More of an discussion piece, but just wanted to generate some thoughts. Sorry for the long post. As a precursor, my affinity between subjective and objective analysis lies very much in the middle. I had a decade long break from DIY audio (Warren Young and Ti Kan's designs were fresh off the block back then) but I think I have now caught up back to speed. Henceforth, this post.
With the development over the past decade of better solid state ICs, there has been an overall drive towards objectively brilliant commercial amps, resulting in JDS (Atom, Element), Topping (A90, now single-ended L30), and THX AAA-based amps dominating large sectors of the market. The ASR.com or "Audio Precision" effect.
Looking at these design topologies, they all use implementations of ultra low-noise opamps (NJM2068 in Atom, OPA1612 in A90) combined with ultra-high feedback loops / nested topologies and buffers (LME49600 in JDS amps, TPA6120A2 "Nested Feedback Composite Amplifier" quad-channel in Topping's A90).
Correct me if I'm wrong but ever since the Objective 2, there does not appear to be many that have made a significant impact in SS-IC amps in the DIY arena. I'm aware of The Wire but haven't seen much more progress for a while. There is also a PCB layout from Pavouk of LME49720 gain + LME49600 DC servo, based on TI's own evaluation board schematic, but again this hasn't really taken off in DIY circles. A rough and readily conjured chinese PCB implementation of this is available for £3 at your favourite auction site. I haven't found any complete non-modular designs which surpass Objective 2's objective qualities.
Then there is Tom's incredible Neurochrome HP-2. However, this is closed source with no schematic available. This is no criticism though, as the design is absolutely first class, with obvious and understandably huge amounts of effort being put in. However, I would classify this more as a commercial implementation.
I'm curious then, why more ultra-low noise solid state IC-based high-feedback designs haven't been pursued any further in open source discussion? Perhaps we've reached a nadir of DIY performance? ASR would disagree, but striving for inaudible gains might not be in the DIY ethos? Perhaps it's a limitation of measurement, given that commercial amps are approaching the noise limits of $25k testing equipment? Are commercial implementations simply too good in value versus performance that it hasn't been worth it? Perhaps DIY audiophiles prefer deliberate sound signature modification through discrete designs? Maybe, I am simply looking in the wrong place and need enlightening?
I really don't know the answers. What are other people's thoughts? Clearly there have been some great discrete DIY amplifiers born from these forums recently and elsewhere, but what is happening to IC-based development?
With the development over the past decade of better solid state ICs, there has been an overall drive towards objectively brilliant commercial amps, resulting in JDS (Atom, Element), Topping (A90, now single-ended L30), and THX AAA-based amps dominating large sectors of the market. The ASR.com or "Audio Precision" effect.
Looking at these design topologies, they all use implementations of ultra low-noise opamps (NJM2068 in Atom, OPA1612 in A90) combined with ultra-high feedback loops / nested topologies and buffers (LME49600 in JDS amps, TPA6120A2 "Nested Feedback Composite Amplifier" quad-channel in Topping's A90).
Correct me if I'm wrong but ever since the Objective 2, there does not appear to be many that have made a significant impact in SS-IC amps in the DIY arena. I'm aware of The Wire but haven't seen much more progress for a while. There is also a PCB layout from Pavouk of LME49720 gain + LME49600 DC servo, based on TI's own evaluation board schematic, but again this hasn't really taken off in DIY circles. A rough and readily conjured chinese PCB implementation of this is available for £3 at your favourite auction site. I haven't found any complete non-modular designs which surpass Objective 2's objective qualities.
Then there is Tom's incredible Neurochrome HP-2. However, this is closed source with no schematic available. This is no criticism though, as the design is absolutely first class, with obvious and understandably huge amounts of effort being put in. However, I would classify this more as a commercial implementation.
I'm curious then, why more ultra-low noise solid state IC-based high-feedback designs haven't been pursued any further in open source discussion? Perhaps we've reached a nadir of DIY performance? ASR would disagree, but striving for inaudible gains might not be in the DIY ethos? Perhaps it's a limitation of measurement, given that commercial amps are approaching the noise limits of $25k testing equipment? Are commercial implementations simply too good in value versus performance that it hasn't been worth it? Perhaps DIY audiophiles prefer deliberate sound signature modification through discrete designs? Maybe, I am simply looking in the wrong place and need enlightening?
I really don't know the answers. What are other people's thoughts? Clearly there have been some great discrete DIY amplifiers born from these forums recently and elsewhere, but what is happening to IC-based development?
Yes, a broad combination of those two things. Schiit is offering up this same debate with the simultaneous launch of the Magni Heresy (opamp) and Magni 3+ (discrete) headphone amps (buy both and send back one).
I think that the O2 is still a standard that everyone should have access to...
As an old fashioned DIYer and Nelson Pass disciple I am more likely to want to build something discrete over something chip based in general. If I ask 'what is Nelson doing in the headphone amp sector?' I would find the Whammy which is a bit chip-based and available as a kit here on this site. I would also find the ACP+ discrete preamp/headphone amp, a pcb for which is due out soon on this site. So we are not starved for choice!
Sounds like more of a university debate on the philosophy of recreational audio than the simple joys and delight of building your own creation that lends nothing to--put a big lump of plastic here ---join with another big lump-- job "done " .
In that case just "dumb down " the actual excitement of building a discrete circuit from scratch --just open up your thick book of IC design
and choose between raspberry flavour and lemon flavour.
Close down DIY audio everywhere and listen to your manufacturing guru telling you --buy our latest chip just add a capacitor/resistor at either end .
Look back in history -not historical revisionism but reality and you will find innovation came from cobbling together some parts and making them work together into an innovative engineering appliance.
Take away that drive ,that spirit of adventure and you are left with a controlled,repressed society , have you watched Brazil the Movie ?
Don,t think this is "pie in the sky " I can quote a very well known UK website I was on for years that wouldn't be out of place in ,30s Germany for its OTT control of how the regulars there -think-act treating them as children.
In that case just "dumb down " the actual excitement of building a discrete circuit from scratch --just open up your thick book of IC design
and choose between raspberry flavour and lemon flavour.
Close down DIY audio everywhere and listen to your manufacturing guru telling you --buy our latest chip just add a capacitor/resistor at either end .
Look back in history -not historical revisionism but reality and you will find innovation came from cobbling together some parts and making them work together into an innovative engineering appliance.
Take away that drive ,that spirit of adventure and you are left with a controlled,repressed society , have you watched Brazil the Movie ?
Don,t think this is "pie in the sky " I can quote a very well known UK website I was on for years that wouldn't be out of place in ,30s Germany for its OTT control of how the regulars there -think-act treating them as children.
A few reasons:
- "bigger is better". Opamps based circuit aren't much to look at. What good is DIY if you can't brag about it ?
- "I can't solder that thing". The tpa6120 in particular, but other IC too, doesn't come in through hole, easy to solder packages.
- "Is it really working fine ?" A multiloop, state of the art amp is a bit more involved stability wise than most discrete designs around. Without a good scope, it might be difficult to properly check.
- "Opamps are not as good as the "real" thing". Years and years of prejudice in DIY circles against opamps, compounded by the marketing of firms appealing to DIYers (such as Burson).
- "It's so easy to have a class A design for headphones, why bother with opamps in class AB ?" See just above.
- "It just ain't fun". Since it's easy to go overboard with headphones since their power requirements are so low, why not go for the outrageous technologies I cannot usually experiment with ? Class A, SE, OTL tubes, etc.
Just a few good and bad reasons.
- "bigger is better". Opamps based circuit aren't much to look at. What good is DIY if you can't brag about it ?
- "I can't solder that thing". The tpa6120 in particular, but other IC too, doesn't come in through hole, easy to solder packages.
- "Is it really working fine ?" A multiloop, state of the art amp is a bit more involved stability wise than most discrete designs around. Without a good scope, it might be difficult to properly check.
- "Opamps are not as good as the "real" thing". Years and years of prejudice in DIY circles against opamps, compounded by the marketing of firms appealing to DIYers (such as Burson).
- "It's so easy to have a class A design for headphones, why bother with opamps in class AB ?" See just above.
- "It just ain't fun". Since it's easy to go overboard with headphones since their power requirements are so low, why not go for the outrageous technologies I cannot usually experiment with ? Class A, SE, OTL tubes, etc.
Just a few good and bad reasons.
I see a lot of discussion of opamp headphone stages on here so I'm totally confused as to what the OP is getting at.
Those are all very relevant points. Thanks for generating this discussion.
I for one would much rather take pride in something self-made. However, I'm also mindful that sonic brilliance takes months of R&D which I'm happy to pay for too. Very good point about achieving stability.
Getting a TPA6120A2 to sing oscillation-free in a quad-nested feedback loop is no easy task on the schematic AND PCB designer.
As per my first post... No where near the performance of current commercial (event budget) amps unless I've missed something glaring? Perhaps you read my title and not the TLDR post 😉
I for one would much rather take pride in something self-made. However, I'm also mindful that sonic brilliance takes months of R&D which I'm happy to pay for too. Very good point about achieving stability.
Getting a TPA6120A2 to sing oscillation-free in a quad-nested feedback loop is no easy task on the schematic AND PCB designer.
As per my first post... No where near the performance of current commercial (event budget) amps unless I've missed something glaring? Perhaps you read my title and not the TLDR post 😉
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I think you have missed something glaring tbh, or at least not checked enough threads on here yet. Composites were the rage only a few months ago on here.
Perhaps, but sadly mostly either experimental (read: unstable), unmeasured, or datasheet replicas. Have sent you a pm to explore this separately.
The SMD argument is a good point. Most hybrid loop designs in their infancy are going to oscillate / distort. Combined with the fact that even with highres scope, we are still talking about requiring audio analyzers to take it to the ultimate refined level. Simply a barrier too much to cross?
This is a DIY site, experimental is the order of the day. I'll be honest I'm happy with my electrostatics so don't pay much interest to dynamic headphone drivers other than having a couple of TI ADSL line driver dev boards lying around. The fancy pants headphone driver chips are mainly repurposed ADSL chips. When I last had a check there was enough information around for anyone who wanted to go this route, with the usual grumbles about some of the surface mount packages around. I'm also of the view that anyone serious about DIYing the composite designs will have a sound card to help with their measurements.
For someone who wants a proven opamp based design TomChr does do the HP-2 as a PCB. You only get the full schematic when you buy the board, but in this case you are buying a guaranteed performance.
This stuff does get discussed a lot more on some of the dedicated headphone forums, or at least was 5 years ago when I last looked.
For someone who wants a proven opamp based design TomChr does do the HP-2 as a PCB. You only get the full schematic when you buy the board, but in this case you are buying a guaranteed performance.
This stuff does get discussed a lot more on some of the dedicated headphone forums, or at least was 5 years ago when I last looked.
I just sent one off to the board shop. It uses a tube-opamp hybrid first stage and opa1622 as line out / headphone out.
Sapphire looks a lot more show !! 🙂
I don't like the new, clean, micro dignity of the current amps, they look so unsalted.
I don't like the new, clean, micro dignity of the current amps, they look so unsalted.
An externally hosted image should be here but it was not working when we last tested it.
