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A Very Compact Hybrid Amp - Page 3

post #31 of 2207
I think standardizing the panels and things would make group buys and casing work a lot easier. I know I suck at case work since I couldn't even case my CMOY properly the first time round.
post #32 of 2207
Quote:
Originally Posted by nsx_23 View Post
I think standardizing the panels and things would make group buys and casing work a lot easier. I know I suck at case work since I couldn't even case my CMOY properly the first time round.
Have to say that I agree with that. I think my cases looked pretty cool in the end but they required a ridiculous amount of work and I had to enlist the help of a few friends and coworkers to get access to the tools I needed. (I am in Aus and most of my tools are in Canada). Next time I will just pay for a hammond case that works for the dimensions. I can say "look at what I made" now but no one appreciates the time and work a customized case takes (except for the rest of us at Head-fi!). In the end I just want to get my builds up and running as fast as possible while still looking nice.

How close is this to being prototyped??
post #33 of 2207
Thread Starter 
Proto boards will probably arrive early next week. Then I will send one to cfcubed and forsakenrider to build out the proto. Perhaps they will take a week to make their builds (have to ask them on the time). If we don't encounter any problems the rest of the proto boards will be available for other prototype builds.

We can talk about the casing then too. I proposed FPE panels for the SOHA II but not enough people wanted them to make it sensible to order some.
Dr. Cavalli gained notoriety with his first DIY amplifier projects. His success has blossomed into Cavalli Audio, a world leader in amplifier design.
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post #34 of 2207
There's been great feedback & ideas already in the thread... Thanks!

Because, as runeight said so concisely a few posts ago:

"The main challenge will be that there are so many devices packed so close together there will be lots of opportunity to put something in the wrong place. So a slow and careful build process will be the best way."

I'm allowing up to one week (of my spare time) from proto PCB receipt to completed build, but I should have PCB populated & tested earlier. I'll try to post the status then (prior to casework) in case others are eager.

WRT panels, will take pictures and make notes during build *and* consider making PDF panel template/drill guides to help here. Often I find myself in the same boat, try as I might holes just don't align exactly as I intend.

Many things can be considered to (possibly) PCB-mount more things, simplifying construction/panel standardization, in a later version of the amp like:
  • Could/should we reduce size/rating of C5P/C10P?
  • Can we consolidate one more pair of single opamps?
  • Could/should we consider faster(260kHz+), more available SMD switcher for heater?
But the more change one makes between PCB designs, the more the new PCB designs start to resemble a new proto runs

Again, how the community receives the amp will have a lot of influence on things.

One thing those interested in building out proto boards can do, besides posting to thread/contacting runeight, is figure out how they'll source the more elusive parts in the build; LM2595T-ADJ, 14mm X 7.5mm .8A vert toroid 220uH, 1N53XX CRDs, NEC EC2-12NJ relay (or very similar) and small pot like panny EVJ-C20 or ALPS RK097. If necessary, perhaps runeight or I could assist with that...
post #35 of 2207
If you could get a whole kit together, that would be even more brilliant.

As far as casing goes, I'm sure that will be worked out once the prototypes are done and more people start showing interest. The millet custom cases were fantastic looking, so something like that would be great.
post #36 of 2207
It looks like Jameco has the LM2595T-ADJ, at a decent price:
Jameco Electronics ICs & Semiconductors: NATIONAL SEMICONDUCTOR: LM2595T-ADJ
No minimum qty, but there would be a minimum order cost I'm sure, unless we buy some other items from them as well.

Arrow also carries it, at triple the price, still not a big ticket, again a minimum order is probably required from them.
LM2595T-ADJ 0135 from National Semiconductor | Arrow Electronics North American Components
We should probably arrange a group buy on the scarce items.
post #37 of 2207
Mouser has the NEC EC2-12NJ relay: http://ca.mouser.com/search/ProductD...auz9TRyhaK7A==
so thats not a biggy..
post #38 of 2207
Thanks MrSlim...

In the current BoM, all the parts / part #s come from Mouser or Digikey (an order from each of them). Mouser having 1N5304s & 1N5313s and Digikey LM2595T-ADJs, decent panny EVJ-C20F02A24 pot and nice chokes (M8403-ND, 732-1428-ND).

Guess we'll call the BoM ready about the time we call the PCB ready
post #39 of 2207
Quote:
Originally Posted by runeight View Post
We can talk about the casing then too. I proposed FPE panels for the SOHA II but not enough people wanted them to make it sensible to order some.
I suspect it was because they were a little expensive. I wonder if such a thing could be sourced from asia? Pre drilled faceplates would make things go much faster for most people though.

I think an important point will be to keep the build cost as low as possible while yielding the best possible result. If the case is sufficiently small then I would probably make my own clear lexan faceplate and not worry about the lettering but others may want something more. If a total package was available inexpensively I would go for it. I think small and slick looking is a good goal.

I would love it if this build had the same sort of treble as the original SOHA with tighter bass and less background hiss. If the experts building the first run could give us all a detailed comparison it would be much appreciated.
post #40 of 2207
As far as cases and panels go, I see very little attraction, personally, in building something that looks exactly like that made by everyone else; maybe it's just me, but it seems far too Heathkit-ish, with all that implies. I know a lot of recent projects have been designed around specific enclosures, but - with one or two exceptions, like the Mini^3, they can still be cased up how anyone wants. I know that with portable designs, size - and enclosure choices - are a major design criteria, but when you start getting into larger, more complicated designs meant for home use, it just seems... artificially and unnecessarily sterile, and limiting, I guess. I know it's still DIY even when all the choices have already been made for you, but half the fun, IMO, is picking and sourcing parts in such a way that your creation is at least a little bit unique. (I just see row upon row of amps and DACs that all look completely identical, shouting the line from _Life of Brian_ in unison: "Yes, we're all individuals!"...) Casework isn't that hard, and people without access to drill presses and so on can still do pretty much everything with hand tools. If nothing else, there's really nothing wrong with plastic cases - EMI/RFI shielding is ridiculously overhyped, IMO, and if people are OCD about it, Pac-Tec do make shielded plastic enclosures... which take nice rectangular endpanels, so fabbing personal, one-of-a-kind "custom" endplates at a place like Ponoko or Pololu is accessible to just about anyone.

I have a sneaking suspicion that the trend towards squeezing the last bit of miniaturization out of designs by mounting everything possible on the board is driving the (hopefully brief) popularity of custom cases and front panels. When the layout is arbitrarily "fixed", and your hole-drilling needs to be accurate to +/-0.5mm, letting someone else do it for you starts to look attractive. It might make sense for portable designs, where space is a primary design criteria, but for "desktop" amps, is there really a good reason not to let people panel-mount stuff where they'd like? Too, from an engineering standpoint, the issue of "future-proofing" comes up: I know everybody likes the little Alps pot (or the big blue one), but if either of those ever become unavailable, their basically unique pinouts spell all kinds of trouble for hobbyists, only because so many PCBs are designed around them.
post #41 of 2207
Quote:
Originally Posted by Nemo de Monet View Post
<snip>Casework isn't that hard, and people without access to drill presses and so on can still do pretty much everything with hand tools.</snip>
With respect, casework is an entirely different skill set than populating a PCB with parts and a small soldering iron on a desktop. I'd venture to guess that the great majority of people on Head-Fi and the other forums are either students or young people in dorms or apartments who have neither the access to a drill press or the wherewithall to purchase one and set it up in a proper space.

Casework is that hard when tubes are involved - if for no other reason than cutting the hole for the tube(s) in the case. Drill bits aren't made big enough that are readily available. Hole saws are almost impossible to handle without a good drill press and a decent punch requires an almost $50 investment - not to mention the socket wrench or breaking bar that's needed to go with it. For that matter, the investment in a good step drill bit comes close to the punch price in some instances (but they aren't big enough, either).

Tubes also develop a lot of heat - especially if regulated heater supplies are used. Plus, Class A bias on the buffer in tube hybrids develop a lot of heat, too. Either one may require the use of cooling holes, which become very problemmatic without a drill press and extremely tedious even with one.

Of course, it's runeight's and cfcubed's decision whether to go for custom endplates, case, etc. or not ... Gosh knows, I can certainly list plenty of reasons not to do it (it's a monumental task, for one), but again with respect - those reasons have little to do with whether they are appropriate for DIY or whether they limit someone's flexibility in building the project.

P.S. Sorry for my intrusion into the thread. My best wishes for the project - it looks cool!
post #42 of 2207
You all, of course, make great points... And as expected in different directions

Some want full kits, some do not want the design limited by those that want full kits. Of course, if a design has PCB landings for jacks, pots, etc. this does not mean builders have to use them.

Certainly, full kits (& maybe PCB support for full kits) do not happen for designs still in the PCB prototype phase, but can be considered later.
How the community receives the amp performance wise will have influence on things at this stage. If an amp's reception appeared as on the order of, say, amb's popular MiniĀ³, this opens up possibilities.

Re: tomb's comments - Thank you for your input & the kudos you posted earlier... Note though that some of what you say may not apply to this headamp, and there are less impactful ($$) ways of achieving good results :
  • Heat - As posted elsewhere, the only hot part here should be the tube. A few others get warm, notably the 24V reg on its heatsink and buffer/rail output TO92s. On the order of say, my heatsink-less, lower-bias JISBOS build for example.
    Our SM regulator implementation for heater, typ operating @ 80%+ eff, only gets hand-warm & that's w/o a heatsink.
  • Drill, tube holes - My Greenlee stepper bit was like $25 shipped from ebay & works well for all such holes. This with my $60 Harbor Freight drill press works wonders
  • Heat, cooling holes - Again, we expect little heat to be generated within the case. But, one will need to provide a minium of ventillation through holes or slots. I envision no holes on top of case other than for the tube itself, mabye several on the plastic back bezel (& possibly some along the side).
  • Cases, general - By using an off-the-shelf case one can provide drill templates as a 1/2 step to custom panels. And, one can always get some customization through color changes. I'm using hammond's "clear" case and gray vinyl dye on the bezels, for example, to try to get something nice

How about we see how the proto PCB builds go now

Clearly, this project has a lot of potential when looking at its design, features, operating points, tube flexibility, size and cost.
We know sound performance is subjective, and not always related to specifications/features....
Heck until recently I was happy listening to tubes running wwwaaayyy below (plate in the 40s) their recommended operating points (e.g. even below spec sheet curves). And w/lower-power opamp buffers to boot.
Beauty is in the eye of the beholder.
post #43 of 2207
Thread Starter 
Quote:
Originally Posted by Nemo de Monet View Post
As far as cases and panels go, I see very little attraction, personally, in building something that looks exactly like that made by everyone else; maybe it's just me, but it seems far too Heathkit-ish, with all that implies. I know a lot of recent projects have been designed around specific enclosures, but - with one or two exceptions, like the Mini^3, they can still be cased up how anyone wants. I know that with portable designs, size - and enclosure choices - are a major design criteria, but when you start getting into larger, more complicated designs meant for home use, it just seems... artificially and unnecessarily sterile, and limiting, I guess. I know it's still DIY even when all the choices have already been made for you, but half the fun, IMO, is picking and sourcing parts in such a way that your creation is at least a little bit unique. (I just see row upon row of amps and DACs that all look completely identical, shouting the line from _Life of Brian_ in unison: "Yes, we're all individuals!"...) Casework isn't that hard, and people without access to drill presses and so on can still do pretty much everything with hand tools. If nothing else, there's really nothing wrong with plastic cases - EMI/RFI shielding is ridiculously overhyped, IMO, and if people are OCD about it, Pac-Tec do make shielded plastic enclosures... which take nice rectangular endpanels, so fabbing personal, one-of-a-kind "custom" endplates at a place like Ponoko or Pololu is accessible to just about anyone.

I have a sneaking suspicion that the trend towards squeezing the last bit of miniaturization out of designs by mounting everything possible on the board is driving the (hopefully brief) popularity of custom cases and front panels. When the layout is arbitrarily "fixed", and your hole-drilling needs to be accurate to +/-0.5mm, letting someone else do it for you starts to look attractive. It might make sense for portable designs, where space is a primary design criteria, but for "desktop" amps, is there really a good reason not to let people panel-mount stuff where they'd like? Too, from an engineering standpoint, the issue of "future-proofing" comes up: I know everybody likes the little Alps pot (or the big blue one), but if either of those ever become unavailable, their basically unique pinouts spell all kinds of trouble for hobbyists, only because so many PCBs are designed around them.
I think there is some truth in what you're saying. The smaller the amp the more reasonable it is to have pre-fabed enclosure pieces. Just because the location of the auxilliary components becomes more critical.

That's why the Bijou is produced as separate boards for amp (single channel) and PS. It needs a bigger enclosure where there will be lots of room for location the pots, jacks, etc. and, therefore, lots of opportunity for creative casing.

OTOH, the SOHA II is a single board with fixed locations for the front panel components, but not the rear. In this case it is a toss up whether someone wants custom panels/enclosure or not.

In this compact amp the front and back panel real estate will have to be used as efficiently as possible. And so it may turn out that everyone will be happy to just take pre-fab'd pieces because there just isn't any other creative way to do it (assuming the Hammond enclosure).
Dr. Cavalli gained notoriety with his first DIY amplifier projects. His success has blossomed into Cavalli Audio, a world leader in amplifier design.
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post #44 of 2207
Nemo, you should try your hand at sourcing parts here in Australia.

Thats why some of us want kits, since many components are often difficult to find overseas or even unavailable. I remember trying to source just a simple ALps volume pot for Joshadot's PCB CMOY, and in the end it took a very nice head-fier to give me theirs (from the US).

Also, some of us here quiet frankly aren't too concerned with doing casework, and would rather just have a pre-fabbed case that everything can be throw into and fit first time round.

Its all about choice. Some will like to do all their own work and source parts individually, and some (like me) would prefer to be able to buy a kit and get building right away (which, for me personally, is the most satisfying bit).
post #45 of 2207
Obviously, views on casework differ; I have no difficulty cutting tube holes - in 1/4" aluminum - with a hole saw and a hand-held electric drill, and I still maintain that anyone scared of working with metal might just as well use a plastic enclosure and ignore the paranoid hype about RF/EM shielding.

Regardless, I think that people should be enthused about a design - should want to build a design - because it sounds good, not because it looks pretty.

Cfcubed said "Of course, if a design has PCB landings for jacks, pots, etc. this does not mean builders have to use them", and that's true, as far as it goes - but, given that board space always seems to be at a premium, I can't help but wonder what better use the space allocated to these sorts of things could be put to. Some things - caps, resistors, diodes, ICs - basically have to be mounted on the board. IMO, those that don't have to be - jacks, pots, switches, whatever - shouldn't be. If people want to put them in what you consider the "obvious" or "logical" spots, then unless we're dealing with portable devices made to cram into the smallest possible enclosure, there's really no reason they can't panel-mount them in the "right" spot and have them up above the board; a mere 5mm is enough to clear resistors, diodes, et cetera with room to spare... Off-board components = more usable (or less wasted) board space = more (or better) features = a win-win situation for everyone.

nsx: That's my point; if you want to give people the whole enchilada, a la Heathkit, then plan from the outset to make complete kits. If not, make projects with enough flexibility to accommodate even those of you in the most outlying areas of the Empire. (I referred before to "future-proofing" of designs, but I think I'll start promoting the plight of you folks down under and use the term "Australia-proofing" instead. ) If people didn't keep designing PCBs with the Alps pots right onboard, you - as an example - could just use whatever stereo pot you could find (or get a $20 stepped attenuator off a Hong Kong seller on eBay), wire it up, and get on with life. I mean, there are pots, switches, jacks, and so on, available in Australia, and just about everywhere else in the world; that they aren't readily, or easily, usable is only because PCB designs are habitually - and for no good reason - inflexible, due to (mis-)design...
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