Is that the power supply for the amplifiers you have shown us, cumbb? Whether it is varnished copper or bare, you will need to reduce the area of the wiring by simplifying and shortening it, best with something thicker that has durable insulation like PVC. Cost can be an issue but building cable is cheap, 5 times heavy enough, solid copper and sometimes you find it for free or at recycling depots.
Many folk like to add a visual element of power by using heavy cables, busbars, capacitors banks etc. but there's not much benefit with a fairly constant load of only one amp or so for 10W here.
Many folk like to add a visual element of power by using heavy cables, busbars, capacitors banks etc. but there's not much benefit with a fairly constant load of only one amp or so for 10W here.
Try a smaller bootstrap like 4u7 polyester ( = > 100V type idealy ) . If measuring the amplifier you might notice slightly more 10 to 500 Hz distortion. As it's class A there should not be any nasty harmonics. If you look at my FET idea a few pages back I used 2u2. It was the point where specs were still good. Often the loop gain is slightly better at LF compared with 10 kHz allowing this to work. Hence we can make a compromise. One should make JLH's 220uF feedback capacitor larger to reduce LF distortion. 1000 uF Non Polar 16 V exist, Non polar is better.
Ian. I think the cheapest transformer wire is the very best. I would guess a metre < 1/100 ohm for 14AWG. For speakers a smaller cross section works best. 0.6 mm is not bad. Generally the thicker the cable is the less treble detail. 0.6mm seems to focus the detail into the 500 Hz to 4 kHz range. Some people bi wire with 0.25 mm to the tweeter. It is possible for a JLH a 0.6mm wire would suit the power supply. I still use a 2 mm section for 0 volts. Being Kirchoffs law the cable will matter in the amplifer or as speaker cables.
If you doubt this get some stranded cable like QED 79 or mains 1.25m^2 to be speaker cables. Use any amplifer of reasonable quality, NAD 3020 or Rotel RA820 will do. The QED 79 sound is exagerated in the treble and not very nice. Next get some 0.5mm ^2 soilid core used for lighting ( or nearest ). It will sound detailed yet dull. Now add the QED and solid together so solid is nearer the speaker. It should sound almost like it's only solid core. Thus the 79 strand is more or less correct, however it is not as nice. The solic cable is a chance to very subtly filter and make what we want to hear more detailed. Photography is similar. I know these things have been said before. As far as I know no one ever said how to do this test. Up to the point I did this I just thought solid wires far better. A word of warning, be gentle with solid wire when taking it off a reel, never buy it as a small length.
One thing I read about solid cables is they might filter radio frequencies a little. If so adding solid to 79 strand sounding better would make sense.
Essex Magnet Wire, 14 AWG Gauge, 0.0675" 1 LB 79ft, Enameled Copper Coil Winding | eBay
This is something of the same type. I like the 2 transistor version. Could use a LM317 current sink to make it simple. Rod's old early El Cheapo class AB could be made into class A. It uses shunt input feedback which I really like. The JLH can be run as shunt feedback if the preamp can drive 32 ohms as my phone can.
Death of Zen - A new Class-A power amp
Death of Zen - A new Class-A power amp
I've made shitloads of "el-cheapo" alikes in late 70's and early 80's; with BC140/160 and 2N3055 (or 3054 for lowpower home fun). The shunt nfb across the output cap (directly from spkr terminal) is essentially good, but implemented in a very bad way here in Rods circuit; it will thump like crazy if you plug/unplug speakers while the amp is "on". There are at least 2 different ways to connect it to minimize or completelly neutralize this unwanted behavior.
My guess is that it would be in essence either similar to a "BJT-ized" PLH - or a Broskie's Triadtron ( Triadtron ).
My guess is that Mr. Cumbb uses a circuit largely similar to the Triadtron but with a NPN splitter (with gain > 1) that uses biasing (a single trim-pot) taken directly from output transistor junction back to the splitter base. (been there myself, but for a low-power design).
El-cheapo is right there on Rod Elliott site. Go to the index and you will find it.
El Cheapo
Simple 40 Watt Power Amplifier
The output darlingtons could be lateral MOS FET's like BUZ900/905. The bias could be class A. I doubt it really needs 68pf to Q2. Q1 is a buffer, it could be an op amp or preamp.
Simple 40 Watt Power Amplifier
The output darlingtons could be lateral MOS FET's like BUZ900/905. The bias could be class A. I doubt it really needs 68pf to Q2. Q1 is a buffer, it could be an op amp or preamp.
eBay JLH 1969 with 2SA1216...
Assembeld PNP A1216 JLH1969 single-ended class A power amp board R33 | eBay
Does anyone have experience or opinions about this version?
Assembeld PNP A1216 JLH1969 single-ended class A power amp board R33 | eBay
Does anyone have experience or opinions about this version?
Dont know, but see if same deal is available on aliexpress. will be much cheaper.
Another option is to look for PCBs on ali or ebay (much cheaper)
and then order parts from a reliable source (mouser, farnell, rscomponents, digikey, etc) Measure the component package once you get hold of PCB and then order components.
regards
Prasi
I have never seen that version, it looks quite a lot different from the NPN version that I'm building, I wanted to build the original first and then consider developments. I was advised to avoid the kits and readymades because of the risk of fake parts, so I bought some plain PCBs that look lovely. I'm assembling it now, it needs some skill to get some bits right. In particular I am unsure of how to arrange the 2N3055s, if the case is collector I will have to isolate them from the heat sink and then make up flying leads to the PCB. Knowing where is a challenge. Good project though.
The kit has been around for more than a year in the PNP version, AFAIK. It seems a good idea to have the output transistors spread well apart and the PCBs mounted directly on a flat faced heatsink. Presumably, 2 heatsinks of around 0.5°C/watt rating will be used for sufficient heat dissipation for a stereo amp. The downside is that the PCB, components and connectors etc. will likely get baked on the heatsink and even if caps are rated 105C, constant heat is not good for DIY assemblies and the typical parts grades/brands we use.
I can't rate just a PCB assembly, since much of the performance is about the power supply and filtering. However, I have compared PNP and NPN versions of some other boards, using the same brand and type of regulated power supplies and a simple, unfiltered supply too. I can only say that when TO3 transistors with parts like 2N3906 with BD139-16 or their opposite genders) are used, the NPN versions seem to be a little better sounding to me. Any super-cheap kit that includes premium grade LAPT Sanken parts has to be suspect, even if they're not actually fake though.
I thought the kits similar to that shown, weren't particularly good sounding but I'm not sure whether that was due to the power transistors being fakes or just off-spec but genuine and still too good to sound right, if you understand me.
I've built and listened to the NPN version of this kit (it sure was cheap!) I'm not convinced there is any benefit from using high frequency, low distortion parts intended for class B, in this class A design though, where the extra distortion produced by the old power devices is actually what helps to make the sound quality what it is
It seems counter-productive to me, but if anyone seriously wanted to use premium parts because they assume the amplifier will sound better, MJ, MJL or NJW21194 and their PNP versions, bought from reputable agencies are a more reliable way to go.
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I have this version. (with njw0302g)
I really like the small pcb very convenient to mount directly on the heatsink.
but like Ian, I'm not convinced by the modern and fast power transistor.
I think to convert it with something slower, will take the time to search.
on the other hand, this pcb has a disadvantage is that we can not adapt many other parts than the origin, there is not much space.
it can be mounted directly between two TO3
I really like the small pcb very convenient to mount directly on the heatsink.
but like Ian, I'm not convinced by the modern and fast power transistor.
I think to convert it with something slower, will take the time to search.
on the other hand, this pcb has a disadvantage is that we can not adapt many other parts than the origin, there is not much space.
it can be mounted directly between two TO3