I'm Jim.

    Default

    Hello Puffin,

    Nice of you to say that, thanks a lot. I have looked at the DIYA thread, up and down it like a yoyo, I see someone people saying one thing and others saying another and a third lot disagreeing, one does feel a bit torn in so many directions at the same time.

    I asked about heat sinks, I got lots of formulaic answers none of which came to a particular conclusion. Looking at the source I see two TO3's on one painted black 100 x 120 mm heat sink, repeated for the other channel and in an open ended metal box, when I asked how they cope with the heat, not a soul deigned to answer.

    Erring on the side of caution I bought 4 of these 100 x 146 mm £5.99 each including the postage from eBay supplied by a very nice gentleman in Hereforshire. https://www.ebay.co.uk/itm/10cm-1-me...X_OJDrQtgPuZ4w

    And sprayed them with some heat resistant paint;

    Baked in the oven at Gas Mk5 for one hour.

    More soon and thanks I did look at the link and what do I see just below your post, "I suspect that this lovely amp may lack grip in the bass department. Contributing factors will be o/p stage bias current & o/p cap". What a load of absolute guff just written to see his comment in writing.

    Cheers - J :-)

  5. #5
    Join Date: May 2020

    Location: England

    Posts: 19
    I'm Jim.

    Default

    Hello all,

    After making two failures I decided to go back to the original source here's a link to a cleaned up copy of it: https://drive.google.com/file/d/1p5k...ew?usp=sharing not a dog eared photocopy.

    This was taken from that PDF and I used Ps to make it a bit easier to see. Mr Hood used plain both sides Electrokit board.


    I used the original schematic and then altered it to suit the components I am using


    The 17V line is the one I am using for my 4.0 Ohm MA CHP-70's, the cheapest ones Mark makes with paper cones.

    Cricklewood electronics still sell this Matrix board which is a far better quality than the stripboard. The reverse side has got single copper pads.


    It's just so ridiculously easy to use, where two components meet I used a U shaped piece of wire to hold then together firmly and soldered them to the pads. The components can then removed and replaced by simply sliding them apart. I know now why there are such long leads on stuff and used the resistor wire bottom left (100k) to connect to the input transistor and then under the board to connect to the trimmer.

    Fair play to Mr Hood, one takes ones hat off.

    Cheers - J
    Last edited by JRead; 05-06-2020 at 12:57.

  6. #6
    Join Date: May 2020

    Location: England

    Posts: 19
    I'm Jim.

    Default

    Hello all,

    This is the Matrix board fully populated and ready to be installed.


    1/. I changed this resistor until I got the Amperage I wanted, using a cheapo digital multimeter, 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 value then halve the resistance. To work out the Wattage output multiply your chosen Voltage by your chosen Amperage and multiply that by 0.31.
    2/. There are two veropins here connected under the board, these are to take Tr1 Collector, Tr2 Emitter, R1, C1 and the output.
    3/. Return the -V from the loudspeaker here.
    4/. Another veropin here this goes to the Star ground
    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


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

    If anyone would like these pics as printable files please send me a message.

    Cheers - J

  7. #7
    Join Date: May 2020

    Location: England

    Posts: 19
    I'm Jim.

    Default

    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;


    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, resoldered 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;


    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 job) 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.

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