It seems the market for low power designs is catered for almost entirely by chipamps? I wondered what discrete amps in the 5-15W power output range were around?
I've searched, but am not turning up any relevant designs, generally either lo-fi fun projects or class-A amplifiers, a few old designs using discontinued parts mabye also. I am interested in a modern, true Hi-Fi discrete class-AB design, like a low power Symasym or similar. I suppose it'd use TO-220 output devices, perhaps even SOT-32.
I am thinking people may want such amplifiers for small, high quality desktop applications. If no applicable designs exist perhaps it'd be a fun design challenge!
I've searched, but am not turning up any relevant designs, generally either lo-fi fun projects or class-A amplifiers, a few old designs using discontinued parts mabye also. I am interested in a modern, true Hi-Fi discrete class-AB design, like a low power Symasym or similar. I suppose it'd use TO-220 output devices, perhaps even SOT-32.
I am thinking people may want such amplifiers for small, high quality desktop applications. If no applicable designs exist perhaps it'd be a fun design challenge!
Just curious, what's wrong with a Class-A design?
Certainly fits the bill for discrete parts & 5-15W 🙂
Certainly fits the bill for discrete parts & 5-15W 🙂
Not strictly against it, if you know any good ones please post links! However, they have large heatsink requirements so won't make an ideal compact desktop amplifier. Something which can fit into a Hammond heatsink case would be great 🙂
Interesting designs, but feel that dissipation is too high, both in terms of heatsinking and supply power requirements.
If I were to build a discrete amplifier instead of using a chip, it'd have to run from 2x12VAC, 75VA, a power supply I've already built but quite a widely useable supply for most I think.
A modern low distortion design is what I think I want, I expect similar to the circuits inside the chips but sans all the protection systems.
If I were to build a discrete amplifier instead of using a chip, it'd have to run from 2x12VAC, 75VA, a power supply I've already built but quite a widely useable supply for most I think.
A modern low distortion design is what I think I want, I expect similar to the circuits inside the chips but sans all the protection systems.
I am working on a project that may be just what you are after. It's a compact top quality amp, but is rated about 80W. However, it will run from lower voltage rails just fine.
Let me know if you are interested.
Let me know if you are interested.
Sounds good! Ideally, it'd use scaled down output devices for low voltage operation or somehow be stripped back to just the drivers (if possible?) to save cost and space.
It uses TO-247 Sanken darlingtons in the output, but you might get away with some decent TO-220 non-darlingtons at the power you want. The PCB wouldn't be any smaller though.
PS my hands are pretty small 😀
An externally hosted image should be here but it was not working when we last tested it.
PS my hands are pretty small 😀
Very nice rich!
Is that a home etched PCB? looks pretty good if it is! Double sided too?
Looks like the sort of thing I want to put in a case I have spare. 160mm wide 50mm high 40mm deep heatsink in it. Got a transformer from a Technics SU-Z55 (which provides about 38V rails) i'd like to use too. Good enough for a small bedroom amp!
Is that a home etched PCB? looks pretty good if it is! Double sided too?
Looks like the sort of thing I want to put in a case I have spare. 160mm wide 50mm high 40mm deep heatsink in it. Got a transformer from a Technics SU-Z55 (which provides about 38V rails) i'd like to use too. Good enough for a small bedroom amp!
Thanks! It is home made, single sided. Would be ideal for your transformer, I designed it to run off 34V rails.
Interesting. What I'd essentially be thinking is, using the Symasym as an example (a very nice amplifier, I've built 4 normal version), to scale the drivers back to BD139/140 type devices and probably be able to move them off the main heatsink, make the output devices TO-220s and could probably loose the rail fuses and downsize the capacitors for lower voltage ones, overall reducing the PCB size by quite a bit:
SymAsym5 - Project
It's only a rough plan, I'd need to find suitable parts and simulate it then build a test version. Possible though?
I noticed though, unfortunately, that the CHR-70 I had sort of intended to drive are 4ohm, which isn't ideal.
SymAsym5 - Project
It's only a rough plan, I'd need to find suitable parts and simulate it then build a test version. Possible though?
I noticed though, unfortunately, that the CHR-70 I had sort of intended to drive are 4ohm, which isn't ideal.
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That's what I did last year. Started with something similar, produced a small pcb by using TO-220's, no rail fuses and kept capacitors with psu on a short leash - worked just fine:
http://www.diyaudio.com/forums/solid-state/140461-tgm-amplifier-21.html#post1818604
Been there; done that. These DiY computer speakers are rated at 3.0W to correspond with the rating of the car replacement wide range speeks used here. The design also served as a low power prototype for the basis of a more powerful SS amp. It works very well indeed, and the biggest limitation is with the speeks (80Hz -- 15KHz) and that needs some help from the audio card equalizer. Still, the results are quite good, with good detail, solid bass (within the limitations of the speeks, of course). These definitely sound much better than any "store bought" products that are comparable.
The circuit boards are built "dead bug" style, and mount right in these Rat Shack "project boxes". The power supply is a separate unit, and uses aircraft type "cannon plugs" to send power to the speaker boxes. The amps were built from the "transistors anonymous" that come 15 to a pack for less than a buck. The finals are 2N3053s in the quasi-comp OTL topology. These are specced at Pc= 5.0W, and are quite adequate for the purpose. I adjusted the sound card output so that this rating wouldn't be exceeded, and that is a possibility since the power supply runs at +/- 16.7Vdc, and could supply as much as 10W of output if driven up against the rails. That would take out the speeks as well as the finals if you let that happen. The over designed power supply contributes to the sonic excellence of this design.
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What about this 8w clasic? There is a thread here that is devoted to it and has some subsitute transistors listed. It dose however call for a verry
low noise power supply. I think the original one used 2 80Ah car batterys
and 2 250,000uf capacitor banks! The name realy applied to the power
supply.
low noise power supply. I think the original one used 2 80Ah car batterys
and 2 250,000uf capacitor banks! The name realy applied to the power
supply.
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The Diamante is a close relation. It is described as a high output current discrete opamp.
The final 3pr output stage could be replaced with 1pr To126 or To220 devices.
The input pair could be replaced with K170 (matched pair)
Wow! Some excellent suggestions there! I'll look more deeply into each and see what fits the bill.
Bigun, I'll have to read the thread right through but that's great to see someone has executed such a design before 🙂
Miles Prower, this sounds interesting and evidently runs from the same power rails I intend, do you have any schematic or design notes for it?
woody, looks a nice design, I'll search out the thread with the modern parts replacements. A regulated supply isn't out of the question so it may be possible.
AndrewT, I really like the sound of this! I've seen the Diamonte design on here and thought it looked excellent, so if I can adapt it to power a speaker with a few watts that'd be ideal. I'll have to see what transistors I have around and if there's any chance of it working on breadboard/plugblock (?) I may have a go at it. I have lots of BD139/140 pairs which should be suitable for low power output, perhaps moderate power with 2-3 pairs on each?
Bigun, I'll have to read the thread right through but that's great to see someone has executed such a design before 🙂
Miles Prower, this sounds interesting and evidently runs from the same power rails I intend, do you have any schematic or design notes for it?
woody, looks a nice design, I'll search out the thread with the modern parts replacements. A regulated supply isn't out of the question so it may be possible.
AndrewT, I really like the sound of this! I've seen the Diamonte design on here and thought it looked excellent, so if I can adapt it to power a speaker with a few watts that'd be ideal. I'll have to see what transistors I have around and if there's any chance of it working on breadboard/plugblock (?) I may have a go at it. I have lots of BD139/140 pairs which should be suitable for low power output, perhaps moderate power with 2-3 pairs on each?
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