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γ3 considerations

gamma3, gamma24 (plug-in for the γ3)

γ3 considerations

Postby OliverD » November 3rd, 2016, 1:41 am

I am currently looking into building either a minimal γ3 or a γ1.5. Either would be used with my 3-channel β22 and mostly headphones. I would prefer building the γ3 but my budget is rather limited these days compared to when I was building the β22 with LCDuino and δ1/δ2.
My primary source would be a laptop USB connection, so the main downside with the y1.5 would be the missing isolation (correct?) and the added psychological effect of knowing I could have built something better ;)

Anyways, I have looked at the γ3 and made some assumptions about modifications to the reference design that I would like to make to cut complexity and cost. I would love to hear feedback on those, e.g. where I went wrong or what I might have forgotten to consider:
In order to cut the cost of the γ3 I would reduce the inputs to usb-only, meaning I wouldn't need to populate the parts on the backplane dedicated to those, especially the pulse transformers. Even though I will try to cut complexity and cost where possible, I will not use suboptimal parts in the parts that I do use.
I won't need the volume control and if my assumption is correct, neither the display nor IR-receiver considering I would set it up once with the display and IR receiver I already have from the β22. This would mean:
1. The LCDuino board would be built, but I would only set it up with a display and IR-receiver once, and then only use the power button to turn it on and off. I assume this would work the same way it currently is with my β22 build, hence turning it on will load the last active configuration.
2. I will use the same σ11 for the dirty side of the γ3 and the LCDuino in the β22.
3. The front panel of the γ3 would only need one hole for the power button which I can drill myself eliminating the need for FPE services.
4. The power supplies for the γ3 and the β22 will share a case I already have, since I bought one that was generously sized when building the β22.
5. This is pretty obvious, yet it somehow belongs here: If I decide to spill out more cash and expand to a full blown build, none of the decisions above limit my ability to do so. This is true for my β22 build which has everything planned in order to be able to upgrade it from 3 channels to a balanced build.

Are these assumptions correct? Any feedback and hints will be greatly appreciated. Thanks in advance!
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Re: γ3 considerations

Postby amb » November 3rd, 2016, 5:25 am

OliverD wrote:... so the main downside with the y1.5 would be the missing isolation (correct?)

Galvanic isolation is one of many advantages of the γ3. It's not confined to a small portable form factor and USB power, therefore if you go through the features list you'll see that γ3 takes a higher-end approach to design and parts selection, from the use of high-end master clock oscillator, clock fan-out buffer, ASRC, two WM8741s in differential mono mode, fully-differential balanced outputs, multiple power supplies and ultra low-noise local voltage regulation, the list goes on. Part of the allure is also the use of the LCDuino-1 in the system, and all the myriad of features it brings to the table. Digital volume attenuator via the DACs, sample rate display, selectable filters and anti-clip mode and remote control are only the tip of the iceberg.

1. The LCDuino board would be built, but I would only set it up with a display and IR-receiver once, and then only use the power button to turn it on and off.

Yes, you could do that, but you'll lose features that are only available with the remote control and shown via the display.

2. I will use the same σ11 for the dirty side of the γ3 and the LCDuino in the β22.

In theory this is ok, but I question the sharing of components between the two. It would lock them together and make them inseparable, and reduce flexibility. What if an occasion arise that would require you to use the γ3 in a different system?

4. The power supplies for the γ3 and the β22 will share a case I already have, since I bought one that was generously sized when building the β22.

Same comment as above.
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Re: γ3 considerations

Postby OliverD » November 3rd, 2016, 10:43 am

First of all, thanks a lot for the quick reply!

amb wrote:Galvanic isolation is one of many advantages of the γ3. It's not confined to a small portable form factor and USB power, therefore if you go through the features list you'll see that γ3 takes a higher-end approach to design and parts selection, from the use of high-end master clock oscillator, clock fan-out buffer, ASRC, two WM8741s in differential mono mode, fully-differential balanced outputs, multiple power supplies and ultra low-noise local voltage regulation, the list goes on. Part of the allure is also the use of the LCDuino-1 in the system, and all the myriad of features it brings to the table. Digital volume attenuator via the DACs, sample rate display, selectable filters and anti-clip mode and remote control are only the tip of the iceberg.

I'm sorry, I didn't mean to belittle the advancements the γ3 brings to the table. The galvanic isolation is merely something I found important in past experiences e.g. with my γ2 and I am unsure whether I am able to fully appreciate the improved sound quality. Using usb on a laptop introduces lots of background noise though, at least from what I remember.

1. The LCDuino board would be built, but I would only set it up with a display and IR-receiver once, and then only use the power button to turn it on and off.

Yes, you could do that, but you'll lose features that are only available with the remote control and shown via the display.

I suppose I would only set it up once anyway and then never touch it again, if that is at all possible, since it's sole purpose will be listening to music fed from the computer anyway.

2. I will use the same σ11 for the dirty side of the γ3 and the LCDuino in the β22.

In theory this is ok, but I question the sharing of components between the two. It would lock them together and make them inseparable, and reduce flexibility. What if an occasion arise that would require you to use the γ3 in a different system?

In the past I have always preferred an integrated approach and besides that, I don't actually have the luxury of a different system. ;)
Maybe this is all just the upgraditis talking, since a β22/γ2 combo (which currently uses a cheapo USB-to-optical adapter for "galvanic isolation") leaves little to be desired apart from a hires usb input.
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Re: γ3 considerations

Postby OliverD » October 31st, 2017, 3:23 pm

Revisiting the y3 idea since winter days are approaching fast and photography will once again be forced to hibernate due to the inavailability of light in my free time, I am wondering if this can be done in 1 HE (4cm) Hifi2000 cases (e.g. https://www.modushop.biz/site/index.php?route=product/product&path=20_27_63&product_id=74).

I guess reducing it to USB-only, doing away with the potentiometer and maybe even the display the y3 backplane board should fit pretty easily into the height of 4cm. I am however uncertain about the power supply part of it. I assume since the power supplies are not taxed all that much in this build, it should be safe to use smaller heatsinks (e.g. Aavid Thermalloy 513002B02500G https://www.aavid.com/products/standard/513002b02500g) for the sigmas?
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Re: γ3 considerations

Postby amb » October 31st, 2017, 3:32 pm

The tallest parts on the σ11/σ22 boards are the heatsinks and the bulk capacitors. If you use the recommended parts in the γ3 parts list, and choosing an appropriate height for the board standoffs, then they might fit. You should check the available internal height of the enclosure and compare against the dimensions of everything to determine if all boards and panel parts will fit. Make sure that the tops of the PSU heatsinks will never touch the top cover when it is installed!
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Re: γ3 considerations

Postby muskyhuntr » November 1st, 2017, 2:31 am

I did mine in those same 1U cases. I did use 2, one for the DAC and one for the power supply. I did use shorter heat sinks in the power supply. SumR was able to do a pair of custom transformers that were shielded and encased that fit in the 1U. I still have to do the front panel to complete the DAC, but my attention was diverted to a trio of B24's.

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Re: γ3 considerations

Postby OliverD » November 2nd, 2017, 8:05 am

Thanks alot guys for clarifying this! :) The confirmation that this indeed works and has already been implemented is much appreciated.
Looking forward to finalizing my plans and placing an order!
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