The cheapskate bodger with the JLH 1969

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JMRead
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#1 The cheapskate bodger with the JLH 1969

Post by JMRead »

Hello all,

My little story.

I'd often wondered about this amplifier would it be any better than my LM3886. I started doing some research on various audio forums and found that one lot said one thing another said something else and a third lot disagreed, this I thought is what you find.

Being somewhat concerned about heat sinks I asked, oh dear, I'm just a simple soul all I wanted was a size ... not a dicky bird. I went to the source Mr Hoods article and read that he used 2 100 x 120 mm finned heat sinks with two transistors on each and asked about those ... silence.

Well I thought there we go make up your own mind Read and I found a very nice gentleman in Herefordshire who sold me four of these 100 x 146MM https://futureeden.co.uk/collections/al ... 6mm-x-22mm

Image

I sprayed them black and baked them in the oven for 1 hour at Gas Mk5.

I would not be able to mount a TO3 transistors on them I wanted a direct mount so I decided to use T0247's.

A big wooden box to bung them in was the next thing, I went to our local DIY shop and bought a 2ft x 4ft piece of 1/4" plywood.

More in a bit

Cheers - J
steve s
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#2 Re: The cheapskate bodger with the JLH 1969

Post by steve s »

Nice project.. I've been looking at that circuit for the last few years.
I had a few mullard 5 watt? 'module' amps about 15 years ago that sounded very nice, but I managed to short them out. I've been looking for something similar ever since.



cheapskate bodger is apt round here.. nice one
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pre65
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#3 Re: The cheapskate bodger with the JLH 1969

Post by pre65 »

Hi J, nice to see a new member here, looking forward to see how the JLH amp progresses.

What part of the country are you in ?
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#4 Re: The cheapskate bodger with the JLH 1969

Post by Cressy Snr »

Yes, welcome to the madhouse. :)
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JMRead
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#5 Re: The cheapskate bodger with the JLH 1969

Post by JMRead »

Hello Steve,

Many thanks for the message, sad about your Mullard amplifier, done the same myself over the years. I do hope you find my stuff useful. I'm pleased to be amongst another lot of cheapskates.

Hello Pre65,

Thanks for your nice comment good of you. I live in Derbyshire, in an old mining village not too far from the M1.

Hello Cressy,

Thanks for the welcome, I get a bit mad at things especially 'In my opinion' with nowt to back it up, but there we go :-)

Cheers - J
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Ray P
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#6 Re: The cheapskate bodger with the JLH 1969

Post by Ray P »

I've built and enjoyed some JLH amps (though not the 1969) and even met him before he passed away (he lived only a couple of miles from me on the edge of Taunton). He was very modest and self-effacing with an old-fashioned British eccentric air about him so it's good to see his designs still going strong as his legacy.

That said, with the original parts obsolete and new ideas coming along there seems to be a proliferation of different 'versions' of his amps around - what's the provenance of the one you have put together? What power supply arrangement are you using?

From the picture, your heatsinks look a bit 'lightweight' - have you built the amp and are they proving up to the job? Instead of the length/height dimensions you really need to size your heatsinks to suit the thermal requirement of the task in hand.

There's a healthy interest in JLH amps over on DIY Audio - I seem to recall there's a very long thread about the '69 design.

The Elliot Sound Products hosts an archive with lots of information about the different JLH designs, including a copy of the orginal Wireless World article describing the '69;

https://sound-au.com/tcaas/index-1.htm

Anyway, welcome to Audio Talk.
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JMRead
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#7 Re: The cheapskate bodger with the JLH 1969

Post by JMRead »

Hello Ray,

Many thanks for your reply and for the welcome and for the comments therein.

I do say the following with great respect to you, regarding the link to the 'original' article on the Class A site, it isn't. Here is the original article it can be downloaded here: https://drive.google.com/file/d/1p5k4Yg ... sp=sharing this is a cleaned up version not a dog eared photocopy, cleaned up in a readable way that is not by altering the text :-)

Taking an image from that article and doing my best with it in Photoshop, this is what Mr Hood used to mount the MJ480's, two on each one. They are 100 x 120 mm the ones in my post are 100 x 146 mm and will have one TIP3055 on each. In further articles Mr Hood was taken to task about the heat and admitted that they got very hot indeed but within the parameters of the transistors. I have asked the question many times about someone using their expertise to work out what is necessary for bodgers like me, no one comes up with an answer. You'd think that after 50 years I would not have to take a guess! I gladly admit that my decision to buy those four was taken in my usual cheapskate fashion, £25 including postage.
Image

Something else that influenced my decision is my speakers a pair of FH3's. When the plans were first released I asked Colin Topps if I could visit and have a listen, he kindly agreed. When I got there he explained that his amplifier was a single ended valve job, I thought oh dear! But was then utterly gobsmacked by the detailed concert level of the sound and in a large room. Two days later I splashed out £17 on some cut MDF oblongs at B&Q.

Do I need 10 Watts worth of wasted power most likely not when 6 or 7 will fill anyone's reasonable sized room. And there's yet another conundrum, ohhh yes by jingo valves are much better that solid state and yet ... quote from the original article; The "Williamson" (state of the art Valve jobbie) and the present class A design (the JLH 1969) 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.

One does wonder :-)

Cheers and apologies for rambling on -J
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#8 Re: The cheapskate bodger with the JLH 1969

Post by JMRead »

Hello all,

To answer another of Ray's, sorry Ray I forgot this bit in my haste to answer you, concerns about the transistors in the amplifier, I must admit to some amusement at the antics of the cognoscenti, leapfrogging over each other to suggest so called better and better transistors. Which led me further and further away from their confusing utterances and back again to the original source.

Later in 1970 Mr Hood said some alternative transistors would work just as well; 2N1711 and 2N3055 in place of 2N697 and MJ480, as I'm going to use 'plastic' one's it'll be TIP3055.

Here's a pic of my big wooden box 17" long x 12" wide x 4" high, I polished the insides of the heat sinks where the TIP's will go with Brasso, they are quite difficult to remove there's so much 'sticktion'.
Image

After many weeks of failures with bits of cheap veroboard I decided yet again to go back to the original and do some digging into another image from the original article and see if I can copy it.

As soon as I have the images on a server I'll post them.

I'm beginning to feel like an electronical archaeologist.

Cheers - J
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Ray P
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#9 Re: The cheapskate bodger with the JLH 1969

Post by Ray P »

Well, semantics maybe, but I did say a 'copy' of the original article - its clearly not facsimiles of pages from a 50year old magazine but JLH's article is essentially there. Anyway...

Assuming that your plan is to build the amp as per JLH's prototype it'll be interesting to see how hot 'very hot' is both from a hazard perspective and potentially limiting the life of some of the components. Are you planning to ventilate the inside of the chassis?

What's the problem with the veroboards?
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Paul Barker
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#10 Re: The cheapskate bodger with the JLH 1969

Post by Paul Barker »

Surely as the heatsinks are same but greater dimensions than JLH ones’ no need to srtike fear in the heart of Op. Transistor class A amps can all fry an egg, just like a Ford Esort bonnet when it has twin choke webbers and no air filter with whta in my industry we call flame lift.
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#11 Re: The cheapskate bodger with the JLH 1969

Post by Ant »

I've got a HiFi yearbook from the early 70s (72 I think) with that pic in it, with a build article for this amp somewhere, I'll dig it out of its of use? Should be able to scan it and upload it
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JMRead
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#12 Re: The cheapskate bodger with the JLH 1969

Post by JMRead »

Hello Ray,

Again with great respect 'semantics' ... more like antics, not one photograph in the Class A site 'original' and that's where all the evidence is. You may have noticed that in the pic above Mr Hood put his heat sinks in a small metal box, have a good think about it the answer will dawn on you one day as it did for me.

[edit] Dear Ray, I think you missed the link to the original cleaned up version in my post here http://www.audio-talk.co.uk/phpBB2/view ... 13#p176913 not a dog eared photo copy

As for the vero no sorry cheapo stripboard and the shouldered instead of knurled pins they come loose when trying to alter components especially with other wires attached, the holes are too big and the pins too small. Solder one back on to the copper strip and another one comes loose. There is a much better way of doing it please see below.

Hello Paul,

My thoughts exactly, I really like the expression 'flame lift' never heard that one before :-)

Hello Ant,

Many thanks for your offer, the pics from the real original have been good enough as you will see below :-)


Hello all,

This is the modified schematic I am going to use
Image

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.
Image

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 and very well made, I can push pins through with my fingernails with the cheapo stripboard I have to use a screwdriver handle with the Matrix board.

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.
Image

1/. 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 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
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
Image

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

I've nearly finished it so keep looking please I will also do a proper comparison with my 3886.
And I'm going to use a cheapskate switch mode power supply.

Cheers - J
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Ray P
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#13 Re: The cheapskate bodger with the JLH 1969

Post by Ray P »

JMRead wrote: Again with great respect 'semantics' ... more like antics, not one photograph in the Class A site 'original' and that's where all the evidence is. You may have noticed that in the pic above Mr Hood put his heat sinks in a small metal box, have a good think about it the answer will dawn on you one day as it did for me.
I don't have the electronics experience or knowledge of most of the chaps who inhabit this place but I wouldn't build an amplifier based on 50year old magazine photographs. The class A site gives you all the information you need to build a version of the amplifier and from that information I would work out how big the heatsinks need to be. The reason JLH put them into a 'box' is, as a safety measure but also I think to create a chimney affect - no particular thinking required - would he have done so if he'd had better heatsinks available, such as the plethora available today.

BTW, I can fry an egg in a frying pan but I wouldn't put my hand in it while doing so as doing so. It is not it true that you can fry an egg on all class A amps.
JMRead wrote: Dear Ray, I think you missed the link to the original cleaned up version in my post here http://www.audio-talk.co.uk/phpBB2/view ... 13#p176913 not a dog eared photo copy
Nope. I made no reference to a dog-eared version.

I posted to try and be encouraging and helpful but as you clearly have all the answers I'll leave you to it. I hope it works out for you.
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Nick
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#14 Re: The cheapskate bodger with the JLH 1969

Post by Nick »

but I wouldn't build an amplifier based on 50year old magazine photographs.
Don't see why not, what’s the worst that could happen? Its such a simple circuit anyway. A lot of diyAudio (IMHO) posters seem more interested in pushing their own pet theories or showing how it would work in a spice sim that actually building something. (may or may not be the case with this amp and its thread, but its why I find it hard to separate the signal from the noise on diyAudio).

CE allows heat sinks as opposed to casework to be up to 80C so beyond what you would want to touch.
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#15 Re: The cheapskate bodger with the JLH 1969

Post by JMRead »

Hello Ray,

Many thanks for the message and for the clarifications, I'm grateful to you.

Hello Nick,

You are quite right, it does work, well it would wouldn't it (paraphrasing Miss Rice-Davies) I am about half way through my 7 day subjective appraisal JLH vs LM3886, in the same manner that Mr Hood used.

Mr Hoods component layout is wonderful and in conjunction with the circuit diagram is very easy to fathom out. It is my intention to as you say Nick, "... to separate the signal from the noise ..." very succinctly put. I intend to offer a PDF showing the above, with the addition of how to identify components, how to solder, a resistor colour chart etc etc. I think all the 'noise' is putting people off who might otherwise make something for themselves for the first time and a/. learn a little bit, b/. have the joy of making something that works and c/. make one of the finest amplifiers ever designed.

And to close this post I note the word Simple in Mr Hoods article title, I don't think he could believe it himself :-)

My review will follow shortly.

Cheers - J
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