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Old 29th September 2010, 02:41 AM   #291
qusp is offline qusp  Australia
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nice work, but the ackodac will not fit there, the regs will hit the caps. hmm the regs extend just over 50mm one way (the bottom) and 62.5 the other (the top) and out the sides, but that only matters for casing choice, the only one of consequence is most likely the top, guess we'll see
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Old 29th September 2010, 02:59 AM   #292
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then again if those are power supply caps, I dont have anything to worry about, because i'll be using external PSU
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Old 29th September 2010, 03:29 AM   #293
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That's more or less what I was thinking... If you're using the Ackodac then the 5V reg for the DAC and the digital input section won't be any good to you. It looks like the daughter boards will still hit the caps from the other regs, but there's not much I can do about that. The Ackodac needs like 10 square feet of space around it, and there just isn't room.

I'd suggest using lower profile (1" tall) heatsinks for the regs, and lower profile caps. If you do that, you can get away with mounting the Ackodac 0.75" above the board and just wiring it in. That's still much better than some of the other I/V solutions I've seen.

If you don't use the on-board regs, then the ackodac should drop right on.

As for the distance of the regs, I don't think it'll be a problem. The output runs over a return ground plane, and each resistor has it's own large ceramic decoupling cap. PSU noise should be a non-issue in this setup.

Cheers,
Owen
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Old 29th September 2010, 03:44 AM   #294
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yep, well as I said in the email, its not designed to be stacked on top, its designed to have something stacked on top of it. this wouldnt be a problem if the IV didnt need a square acre and 10lb of alloy to do away with the waste heat from 12 devices . for what there is there, it still takes up very little space. try using 8 PH regs on your buff and see how much space it takes up and thats effectively whats gong on here. (except these are discrete linear regs, so heatsinking isnt a problem like shunts)

but hey i'm cool with that, I may even be able to use the spare space from the vacant power supply for mounting my USB->i2s board and async reclocker. so sounds like its all covered, like I said, was a real question about the track lengths, i'm not a designer and forgot about the ground plane for the return path

Last edited by qusp; 29th September 2010 at 03:49 AM.
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Old 29th September 2010, 01:06 PM   #295
CeeVee is offline CeeVee  Portugal
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I havent ben following ackodac since i'll be using BuffaloII but if you want , and give me the detais, i'll render the ackodac's major components in and we can have a look at what it will look like.


Edit: Ok went for a quick search and it seems that the ackodac's apendages are the issue....don't see how they can fit in.

If this board was only for Buffalo the we could even maybe fit in Salas regs. ...no qusp i'm not forgeting you, just thinking out loud.

Doing two version of the board ( one or Buffalo, one for Ackodac ) is out of the question ?

excuse the joke but making a suit that will be good for both Laurel and Hardy is ....well kinda dificult.

...I'm not telling who is Laurel and who is Hardy.

Don't get me wrong it's just that i like to try to optimize things and...opc has a dificult task here.



CV

Last edited by CeeVee; 29th September 2010 at 01:26 PM.
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Old 29th September 2010, 01:36 PM   #296
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I could go for a Buff-II version with Salas regs on it.

Even neater would be a Buff-II Salas reg board with 6 regs to replace the three on-board regs, the separate 5.5v reg, and the dual-reg adder board. I don't think this could be combined with the OPC D1 I/V board, but the reg board could mount on the bottom, the Buff-II above, and the OPC D1 board above.

Just a thought... I'll go with what the consensus is.

Greg in Mississippi
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Old 29th September 2010, 02:06 PM   #297
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Good work!

I am only chiming in because of all the Buff II talk.

Just a couple comments if I may...

FWIW... I already have designed a stackable BUF-II version of a single FET per side common gate I/V PCB, but I had no idea there was any real interest in it since Legato is really IMO a better fit.

The PCB features a bone standard FET based common gate I/V with no buffer. I actually did not think there would be much if any interest in it because of the extremely high voltage/power needed to get decent results.

The voltage/power issue is one reason why I designed Legato, but the biggest reason is better performance by dramatically increasing transconductance. It uses the same common base/gate principle but produces better (measured) results with far less power and a lot less hassle.

I think the attraction to the "D1" must simply be because of the name? Nostalgia? I am honestly curious. In any case if there is enough interest I will be glad to revive the "classic" FET only PCB, and even enhance it if desired. The original was purely for my testing in development leading up to Legato.

Cheers!
Russ
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Old 29th September 2010, 03:36 PM   #298
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Hi Guys,

CeeVee:

Thanks for the great job on the rendering, everything looks pretty good! I can send you the same basic layout info that qusp sent to me, but at this point I think good enough is just going to have to do for the Ackodac.

The acko will fit, if you omit the regs from the board, or as I said, if you mount it about 3/4" above the board and use 1" heatsinks and low profile caps. To be honest, it actually makes sense. People who bought the Acko did so because they like to tweak the regulators and supplies, so they probably won't like my "ho hum" LM based regs anyhow. I'll provide the option for off-board power supplies, and hopefully that's enough for everyone. If you think different regs will make significant difference, then you're free to use anything you like.

qusp:

Are you reasonably happy with the layout as it is? I'll post the routed images later today for a final check over.

Russ:

Could you post some measurements for the legato? I've checked your website and I don't see anything there. If you've got access to an AP I'd prefer that.

I think the interest in this particular circuit is that it's a simple, single stage/single device design with no feedback and THD performance that is so good it's unmeasurable with state of the art measurement equipment. Can you think of a reason it wouldn't be interesting? Power dissipation is the only drawback, but at 42 watts, it's a small fraction of what even a small class A amp would draw.

The legato is a two stage design with 4 active devices per branch and feedback. I'm sure it works quite well, but it's a fundamentally different circuit. I'd also be surprised if the Legato's measured THD+N was better than -112dB (measurement floor of the AP).

I like simplicity, and I like the idea of minimizing component count and circuit complexity. There's nothing special here with this circuit, I just took it a little farther than others have, and took the time to tweak the individual parts both with listening and measurements. I've posted all my results here for everyone to see, so there's no black magic or mystical claims. It's just a really good/cheap/simple circuit that performs incredibly well at the cost of a little bit of heat.

Cheers,
Owen
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Old 29th September 2010, 03:44 PM   #299
qusp is offline qusp  Australia
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Quote:
Originally Posted by CeeVee View Post
I havent ben following ackodac since i'll be using BuffaloII but if you want , and give me the detais, i'll render the ackodac's major components in and we can have a look at what it will look like.


Edit: Ok went for a quick search and it seems that the ackodac's apendages are the issue....don't see how they can fit in.

If this board was only for Buffalo the we could even maybe fit in Salas regs. ...no qusp i'm not forgeting you, just thinking out loud.

Doing two version of the board ( one or Buffalo, one for Ackodac ) is out of the question ?

excuse the joke but making a suit that will be good for both Laurel and Hardy is ....well kinda dificult.

...I'm not telling who is Laurel and who is Hardy.

Don't get me wrong it's just that i like to try to optimize things and...opc has a dificult task here.



CV
start talking about that kinda thing and the design as a whole will never happen, just 'dropping in' 8 discrete shunt regs is not easy, especially when some are required to be low noise 1.2v supplies. this would require an entirely new and extensive development phase. i'm not sure if you have read my posts, because there really isnt anything to sort out. i'm not using the onboard power supply, I already have power supply for everything sorted for Pierre's PCB including potted transformer etc, without this it'll fit just fine. there will not be enough people who wanted an ackodac version and yeah I have no need for it, I just want the IV and to be able to bolt the dac board to it, thats all, I wont be using the spdif, I wont be using the power supply. I would love if the power supply section could be snapped off somehow to save space for those who wont use it.

WRT buff vs ackodac, I have both; easy picking a favorite

Last edited by qusp; 29th September 2010 at 03:59 PM.
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Old 29th September 2010, 03:56 PM   #300
qusp is offline qusp  Australia
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but then apart from the dac chip itself I built the dac from scratch, so that may have something to do with it.
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