Curious question: The wall wart specified in the BOM spreadsheet is a type with a fixed/built-in AC mains plug for US mains. How are you planning to support the European builds?
From the schematic, I gather that the supply (+) output is used for the circuit ground and its (-) output used for the negative supply rail. This will require that the supply is floating (i.e. that the secondary is not connected to mains ground), which again means that the various laptop bricks that people are likely to have floating around will most likely not be usable. Such laptop bricks tend to connect mains ground to the (-) output of the supply.
Do you have a list of power supplies that'll work internationally?
Tom
From the schematic, I gather that the supply (+) output is used for the circuit ground and its (-) output used for the negative supply rail. This will require that the supply is floating (i.e. that the secondary is not connected to mains ground), which again means that the various laptop bricks that people are likely to have floating around will most likely not be usable. Such laptop bricks tend to connect mains ground to the (-) output of the supply.
Do you have a list of power supplies that'll work internationally?
Tom
Tom, excellent points.
A diyAudio member provided the Mouser part number of a wall wart that works for European builders, in post #57. I suppose it wouldn't hurt to scare up a list of several others, from which to choose. I'll do this quickly, before the boards are shipped from the PCB fab to the diyAudio store. Spoiler: yes the Store has sent the T2 Gerbers out for fab. {We called that event "tape out" in the semiconductor industry, 30+ years ago. Mag tapes were the preferred (only) transfer vehicle when Carter was in the White House.}
Also please have a look at post #54, it discusses T2 power supplies and Protective Earth. I will emphasize this topic at greater length, in the "how to order parts" documentation that Store customers receive.
A member found another wall wart that he liked better, and posted its Mouser part number, in post #113. This one's made by Mean Well instead of Triad, and he prefers its aesthetics.
A diyAudio member provided the Mouser part number of a wall wart that works for European builders, in post #57. I suppose it wouldn't hurt to scare up a list of several others, from which to choose. I'll do this quickly, before the boards are shipped from the PCB fab to the diyAudio store. Spoiler: yes the Store has sent the T2 Gerbers out for fab. {We called that event "tape out" in the semiconductor industry, 30+ years ago. Mag tapes were the preferred (only) transfer vehicle when Carter was in the White House.}
Also please have a look at post #54, it discusses T2 power supplies and Protective Earth. I will emphasize this topic at greater length, in the "how to order parts" documentation that Store customers receive.
A member found another wall wart that he liked better, and posted its Mouser part number, in post #113. This one's made by Mean Well instead of Triad, and he prefers its aesthetics.
For reference, I used this one from Farnell / Element14:
https://au.element14.com/ideal-power/25hk-ay-240a100-dh/adaptor-ac-dc-24v-1a/dp/2771463
An externally hosted image should be here but it was not working when we last tested it.
It is a Class II unit and requires a common power lead that can be whatever your local flavour is, making it universal.
Ripple is 200mV max and the output (for me) was a very stable 24.1v.
It cost me $20AUD which is about $14USD or 12GBP.
The datasheet is here for anyone interested:
http://www.farnell.com/datasheets/2330098.pdf
Nope, no idea about when the Store will put up their T2 product page and start selling + shipping. Until then I do have a few extra copies of the 3-board set, all in black: (amp PCB, front panel PCB, rear panel PCB, photos in post#159) which I am selling to other DIY hobbyists at my cost. $16.50 inside USA, $26.50 outside USA, includes shipping. PM for PayPal info.
What will the Store charge for these? I don't work there and I don't know. I do know that my experimental batch of 20 copies of each of three boards, cost me $230 including shipping from China to California. So that's $11.50 per set of three boards. But the Store PCBs are going to be more expensive to make since they specify double thickness copper plus gold surface finish "ENIG". And, unlike me, the store is a business not a hobby. They actually pay people to inventory the boards, to affix and manage SKUs, to fulfill orders, to pack and ship, and to log each product movement and sales transaction in their accounting software. (It's a third-party "fulfillment house".) Whereas I do all of that for free.
Add on the cost of a bubble mailer, plus First Class postage for a 7oz parcel, and you get my total cost. Which equals my selling price, hobbyist to hobbyist, for these remaining few board sets.
edit- I didn't pay a 25% tariff on the boards I imported from China, but I think this might change soon (?)
_
What will the Store charge for these? I don't work there and I don't know. I do know that my experimental batch of 20 copies of each of three boards, cost me $230 including shipping from China to California. So that's $11.50 per set of three boards. But the Store PCBs are going to be more expensive to make since they specify double thickness copper plus gold surface finish "ENIG". And, unlike me, the store is a business not a hobby. They actually pay people to inventory the boards, to affix and manage SKUs, to fulfill orders, to pack and ship, and to log each product movement and sales transaction in their accounting software. (It's a third-party "fulfillment house".) Whereas I do all of that for free.
Add on the cost of a bubble mailer, plus First Class postage for a 7oz parcel, and you get my total cost. Which equals my selling price, hobbyist to hobbyist, for these remaining few board sets.
edit- I didn't pay a 25% tariff on the boards I imported from China, but I think this might change soon (?)
_
Last edited:
Fair enough. I just thought I'd ask as perhaps you've discussed this with them already.
Yep. Businesses have overhead costs that hobbyists often cover out of their own pocket. I know a bit about that...
I generally find the prices in the DIY Audio store to be very reasonable, and I'm sure that'll be the case for your amp as well.It probably depends on whether your package was pulled out for customs processing and duty/tariff collection. The total declared amount plays in as well. When I ship to the US, there're no duties or import fees for orders under $800. Now, I don't know if this threshold applies to imports from China as well, but I'm sure there's a "petty cash" threshold of some sort.
I do know that the various US component houses have factored in the 25% tariff on Chinese imports. Just last week I was getting quotes from one of the US distributors of the Mean Well power supplies. They listed the 25% (Section 301) tariff as a line item on the invoice. Unfortunately for them, the tariff meant that they lost my business. I can get the same supplies for less at Future Electronics in Canada. Oh, well... Such is life ... and business.
Tom
DACT question for MJ
Hi Mark
I see in post #159 you used a DACT attenuator. I recently tried an inexpensive ($17 incl. shipping from Hong Kong) DACT SMD stepped attenuator that is listed as 50K audio. Primary considerations were low cost and "D" shaft (many are serrated).
Now I see what all the VC fuss is about. Imaging is noticeably better than the Alps RK27. My issue is the attenuation curve. So far, I've tried it in a Whammy. Your T2 will be next to see if circuit gain changes my results:
This DACT appears to be pure logarithmic, which I find to have not enough change between steps in the first half of rotation and gain jumps that quickly become too large in the second half. I really like the Alps 15A curve which is a specialized audio taper that is not logarithmic.
Have you noticed any similar issues with your DACT? Is it 50K, 100K, other? I'm looking for one with a good curve.
This is the one I bought. Love the way it sounds but really can't recommend it due to the curve:
DACT Type SMD Stepped Attenuator 21 step volume control pot D Shape Shaft | eBay
Brian
Hi Mark
I see in post #159 you used a DACT attenuator. I recently tried an inexpensive ($17 incl. shipping from Hong Kong) DACT SMD stepped attenuator that is listed as 50K audio. Primary considerations were low cost and "D" shaft (many are serrated).
Now I see what all the VC fuss is about. Imaging is noticeably better than the Alps RK27. My issue is the attenuation curve. So far, I've tried it in a Whammy. Your T2 will be next to see if circuit gain changes my results:
This DACT appears to be pure logarithmic, which I find to have not enough change between steps in the first half of rotation and gain jumps that quickly become too large in the second half. I really like the Alps 15A curve which is a specialized audio taper that is not logarithmic.
Have you noticed any similar issues with your DACT? Is it 50K, 100K, other? I'm looking for one with a good curve.
This is the one I bought. Love the way it sounds but really can't recommend it due to the curve:
DACT Type SMD Stepped Attenuator 21 step volume control pot D Shape Shaft | eBay
Brian
Hi Brian,
I am glad that I tried out the eBay DACT attenuator module, and in listening tests it seems not to change the sonic presentation at all. I.e. same as the ALPS.
However, I discovered that I like the ALPS more, for other reasons. The DACT has "only" 21 steps, which is too few for my taste. I prefer the continuous adjustment on the ALPS. Worse, the DACT has less friction; it's far easier to turn the volume knob than on the ALPS. I prefer the stiffness / solidity of the ALPS.
For me: good experiment, worthwhile results, non ambiguous conclusion.
edit- whoops, forgot to say, mine is 20Kohms. I bought from the seller who offers them two to a package.
I am glad that I tried out the eBay DACT attenuator module, and in listening tests it seems not to change the sonic presentation at all. I.e. same as the ALPS.
However, I discovered that I like the ALPS more, for other reasons. The DACT has "only" 21 steps, which is too few for my taste. I prefer the continuous adjustment on the ALPS. Worse, the DACT has less friction; it's far easier to turn the volume knob than on the ALPS. I prefer the stiffness / solidity of the ALPS.
For me: good experiment, worthwhile results, non ambiguous conclusion.
edit- whoops, forgot to say, mine is 20Kohms. I bought from the seller who offers them two to a package.
Last edited:
I have the same impressions. I prefer the Alps (although it is not perfect).
That's beautiful, blackdod. Congratulations on a lovely build!
Are you also going to pursue the two-chassis option?
Are you also going to pursue the two-chassis option?
Thanks Mark. The merit is yours 
. I have only "assembled" the amplifier.
I have taken some time to do some tests with two chassis with the same switched PSU but honestly I have not found differences. I have used quite sensitive headphones (ATH, Grados...) and with both configurations the amplifier is completely silent. I think that due to the isolation of the switched PSU and especially the filtering of your PSU. I think this section is very important.
So I have decided on a "simple" assembly following your philosophy with a single chassis and this PSU that for me it is more comfortable (and more powerful) than the "wall charger".
PD: As you can see, I have not used many of the points of ground. I recommend using only the essential ones to avoid loops.
. I have only "assembled" the amplifier.I have taken some time to do some tests with two chassis with the same switched PSU but honestly I have not found differences. I have used quite sensitive headphones (ATH, Grados...) and with both configurations the amplifier is completely silent. I think that due to the isolation of the switched PSU and especially the filtering of your PSU. I think this section is very important.
So I have decided on a "simple" assembly following your philosophy with a single chassis and this PSU that for me it is more comfortable (and more powerful) than the "wall charger".
PD: As you can see, I have not used many of the points of ground. I recommend using only the essential ones to avoid loops.
Last edited:
It's your DIY project, build it your way! Congratulations on a good looking result.
If the wires to your front panel switch carry the full mains voltage, you might be interested in experimenting with some kind of a shield, connected to chassis, that prevents coupling from the mains wires to the rest of the circuitry. On an early prototype of T2 I used this stuff from K&S, and found it very easy to work with. They sell it at my local "Ace Hardware" store.
Square Tubing - K & S Precision Metals: Full Line Metal Specialists
If the wires to your front panel switch carry the full mains voltage, you might be interested in experimenting with some kind of a shield, connected to chassis, that prevents coupling from the mains wires to the rest of the circuitry. On an early prototype of T2 I used this stuff from K&S, and found it very easy to work with. They sell it at my local "Ace Hardware" store.
Square Tubing - K & S Precision Metals: Full Line Metal Specialists
Speaking of grounds, where does the yellow-green wire disappear to? Screwed to chassis, I assume?
Where did you find a -24V or so SMPS? Or does this one have a floating secondary side so you can still connect the mains filter to PE regardless of whether you're using it for + or -24 V?
I used these ones from Vishay:
https://au.element14.com/webapp/wcs...01&langId=43&storeId=10184&partNumber=1166118
- Status
- Not open for further replies.