One day when bored I built this. It almost is a good idea. Distortion was so low loop or global feedabck made no difference. If an SE valve amp we might prefer as drawn.
I was surprised how little bias was required. Different diodes might be easier. The diodes fixed with epoxy to the combination. I didn't really care what the bias was as long as ball park. The heatsink was 0.25 degrees per watt so made life easy. I still have it. Bias was excellent once warmed up. PSU was many uF not regulated. Worked first time.
The circa 21 V +/- was within the OPA604 range. Above 18V nothing happens except being useful to have. You can use most op amps above rated voltage if not requiring full current output. Sometimes much more than you would guess. No real advantge so best not.
In GEM I recognise valve verses transistor critisms that might be true here. OPA 604 might cope better than NE5534. Everthing was like a test flight and getting into the air a victory in itself. Hope I drew it as it was. Absolutely no stability isusses close loop global ( second red blob ). It's an old drawing and meant only for me.
The technical spec was remarkable and dynamic power into 4 ohms very good. I know someome will say remarkable in whose book. I don't really care. If 2 ohms it should be even better. A nominal 4R speaker could be that. I have some old Dynaco A25. I fancy it would like them.
Hello all,
May I ask a question about the 1969 version please, I've bought this from China;
Reading the very start of this thread (and a lot more) I notice that many posters advocate MJ15003 in place of 2N3055. Though I have used the search for two days now I cannot find if the MJ's would be suitable for the single rail supply.
I have also searched for heat sinks and came across Future Eden in Herefordshire who amongst other things sell heat sinks by the 100mm length. I bought two 146 x 200mm for £25 including free postage, they weigh 518 grams each.
And a link to the page on their web site: 100 - 1000mm Aluminium Heatsinks for Power LEDs, Amps and Transistors – Future Eden Ltd
I should have ordered 4 off 146 x 100 so will cut the 200mm ones in half and position them side by side.
Cheers
May I ask a question about the 1969 version please, I've bought this from China;
Reading the very start of this thread (and a lot more) I notice that many posters advocate MJ15003 in place of 2N3055. Though I have used the search for two days now I cannot find if the MJ's would be suitable for the single rail supply.
I have also searched for heat sinks and came across Future Eden in Herefordshire who amongst other things sell heat sinks by the 100mm length. I bought two 146 x 200mm for £25 including free postage, they weigh 518 grams each.
And a link to the page on their web site: 100 - 1000mm Aluminium Heatsinks for Power LEDs, Amps and Transistors – Future Eden Ltd
I should have ordered 4 off 146 x 100 so will cut the 200mm ones in half and position them side by side.
Cheers
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MJ15003 will work with single and dual supply. You can get them as samples from onsemi if you're not in a hurry.
You need bigger capacitors than the ones that comes with the kit. Replace input cap and output cap minimum, but the bootstrap and feedback caps are also recommended. It was discussed in this thread not so long ago.
You can try them as they are to start with, but they will definitely improve with 'upgrades'.
My recommendations on minimum cap values:
Input 10uF
Output 10000uF (low ESR, maybe something for switched supplies would be good or many in parallel)
Bootstrap 1000uF
Feedback (to ground) 1000uF
This is only from memory, but should be int he right ballpark.
Bigger is better in my opinion.
You need bigger capacitors than the ones that comes with the kit. Replace input cap and output cap minimum, but the bootstrap and feedback caps are also recommended. It was discussed in this thread not so long ago.
You can try them as they are to start with, but they will definitely improve with 'upgrades'.
My recommendations on minimum cap values:
Input 10uF
Output 10000uF (low ESR, maybe something for switched supplies would be good or many in parallel)
Bootstrap 1000uF
Feedback (to ground) 1000uF
This is only from memory, but should be int he right ballpark.
Bigger is better in my opinion.
In 6082 for fun I listed an amplifier that exceeds the JLH whilst being easy to make. Specifically in can offer better dynamics. The gamble is would it have sufficiently low output impedance to work. As a rule a damping factor of three does a good job. Many trendy valve designs are no better like RH34.
I am not a great fan of op amps. Here it's not so bad as speaker back emf never meets the op amp. The opamp is fet input which helps. It looks much like a capacitor where important.
The ability to drive 2 ohms may be a decisive factor. That 5 watts A is possible can't be bad.
If smps used simple resistor bias might be possible. That is that it is regulated.
I am not a great fan of op amps. Here it's not so bad as speaker back emf never meets the op amp. The opamp is fet input which helps. It looks much like a capacitor where important.
The ability to drive 2 ohms may be a decisive factor. That 5 watts A is possible can't be bad.
If smps used simple resistor bias might be possible. That is that it is regulated.
hello gemraid, i think the heatsinks could be a little small. Double size should be fine. The gain of the mj15003 rises with temperature. In my opinion the heatsinks shoulnt get hotter than 70 C which makes the mj15003 about 85 at the transistor. I had made the same thing as you are intending an i found that it sounded best with about 2A quiescent. You should be able to touch the heatsinks for about 5 to 10 sek.
Hello Nigel,
Many thanks for the suggestion, I did see the diagram, sadly though I had already ordered the parts for the JLH69 and I have a large toroid bought on eBay years ago that is 12-0-12v and the reason I chose the JLH. I do use the original CHP70's at 4 Ohms so it would have been ideal, such is life
Hello Horu5,
Oddly enough I had just come in from the garage after cutting one of them in 1/2, here in the pic they are side by side
100 mm deep x 146 mm long they will have one transistor each.
One does notice that heat sinks are somewhat of a rip off with a lot of confusing information. With that in mind I chose size and weight as my criteria I have found lighter heat sinks at 370 grams and twice the price for this amplifier, the originals use by Mr Hood were 125 x 100 mm and look as though they weighed all of 200 grams, and both these advocated for both transistors.
Thanks for the power supply suggestion I do already have a nice big toroid.
Cheers both good of you to reply.
Many thanks for the suggestion, I did see the diagram, sadly though I had already ordered the parts for the JLH69 and I have a large toroid bought on eBay years ago that is 12-0-12v and the reason I chose the JLH. I do use the original CHP70's at 4 Ohms so it would have been ideal, such is life
Hello Horu5,
Oddly enough I had just come in from the garage after cutting one of them in 1/2, here in the pic they are side by side
100 mm deep x 146 mm long they will have one transistor each.
One does notice that heat sinks are somewhat of a rip off with a lot of confusing information. With that in mind I chose size and weight as my criteria I have found lighter heat sinks at 370 grams and twice the price for this amplifier, the originals use by Mr Hood were 125 x 100 mm and look as though they weighed all of 200 grams, and both these advocated for both transistors.
Thanks for the power supply suggestion I do already have a nice big toroid.
Cheers both good of you to reply.
Being able to touch and hold a finger on the heatsinks for 5-10 seconds suggests a temperature of ≤ 60C. I know that at 60C, I can't stand more than 5 seconds without considerable pain. Each of us will have slightly different pain thresholds but an exposed heatsink, even at 60-70C, is a safety hazard and you don't need that, even if no one else comes near it.
I have a 20W class A amp. which has serious heatsinks rated at 0.38K/Watt (that's a 300x80x47mm heavy aluminium casting, BTW) for each channel and with just 1.3A bias current, the heatsinks rise to 56C when the ambient temp. is 20C. Honestly, class A means lots of heat, most of it directly related to the bias power consumption and that means a lot more heatsink than you might think.
The examples of suitable heatsinks that you see in promotional images of the JLH '69 kits are woefully undersized, even for a low, 10W rating. The finished amplifiers also sold from China, have an extra problem as their controls and switches are also attached to the hot chassis and those fitted with volume controls and low grade plastic terminals etc, won't last long if the amplifier is in regular use, warming up etc.
BTW, the shiny new 2N3055 transistors with the old Motorola symbol are obvious fakes so who would bother trying to sell you a fake brand of the world's cheapest TO3 transistor anyway? Try a little solvent on the ink marking - I doubt it will be a permanent label but I mention this for people trying to find something better than the alleged 2N3055 types supplied with kits.
Beware of what you really have for comparison - it's not likely what the marking shows and some examples may actually perform better than genuine On-semi TO3 types. I know that a friend of mine realized this when he substituted original ST Micro 2N3055 and On-semi MJ15003 and found the supplied fakes sounded better, in his opinion
I have a 20W class A amp. which has serious heatsinks rated at 0.38K/Watt (that's a 300x80x47mm heavy aluminium casting, BTW) for each channel and with just 1.3A bias current, the heatsinks rise to 56C when the ambient temp. is 20C. Honestly, class A means lots of heat, most of it directly related to the bias power consumption and that means a lot more heatsink than you might think.
The examples of suitable heatsinks that you see in promotional images of the JLH '69 kits are woefully undersized, even for a low, 10W rating. The finished amplifiers also sold from China, have an extra problem as their controls and switches are also attached to the hot chassis and those fitted with volume controls and low grade plastic terminals etc, won't last long if the amplifier is in regular use, warming up etc.
BTW, the shiny new 2N3055 transistors with the old Motorola symbol are obvious fakes so who would bother trying to sell you a fake brand of the world's cheapest TO3 transistor anyway? Try a little solvent on the ink marking - I doubt it will be a permanent label but I mention this for people trying to find something better than the alleged 2N3055 types supplied with kits.
Beware of what you really have for comparison - it's not likely what the marking shows and some examples may actually perform better than genuine On-semi TO3 types. I know that a friend of mine realized this when he substituted original ST Micro 2N3055 and On-semi MJ15003 and found the supplied fakes sounded better, in his opinion
See Post 5901 and 5904. Have tested the MJ15003 bought from digikey and some of Chinese Kits. The MJ15003 had a rise from about 30% in Gain which stopped at about 85 or 90°C. Gains at 85 were between 100 and 130. For the Chinese Kits, some had really bad used "original" 2N3055 which had gains about 40 and 80. Some of the kits had probably "faked" 3N3055. These kits were more expensive, and had L-connectors with 40/40/5mm -> the others had L-connectors 30/30/3. Those "faked" transistors were pretty well matched, and had higher gains than the MJ15003 and even their gains didn't change with temperature as the MJ15003 did. Yet I didn't compare how they sounded but could be true what Finch considers about it.
For your speakers, if you have the "cheap" version, change to the MJ15003 and attach vertically to the heatsink so that all parts have a better ventilation and dont do any further changes, because these boards are a mess to solder. If you destroy them you have to wait for weeks for new ones. If you want to experiment start with an empty board an buy all the parts. measure temperature.. about 65°C for the heatsinks. First I started with an LM3886 chipamp but wasnt satified with the sound (I always had the feeling that something is missing). Switching to those boards made a clear improvement. So now i use the LM3886 for the sub and the JLH for fullrange > 175hz. further improvement was to use a multichannel soundcard and do Bi-Amping/ FIR filtering with EQAPO / rephase/ REW. that was another clearly audible improvement. Before i would experiment with other transistors etc. i would do crossover optimization. First I thought that it was something about digital source and DAC.. but after studying the matters a good external soundcard, digital filters, must be FIR and class A amplification should be the cleanest thing. I tried analog active crossover, Minidsp analog, minidsp digital (IIR) measured a lot with REW. My system is a magnetostat > 175hz and sub, total THD > 200hz is about 0.1-0.2%, Phase now is an absolutely flat, line. It sounds very clean, close, warm and real. Important is to get clean uncompressed recordings and you'll hear the differences in mastering.. so the same songs, uncompressed will sound different f.ex. Deezer (bad mastering) compared with tidal (much better dynamics)..
Hello Ian,
Thanks for the size of your heatsinks Ian and for the advice about the 'finger'test Horu5.
Hmmmm! Well if I take half of your size there would be two 150 x 80 x 47 per transistor which is very similar to the ones I am going to use which incidentally weigh 258 grams each.
Hello Horu5,
Your both right about some cheap stuff from China some of it's a joke with a price to match, but of unrivaled quality. Model railway enthusiasts being ripped off for motors for instance.
YouTube
A cardboard loco (including the chassis) with a £2.20 (including shipping) 5 pole, skewed armature, double shaft motor. Powered by a three semiconductor controller of JLH era. Some things like bicycles can't be improved upon except for better components.
Cheers both and thanks for your input.
Thanks for the size of your heatsinks Ian and for the advice about the 'finger'test Horu5.
Hmmmm! Well if I take half of your size there would be two 150 x 80 x 47 per transistor which is very similar to the ones I am going to use which incidentally weigh 258 grams each.
Hello Horu5,
Your both right about some cheap stuff from China some of it's a joke with a price to match, but of unrivaled quality. Model railway enthusiasts being ripped off for motors for instance.
YouTube
A cardboard loco (including the chassis) with a £2.20 (including shipping) 5 pole, skewed armature, double shaft motor. Powered by a three semiconductor controller of JLH era. Some things like bicycles can't be improved upon except for better components.
Cheers both and thanks for your input.
I have been watching French TV to see if I can retrieve a little French. Fairly easy to follow as the subject is the obvious. All the same far better to know. How are others passing the time? I fool myself with this as the French on France 24'is impeccable. Highly related to hi fi. The more impeccable the better we hear.
Comparing heatsinks by a rough volume assessment is not really a like-for-like comparison. The problem of rapid heat transfer from the transistor to the furthest fin from it, is the matter and that is about thickness of the backplate and the tapered geometry of the fins themselves, to a lesser extent.
A cheap, low efficiency extruded heatsink will be thin walled, low profile and have a high thermal resistance and that's before you look at surface area and air flow speed through the fins, which really determine the efficiency of heat loss. Then there is the need for a satin or matt black finish to maximize radiant heat loss. That may only contribute a marginal overall increase but still a significant boost to efficiency for the little cost of DIY anodizing or a thinned coat of heat resistant matt black paint. As you buy them, natural finish extrusions have an oxide surface layer which forms rapidly and prevents good adhesion - one reason why black anodizing is better but not everyone is comfortable with DIY electroplating.
For interest, here's what I refer to regarding efficient design. The style shown is not the only type but is indicative of what we use with typical rack style enclosures and the facts are tabulated for each variation: Conrad Heatsinks - Products.
A cheap, low efficiency extruded heatsink will be thin walled, low profile and have a high thermal resistance and that's before you look at surface area and air flow speed through the fins, which really determine the efficiency of heat loss. Then there is the need for a satin or matt black finish to maximize radiant heat loss. That may only contribute a marginal overall increase but still a significant boost to efficiency for the little cost of DIY anodizing or a thinned coat of heat resistant matt black paint. As you buy them, natural finish extrusions have an oxide surface layer which forms rapidly and prevents good adhesion - one reason why black anodizing is better but not everyone is comfortable with DIY electroplating.
For interest, here's what I refer to regarding efficient design. The style shown is not the only type but is indicative of what we use with typical rack style enclosures and the facts are tabulated for each variation: Conrad Heatsinks - Products.
That's why a class A plus AB makes sense. Studies of hearing suggests five watts is plenty of power and in A+AB 1 watt could be plenty. An overbiased AB being so simple to do with simple maths. If a current limited PSU used even the safety of pure class A is available. My version had approximately 5 watts A and 16 watts AB 4ohns. About 50 watts static dissipation stereo. A 0.5 degrees per watt heatsink seemed about right. 20 watts if using 1 watt hypothesis. The supply +/- 15 V.
Hello Ian,
Having done a search through the thread some weeks ago for "Heat sinks" and being utterly confused by the comments most of which come to no particular conclusion. I went back to the source and the following therein.
"Since the supply voltages and output currents involved lead to dissipatons of the order of 17 watts in each output transistor, and since it is undesirable (for component longevity) to permit high operating temperatures, adequate heat sink area must be provided for each transistor. A pair of separately mounted 5in x 4in finned heat sinks is suggested. This is, unfortunately, the penalty which must be paid for class A operation"
One can see that all 4 transistors are mounted onto the two heat sinks and in a metal box with a sealed base. There may be a slotted vent at the back though, but the white patch one can see may have had some text on it.
The modern version of the above at 96 x 90 x 30
I do hesitate to say this but 17 Watts does seem rather insignificent. But. In the light of your comments and similar from many others I have come across in the thread perhaps Mr Hood is entirely incorrect.
Hello Nigel,
Fair play to you I might make your amp yet. In 2012 I fancied making a pair of FH Mk3's and Colin Topps was kind enough to invite me to his house for a listen to them. He was using a 4 Watt SE valve jobbie which had no trouble giving us a concert level volume. Eight years later I am still in awe of the ones I made.
Cheers both.
Having done a search through the thread some weeks ago for "Heat sinks" and being utterly confused by the comments most of which come to no particular conclusion. I went back to the source and the following therein.
"Since the supply voltages and output currents involved lead to dissipatons of the order of 17 watts in each output transistor, and since it is undesirable (for component longevity) to permit high operating temperatures, adequate heat sink area must be provided for each transistor. A pair of separately mounted 5in x 4in finned heat sinks is suggested. This is, unfortunately, the penalty which must be paid for class A operation"
One can see that all 4 transistors are mounted onto the two heat sinks and in a metal box with a sealed base. There may be a slotted vent at the back though, but the white patch one can see may have had some text on it.
The modern version of the above at 96 x 90 x 30
I do hesitate to say this but 17 Watts does seem rather insignificent. But. In the light of your comments and similar from many others I have come across in the thread perhaps Mr Hood is entirely incorrect.
Hello Nigel,
Fair play to you I might make your amp yet. In 2012 I fancied making a pair of FH Mk3's and Colin Topps was kind enough to invite me to his house for a listen to them. He was using a 4 Watt SE valve jobbie which had no trouble giving us a concert level volume. Eight years later I am still in awe of the ones I made.
Cheers both.
It is very hard to be exact. 60C at the heatsink seems as high as I would dare go. .Say that the room might be 30C. If we say 1.2 amps at 34 V we get circa 40 watts of heat mono. That suggest to me 0.5 degrees per watt is about right and a typical good value type. RS have one looking like a Quad 303.
Where a big difference exists is the transistor heat transfer washer. Even with the heat sink at 50C the transistor might be at 90C which could be 150C at the silicon. 3055H has about 25C extra tollence which helps. Research the best washers. They can double the problems if poor quality.
Where a big difference exists is the transistor heat transfer washer. Even with the heat sink at 50C the transistor might be at 90C which could be 150C at the silicon. 3055H has about 25C extra tollence which helps. Research the best washers. They can double the problems if poor quality.
Hello Nigel,
Nice suggestion that of yours about what is every else doing, I would like to add my 10p worth.
I'm a Photoshop fiddler from this
To this. The 'warning' on the left is mostly in Chinese and on a transformer, it was my 'handle' for the rest of the image.
Once a few software steps are learned 99% of it is imagination, I started teaching myself montages in 2011 as a single image photographer of 50+years. It's still the most difficult thing I've ever done but at the same time the most rewarding when something good emerges. If anyone else is interested I will gladly do a screen cast and don't worry about the software or a source of suitable free images.
I also dug the side garden through the winter, used my little Honda yesterday to make it ready for the potatoes.
And lastly some abstract images I created in a slowly cross fading video. With a sound track I made using Rob Jackson's iPad app Moodscaper. I hope it's quite relaxing.
YouTube
I see you have tacitly agreed albeit with some proviso's that Mr Hood did not make a mistake with his little 5" x 4" (125 x 100) heat sinks. Your the first one, thank you.
Cheers and take care.
Nice suggestion that of yours about what is every else doing, I would like to add my 10p worth.
I'm a Photoshop fiddler from this
To this. The 'warning' on the left is mostly in Chinese and on a transformer, it was my 'handle' for the rest of the image.
Once a few software steps are learned 99% of it is imagination, I started teaching myself montages in 2011 as a single image photographer of 50+years. It's still the most difficult thing I've ever done but at the same time the most rewarding when something good emerges. If anyone else is interested I will gladly do a screen cast and don't worry about the software or a source of suitable free images.
I also dug the side garden through the winter, used my little Honda yesterday to make it ready for the potatoes.
And lastly some abstract images I created in a slowly cross fading video. With a sound track I made using Rob Jackson's iPad app Moodscaper. I hope it's quite relaxing.
YouTube
I see you have tacitly agreed albeit with some proviso's that Mr Hood did not make a mistake with his little 5" x 4" (125 x 100) heat sinks. Your the first one, thank you.
Cheers and take care.
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