tl;dr: I built 2 Linsley-Hood 1969 amps from kits I bought on amazon, swapped some parts, and they are amazing.
So I gotta be honest, of all the diy audio stuff I get into, I have stayed away from amps because the waters seem so full of snake oil, and also, I'm afraid of shocking my nuts off with 1000 watts of accidental test tone. Anyway, a friend got the hook baited just enough for me to bite, and I bought that Linsley-Hood 10W amp that you can buy on amazon right now. A cute little kit with all the parts, and it's a mirror-imaged stereo PCB setup, to boot.
I built one up, it tested ok, but I wasn't much moved. Immediately suspected that the components that came with the kit were worth testing. One thing I do know is that a good Class A amp should sound super nice and clean, which wasn't what I was hearing. (Whenever I hear a known good Class A amp, I'm usually pleasantly surprised.) I popped out the power 2N3055s and sure enough, the Beta values were all over the map. I bought a bunch of legit ones from Mouser, tested them all (they were great; the beta values were consistent across the entire batch), and installed those, then replaced the coupling caps with better ones. Not like, break-the-bank prices, just good ones from Mouser. Like $8 or so for film and $2 for electro.
Anyway, I put it all together and matched them up with suitable meanwell power supplies and put it all in a little red tool box.
Boys, it sounds freaking great. Really, really good. I haven't even dialed it in yet. Tests on the scope look great. Passes audio beyond 100kHz.
So I gotta be honest, of all the diy audio stuff I get into, I have stayed away from amps because the waters seem so full of snake oil, and also, I'm afraid of shocking my nuts off with 1000 watts of accidental test tone. Anyway, a friend got the hook baited just enough for me to bite, and I bought that Linsley-Hood 10W amp that you can buy on amazon right now. A cute little kit with all the parts, and it's a mirror-imaged stereo PCB setup, to boot.
I built one up, it tested ok, but I wasn't much moved. Immediately suspected that the components that came with the kit were worth testing. One thing I do know is that a good Class A amp should sound super nice and clean, which wasn't what I was hearing. (Whenever I hear a known good Class A amp, I'm usually pleasantly surprised.) I popped out the power 2N3055s and sure enough, the Beta values were all over the map. I bought a bunch of legit ones from Mouser, tested them all (they were great; the beta values were consistent across the entire batch), and installed those, then replaced the coupling caps with better ones. Not like, break-the-bank prices, just good ones from Mouser. Like $8 or so for film and $2 for electro.
Anyway, I put it all together and matched them up with suitable meanwell power supplies and put it all in a little red tool box.
Boys, it sounds freaking great. Really, really good. I haven't even dialed it in yet. Tests on the scope look great. Passes audio beyond 100kHz.
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Its the best way to drive the JLH, just massive current power to recharge caps,
Congratulation! That is kinda what I use.
Congratulation! That is kinda what I use.
I just have a little pair of JBL 2050s in the dining room. It’s for dinner time listening so I’m not driving anything super hard, but the minute I get a big heat sink on this baby I’m gonna drive a pair of 4412s in my basement and see what happens
It's a Class A amp. It will generate the same amount of heat regardless of volume. Some say even less heat at full volume.
Yes, you are right. I guess I expected everyone to read my mind: I want to get the heat sinks mounted, so I can turn up the current on the power transistors to a higher number to get more power (and more heat). Once I do so, I'm going to plug it into my nice speakers and let er rip.
Ah, interesting. When I was doing initial bench tests, it was clear I could really let those output transistors eat. I think I initially ran them at like 1.25 A and was like, "this is crazy". I was going to shoot from the hip and just set them at 1A. Too much? Too conservative? I'm using a 24V rail.
You are wasting the power , 120ma way sufficient
It will benefit given it can support a higher voltage 40+
It will benefit given it can support a higher voltage 40+
You mean 120ma out of the wall, right? the 1 amp I'm referring to is the current going through the entire amp. Assuming that most of it is going through the power transistors and that a far lower amount is going through the rest of the circuit.
you should adjust it for that.
I run mine at 50ma ... but my version is different, it has one 50V rail, less feedback.
I run mine at 50ma ... but my version is different, it has one 50V rail, less feedback.
Some references: https://sound-au.com/tcaas/jlhab3.htm
this is pseudo class AB, it is not a real class AB amp, the powersupply is unipolar.
this is pseudo class AB, it is not a real class AB amp, the powersupply is unipolar.
Source:
The transient response of the 10-watt class A design (as originally published(1), without the modifications(2), suggested in October 1969 to reduce the h.f. bandwidth) is superior to that of the present circuit in the range 50kHz-2Mhz under load conditions of fairly low capacitive reactance. Under more adverse load conditions the present design will be (technically) better. However, the most careful comparative listening trials, with several of the author's long-suffering friends, have failed to uncover any audible difference between these two designs, both of which will almost certainly surpass in performance the best available valve-operated, transformer-coupled units.
With some tweaks you get a better slew rate also, with OPAMP input stage.
just do this class AB , stabilize it with some local feedback and output inductor, you are in business.
It is way more stable in class AB like this schematic. But the input stage needs also some work.
Just keep it as it is, no bipolar supplies, no complex input etc. (diamonds, parallel etc)
The transient response of the 10-watt class A design (as originally published(1), without the modifications(2), suggested in October 1969 to reduce the h.f. bandwidth) is superior to that of the present circuit in the range 50kHz-2Mhz under load conditions of fairly low capacitive reactance. Under more adverse load conditions the present design will be (technically) better. However, the most careful comparative listening trials, with several of the author's long-suffering friends, have failed to uncover any audible difference between these two designs, both of which will almost certainly surpass in performance the best available valve-operated, transformer-coupled units.
With some tweaks you get a better slew rate also, with OPAMP input stage.
just do this class AB , stabilize it with some local feedback and output inductor, you are in business.
It is way more stable in class AB like this schematic. But the input stage needs also some work.
Just keep it as it is, no bipolar supplies, no complex input etc. (diamonds, parallel etc)