Clone 1969
Hello everyone, hope all is well during these times.
My Yamaha receiver is starting to show it's age (over 20 years) and I'm planning on replacing it while trying something new. I've always wanted to own a class A amplifier since I've heard them in many places and love the sound. Since I'm short on budget and don't have the space for a proper reputable class A amp from reputable companies I decided to turn to eBay to see what I can find. Surprised, I found some options that are in budget, of course coming from over seas. Speakers being used are of the DIY type, 4 ohms nominal. 5 inch woofer and aluminum tweeter; I use them as near field for doing some light mixing and primarily just enjoyment. What I am looking for in these is something that is quite solid and wont fail anytime soon. I am also pretty familiar with electronics and would like something that has a good upgrade path. For example later down the road I might want to re-cap it and put a bigger power supply filtering board in it to increase the sound quality in particular frequencies.
One of the options I came across uses the iconic "hood" transistors and the VU meters look really cool, even if they aren't acurate. Another plus is that this amp has a passive pre-amp, which is just done by a *hopefully* legit Alps blue velvet. Here's the link as it's sold with multiple names: HiFi Pure Class A Power Amplifier 2.0 Channel Stereo Audio Amp Ref to HOOD 1969 | eBay
Another option I was considering has already been talking about here, and some other forums. It's the sometimes fake "Krell" branded ones which everyone knows aren't made by Krell. There seems to be two versions, the standard and then the "Upgraded" model which boasts 18w per channel: Upgraded version Hood1969 Gold seal power tube class A 18W *2 finished amplifier | eBay Standard version: HOOD 1969 class A amplifier /finished amplifier power amp 10W+10W | eBay
What do you guys think? Anyone have experience with these amps? If so, will I see a noticable sound improvement over my current Yamaha? Just some quick specs on it, it uses Class AB topology and is discrete, meaning no IC's for amplification and rather just mosfets.
Thanks everyone!
Hello everyone, hope all is well during these times.
My Yamaha receiver is starting to show it's age (over 20 years) and I'm planning on replacing it while trying something new. I've always wanted to own a class A amplifier since I've heard them in many places and love the sound. Since I'm short on budget and don't have the space for a proper reputable class A amp from reputable companies I decided to turn to eBay to see what I can find. Surprised, I found some options that are in budget, of course coming from over seas. Speakers being used are of the DIY type, 4 ohms nominal. 5 inch woofer and aluminum tweeter; I use them as near field for doing some light mixing and primarily just enjoyment. What I am looking for in these is something that is quite solid and wont fail anytime soon. I am also pretty familiar with electronics and would like something that has a good upgrade path. For example later down the road I might want to re-cap it and put a bigger power supply filtering board in it to increase the sound quality in particular frequencies.
One of the options I came across uses the iconic "hood" transistors and the VU meters look really cool, even if they aren't acurate. Another plus is that this amp has a passive pre-amp, which is just done by a *hopefully* legit Alps blue velvet. Here's the link as it's sold with multiple names: HiFi Pure Class A Power Amplifier 2.0 Channel Stereo Audio Amp Ref to HOOD 1969 | eBay
Another option I was considering has already been talking about here, and some other forums. It's the sometimes fake "Krell" branded ones which everyone knows aren't made by Krell. There seems to be two versions, the standard and then the "Upgraded" model which boasts 18w per channel: Upgraded version Hood1969 Gold seal power tube class A 18W *2 finished amplifier | eBay Standard version: HOOD 1969 class A amplifier /finished amplifier power amp 10W+10W | eBay
What do you guys think? Anyone have experience with these amps? If so, will I see a noticable sound improvement over my current Yamaha? Just some quick specs on it, it uses Class AB topology and is discrete, meaning no IC's for amplification and rather just mosfets.
Thanks everyone!
fairy talesI would say how rude but I would make a better point. Most of us are happy to have paid work. For years now I have done general engineering. Most of it I have no qualifications for. Real world engineers don't care because they see engineering as solving problems. They strongly dislike on paper engineers. The one who say how to do it when the real engineer knows it will fail. All the real engineer wants is accurate information. For example a bearing needs the oil to be specified. Motorcar oil in many applications is wrong. Most assume oil is oil and expensive motorcar oil unbeatable. Alas no.
The motorcycle analogy was an iconic motorcycle that is actually a breast. Iconic like the JLH. What I was saying is work out what's best. I worked for Aylesbury traffic Police as a motorcycle instructor. I would love another but admit you are right about danger.
The JLH amplifier is distinctly different from typical integrated power amplifiers that most people own, because of its vintage, class A design, low power and the fact that whilst you would be buying a commercial product, it's still a DIY design with all the limitations on the tech. features that existed wayback. Yes, it can be beefed up from its basic 10W state but not by much or not without serious changes and proportionally greater heat generation.
I suggest you have a look at the original articles describing this DIY amplifier and its upgrades from 1969, 1996, 2003 and so on before looking to it as a replacement for your old commercial gear, with all their extra features you may be looking for. It's easy and informative reading anyway. Enjoy.
The host site: Elliott Sound Products - The Audio Pages (Main Index)
The original archived article: https://www.sound-au.com/tcaas/jlh1969.pdf
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Hi Ian. This is where we've been recently. To risk a motorcycle analogy again. The most famous British motorcycle might be the BSA Goldstar. The racing version the Manx Norton. Yet the best is the Norton ES2 which can just about get you into trouble with the police. It's best because it is easy to own and has unbeatable road holding ( for a bike ). Making an ES2 into a Ducati won't happen. Better to have the modest version and have less trouble. When I had a Honda CB900F an ES2 taught me how fast they really are. On a country road the power isn't required. Same with the JLH. Also it is less dangerous for the ears. Yamaha had a wonderful class A/AB amplifier. And I think they made a motorcycle when it suited them ( Toyota engines also ).
The JLH is the same. Give it more power to give it more problems.
Ian. I have to say one thing you said about the NAD 3020 is 101 % true and not just caution. The 47uF 63V in the tone controls is running at 74 VDC. 78 VDC at 253 VAC. How did it last so long? The only nice one I have is 47uF 250V, should do nicely, it will form to a higher value no doubt.
The JLH is the same. Give it more power to give it more problems.
Ian. I have to say one thing you said about the NAD 3020 is 101 % true and not just caution. The 47uF 63V in the tone controls is running at 74 VDC. 78 VDC at 253 VAC. How did it last so long? The only nice one I have is 47uF 250V, should do nicely, it will form to a higher value no doubt.
It shouldn't be difficult for you to limit the power output of your equipment to 10 watts to appreciate this. Most of the equipment offered from China under the JLH brand is various devices with a capacity of 3-10 watts. As a rule, integrators assemble low-volume equipment from ready-made assemblies from other Chinese manufacturers from Chinese parts.
How does it do? I read that it’s not a good idea to pair it with low impedance loads. How’s the low frequency? How do the mids sound?
Adjusted to 24v and used the scope to balance the clipping to be equal . The amp is driving a set of will burrow betsy speakers. Bass starts to drop on scope about 100hz. Quite quiet when set to 24 volts. Hiss at 22v when full volume no signal. I listen at 60 to 80 db and sounds fine. Speakers with wide impedance curves will be a problem. The amp did not do well with the model 15 Altecs I tried. I do not know why the wave forms posted vertical.
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That looks like the "Gold Seal" Chinese built JLH version with some different output caps. For the record, I have a similar one and its nice to use - even has a faked ALPS RK27 volume pot. Perhaps all the component brands are faked but its it's still a nice sounding and very simple little amp., provided you weren't expecting to get the power needed for low impedance, low sensitivity speakers.
Heat's a problem with the small chassis too - the whole thing, including the volume knob goes over 50C in summer and that's not so good for pots or even the gold finish.
Heat's a problem with the small chassis too - the whole thing, including the volume knob goes over 50C in summer and that's not so good for pots or even the gold finish.
There has been a lot of talk about transistor substitutions. One transistor that was commonly recommended as a replacement for the 2n3055 was mj15003. Was this all about speed? Some older 2n3055 were slow. It seems that there are brand name 2n3055 made which are 6MHz.
2N3055AG ON Semiconductor | Mouser Australia
This is much faster than mj15003 which is 2MHz.
MJ15003G ON Semiconductor | Mouser Australia
2N3055AG ON Semiconductor | Mouser Australia
This is much faster than mj15003 which is 2MHz.
MJ15003G ON Semiconductor | Mouser Australia
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I built a slow version and it would do 250 kHz which is rather good. As I pointed out the fast transistors have high gain which can help as long as they don't oscillate ( 90% certain they will ). 2SC5200 was running away a litte bit in the PSU test. I was surprised as the TIP3055 didn't ( a tribute device that is like it's relation to 2N3055 ). That also is a factor.
The mistake many seem to make is they think the salvation quality for class AB is the same for class A. The whole point of class A is to overcome that need. AB switches, A doesn't ( if it's real class A ). Class D finds bipolar transistors too slow. C5200/A1943 would be far too slow. MOSFETs used instead.
From my tests the driver transistor was more the question. Even so a totally excellent device in itself could ruin the amplifer. I sort of think BD139 is good for this device.
The other problem is the driver should be high current gain to take load off of these input transistor. My final design used BC327-40 BC337-40 and 2N3055E ( MJ15015 also looks good ). Distortion was 0.03% at 10 kHz 8 watts. It was less at the lower wattages/ frequencies. I now realise on paper the BC337-40 was too smalll. It must have been close to it's limit. It wasn't 100% stable before a small capacitor was added which means the amplifier has an optimum speed that even 2N3055 can exceed. All I have is the 1W test. I had to build a special oscillator to measure as it's close to no distortion. You will never get 1 watt in real music at 10 kHz ( I think, Not even Rick Wakeman ) . Notice no RF output. That wasn't true at first.
By the way. Modern 2N3055 seem to be a modern transistor with the old number. As far as I can see MJ15015 that fails the voltage test is sold as a 2N3055. It's a high voltage at very little current that shows the limit without killing the device. BD139/135 the same. MPSA44 is a selected MPSA42.
The mistake many seem to make is they think the salvation quality for class AB is the same for class A. The whole point of class A is to overcome that need. AB switches, A doesn't ( if it's real class A ). Class D finds bipolar transistors too slow. C5200/A1943 would be far too slow. MOSFETs used instead.
From my tests the driver transistor was more the question. Even so a totally excellent device in itself could ruin the amplifer. I sort of think BD139 is good for this device.
The other problem is the driver should be high current gain to take load off of these input transistor. My final design used BC327-40 BC337-40 and 2N3055E ( MJ15015 also looks good ). Distortion was 0.03% at 10 kHz 8 watts. It was less at the lower wattages/ frequencies. I now realise on paper the BC337-40 was too smalll. It must have been close to it's limit. It wasn't 100% stable before a small capacitor was added which means the amplifier has an optimum speed that even 2N3055 can exceed. All I have is the 1W test. I had to build a special oscillator to measure as it's close to no distortion. You will never get 1 watt in real music at 10 kHz ( I think, Not even Rick Wakeman ) . Notice no RF output. That wasn't true at first.
By the way. Modern 2N3055 seem to be a modern transistor with the old number. As far as I can see MJ15015 that fails the voltage test is sold as a 2N3055. It's a high voltage at very little current that shows the limit without killing the device. BD139/135 the same. MPSA44 is a selected MPSA42.
2n3055 is a synonym for a powerful general-purpose silicon transistor in TO3 package.
Different manufacturers used different crystals at different times.
MJ15003 are more powerful.
You can use different transistors (plastic is more convenient).
Selection by Hfe is required (more than 100).
Different manufacturers used different crystals at different times.
MJ15003 are more powerful.
You can use different transistors (plastic is more convenient).
Selection by Hfe is required (more than 100).
I see TIP3055 as excellent if you only need 1.2 amps ( 27 VDC 1969 version ). T03 package for anything greater. MJ15015 is called 2N3055A if lower voltage. MJ802 still seems to be around.
You could use a high speed transistor like 2SC5200 and use a small cog ceramic capacitor collector to base. Try multiples of the data sheet value given ( 220 pF ? ). That way do get the gain without the trouble. You still might get bias drift. All bipolar transistors drift. These seem more variable than others. It could be 47pF is ideal. My heatsink was large so not that.
JLH did warn that very fast transistors sounded worse and didn't really know why. It can be mild instability only music finds ( I have no idea either ). One description is chromium plated sound.
You could use a high speed transistor like 2SC5200 and use a small cog ceramic capacitor collector to base. Try multiples of the data sheet value given ( 220 pF ? ). That way do get the gain without the trouble. You still might get bias drift. All bipolar transistors drift. These seem more variable than others. It could be 47pF is ideal. My heatsink was large so not that.
JLH did warn that very fast transistors sounded worse and didn't really know why. It can be mild instability only music finds ( I have no idea either ). One description is chromium plated sound.
i use 60MHz transistors for the output (80MHz at 2A) without any problems and i have to say the sound is much better than with slow transistors so i can say with certainty that the faster transistor is still better
i did the same for Hiraga Le Monstre and the result is the same, faster transistors sound better
https://www.diyaudio.com/forums/solid-state/5462-hiraga-le-monstre-183.html#post6232063
i did the same for Hiraga Le Monstre and the result is the same, faster transistors sound better
https://www.diyaudio.com/forums/solid-state/5462-hiraga-le-monstre-183.html#post6232063
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Yes I now notice that mj15003 is rated at 250W.
The 6MHz 2N3055AG i linked to seems to only have 2.5hFE. If this is correct then i assume it is unsuitable.
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