In the past, I built a range of fairly simple (speaker) amplifiers using ready-made PCBs, which were successful and quite fun. Prompted by a kind PM from another member, I'm toying with the idea of trying something just a little bit more sophisticated next, with particular interest in low noise design (for use as power amps for close and potentially sensitive speakers). Such as having good power supply rejection ratio and low noise input stage etc.
I've some idea of features this might entail, but to increase chances of success I'm really looking for proven designs to either make or at least start from. I've decided that class AB would suit me best, but there are still a bewildering array of possibilities on diyAudio. So I wondered if people could suggest some good low-noise designs that I might look at trying to build?
Thanks,
Kev
I've some idea of features this might entail, but to increase chances of success I'm really looking for proven designs to either make or at least start from. I've decided that class AB would suit me best, but there are still a bewildering array of possibilities on diyAudio. So I wondered if people could suggest some good low-noise designs that I might look at trying to build?
Thanks,
Kev
What power output are you looking for? In a 100W range the VHex+ is very easy to make low noise. https://www.diyaudio.com/community/threads/sons-of-vhex.294632/post-4827456
https://virtualzeroaudio.com/collec...ily/products/vhex-classic-boards-set-2-x-pcbs
https://virtualzeroaudio.com/collec...ily/products/vhex-classic-boards-set-2-x-pcbs
I've a few possible applications, and so would be interested in circuits of almost any typical (home/hifi amp) type power capability. Lets say from (roughly) 20watts upwards. I probably wouldn't need more than 50W but more doesn't have to be a problem as such, especially if lower voltage PSUs could be employed where wanted. So perhaps rather than wattage, the upper end might be defined by designs having rail voltages low enough to use low-noise semiconductors easily and simply, and avoid getting into complication or expense for voltages/powers I'd not make use of?
Thanks for the links, that amp looks very successful! Though I can't see the circuit design on their page, perhaps I need to create an account, but I see there are some on that long diyaudio thread; I'll have a read!
BTW, I'm in the UK, and on past experience it can be costly (or difficult) to get things posted/imported from around the world. So I'd also be interested in designs without physical PCBs, too. I'd certainly need to learn something about layout of amp boards, but for other electronics I have made my own single-layer PCBs in the past, which some designs might be okay with. Maybe not smd, though I guess there are fairly cheap services to make multi-layer boards for you, these days.
Thanks for the links, that amp looks very successful! Though I can't see the circuit design on their page, perhaps I need to create an account, but I see there are some on that long diyaudio thread; I'll have a read!
BTW, I'm in the UK, and on past experience it can be costly (or difficult) to get things posted/imported from around the world. So I'd also be interested in designs without physical PCBs, too. I'd certainly need to learn something about layout of amp boards, but for other electronics I have made my own single-layer PCBs in the past, which some designs might be okay with. Maybe not smd, though I guess there are fairly cheap services to make multi-layer boards for you, these days.
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FYI elektor has come out with a new audio power amp design available in kit form. It’s using some onsemi thermal track devices for an output stage. It uses low noise complementary bc5??? parts for the input stage. mono block construction.
The article is free for download
The article is free for download
"Low noise" is a result of less parts.
Do use a 1-step-(complementary-transes)-push-pull-follower: 2 diodes, 2 power-resistors, 2 trimmers, 2 transes.
Do use a 1-step-(complementary-transes)-push-pull-follower: 2 diodes, 2 power-resistors, 2 trimmers, 2 transes.
Okay, I've read some of that long vhex thread now: it is quite inspiring, thank you for the suggestion!
It is certainly more sophisticated than my past projects, and the measurements are much better; yet without looking hopelessly complicated. By standing on the shoulders of the giants who designed it, even I could have a chance of making it. I'll go through the rest of the thread later when I've more time, try to understand more about it and also look at availability of components and so on. 🙂
Thanks again,
Kev
I would suggest a vintage design made very popular by Maplin in the UK.
It uses lateral mosfets outputs sold nowadays by Profusion (also in the UK I think).
Probably the simplest design you can get for that sound quality and power (~50W/8ohms).
PCB shown was drawn by Prasi, an active member here.
Works surprisingly well.
It uses lateral mosfets outputs sold nowadays by Profusion (also in the UK I think).
Probably the simplest design you can get for that sound quality and power (~50W/8ohms).
PCB shown was drawn by Prasi, an active member here.
Works surprisingly well.
Attachments
Gosh, that brings back memories. I shall have a look around and see if I can find any noise measurements for it. As a design I perhaps like the vhex+ more, however I have some of the output devices mentioned for the maplin amp. So it is well worth knowing about; I might build one, whether for this application or another.
Thanks, Kev
Thanks for the suggestion, that is new to me. I couldn't see too much about it in detail; elsewhere there were some opinions suggesting that it might depend a lot on the power supply for its performance figures, and might perhaps struggle for stability in some cases. But they could just be ill-informed or sour grapes; from the blurb it does seem like it would address my goals well, a very interesting kit.
But at the moment, I'm not really looking for a full kit. I fancy trying to go slightly more DIY, and I already have numerous big heatsinks and various other components which wouldn't need re-purchasing. Though that feeling may go away quite quickly, if I have trouble sourcing components or getting the thing to work.
Low noise has a lot to do with case & power supply design. If you buy a worn out pro amp you get copper bound EI transformer, metal shield between transformer and input parts, steel case to keep AM/CB/Police/Fire/ham radio out.
Then replace rubber parts (e-caps) pots connectors as required.
I've built an AX6 with point to point wires in a ST120 chassis, and it was low noise until a wire popped loose. Now with the ground wire reinstalled in the wrong location, it hums. Layout is critical. https://www.diyaudio.com/forums/solid-state/236256-retro-amp-50w-single-supply-42.html
Parts are not critical, nobody sells actual tested low noise transistors anymore because all high yield processes (economically successful) avoid the dust dirt and fab errors that plagued transistors in the 1970's. Those BC550c transistors everybody slobbers over had a noise spec from Siemens, but the modern datasheets from fairchild ST leave that number off. Exception, use metal film resistors, they are a lot quieter than carbon composition and some quieter than carbon film.
Then replace rubber parts (e-caps) pots connectors as required.
I've built an AX6 with point to point wires in a ST120 chassis, and it was low noise until a wire popped loose. Now with the ground wire reinstalled in the wrong location, it hums. Layout is critical. https://www.diyaudio.com/forums/solid-state/236256-retro-amp-50w-single-supply-42.html
Parts are not critical, nobody sells actual tested low noise transistors anymore because all high yield processes (economically successful) avoid the dust dirt and fab errors that plagued transistors in the 1970's. Those BC550c transistors everybody slobbers over had a noise spec from Siemens, but the modern datasheets from fairchild ST leave that number off. Exception, use metal film resistors, they are a lot quieter than carbon composition and some quieter than carbon film.
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Wolverine Class A/AB
Neurochrome Audio Modulus 686 (somewhat prebuilt, but definitely proven). Also: Choosing your amp
Hifisonix KX-2
Best,
Anand.
Neurochrome Audio Modulus 686 (somewhat prebuilt, but definitely proven). Also: Choosing your amp
Hifisonix KX-2
Best,
Anand.
Member
Joined 2009
Paid Member
I've read that the Circlophone, not necessarily designed for low noise as a priority, has proven to be especially quiet in operation. I've not heard one but I respect the reports that I've received on this amplifier.
https://www.diyaudio.com/community/threads/my-little-cheap-circlophone-c.189599/
Let me be the first to qualify that this is not strictly class AB, but I suggest you take a look at it.
https://www.diyaudio.com/community/threads/my-little-cheap-circlophone-c.189599/
Let me be the first to qualify that this is not strictly class AB, but I suggest you take a look at it.
Thank you everyone, looks like another good couple of contenders to look at; I'd not even heard of the circlophone or kx-2 before so some reading and evaluation ahead of me, there.
Yes, I realise there is more (much more) to low noise than the amp design/circuit itself; this is really just the starting point. I have gained some experience of power supply, layout, grounding and shielding from previous projects, but (as ever) still more to learn. The suggestion of salvaging case, transformer etc from a tired amp is also a good one, if i can find something suitable at a reasonable price.
Thanks,
Kev
Yes, I realise there is more (much more) to low noise than the amp design/circuit itself; this is really just the starting point. I have gained some experience of power supply, layout, grounding and shielding from previous projects, but (as ever) still more to learn. The suggestion of salvaging case, transformer etc from a tired amp is also a good one, if i can find something suitable at a reasonable price.
Thanks,
Kev
As Bigun mentioned, the C was not especially designed with exceptionally low noise in mind: it was a good, all-purpose discrete amplifier, but some members noticed this unexpected aspect.
Noise measurements were good, but not stellar, however a listening test revealed a remarkable (and as yet unexplained) quietness.
Some details here:
https://www.diyaudio.com/community/...-the-circlophone-topology.205225/post-2876352
Noise measurements were good, but not stellar, however a listening test revealed a remarkable (and as yet unexplained) quietness.
Some details here:
https://www.diyaudio.com/community/...-the-circlophone-topology.205225/post-2876352
Thank you for the additional thoughts and link. I shall do some reading up on it later, but at least initially the circlophone does seem to be very suitable; low noise yet quite approachable for a relative novice. Possibly simpler and cheaper than some alternatives, too.
Good stuff that is at least two, possibly three good options for me to consider. I suppose there is no reason why I couldn't build a couple of them rather than choose just one. I have a few applications and some ( for active crossovers) need more than one amp, with slightly different requirements for each.
Thanks again,
Kev
Good stuff that is at least two, possibly three good options for me to consider. I suppose there is no reason why I couldn't build a couple of them rather than choose just one. I have a few applications and some ( for active crossovers) need more than one amp, with slightly different requirements for each.
Thanks again,
Kev
The C also has a building thread, with useful practical info:
https://www.diyaudio.com/community/...ssories-beginner-friendly.209907/post-2968086
https://www.diyaudio.com/community/...ssories-beginner-friendly.209907/post-2968086
I suggest furthermore:
Hiraga Le Classe A
Hiraga Le Monstre.
Just 4-step-half-waves-symmetric-push-pull-amps.
For lower noise do use just two lateral-pairs of transes.
Great stuff, even it is not "highend" - because push-pull.
Hiraga Le Classe A
Hiraga Le Monstre.
Just 4-step-half-waves-symmetric-push-pull-amps.
For lower noise do use just two lateral-pairs of transes.
Great stuff, even it is not "highend" - because push-pull.
Thank you for the suggestion. Currently I don't really want to use class-A for this, but if that changes I'll certainly look into those designs. The simplicity is definitely quite nice, even if the (power) inefficiency is somewhat less tempting.
Anyway, I've been reading the various threads on the VHex+ and also the Circlophone and find both very appealing; I think either would fulfill my criteria. Though they have quite different objectives and qualities, so rather than choose I'll very likely end up building both, possibly starting with the slightly easier and cheaper circlophone. It'll be a while before I can start, but I needed to decide now what my strategy will be for amplification: whether to buy new, buy used or make the amps.
Thanks to everyone for their thoughts and advice!
Kev
Anyway, I've been reading the various threads on the VHex+ and also the Circlophone and find both very appealing; I think either would fulfill my criteria. Though they have quite different objectives and qualities, so rather than choose I'll very likely end up building both, possibly starting with the slightly easier and cheaper circlophone. It'll be a while before I can start, but I needed to decide now what my strategy will be for amplification: whether to buy new, buy used or make the amps.
Thanks to everyone for their thoughts and advice!
Kev